Fundamentals of Refining and Petrochemical Engineering_Final_1.pdf

Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 i Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 COURSE INSTRUCTOR: Dr Solomon Adjei Marfo, Depa...

Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 i Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 COURSE INSTRUCTOR: Dr Solomon Adjei Marfo, Department of Chemical and Petrochemical Engineering, University of Mines and Technology, Ghana Emails: [email protected] Phone: +233 55 33 73 883 ASSESSMENT OF STUDENTS: Students’ assessment will be in two (2) forms: 1. Continuous Assessment - [40 marks] Class Attendance Quizzes/Assignments/ Presentations 2. End of Semester Examinations – [60 marks] ASSESSMENT OF COURSE LECTURER: At the end of the course, each student will be required to evaluate the course and the lecturer’s performance by answering a questionnaire specifically prepared to obtain the views and opinions of the students about the course and lecturer. COURSE CONTENT: Chapter one: origin and properties of crude Chapter two: oil recovery (drilling). Chapter three - petroleum refining. Chapter four: chapter four: natural gas Chapter five: refinery products OBJECTIVES and LEARNING OUTCOMES Objective This course is intended to give student a general overview of petroleum refinery design, processes and its various products. Students are expected at the end of the course to be equipped with the various distillations and solvent refining processes as well as the refinery equipment and machines. This course also exposes student to the petrochemical aspects of petroleum products from the refineries Learning Outcomes Having completed this course students will be able to: recognize the significance of petroleum fuels in the energy supply; express the overall objectives of petroleum refining; identify the economic and environmental drivers of petroleum refining; describe the overall approach to petroleum refining and categorize refinery processes and products; portray chemical constitution of petroleum. ii Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 Contents COURSE INSTRUCTOR:......................................................................................................ii Contents..................................................................................................................................iii List of Tables......................................................................................................................... vii List of Figures...................................................................................................................... viii CHAPTER ONE: ORIGIN AND PROPERTIES OF CRUDE............................................. 1 Learning Outcomes.................................................................................................................. 1 1.1 Introduction........................................................................................................................ 1 1.2 Origin of Petroleum............................................................................................................ 2 1.2.1 Unscientific concepts.................................................................................................... 2 1.2.1.1Fertile Paradise Concept............................................................................................. 2.1.2.1.2 Wet Whale Concept.................................................................................................. 2 1.2.2 Two Theories................................................................................................................. 2 1.2.3 The Organic Theory...................................................................................................... 3 1.2.3.1 Outline.......................................................................................................................... 3 1.2.3.2 Evidence in Favour of Organic Theory........................................................................ 4 1.2.4 The Non-Organic theory............................................................................................... 4 1.2.4.1 Historical Development.................................................................................................. 4 1.2.4.2 Metal Carbide Theory................................................................................................ 4 1.2.4.3 Volcanic Origin Theory............................................................................................. 5 1.2.4.4 Earthquake Outgassing................................................................................................ 5 1.2.4.5 Outline of the Theory.................................................................................................... 5 1.2.4.6 Evidence in favour of the Non-Organic Theory.............................................................. 5 Geographical Location.......................................................................................................... 5 1.2.4.7 Extra-terrestrial Hydrocarbons........................................................................................ 6 1.2.4.8. Experimental Verification................................................................................................ 7 1.2.4.9 Abundance of Oil in Middle East................................................................................. 8 1.3 Fossil Fuels......................................................................................................................... 8 1.3.1 Classification of Fuels..................................................................................................... 9 1.3.2 Characteristics of a Good Fuel........................................................................................ 9 1.3.2.1 High calorific value:................................................................................................... 10 1.3.2.2 Moderate ignition temperature:.................................................................................. 10 1.3.2.3 Low moisture content:................................................................................................ 10 1.3.2.4 Low non – combustible matter content:..................................................................... 10 1.3.2.5 Moderate velocity of combustion:.............................................................................. 10 1.3.2.6 Products of combustion should not be harmful:........................................................ 10 1.3.2.7 Low cost:.................................................................................................................... 10 1.3.2.8 Easy to transport:........................................................................................................ 10 1.3.2.9 Combustion should be easily controllable:................................................................ 10 1.3.2.10 Should not undergo spontaneous combustion:......................................................... 10 1.3.3 Advantages and disadvantages fuels............................................................................. 11 1.3.3.1 Solid Fuel................................................................................................................... 11 1.4 COAL............................................................................................................................... 13 1.4.1 Classification of Coal.................................................................................................... 13 1.5 Properties of Petroleum.................................................................................................... 14 1.5.1 Physical Properties...................................................................................................... 15 1.5.1.1 API Gravity................................................................................................................ 15 1.5.1.2 Viscosity..................................................................................................................... 17 1.5.1.3 Pour and Cloud Points................................................................................................ 18 iii Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 1.5.1.4 Refractive Index......................................................................................................... 18 1.5.1.5 Optical Activity.......................................................................................................... 18 1.5.1.6 Volume....................................................................................................................... 19 1.5.1.7 Fluorescence............................................................................................................... 19 1.5.1.8 Colour......................................................................................................................... 19 1.5.1.9 Odour.......................................................................................................................... 19 1.5.1.10 Coefficient of Expansion.......................................................................................... 19 1.5.1.11 Aqueous Solubility................................................................................................... 20 1.5.1.12 Surface tension Effect.............................................................................................. 20 1.5.1.13 Flash Point................................................................................................................ 20 1.5.1.14 Lower Flammable Limit (LFL)................................................................................ 20 1.5.1.15 Upper Flammable Limit (UFL)................................................................................ 21 1.5.1.16 Characterization Factors........................................................................................... 21 1.5.1.17 Reid Vapour Pressure............................................................................................... 21 1.5.2 Chemical Properties...................................................................................................... 22 1.5.2.1 Concentration of Various Contaminants.................................................................... 22 1.5.2.2 Sulphur Content.......................................................................................................... 22 1. 5.2.3 Nitrogen Content....................................................................................................... 22 1. 5.2.4 Metals Content.......................................................................................................... 23 1. 5.2.5 Total Acid Number.................................................................................................... 23 1. 5.2.6 Carbon Residue......................................................................................................... 23 1. 5.2.7 Basic Sediment and Water (BS&W)......................................................................... 23 1. 5.2.8 Salt Content............................................................................................................... 23 1.5.2.9 Distillation and Boiling Points................................................................................... 23 1.5.2.10 Water Content.......................................................................................................... 24 1.5.3 Composition of Petroleum..................................................................................... 24 1.5.3.1 Paraffins................................................................................................................. 24 1.5.3.2 Olefins..................................................................................................................... 25 1.5.3.3 Naphthenes (Cycloparaffins)............................................................................ 25 1.5.3.3 Aromatics............................................................................................................... 26 1.5.4 Crude Assay.................................................................................................................. 27 End of Chapter Assessment.................................................................................................. 29 CHAPTER TWO: Oil Recovery (Drilling)........................................................................... 30 2.1 Sectors in the Petroleum Industry.................................................................................... 30 2.1.1 Upstream Sector............................................................................................................ 30 2.1.2 Midstream...................................................................................................................... 31 2.1.3 Downstream.................................................................................................................. 31 2.2 Wells................................................................................................................................. 32 2.2.1 Well Integrity................................................................................................................ 32 2.2.2 Well Design and Construction...................................................................................... 32 2.2.3 Site Selection and Preparation....................................................................................... 32 2.2.4 Drilling the well............................................................................................................ 33 2.2.5 Directional drilling........................................................................................................ 35 2.2.5.2 Pad wells.................................................................................................................... 35 2.2.6 Drilling fluids and rock cuttings.................................................................................... 36 2.2.7 Well operations............................................................................................................. 36 2.2.8 Well abandonment......................................................................................................... 36 2.3 Petroleum Reserves and Evaluation:................................................................................ 36 2.3.1Petroleum Resources...................................................................................................... 36 iv Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 2.3.2 Petroleum resources management systems................................................................... 36 2.3.2.1 Proved Petroleum System.......................................................................................... 37 2.3.2.2 Hypothetical Petroleum System................................................................................. 37 2.3.2.3 Speculative Petroleum System................................................................................... 37 2.3.3 Resource classification.................................................................................................. 37 2.4 The Future of Fossil Fuels................................................................................................ 39 2.4.1 Peak oil.......................................................................................................................... 39 2.5 The Ghanaian Context...................................................................................................... 41 End of Chapter Assessment.................................................................................................. 43 CHAPTER THREE - PETROLEUM REFINING.............................................................. 44 3.1 Objective of Crude Oil Refining...................................................................................... 44 3.2 Overall Refinery Flow...................................................................................................... 44 3.2.1 Separation Processes..................................................................................................... 45 3.2.1.1 Desalting..................................................................................................................... 46 3.2.1.2 Distillation.................................................................................................................. 48 3.2.1.3 Operation and Types of Distillation Processes.................................................................. 48 3.2.1.4 Light Ends Unit.......................................................................................................... 49 3.2.1.5 Catalytic Reformer..................................................................................................... 50 3.2.1.6 Catalytic Hydrotreatment........................................................................................... 50 3.2.1.7 Paths for Upgrading Heavy Oil.................................................................................. 51 3.2.1.8 Atmospheric and Vacuum Distillation Units............................................................. 52 3.2.1.9 Other Separation Processes: Absorption, Stripping, Extraction, and Adsorption...... 54 3.2.1.10 Deasphalting............................................................................................................. 55 3.2.1.11 Dewaxing................................................................................................................. 56 3.2.2 Conversion Processes.................................................................................................... 57 3.2.2.1 Thermal Conversion Processes.................................................................................. 57 3.2.2.1.1 Thermal Cracking.................................................................................................... 58 3.2.2.1.2 Visbreaking............................................................................................................. 58 3.2.2.1.3 Coking..................................................................................................................... 59 3.2.2.2 Catalytic Conversion Processes................................................................................. 59 3.2.2.2.1 Houdry Catalytic Cracking...................................................................................... 60 3.2.2.2.2 Thermafor Catalytic Cracking (TCC)..................................................................... 61 3.2.2.2.3 Fluid Catalytic Cracking (FCC).............................................................................. 61 3.2.2.2.4 Catalytic Hydrocracking......................................................................................... 62 3.2.3 Finishing Processes....................................................................................................... 63 3.2.3.1 Hydrogenation............................................................................................................ 63 3.2.3.2 Hydrodesulfurization.................................................................................................. 63 3.2.3.3 Hydrodenitrogenation................................................................................................. 64 3.2.3.4 Product Blending........................................................................................................ 65 3.2.4 Supporting Processes..................................................................................................... 65 3.2.4.1 Gas Processing Unit................................................................................................... 66 3.2.4.2 Sulphur Recovery....................................................................................................... 66 3.2.4.3 Hydrogen Production................................................................................................. 66 3.2.4.4 Wastewater Treatment................................................................................................ 66 3.2.4.5 Environmental Regulation of Refineries.................................................................... 67 End of Chapter Assessment.................................................................................................. 68 CHAPTER FOUR: NATURAL GAS................................................................................... 69 4.1 Natural Gas conditioning and Processing........................................................................ 69 v Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 4.2 Shale Gas.......................................................................................................................... 71 4.3 Natural Gas Liquids......................................................................................................... 71 4.4 Important impurities found in natural gas]....................................................................... 72 End of Chapter Assessment.................................................................................................. 72 CHAPTER FIVE: REFINERY PRODUCTS...................................................................... 73 5.1 Low-Boiling Products............................................................................................... 73 5.2 Gasoline......................................................................................................................... 74 5.3 Distillate Fuels............................................................................................................. 75 5.3.1 Jet and Turbine Fuels............................................................................................. 75 5.3.2 Automotive Diesel Fuels....................................................................................... 76 5.3.3 Railroad Diesel Fuels.............................................................................................. 76 5.3.4 Heating Oils................................................................................................................... 76 5.3.5 Residual Fuel Oils................................................................................................... 77 5.3.6 Liquefied Petroleum Gas (LPG)................................................................................... 77 5.3.7 Coke and Asphalt.......................................................................................................... 77 5.3.8 Solvents......................................................................................................................... 77 5.3.9 Petrochemicals Feedstocks............................................................................................ 77 5.3.10 Lubricants.................................................................................................................... 77 5.3.11.1 Leaded Gasoline Additives........................................................................................ 78 5.3.11.2 Oxygenates................................................................................................................. 78 5.3.11.3 Caustics...................................................................................................................... 78 5.3.11.4 Sulfuric Acid and Hydrofluoric Acid........................................................................ 78 5.4 Uses of Petrochemicals.................................................................................................... 78 5.4.1 The Primary Hydrocarbons........................................................................................... 78 5.4.2 Medicine........................................................................................................................ 79 5.4.3 Food............................................................................................................................... 79 5.4.4 Agriculture.................................................................................................................... 79 5.4.5 Household Products....................................................................................................... 79 5.4 The Ghanaian Context –Tema Oil Refinery (TOR)......................................................... 82 5.4.1 Liquified Petroleum Gas............................................................................................... 82 5.4.2 Gasoline (Petrol)........................................................................................................... 82 5.4.3 Kerosene........................................................................................................................ 82 5.4.4 Aviation Turbine Kerosine............................................................................................ 82 5.4.5 Gasoil (Diesel)............................................................................................................... 82 5.4.6 Premix........................................................................................................................... 82 5.4.7 Cracked fuels................................................................................................................. 82 End of Chapter Assessment.................................................................................................. 83 Sample Questions................................................................................................................... 84 6.0 Reference Materials Used:............................................................................................... 85 vi Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 List of Tables Table 1.1 Composition of petroleum....................................................................................... 15 Table 2.1 Overview of the Ghanaian sector............................................................................. 42 Table 3.1—Amount of water wash and temperature vs. crude gravity.............................. 48 Table 4.1—Composition of a typical natural Gas................................................................... 70 Table 4.2: NGL Attribute Summary (EIA).............................................................................. 71 Table 5.1 Physical Properties of Paraffins........................................................................... 74 vii Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 List of Figures Figure 1.1 History of energy consumption in the United States (1776 -2012) quadrillion Btu 8 Figure 1.2 Classification of fuels............................................................................................... 9 Figure 1.3 formation of coal.................................................................................................... 14 Figure 1.4 Stages in coal formation over millions of years..................................................... 14 Figure 1.5 Relationship between API and specific gravity of Crude...................................... 17 Figure 1.6 Relationship between LEL and UEL...................................................................... 21 Figure 1.7 Homologous series of paraffins.............................................................................. 25 Figure 1.8 Olefins.................................................................................................................... 25 Figure 1.9 Naphthenes in crude oil..................................................................................... 26 Figure 1.10 Aromatics in Crude oil......................................................................................... 27 Figure 1.11 Density of Crude oil Figure 1.12 Kinematic Viscosity.................................... 28 Figure 1.13 Pour & Cloud Point Figure 1.14 Sulfur Content.............................................. 28 Figure 1.15 Distillation test Figure 1.16 Component analysis.......................................... 28 Figure 2.1 Overview of the sectors in the Petroleum industry................................................ 30 Figure 2.2 Organisation of the Petroleum sector in Ghana...................................................... 31 Figure 2.3. Drill Bit. Credit Santos (2016).............................................................................. 33 Figure 2.4. Drill pipes Santos (2016)....................................................................................... 33 Figure 2.5. Threaded connection of steel casing. Santos (2016)............................................. 34 Figure 2.6. Drilling fluid. Santos (2016).................................................................................. 34 Figure 2.7 horizontal/high angle wells Santos (2016)............................................................ 35 Figure 2. 8 Resource classification framework........................................................................ 37 Figure 2.9 Campbell and Laherre Forecast on Peak Oil........................................................ 40 Figure 2.10 Revision on Peak Oil based on improved technology and knowledge.............. 41 Figure 2.11 Odell’s Forcast on Peak Oil................................................................................ 41 Figure 3.1—An overall refinery block flow diagram indicating an integrated network of major separation, conversion, finishing, and supporting processes................................................... 45 Figure 3.2—three general methods for the desalting of crude oil based on three oil/water separation methods: (a) settling, (b) use of an electric field, and (c) use of a packed column................................................................................................................................................... 48 Figure 3.3 Shows a simple diagram of atmospheric and vacuum distillation units................. 49 Figure 3.4 Light Ends Distillation unit................................................................................. 50 Figure 3.5 Catalytic Reformer unit.......................................................................................... 50 Figure 3.6 Catalytic Hydrotreatment schematic representation............................................... 51 Figure 3.7. An overall flow for fractional distillation of crude oil.......................................... 52 Figure 3.8 A schematic diagram of atmospheric distillation unit illustrating the feed exchangers, pumps around loops, and side steam strippers..................................................... 53 Figure 3.9 Vacuum distillation unit and processing paths for vacuum distillates................... 53 Figure 3.10 Examples of packing materials to achieve low – pressure drop in vacuum distillation columns.................................................................................................................. 54 Figure 3.11 Solvent fractionation of vacuum distillation residue (VDR)................................ 56 Figure 3.12 Configuration of deasphalting and dewaxing process in a refinery..................... 56 Figure 3.13 Feedstock for dewaxing and hydrocarbon composition of the feed and products57 Figure 3.14 Overall chemistry of visbreaking – breaking up long chains of hydrocarbons.... 58 Figure 3.15 Photographs of shot coke and sponge coke.......................................................... 59 Figure 3.16 Catalytic cracking process configuration............................................................. 61 Figure 3. 17 Process configuration for Fluid Catalytic Cracking (FCC) process.................... 62 Figure 3.18 Reactions of hydrocracking (Source: Eser et al., 2013)....................................... 63 Figure 3.19 Types of nitrogen containing compounds in crude oil......................................... 64 Figure 3.20. HDS Process Configuration (Source: Eser et al., 2013)...................................... 64 viii Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 Figure 3.21 Refinery supporting processes.............................................................................. 66 Figure 3.22 Wastewater streams in a refinery......................................................................... 67 Figure 4.1—schematic diagram of an associated gas reservoir............................................... 70 Figure 5.1 Products from a barrel of crude oil......................................................................... 80 Figure 5.2 Fractionation of Crude oil...................................................................................... 80 Figure 5.3 Fractionation of Crude oil with various products................................................... 81 ix Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 CHAPTER ONE: ORIGIN AND PROPERTIES OF CRUDE Learning Outcomes 1. At the end of this Chapter, students will be able to 2. Give an overview of the different theories regarding the origin of crude oil 3. Identify the essential properties of crude oil 4. Explain the various types of fuels and name their characteristics Learning Outcomes By the end of this lesson, you should be able to: define the significant properties of crude oil, including density, viscosity, average boiling point, sulphur, and salt content; understand the significance of crude oil properties in terms of refinery objectives, and describe crude oil assay; define and interpret the classification factors (Watson, UOP, VGC, and BMCI) as they relate to the hydrocarbon composition of crude oils; calculate average boiling points for crude oils using different averaging techniques and differentiate Watson and UOP characterization factors; analyze the elemental composition of crude oils and outline ternary classification of crude oils with respect to hydrocarbon composition, i.e., aromatics, paraffins, and naphthenes; assess the use of ternary classification of crude oils to estimate the refinery product yields. 1.1 Introduction Petroleum is the foundation of this Industrial Civilization. It is from petroleum that the world obtains its chemicals, its fuel for automobiles, engines, airplanes, etc. and its energy supply for its power stations. Empires have risen and fallen due to the annexation or loss of oil fields. Historically, petroleum and its derivatives have been known and used for millennia. Ancient workers recognized that certain derivatives of petroleum (asphalt) could be used for civic and decorative purposes, while others (naphtha) could provide certain advantages in warfare. Scientifically, petroleum is a carbon-based resource and is an extremely complex mixture of hydrocarbon compounds, usually with minor amounts of nitrogen-, oxygen-, and sulphur- containing compounds, as well as trace amounts of metal-containing compounds. In the crude state, petroleum, has minimal value, but when refined provides high-value liquid fuels, solvents, lubricants, and many other products. The fuels derived from petroleum contribute approximately one-third to one-half of the total world energy supply and are used not only for transportation fuels (i.e., gasoline, diesel fuel, and aviation fuel, among others) but also to heat buildings. Petroleum products have a wide variety of uses that vary from gaseous and liquid fuels to near-solid machinery lubricants. In addition, asphalt (a once-maligned by- product and the residue of many refinery processes) is now a premium value product for highway surfaces, roofing materials, and miscellaneous waterproofing use. 1 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 1.2 Origin of Petroleum Despite the immense amount of research devoted to the origin of petroleum, there are more uncertainties concerning it than any other common natural substance. The first attempt to explain the origin of petroleum dates back to antiquity. For example, the Greek scientist Strabon, who lived about 2000 years ago wrote: "At the place named Nymphey, there is a rock spiting fire, and under it are the sources of warm water and asphalts." Strabon united two facts: the eruption of volcanoes and the formation of asphalts (the way he named petroleum). This connection between the two facts was a mistake. In the places mentioned by his work, there were no erupting volcanos. The events which Strabon described as "eruptions" were actually "emissions", i.e. breaking out of underground waters (so called geysers), accompanied by outputs of petroleum and gas on the surface. M.V. Lomonosov was one of the first scientists to introduce a reasonable scientific concept of the origin of petroleum. In his mid-eighteenth-century work on "terrestrial layers", this Russian scientist wrote: "It is expelled from underground with heat, prepared from stone coal and brown coal, this black oily material. And this is a birth of a different grade of combustible liquid and dry hard matter. This is the essence of stone oil, liquid pitch, petroleum, and similar materials which are different by cleanliness, but occur from the same origin. It can therefore be stated that the idea of the organic origin of petroleum from stone coal was conceived more than 200 years ago. The initial substance was an organic material transformed at first into coal and then into petroleum. 1.2.1 Unscientific concepts Lomonosov was not the only one who addressed the question of the origin of petroleum in the eighteenth century. However, some of the other hypotheses formed at this time were less than scientific. 1.2.1.1Fertile Paradise Concept A hypothesis credited to a Warsaw priest was that the Earth was very fertile in the paradise period. The core of the earth contained a fatty impurity. After the paradise period, this fat was partially evaporated, and the vapor partially condensed on the ground where it mixed up with a variety of materials. This was later transformed to petroleum by the world flood..1.2.1.2 Wet Whale Concept At the end of the nineteenth century, the authoritative German geologist H. Hefer reported of an American petroleum industrialist who considered petroleum to have resulted from wet whales that existed at the bottom of polar seas. This petroleum penetrated into Pennsylvania by seeping through underground channels. 1.2.2 Two Theories By the end of the nineteenth century, two different hypotheses of the origin of petroleum had emerged: organic (biogenic) and nonorganic (inorganic/ abiogenic, abiotic, non - biogenic) hypothesis. The former holds that petroleum is of an organic origin and is the currently favoured proposal. It predicts limited reserves worldwide (Peak Oil). The latter maintains that it is of a non-organic genesis, supposedly of primordial origin. On the basis of this theory, oil resources would be much larger than those predicted by the biogenic theory. 2 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 Notwithstanding these, both are similar in postulating that, underground oil accumulations are formed when three conditions are met: First, there must be a ‘source’ rock rich in hydrocarbons and buried deep enough so that the heat from the Earth’s core can ‘cook’ them into oil. Second, there should be a porous rock nearby in which oil can accumulate (it is often sandstone). If the holes in the rock are interconnected, then oil can flow easily out of the rock. This condition is called permeability. The porous rock must have good permeability. Third, there is usually a ‘cap rock’ or seal to trap the oil in the underground reservoirs and prevent it from seeping to the surface. Within these reservoirs, hydrocarbons are typically organized like a three-layer cake—with a layer of water below the oil and a layer of gas above it. 1.2.3 The Organic Theory Historical Development The most widespread ideas among the scientists in the nineteenth century centered on the organic origin of petroleum." Disputes were mainly around the initial material for petroleum formation: animals or plants? German scientists H. Hefer and K. Engler carried out experiments in 1888 in which they sought to prove that petroleum formation was from animal origin. The experiments were performed by evaporation of fish fat at 400°C and 1 bar. Oil, combustible gases, water, fats and different acids were formed from the 492 kg of fat used. The largest fraction of evaporated material was oil (299 kg, or 61%) with a density of 0.8105 g/cm3. Subsequent evaporation of the oil product yielded saturated hydrocarbons (ranging from pentane to nonane), paraffin, lubricant oils as well as olefins and aromatic hydrocarbons. Later, a Russian scientist (N.D. Zelinskiy) carried out a similar experiment in 1919. However, his initial material was organic silt of mainly vegetative origin from Lake Balhash. The evaporation products in this case were: crude pitch - 63.2%, coke - 16.0%, and gases (methane, carbon oxides, hydrogen, hydrogen sulphide) - 20.8%. Subsequent processing of the pitch yielded gasoline, jet oil and heavy oil. 1.2.3.1 Outline All seas and oceans are populated with biomass which are essentially a wide variety of animals and plants. Of all sea biomass, the ones with the most significant role in petroleum formation are microorganisms, typically plankton, 90% of which is microscopic seaweed (phytoplankton). Plankton is the basic source of organic material in the sea. Plankton is contained not only in the silts at the bottom of seas or lakes but also dispersed or dissolved in the water. The organic theory holds that the first stage of the genesis of petroleum involves plankton (single-celled organisms that float on the oceans). These die and gradually accumulate on the ocean floor. Other sediments start accumulating too, and after a few million years the plankton are buried under several km of sediment. The plankton, which have remained unoxidised, under the increased values of pressure and temperature, are now transformed into kerogen. Under favourable conditions of time and temperature this kerogen, after further burial and heating, is transformed, via cracking, into petroleum and natural gas. These then migrate towards the surface and end up either reaching it (and drying up to yield bitumen or tar) or being arrested on the way in traps (where, millions of years later, drillers of the present industrial age make their big strikes). 3 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 1.2.3.2 Evidence in Favour of Organic Theory Traditionally, the following points have been considered as supporting the biological theory: (1) Since it is known that hydrocarbons can be produced by photosynthesis, it is natural to expect petroleum to be of an organic origin. (2) Molecules thought to be of biological origin, e.g.: porphyrins, isoprenoids, hopanoids, etc. were found in petroleum, thereby providing support for the organic theory. (3) The organic carbon in plants is depleted in carbon-13 due to the process of photosynthesis. In dead organic material the C-13 is further depleted due to radioactive decay. Since it was found that most petroleum and natural gas showed the same depletion, it was viewed as a strong proof in favour of an organic origin. (4) Sediments are the most important host rocks yielding petroleum, i.e. the oil produced from oil wells is generally obtained from a porous sandstone deep below. Often sediments are associated with biological material that could have acted as a source of the petroleum. (5) The existence of large quantities of oil shale from which a hydrocarbon mix similar to petroleum could be distilled was seen as a support in favour of an organic origin. This followed easily, since the oil shale was taken to be the kerogen source rock which, on sufficient burial, purportedly yielded petroleum. 1.2.4 The Non-Organic theory 1.2.4.1 Historical Development The Non-organic theory of the genesis of petroleum has a long history, dating back to the early days of the oil industry. Its development has led to the birth of a number of variants, the most important of which are outlined below: 1.2.4.2 Metal Carbide Theory The founder of the non-organic theory was Mendeleev, the Russian chemist who proposed the modern version of the periodic table. In 1877, he wrote that the petroleum deposits of the world seem to be controlled more by large- scale tectonic features than by the ages of sedimentary rocks. To explain these observations, he put forth the metal carbide theory. Many contemporary investigators, mostly Russian, supported Mendeleev’s view. In this model metal carbides deep within the earth reacted with water at high temperatures to form acetylene which subsequently condensed to form heavier hydrocarbons (as is readily formed in the lab). The following reaction CaC2 + 2H2O = C2H2 + Ca(OH)2 is still popular amongst some astronomers and certain Russian geologists as a major petroleum-forming possibility. 4 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 1.2.4.3 Volcanic Origin Theory This postulate involves outgassing of the mantle via volcanic activity. 1.2.4.4 Earthquake Outgassing This theory proposes that outgassing occurs via deep faults, and that this is still occurring today. V.I. Vernadsky propounded the notion that hydrocarbon compounds would be stable against dissociation and oxidation at great depths and would replace carbon dioxide as the chief carbon-bearing fluid. N.A. Kudryavtsev set forth the observations supporting what was later to be known as Kudryavtsev’s rule. T.Gold has become the main proponent of the idea of a non-organic origin in the West. Due to his initiative, a hole was drilled into crystalline basement rock which Gold predicted should yield petroleum. Only non-commercial quantities of petroleum, if any, were found. Moreover most of Gold’s colleagues were not convinced. However, recently a nearby hole did strike oil. 1.2.4.5 Outline of the Theory The theory suggests that most of the hydrocarbons on earth are in fact primordial. Carbonaceous chondrites appear to have been the most abundant source rock during the formation of the earth. This type of meteorite contains a significant amount of hydrocarbons. As the earth formed, it would have acquired these hydrocarbons via accretion (bodies of roughly equal size clumping together through collisions), and later through meteorite impacts (including hydrocarbons formed by the reaction of meteoritic carbon with H2 at high pressures and temperatures on impact). Then as the earth gradually cooled, a solid crust developed, while the interior remained liquid or semisolid. The volatile substances would be expelled from the interior. It is such gases that yielded, after biological modification, the present atmosphere. That hydrocarbons are being evolved from the inner parts of the earth is evident from the presence of mud volcanoes, flames seen during earthquakes, etc. On the way up, it is supposed, the oil (dissolved in methane) would be trapped in suitable formations creating the world’s oil and gas, tar sands, oil shales, bitumen, mud volcanoes, etc. Kropotkin and Valyaev pointed out that the hydrocarbons, carried upwards by streams of compressed gases, would have two possible destinies: (1) In volcanic regions, they would be oxidised to carbon dioxide and water, and (2) In ‘cool’ regions the hydrocarbons would form oil and gas reservoirs after condensation from the rising stream at levels possessing the requisite values of temperature and pressure. 1.2.4.6 Evidence in favour of the Non-Organic Theory Geographical Location The major oil fields of the world are concentrated on or near belts of major tectonic activity or in fact along fault zones. Some of the phenomenal Arabian fields, the world’s largest petroleum province, lie along the Persian Zagros Mt. belt. The large North Sea reserves that have made much of Northern Europe self- sufficient in oil production lie along the North Sea trench. The oil fields of Indonesia and Burma closely follow the seismic belt running from New Guinea to Burma, while the oil fields of Gujarat appear to be associated with the Cambay fault. Hydrocarbons are found in the Red Sea rift Valley, the East African 5 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 rift and the eastern branch of the Pacific Rift. These and many other examples that exist should illustrate the association of hydrocarbons with large deep-seated cracks in the Earth’s crust rather than any local sediments. However, note that the idea of deep-seated cracks may also be required to explain the migration of petroleum within the organic theory. According to the non-organic theory, petroleum should occur universally in areas of tectonic activity. This does not appear to hold true, and this seems to be a problem for the non-organic theory. (i) Stability with Depth It was once thought that petroleum and natural gas would not be able to survive at depths greater than a few tens of kilometres below the surface as the temperatures occurring there exceeded those observed to destroy petroleum and natural gas in labs. Hence, it was reasoned, it was pointless to look for either the fuel or its origin in the depths of the Earth. However that picture has changed radically. Huge quantities of gas have been discovered at great depths e.g. in the Anadarko basin in Oklahoma. Reservoirs of ‘geopressured gas’ have been found to underlie all major oil-bearing regions. These are sandstones and shales containing enormous amounts of gas dissolved in salt brines. Reserves of such gas are estimated at 60000 TCF (trillion cubic feet) in the U.S. alone, exceeding by several factors the total conventional gas reserves of the world. In addition, vast domains of gas exist in open fractures of non-sedimentary basement rock. A deep hole currently being drilled in Germany has found these at depths of up to 4km. Theory had to be revised as it has been showed that not only could natural gas exist at extreme depths but petroleum could, too. (ii) Earthquakes The eruptions of gas mentioned above, the generation of which is not disputed by the organic theory, should cause earthquakes. In fact, earthquakes have been observed to be associated with gas ejection throughout recorded history: 1.2.4.7 Extra-terrestrial Hydrocarbons (i) Meteorites If primordial hydrocarbons were incorporated in the earth during the process of formation, then one should expect to find such substances in ancient material dating from the formation of the solar system. Such material exists in the form of carbonaceous chondrites, a class of meteorites. Moreover, this type of meteorite seems to be very common. In fact, asteroids and interplanetary material seem to be of largely carbonaceous derivation. Materials previously thought to be exclusively biological in origin have now been found on meteorites. Porphyrin-type molecules are found in meteorites and are almost certainly not of a biological derivation. (ii) Planets The outer planets have their atmospheres largely in the form of hydrocarbons, chiefly methane. Uranus’ atmosphere may contain as much as 14% of methane gas. Neptune’s 6 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 atmosphere consists of hydrogen, helium and methane while the inner liquid shell is thought to consist of water, methane and ammonia. (iii) Comets Halley’s Comet (1986) was found to emit hydrocarbon gases. The core was observed to be black, presumably because of it being composed of carbonaceous material. Lang and Whitney describe the interior as blacker than coal, its blackness perhaps being due to ‘an admixture of minerals, organic compounds and metals’. 1.2.4.8. Experimental Verification The final proof would involve an actual experimental verification of the theory. Deep wells are good tests, since organic materials cannot occur in crystalline basement rocks. Several are under way: 7 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 The Kola Superdeep Hole At 12 km, this is the world’s deepest well (1984). Located in the Kola peninsula, now Russia, it reached deep down into the crystalline basement. The drilling released flows of gas at all levels. The liberated gases included helium, hydrogen, nitrogen, methane and other hydrocarbons and CO2. This provides convincing support for the suggestion that hydrocarbon gases exist at such great depths inside the earth that they cannot be of a biological origin. 1.2.4.9 Abundance of Oil in Middle East The concentration of oil in the Middle East implies that that region must have been exceptionally prolific in plant and animal life over long periods of the Earth’s history. This is unlikely, since life tends to be more dispersed, even today 1.3 Fossil Fuels Due to the rapid increase in the world’s population, there has been a concomitant demand for energy. Most of the world’s energy is supplied by fossil fuels. Fossil fuel’s account for about 82% of the world’s energy, according to the World Energy Outlook report of 2017. Fossil Fuels are the energy rich substances formed from the remains of once-living organisms. The three major fossil fuels are coal, oil and natural gas. Fossil fuels are made of hydrocarbons, they contain carbon and hydrogen and upon combustion release heat (energy) in addition to other products such as carbon dioxide and water. Figure 1.1 History of energy consumption in the United States (1776 -2012) quadrillion Btu Fuel is a combustible substance, containing carbon as a main constituent, which on proper burning gives large amount of heat, and can be used economically for domestic and industrial purposes. 8 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 The process of burning a fuel is called combustion. Combustion requires three elements in order to take place. There has to be the presence of fuel, oxygen (air) and a heat source. These three together are referred to as the fire triangle. 1.3.1 Classification of Fuels A fuel is defined as naturally occurring or artificially manufactured combustible carbonaceous material which serves particularly as source of heat and light and also in few cases as a source of raw material. Bases on their physical state fuel are classified into a) Solid b) Liquid c) Gaseous fuels Based on their origin they are classified into a) Primary fuels b) Secondary fuels. a) Primary Fuels: There are naturally occurring fuels which serve as source of energy without any chemical processing. Examples of these are Wood, Coal, Crude oil, Natural gas, Peat, Lignite, Anthracite. b) Secondary Fuels: - They are derived from primary fuels and serve as source of energy only after the primary fuel is subjected to chemical processing. Examples of these are Charcoal, Coke, producer gas, Petrol, Diesel etc. Figure 1.2 Classification of fuels 1.3.2 Characteristics of a Good Fuel A good fuel should meet certain criteria as outlined below. 9 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 1.3.2.1 High calorific value: Fuel should possess high calorific value, since the amount of heat liberated and temperature attained thereby depends upon the calorific value of the fuel. 1.3.2.2 Moderate ignition temperature: Ignition temperature is the lowest temperature to which the fuel must be pre-heated so that it starts burning smoothly. Low ignition temperature is dangerous for storage and transport of fuels, since it can cause fire hazards. On the other hand, high ignition temperature causes difficulty in kindling (or igniting) the fuel, but the fuel is safe during storage, handling and transport. Hence, an ideal fuel should have moderate ignition temperature 1.3.2.3 Low moisture content: The moisture content of the fuel reduces the heating value and involves a loss of money, because it is paid for at the same rate as the fuel. Hence, fuel should have low moisture content. 1.3.2.4 Low non – combustible matter content: After combustion, the non-combustible matter remains, generally, in the form of ash or clinker. The non-combustible matter reduces the heating value, besides additional cost of storage, handling and disposal of the waste products produced. Each percent of non-combustible material in fuel means a heat loss of about 1.5 %. Hence, a fuel should have low content of non – combustible matter. 1.3.2.5 Moderate velocity of combustion: If the rate of combustion is low, then the required high temperature may not be possible, because a part of the heat liberated may get radiated, instead of raising the temperature. On the other hand, too high combustion rates are also not required. 1.3.2.6 Products of combustion should not be harmful: Fuel, on burning, should not give out objectionable and harmful gases. In other words, the gaseous products of combustion should not pollute the atmosphere. CO, SO2, H2S, PH3, etc., are some of the harmful gases. 1.3.2.7 Low cost: A good fuel should be readily available in bulk at a cheap rate. 1.3.2.8 Easy to transport: Fuel must be easy to handle, store and transport at a low cost. Solid and liquid fuels are easily transported from one place to another. On the other hand, transportation of gaseous fuels is costly and can even cause fire hazards. 1.3.2.9 Combustion should be easily controllable: Combustion of the fuel should be easy to start or stop when required. 1.3.2.10 Should not undergo spontaneous combustion: Spontaneous ignition can cause fire hazards. 10 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 1.3.3 Advantages and disadvantages fuels Though the different states of fuel are all important and hold immense benefits, there are advantages and disadvantages of each. These are described in this section. 1.3.3.1 Solid Fuel Advantages a) They are easy to transport. b) They are convenient to store, without any risk of spontaneous explosion. c) Their cost of production is low d) They possess moderate ignition temperatures Disadvantages a) Their ash content is high. b) Their large proportion of heat is wasted during combustion. In other words, their thermal efficiency is low. c) They burn with clinker formation. d) Combustion control during operation is quite byzantine. e) Their cost of handling is high. f) Their calorific value is lower as compared to that of liquid fuels. g) They require large excess of air for complete combustion. h) They cannot be used as internal combustion engine fuels. 1.3.3.2 Liquid fuels Liquid fuels are the important commercial and domestic fuels used in our daily life. Most of these fuels are obtained from the naturally occurring petroleum or crude oil called as primary fuel. Advantages a) They possess higher calorific value per unit mass than solid fuels. b) They burn without forming dust, ash, clinkers, etc. c) Their firing is easier and also, fire can be easily extinguished by stopping the liquid fuel supply. d) They are easy to transport through pipes. e) They can be stored indefinitely, without any loss. f) They are clean in use and economic in labour. g) Loss of heat to chimney is very low, due to greater cleanliness. h) They require less excess of air for complete combustion. i) They require less furnace space for combustion. j) There is no wear and tear of grate bars and cleaning of fires, etc., unlike solid fuels. k) They can be used as internal combustion fuels. l) The flame produced by burning liquid fuels can easily be controlled by adjusting the liquid fuel supply. m) Liquid fuels are, generally, handled by pipes and one man can easily and economically regulate a large number of furnaces simultaneously. Disadvantages 11 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 a) The cost of liquid fuel is relatively much higher as compared to solid fuels. b) Costly special storage tanks are required for storing liquid fuels. c) There is a greater risk of fire hazards, particularly in case of a highly inflammable and volatile liquid fuel. d) They give bad odour. e) For efficient burning of liquid fuels, specially constructed burners and spraying apparatus are required. f) Choking of sprayers (during liquid fuel combustion) is a drawback of oil firing. 12 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 1.3.3.3 Gaseous fuels - Advantages Gaseous fuels occur in nature, besides being manufactured from solid and liquid fuels. Advantages a) They can be conveyed easily through pipelines to the actual place of need, thereby eliminating manual labour in transportation. b) They can be lighted at moment’s notice. c) They have high heat content and hence, help gives higher temperatures. d) They can be preheated by the heat of hot waste gases, thereby affording economy in heat. e) Their combustion can readily be controlled for changes in demand like oxidizing or reducing atmosphere, length of flame, temperature, etc. f) They burn without any soot (or smoke) and are ashless, so there is no labour involved in ash handling, etc. g) They are clean in use. h) They are free from solid and liquid impurities. Hence, they do not affect the quality of metal produced, when used as a metallurgical fuel. Disadvantages a) Very large storage tanks are needed for them. b) They are highly inflammable, so chances of fire hazards are high in their use. c) They are more costly as compared to solid and liquid fuels. 1.4 COAL Coal is regarded as a fossil fuel produced from large accumulations of vegetable debris due to partial decay and alteration by the action of heat and pressure over millions of years. Coal is a highly carbonaceous matter that has been formed as a result of alteration of vegetable matter (e.g., plants) under certain favourable conditions. It is chiefly composed of C, H, N, and O, besides non-combustible inorganic matter. 1.4.1 Classification of Coal Coals are classified on the basis of their rank. Rank is defined as the degree or extent of maturation and is therefore a qualitative measure of carbon contents. Peat, lignite and sub- bituminous coals are referred to as low rank coals. Bituminous coals and anthracites are classed as high rank. In European terminology, the lignite and sub-bituminous coals are called soft coals while bituminous coals and anthracite coals are termed as hard coals. 13 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 Figure 1.3 formation of coal Figure 1.4 Stages in coal formation over millions of years. Peat is a soil material made of moist, partially decomposed organic matter and is not classified as a coal, although it too is used as a fuel. The different major types of coal vary in the amounts of heat, carbon dioxide, and sulfur dioxide released per unit of mass when they are burned. Despite its poor environmental credentials, coal remains a crucial contributor to energy supply in many countries. Coal is the most wide-spread fossil fuel around the world, and more than 75 countries have coal deposits. The current share of coal in global power generation is over 40%, but it is expected to decrease in the coming years, while the actual coal consumption in absolute terms will grow. 1.5 Properties of Petroleum Physical properties and composition of crude oil provide critical information for the optimum operation of a petroleum refinery. This information does not only help predict the physical behavior of crude oil in refinery units but also gives insight into its chemical composition. Therefore, the physical properties can be related to chemical properties of crude oil and its fractions and the characteristics of the resulting refinery products. The most important properties of crude include density, viscosity, boiling point distribution, pour point, and the concentration of various contaminants. 14 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 Whereas properties such as viscosity, density, boiling point, and colour of petroleum may vary widely, the ultimate or elemental analysis varies, over a narrow range for a large number of petroleum samples. The carbon content is relatively constant, while the hydrogen and heteroatom contents are the major variants in the elemental composition of petroleum. The nitrogen, oxygen, and sulfur can be present in only trace amounts in some petroleum, which as a result consists primarily of hydrocarbons. Coupled with the changes brought about to the feedstock constituents by refinery operations, it is not surprising that petroleum characterization is a monumental task. 1.5.1 Physical Properties A physical property is any property that is measurable and the value of which describes the physical state of petroleum that do not change the chemical nature of petroleum. The changes in the physical properties of a system can be used to describe its transformations (or evolutions between its momentary states). They vary according to the composition of the oil, the relative abundance of the groups of hydrocarbons, and essentially depend on reservoir temperatures and pressures. Physical properties are contrasted with chemical properties, which determine the way a material behaves in a chemical reaction. A typical range of petroleum is given in Table 1.2 Table 1.1 Composition of petroleum Component Percentage Carbon 83.0%–87.0% Hydrogen 10.0%–14.0% Nitrogen 0.1%–2.0% Oxygen 0.05%–1.5% Sulfur 0.05%–6.0% Metals (Ni and V) 30), medium (30>°API>22), and heavy (°API5%), many of the properties measured do not represent the properties of the ‘dry’ oil. Water contents can be determined by Karl Fischer titration using a Metrohm 701 KF Automatic Titrator. For more details, see Appendix 1. 1.5.3 Composition of Petroleum Crude oils and high-boiling crude oil fractions are composed of many members of a relatively few homologous series of hydrocarbons. The composition of the total mixture, in terms of elementary composition, does not vary a great deal, but small differences in composition can greatly affect the physical properties and the processing required to produce salable products. Petroleum is essentially a mixture of hydrocarbons, and even the nonhydrocarbon elements are generally present as components of complex molecules, predominantly hydrocarbon in character, but containing small quantities of oxygen, sulphur, nitrogen, vanadium, nickel, and chromium. The hydrocarbons present in crude petroleum are classified into three general types: paraffins, naphthenes, and aromatics. In addition, there is a fourth type, olefins, that is formed during processing by the cracking or dehydrogenation of paraffins and naphthenes. There are no olefins in crude oils. 1.5.3.1 Paraffins The paraffin series of hydrocarbons is characterized by the rule that the carbon atoms are connected by a single bond, and the other bonds are saturated with hydrogen atoms. The general formula for paraffins is CnH2n+2. The simplest paraffin is methane, CH4, followed by the homologous series of ethane; propane; normal and isobutane; and normal, iso-, and neopentane (Figure 1.7). When the number of carbon atoms in the molecule is greater than three, several hydrocarbons may exist that contain the same number of carbon and hydrogen atoms but have different structures. This is because carbon is capable not only of chain formation, but also of forming single- or double-branched chains that give rise to isomers that have significantly different properties. For example, the motor octane number of n-octane is – 17 and that of isooctane (2,2,4-trimethyl pentane) is 100. The number of possible isomers increases in geometric progression as the number of carbon atoms increases. There are 2 paraffin isomers of butane, 3 of pentane, and 17 structural isomers of octane, and by the time the number of carbon atoms has increased to 18, there are 60,533 isomers of cetane. Crude oil contains molecules with up to 70 carbon atoms, and the number of possible paraffinic hydro- carbons is very high. 24 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 Figure 1.7 Homologous series of paraffins 1.5.3.2 Olefins Olefins do not naturally occur in crude oils but are formed during processing. They are very similar in structure to paraffins, but at least two of the carbon atoms are joined by double bonds. The general formula is CnH2n. Olefins are generally undesirable in finished products because the double bonds are reactive and the compounds are more easily oxidized and polymerized to form gums and varnishes. In gasoline boiling-range fractions, some olefins are desirable because olefins have higher octane numbers than paraffin compounds with the same number of carbon atoms. Olefins containing five carbon atoms have high reaction rates with compounds in the atmosphere that form pollutants and, even though they have high research octane numbers, are considered generally undesirable. Some diolefins (containing two double bonds) are also formed during processing, but they react very rapidly with olefins to form high- molecular-weight polymers consisting of many simple unsaturated molecules joined together. Diolefins are very undesirable in products because they are so reactive they polymerize and form filter- and equipment-plugging compounds. Figure 1.8 Olefins 1.5.3.3 Naphthenes (Cycloparaffins) Cycloparaffin hydrocarbons in which all of the available bonds of the carbon atoms are saturated with hydrogen are called naphthenes. There are many types of naphthenes present in crude oil, but, except for the lower-molecular-weight compounds such as cyclopentane and cyclohexane, they are generally not handled as individual compounds. They are classified according to boiling range and their properties determined with the help of correlation factors such as the KW factor or CI. Some typical naphthenic compounds are shown in Figure 1.9 25 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 Figure 1.9 Naphthenes in crude oil. 1.5.3.3 Aromatics The aromatic series of hydrocarbons is chemically and physically very different from the paraffins and cycloparaffins (naphthenes). Aromatic hydrocarbons contain a benzene ring, which is unsaturated but very stable, and frequently behave as saturated compounds. Some typical aromatic compounds are shown in Figure 1.10. The cyclic hydrocarbons, both naphthenic and aromatic, can add paraffin side chains in place of some of the hydrogen attached to the ring carbons and form a mixed structure. These mixed types have many of the chemical and physical characteristics of both of the parent compounds, but generally are classified according to the parent cyclic compound. 26 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 Figure 1.10 Aromatics in Crude oil 1.5.4 Crude Assay Crude oil assay consists of a compilation of data on properties and composition of crude oils. The assay provides critical information on the suitability of crude oil for a particular refinery and estimating the desired product yields and quality. It also indicates how extensively a given crude oil should be treated in a refinery to produce fuels that are in compliance with environmental regulations. A typical crude assay should include the following major specifications: API Gravity Total Sulphur (% wt) Pour Point (°C) Viscosity @ 20°C (cSt) Viscosity @ 40°C (cSt) Nickel (ppm) Vanadium (ppm) Total Nitrogen (ppm) Total Acid Number (mgKOH/g) Distillation Data Characterization factor KUOP, KW 27 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 Figure 1.11 Density of Crude oil Figure 1.12 Kinematic Viscosity Figure 1.13 Pour & Cloud Point Figure 1.14 Sulfur Content Figure 1.15 Distillation test Figure 1.16 Component analysis 28 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 End of Chapter Assessment 1. What are the two main theories regarding the origin of crude oil 2. State four characteristics of a good fuel. 3. Identify four physical properties of petroleum 4. What are the types of hydrocarbons present in crude oil? 5. Determine the liquid thermal conductivity of benzene (C6H6) at a temperature of 340K given the following regression coefficients A= -1.6846, B= 1.052, C= 562.16 6. Calculate the solubility of pentane (C5H12) in salt water with concentration of salt (NaCl) in water being 100,000 ppm (wt). Take A = 1.5966, B= - 4.5956×10-6, C = 2.2978×10-12 7. Calculate the energy required to heat gaseous ethyl chloride (C2H5Cl) from 250 to 500 K. Take A= 35.946, B = 0.052294, C = 0.000203, D = -2.28 × 10-7, E= 6.9123 × 10-11 29 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 CHAPTER TWO: Oil Recovery (Drilling). Learning Outcomes At the end of this chapter, Students should be able to: 1. Differentiate between the various sectors in the petroleum industry 2. Give an overview of well construction and design 3. Know petroleum resources classifications 2.1 Sectors in the Petroleum Industry The petroleum industry is divided into three main parts referred to as the upstream, midstream and the downstream Sectors. Figure 2.1 shows an overview of these sectors Figure 2.1 Overview of the sectors in the Petroleum industry 2.1.1 Upstream Sector The upstream sector of the petroleum industry includes all the steps involved from the preliminary exploration through the extraction of the resource. Upstream companies can be involved in all the steps of this phase of the life cycle of the industry, or they may only be involved in part of the upstream sector. Another name for the upstream sector, which is actually more representative of what occurs in this stage of development is the exploration and production (E&P) sector. The E&P segment is the earliest portion of the oil and gas production process. Companies within this segment are primarily focused on locating and extracting commodities from the earth. The exploration stage involves the search for hydrocarbons, which are the primary components of petroleum and natural gas. Land surveys are performed to help identify the areas that are the most promising. The goal is to locate specific minerals underground in order to estimate the amount of oil and gas reserves before drilling. Geologists study rock formations and layers of sediment within the soil to identify if oil or natural gas is present. The process can involve seismology, which uses substantial vibrations as a result of machinery or explosives to create seismic waves. How the seismic waves interact with a reservoir containing oil and gas helps to pinpoint the reservoir's location. Once it has been 30 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 determined that there appear to be reserves beneath the ground, the test drilling process can begin. When the resource has been extracted, the upstream part of the business is over 2.1.2 Midstream Midstream companies gather the raw resource and transport the resource via pipeline, railway, or tanker truck to refineries. Midstream activities include the processing, storing, transporting, and marketing of oil, natural gas, and natural gas liquids. Midstream companies deliver the reserves to companies involved in the final stage of production called downstream. 2.1.3 Downstream Companies in the downstream sector are those that provide the closest link to everyday users. Refineries are the downstream phase of the oil and gas industry. Downstream operations are the processes involved in converting oil and gas into the finished product. The closer an oil and gas company is to the process of providing consumers with petroleum products, the further downstream the company is said to be. These include refining crude oil into gasoline, natural gas liquids, diesel, and a variety of other energy sources. They also sell and distribute natural gas and the products that are derived from crude oil. The Ghanaian oil and gas sector also has these three sectors in place. Figure 2.2 shows how these sectors are organised in Ghana and indicates some of the stakeholders involved. Figure 2.2 Organisation of the Petroleum sector in Ghana 31 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 2.2 Wells After geologists of an oil company have located the general area in which petroleum is thought to occur, a well is drilled. Selecting the site for drilling requires detailed knowledge of the geologic features under the earth's surface. 2.2.1 Well Integrity In a technical sense, “well integrity” refers to the zonal isolation of liquids and gases from the target formation or from intermediate layers through which the well passes. In a practical sense, it means that a well doesn’t leak. Drilling companies emphasize well integrity because a faulty well is expensive to repair and, in the rarest of cases, costs lives. Well integrity is essential for two reasons: 1. To isolate the internal conduit of the well from the surface and sub-surface environment. This prevents the migration of fluids between sub-surface layers and is critical for protecting groundwater, and the surface and sub-surface environment. 2. To isolate and contain the well’s produced fluid (i.e. the hydrocarbons) within the production casing of the well In addition to protecting ground and surface waters, effective well sealing prevents leakage of methane and other gases into the atmosphere, which can greatly reduce global warming as methane is 86 times more effective than CO2 at trapping heat in the atmosphere over a 20-year period and 34 times more effective over a century. 2.2.2 Well Design and Construction Oil and gas wells are designed and constructed to safely access and produce hydrocarbons; whilst appropriately managing the risk to people, the environment and property. Key objectives when designing a new well include: a) Prevention of any interconnection between petroleum reservoirs and water aquifers. b) Ensuring formation fluids are contained within the well and there is no leakage. c) No substances are introduced that may cause environmental harm. 2.2.3 Site Selection and Preparation When determining a drilling location, key factors including geography, topography, ecology and cultural heritage are taken into account and land access agreements put in place. Before any drilling takes place, appropriate approvals must be granted by the government and the site prepared prior to a drilling rig arriving on location. The area from which single or multiple wells are drilled is known as a lease or pad, and construction typically involves creating a level and stable area to provide a suitable working platform for drilling and well operations. The lease will be constructed to allow for the following activities and infrastructure: a) Permanent wellhead facilities. b) Sufficient space for maneuverability of the drilling rig and associated equipment. 32 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 c) Office building. d) Turkey’s nest for freshwater storage. e) Sump for collection of drilling mud and cuttings. f) Temporary camps. Unconventional Gas Mining 2.2.4 Drilling the well Once the drilling rig has been moved in sections onto the drilling lease and has been ‘rigged up’, drilling operations commence. Drilling of an oil or gas well commences when the drill bit (Figure 2.3) first penetrates the ground (spudding of the well) and continues until the target depth has been reached. The duration for the drilling of an oil or gas well depends on factors such as geology, depth of the well, nature of the well that is whether the well is vertical, deviated or horizontal. Figure 2.3. Drill Bit. Credit Santos (2016). The well is drilled by rotating a drill bit which is located at the end of the bottom hole assembly (BHA). The BHA refers to the lowest part of the drill string, extending from the drill bit to the drill pipe. The BHA consists of various components that control wellbore geometry and direction plus may contain tools that measure both wellbore and rock properties. The BHA is connected to surface by drill pipes (Figure 2.4) where rotation and torque is applied to the drill string. The weight of the BHA is used to allow the bit to drill through different rock formations. Figure 2.4. Drill pipes Santos (2016). 33 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 The first hole section drilled is called the surface hole. This hole section is drilled across any regional water aquifers that could be used for domestic and agricultural purposes and into a geological rock layer that has sufficient strength to withstand gas or oil reservoir pressure. Once the hole section is drilled to the required depth, the drill pipe and BHA are pulled out of the well and a steel pipe known as casing is run into the well. The joints of casing are approximately 12 metres in length and have a threaded connection (Figure 2.5) on each end. The industry standard for oil and gas casing is provided by the American Petroleum Institute (API) in Specification 5CT. Figure 2.5. Threaded connection of steel casing. Santos (2016). Once the casing has been run in the well to the pre-determined depth, it is cemented in place by a process where the cement slurry is pumped down the inside of the casing. When sufficient cement slurry has been pumped to fill the volume between the casing and the exposed rock, the cement is displaced down the casing with drilling fluid (Figure 2.6). Figure 2.6. Drilling fluid. Santos (2016). 34 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 At the end of the cementing process, the inside of the casing contains drilling fluid, and the space between the outside of the casing and the exposed rock is filled with cement, typically to surface for surface casing. This means the well is isolated from any aquifers by the casing and a layer of cement. The surface casing is then pressure tested to ensure there are no leaks. If the well is to be completed as a production well, production casing is usually run and cemented in place. Following release of the drilling rig, additional activities are required in order to bring the well into production. This is dependent on the completions program and may include operations such as hydraulic fracture stimulation. Additional equipment is also installed on the wellhead to support any further steel tubing run in the well and to control the flow of fluids from the reservoir. 2.2.5 Directional drilling Directional drilling practices enable the trajectory of the well to be controlled during drilling. The ability to control trajectory gives engineers many options when it comes to designing a new well. Two of the key options include horizontal/high angle wells (Figure 2.7) and pad drilling. Figure 2.7 horizontal/high angle wells Santos (2016). 2.2.5.1 Horizontal/high angle wells One reason for controlling wellbore trajectory is to drill horizontal or high angle wells through the target reservoir. By increasing the contact area between the wellbore and the reservoir, the hydrocarbon flow rate and volume recovered per well can be increased. This can result in a reduction in the number of wells required to efficiently drain a reservoir compared to if vertical wells are used, reducing the area of impacted land. 2.2.5.2 Pad wells In pad drilling, all of the wells are grouped closely together at surface. Below the surface however, the wellbores can step out large distances and cover a greater area. Although the size of the pad required for multiple wells is larger than required for a single well, the number of pads required is reduced and therefore the total area required is less. This substantially reduces the environmental footprint of activities and increases the efficiency of well construction. 35 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 2.2.6 Drilling fluids and rock cuttings While drilling, drilling fluid is continuously circulated down the drill pipe and back up the annulus (area between the outside of the drill pipe and the exposed rock or casing) to surface. Drilling fluid serves a number of purposes including: a) Lubricates and cools the drill bit. b) Filtrate from the drilling fluid forms a layer (referred to as filter cake) on the wall of the well which helps minimise fluid losses to permeable formations. c) Removes rock cuttings from the well generated by the interaction between the drill bit and the rock. d) Provides hydrostatic pressure to ensure the pressure exerted by the fluid column in the well is greater than the pressure of the fluid (oil, gas, or water) in the formation. This prevents formation fluids from entering the well. 2.2.7 Well operations Regular monitoring takes place throughout the life cycle of all wells to ensure that all operations are within established parameters and in accordance with the relevant well design and regulatory requirements. 2.2.8 Well abandonment When a well reaches the end of its productive life, it is abandoned and the surface location rehabilitated in accordance with policies, procedures and all regulatory requirements. For an onshore location, this includes removing all above ground infrastructure including the wellhead, backfilling the cellar, replacing top soil and reprofiling the area (if required). The end goal of any well abandonment program is that there should be minimal evidence that oil and gas operations have taken place. 2.3 Petroleum Reserves and Evaluation: 2.3.1Petroleum Resources Petroleum resources are the estimated quantities of hydrocarbons naturally occurring on or within the Earth’s crust. It encompasses all quantities of petroleum naturally occurring on or within the Earth’s crust, discovered and undiscovered (recoverable and unrecoverable), plus those quantities already produced. Further, it includes all types of petroleum whether currently considered “conventional” or “unconventional.” Resource assessments estimate total quantities in known and yet-to-be discovered accumulations; resources evaluations are focused on those quantities that can potentially be recovered and marketed by commercial projects. 2.3.2 Petroleum resources management systems A petroleum resources management system thus provides a consistent approach to estimating petroleum quantities, evaluating development projects, and presenting results within a comprehensive classification framework. A petroleum system can be identified in terms of oil-source correlation at three levels of certainty: a) proved, 36 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 b) hypothetical, c) speculative. Speight (2014), however, goes into more detail classifying resources as proved, unproved, probable, possible, and undiscovered. This also confirms that there are levels of uncertainty in relation to petroleum resources. 2.3.2.1 Proved Petroleum System A proved identification includes those petroleum systems where successful oil-source rock correlations are obtained. 2.3.2.2 Hypothetical Petroleum System A hypothetical petroleum system is one where oil or gas deposits can be shown to be genetically related and where source rocks can be geochemically identified, but no geochemical correlation presently exists. 2.3.2.3 Speculative Petroleum System In a speculative petroleum system only the geological evidence supports a relation between the petroleum deposit and its source rock. 2.3.3 Resource classification Figure 2.8 is a graphical representation of resources classification system. The system defines the major recoverable resources classes: Figure 2. 8 Resource classification framework a) Production, b) Reserves, c) Contingent Resources, d) Prospective Resources, 37 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 e) Unrecoverable petroleum. 1C, denotes low estimates scenario of Contingent Resources, 2C,best estimate scenario of Contingent Resources, 3C denotes high estimate scenario of contingent resources while 1P is equivalent to proved Reserves denoting low estimate scenario of reserves, 2P is taken to be equivalent to the sum of proved plus probable reserves; denoting best estimate scenario of reserves while 3P is taken to be equivalent to the sum of proved plus possible reserves, denoting high estimate scenario of reserves. The “Range of Uncertainty” on the horizontal axis reflects a range of estimated quantities potentially recoverable from an accumulation by a project, while the vertical axis represents the “Chance of Commerciality, that is, the chance that the project will be developed and reach commercial producing status. The following definitions apply to the major subdivisions within the resources classification: 2.3.3.1 Total Petroleum Initially-in-Place is that quantity of petroleum that is estimated to exist originally in naturally occurring accumulations. It includes that quantity of petroleum that is estimated, as of a given date, to be contained in known accumulations prior to production plus those estimated quantities in accumulations yet to be discovered -equivalent to “total resources” (Figure 2.8). 2.3.3.2 Discovered Petroleum Initially-in-Place is that quantity of petroleum that is estimated, as of a given date, to be contained in known accumulations prior to production. (Figure 2.8) 2.3.3.3 Production is the cumulative quantity of petroleum that has been recovered at a given date. While all recoverable resources are estimated and production is measured in terms of the sales, product specifications, raw production (sales plus non-sales) quantities are also measured and required to support engineering analyses based on reservoir voidage. Multiple development projects may be applied to each known accumulation, and each project will recover an estimated portion of the initially-in-place quantities. The project is thus subdivided into Commercial and Sub-Commercial, with the estimated recoverable quantities being classified as Reserves and Contingent Resources respectively, as defined below. 2.3.3.4 Reserves are those quantities of petroleum anticipated to be commercially recoverable by application of development projects to known accumulations from a given date forward under defined conditions. Reserves must further satisfy four criteria: they must be discovered, recoverable, commercial, and remaining (as of the evaluation date) based on the development project(s) applied. Reserves are further categorized in accordance with the level of certainty associated with the estimates and may be sub-classified based on project maturity and/or characterized by development and production status. 2.3.3.5 Contingent Resources are those quantities of petroleum estimated, as of a given date, to be potentially recoverable from known accumulations, but the applied project(s) are not yet considered mature enough for commercial development due to one or more contingencies. Contingent Resources may include, for example, projects for which there are currently no 38 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 viable markets, or where commercial recovery is dependent on technology under development, or where evaluation of the accumulation is insufficient to clearly assess commerciality. Contingent Resources are further categorized in accordance with the level of certainty associated with the estimates and may be subclassified based on project maturity and/or characterized by their economic status. 2.3.3.6 Undiscovered Petroleum Initially-in-Place is that quantity of petroleum estimated, as of a given date, to be contained within accumulations yet to be discovered. 2.3.3.7 Prospective Resources are those quantities of petroleum estimated, as of a given date, to be potentially recoverable from undiscovered accumulations by application of future development projects. Prospective Resources have both an associated chance of discovery and a chance of development. Prospective Resources are further subdivided in accordance with the level of certainty associated with recoverable estimates assuming their discovery and development and may be sub-classified based on project maturity. 2.3.3.8 Unrecoverable is that portion of Discovered or Undiscovered Petroleum Initially-in Place quantities which is estimated, as of a given date, not to be recoverable by future Development projects. A portion of these quantities may become recoverable in the future as commercial circumstances change or technological developments occur; the remaining portion may never be recovered due to physical/chemical constraints represented by subsurface interaction of fluids and reservoir rocks. Estimated Ultimate Recovery (EUR) is not a resources category, but a term that may be applied to any accumulation or group of accumulations (discovered or undiscovered) to define those quantities of petroleum estimated, as of a given date, to be potentially recoverable under defined technical and commercial conditions plus those quantities already produced (total of recoverable resources). 2.4 The Future of Fossil Fuels Fossil fuel is a nnonrenewable resources and as such it is expected to run out after some time. Models have been put up to give an indication when we will run out of oil. Most of these forecasts use the concept of Peak oil. 2.4.1 Peak oil Peak oil doesn’t mean running out of oil, as it is sometimes wrongly stated. It simply means that the yield of extraction, in economic and energy terms, gradually declines to the point that it is not convenient any longer to invest the huge amounts of financial resources that would be needed to keep production increasing. How long can we depend on Petroleum? In June2000, it was projected that for a total estimate of 1016,000 million barrels worldwide at a recovery rate of 73 million bbls/day, the world should run out of oil in 13,967 days= 38.1 years (2039) 39 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 The Future of Natural Gas In June2000, it was projected that for a total estimate of 5240 T cu. Ft worldwide at a recovery rate of 84.2 T. Cu.ft per year, the world should run out of oil in 62 years (2063) The question as to when the world will we run out of oil (and natural gas) should probably be “when will production begin to decline?” (ie, “when will peak oil production occur?”). In March 1998, two retired petroleum geologists (Campbell and Laherre) claimed that oil would peak in the first decade of the 21st century base on their forecast as shown in Figure 2.9 Figure 2.9 Campbell and Laherre Forecast on Peak Oil Further forecasts by other researchers based on improving technology and better recovery methods and better understanding of petroleum resources moved Peak Oil from 2003 to 2032 and further to 2064 (Odell’s forecast) 40 Fundamentals of Refining and Petrochemical Engineering (RP 170), 2022 Figure 2.10 Revision on Peak Oil b