GEOL40310 Lecture A7: Appraisal 2 Fossil Fuels and Carbon Capture & Storage (CCS) 2023 PDF

Geol 40310 Fossil Fuels and Carbon Capture & Storage (CCS) Lecture A7: Appraisal 2: Fluids Autumn 2023-24 T Manzocchi, University College Dublin 1 1 Lecture A7 - Appraisal 2: Fluids Part 1: Physical and Chemical classifications of petroleum: Physical Classification: Density, Viscosity. Chemical...

Geol 40310 Fossil Fuels and Carbon Capture & Storage (CCS) Lecture A7: Appraisal 2: Fluids Autumn 2023-24 T Manzocchi, University College Dublin 1 1 Lecture A7 - Appraisal 2: Fluids Part 1: Physical and Chemical classifications of petroleum: Physical Classification: Density, Viscosity. Chemical Classification natural gas The Paraffin series Hydrocarbon-associated gasses: H2S, CO2 Chemical Classification of crude oil PNA (Paraffin, Naphthene, Aromatics) classification. Normal crude, waxy crude, heavy crude Part 2: PVT behaviour of 5 conventional hydrocarbons: Dry gas, Wet Gas, Gas Condensate, Volatile Oil, Black Oil. Saturated and unsaturated reservoirs. Pressure-volume properties of oil reservoirs: Oil Formation volume factor Solution Gas:Oil ratio 2 2 GEOL 40310 Lecture A7 1 Physical classification of petroleum Unconventional Conventional Based on viscosity and liquid gravity.  API = 141.5 oil  water − 131.5 3 3 Density of Crude oils  API = 141.5 oil  water − 131.5 Black Brown Light La Brea Pitch lake, Trinidad. Colourless Crude oil samples from New Zealand fields (Trans-Orient Oil) 4 4 GEOL 40310 Lecture A7 2 Viscosity: Resistance to shearing Increasing viscosity https://www.youtube.com/watch?v=V5a4kP-5Jiw 5 5 Viscosity of petroleum-related fluids Units of viscosity: the centipoise (cp) Dry gas Crude oil Formation water 0.06 2 1000 1.8 1.6 Viscosity (cp) Pressure (psia) 0.05 0.04 1.4 100 0.03 1.2 1 10 0.8 0.02 0.6 1 0.4 0.2 0.01 0.1 0.1 0 0 50 100 150 200 250 300 350 10 20 Temperature (°F)  F= 9 C + 32 5 30 40 50 Oil Gravity (°API)  API = 141.5 oil  water 60 0 50 100 150 200 250 300 350 Temperature (°F) − 131.5 6 6 GEOL 40310 Lecture A7 3 Hydrocarbon Gas Natural Gas: A mixture of hydrocarbon and varying quantities of non-hydrocarbons the exist either in the gaseous phase or in solution with crude oil in natural underground reservoirs. “stock-tank” Reservoir gas oil gas Dry gas GWC water Wet gas or Gas condensate (Vaporised oil at reservoir conditions) gas GWC water gas Gas cap and oil leg (“Saturated” reservoir) GOC OWC oil water (Dissolved gas at reservoir conditions) Dissolved Gas oil OWC water 7 7 Chemical composition of natural gas Butane: C4H10 Methane: CH4 H H C H H H Ethane: C2H6 Propane : C3H8 H H H H H C C C C C H H H H H H H H H H H H C C C C H H H H H Normal butane (n-butane) H H H C H H H H C C C H H H H Iso-butane (i-butane) 8 8 GEOL 40310 Lecture A7 4 The Paraffin series Basic formula: CnH2n+2 n = 1-4: Gases. n = 5-15: Liquids. n > 15: Solids Selley (1998) 9 9 Hydrocarbon associated Gases Carbon Dioxide: - Natural bi-product of thermal maturation of kerogen. - Very high levels associated with areas of volcanic activity. - Mixes with water to produce carbonic acid – possible corrosion issue. - Greenhouse Gas. Hydrogen Sulphide: - Associated with volcanic activity and presence of evaporites Anhydrite (CaSO4) + organics → calcite (CaCO3) + H2O + CO2 + H2S - Poisonous and smelly (sour) - H2S-rich field are referred to as “sour gas” - Highly corrosive to steel. Selley (1998) 10 10 GEOL 40310 Lecture A7 5 Shah Sour Gas field, Abu Dhabi. Natural gas reservoir with 23% H2S and associated CO2 Began commercial production mid 2015: • One billion cubic feet (BCF) a day of sour gas. • Conversion to: 500 million cubic feet of fuel, and 10,000 tonnes of solid sulphur, per day for sale. • UAE looking to become global leader in sulphur production 11 11 Global sulphur production Million tonnes China Sulphur production by source 12 12 GEOL 40310 Lecture A7 6 Fizzy and Oak Fields, Southern Gas Basin, UKCS Fizzy and Oak fields: 50% CO2, 9% N2 Anomalous fluids associated with unusual timing of fault inversion. Production from these fields is too problematic: they have been left undeveloped. 13 Underhill et al. (2009) 13 Crude oil Crude oil is unrefined petroleum. Petroleum is a naturally occurring liquid hydrocarbon. “stock-tank” Reservoir gas oil gas Dry gas GWC water Wet gas or Gas condensate (Vaporised oil at reservoir conditions) gas GWC water Gas cap and oil leg (Saturated reservoir) Black oil, or volatile oil reservoir gas oil water GOC OWC (Dissolved gas at reservoir conditions) oil water OWC 14 14 GEOL 40310 Lecture A7 7 Crude oil Density and Sulphur content Crude properties reflect their origin Sweet, light crude (e.g. Brent) generally sell at a premium Refineries are designed to process particular crudes 15 15 Crude oil Each crude oil contains different combinations of hundreds of different molecules. Main components of 141 molecules identified in a sample of Oklahoma crude. These accounted for 44% of the total crude volume. 16 SPE Petrowiki 16 GEOL 40310 Lecture A7 8 Three main classes of organic molecules in crude oil C Paraffins CnH2n+2 (a.k.a alkanes). C C C C C C C C n-alkanes C C i-alkanes C n = 1-4: Gases. n = 5-15: Liquids. Naphthenes CnH2n (a.k.a. cycloalkanes) One or more cyclic structure joined by single bonds. n > 15: Solids C C C C C C C C C cyclopentane Liquid at normal conditions. Make up ca. 40% of crude oil C C cyclohexane Parafins and Naphthenes are termed saturated, meaning that they contain no double bonds. Many unsaturated hydrocarbons (olefins, diolefins, and acetylenes) are unstable and therefore rare in crude oil. An exception are aromatics. 17 17 Three main classes of organic molecules in crude oil Aromatics CnH2n-6 (a.k.a. cycloalkenes) Contain one or more ring structure comprising six identical bonds intermediate between single and double bonds. CH3 CH3 C e.g. C C C C C C Benzene C C C C C C CH3 C C C C CH3 C C Toluene C C C C CH3 C Xylene Liquid at normal conditions. Make up ca. 10% of light oil, up to 30% of heavy oils NB: alkanes (saturated): no double bonds alkenes (unsaturated): some double bonds 18 18 GEOL 40310 Lecture A7 9 Classification of Crude oils PNA classification: (Paraffins, Naphthenes, Aromatics) Aromatics 541 Crude oils High wax Crude oils Paraffins Mostly heavy degraded oils Normal crude oils Naphthenes Selley (1998) 19 19 Waxy crude oils Waxy crude oils contain high concentrations of longer-chain paraffins. The paraffin series: Basic formula: CnH2n+2 n = 1-4: Gases. n = 5-15: Liquids. n > 15: Solids Paraffin wax20 20 GEOL 40310 Lecture A7 10 Properties of waxy crude oils Viscosity, cp. Temperature, °C Cloud point: temperature below which wax is present in the liquid. Pour point: temperature below which the oil solidifies. Wax concentration wt% Temperature, °C 21 21 Barryroe Field, North Celtic basin Source: Providence presentation at Atlantic Ireland 2014: (http://www.pip.ie/page/350) Discovered by Esso, 1983. Currently operated by Providence Resources. Waxy crude: 43° API oil, 17% wax content Pour point : 21° C Cloud Point: 46° C Reservoir temperature: 66° C 0.8 cP viscosity at reservoir conditions. Solid at surface conditions. Providence appraisal well 2012. Tested at 3,500 BOPD. 22 22 GEOL 40310 Lecture A7 11 Biodegraded Heavy oils and bitumen Alberta tar sands 23 23 Biodegraded Heavy oils Asphaltics: Aromatic compounds with three or more rings per molecule common in biodegraded oils. Two types: Resins: Components with a highly polar end group (aromatic and naphthenic rings) and long alkane tails. Heavy liquids or sticky solids. Asphaltenes : Large highly polar components made up of condensed aromatic and naphthenic rings. Asphaltenes from Canadian bitumen Asphaltenes from traditional heavy crudes. 24 24 GEOL 40310 Lecture A7 12 Viscosity: Conventional vs. unconventional crudes Viscosity (cp) Heavy oils and bitumens Farouq Ali (2002) 25 25 Part 2: Hydrocarbon PVT properties “stock-tank” Reservoir gas oil gas Dry gas GWC water Wet gas to Gas condensate (Vaporised oil at reservoir conditions) gas GWC water Saturated reservoir (wet gas + volatile oil) volatile oil to black reservoir gas oil water GOC OWC (Dissolved gas at reservoir conditions) oil water OWC 26 26 GEOL 40310 Lecture A7 13 Pressure conditions in a reservoir and surface facilities gas Well Head Gas production rate: Mscf/day Separator Pwh (Million standard cubic feet) Psp Wellhead pressure Stock tank Separator pressure PST Reservoir Pwf PR Bottomhole flowing pressure Reservoir Pressure Stock tank pressure Oil production rate: STB/day (Stock tank barrels) SCF: Standard cubic feet. STB: Stock tank barrels. Production rates and fluid types reported are at surface conditions: 1 atm (14.7 psia), 60° F. Classification and management of hydrocarbon reservoirs depends on the fluid PVT properties from the reservoir to the stock-tank. 27 27 Pressure-Volume behaviour of a single component at a constant temperature 1 All liquid isotherm line 2 First gas bubble Two phases 4 Pressure 1 3 2 3 4 Last liquid drop 5 Bubble point 5 Dew point All gas Volume 28 28 GEOL 40310 Lecture A7 14 Pressure-Volume-Temperature behaviour of a single component Lines show behaviour at increasing temperature isotherm line Supercritical fluid Liquid 1 Pressure Pressure Critical point 2 3 4 5 Gas Bubble point Liquid+gas Dew point Volume Volume 29 29 PVT behaviour of a single component (i.e. a single molecular composition) Behaviour at increasing temperature Supercritical fluid Supercritical fluid Liquid Pressure Pressure Critical point Liquid Critical point Gas Gas Liquid+gas Volume CP solid Temperature P TP gas T 30 30 GEOL 40310 Lecture A7 15 PVT behaviour of a mixed component system (i.e. a natural hydrocarbon) Behaviour at increasing temperature Supercritical fluid Critical point Pressure Pressure Liquid Supercritical fluid Liquid Critical point Gas Gas Liquid+gas Temperature Volume 31 31 Pressure- temperature behaviour of the five conventional hydrocarbons Dry gas Volatile oil Wet gas Gas condensate Black oil Pressure Contours of liquid fraction: 100% on bubble-point line, 0% on dew point line. Redrawn from McCain (1990) Temperature 32 32 GEOL 40310 Lecture A7 16 Fluid type and context • Pressure • • A Critical point The difference in hydrocarbon type depends on composition, but also on context. For example the same hydrocarbon in reservoirs at different conditions can a volatile oil (A) or a wet gas (B). In both cases, however, the fluids at surface are identical, defined by the Gas:Oil ratio (for Oils) and the liquid fraction (OGR) for gas. B separator oil Temperature A B water OWC gas GWC water 33 33 • A Critical point B C • • Pressure Temperature A fluid with PT conditions on the bubble-point / dew point line is said to be saturated, and if it is within the single-phase region it is unsaturated. This line is therefore called the saturation line. A fluid in the two-phase region is gravitationally unstable, and therefore buoyancy effects will segregate it into an oil column with a gas cap. At the GOC both phases are saturated, and therefore the PT conditions at the GOC is the intersect of the saturation lines for an oil and gas phase. oil A Oil critical point C B water OWC gas unsaturated Pressure Saturated and unsaturated conditions GWC Gas critical point water Temperature C gas oil water GOC OWC Saturated 34 34 GEOL 40310 Lecture A7 17 Hydrocarbon Volumes The surface volumes of oil and gas can be related to the reservoir volumes using gas and oil “formation volume factors” and the “solution Gas:Oil ratio” (GOR). “stock-tank” Reservoir gas oil gas Dry gas GWC water Wet gas or Gas condensate (Vaporised oil at reservoir conditions) gas GWC water Gas cap and oil leg (Saturated reservoir) Black oil, or volatile oil reservoir gas oil water GOC OWC (Dissolved gas at reservoir conditions) oil OWC water 35 35 Hydrocarbon Volumes The surface volumes of oil and gas can be related to the reservoir volumes using gas and oil “Formation Volume Factors” (FVF) and the “solution Gas:Oil ratio” (GOR). Stock-tank barrel Reservoir barrel In an oil reservoir: • • Oil FVF: The volume of oil at reservoir conditions as a fraction of the volume of oil at surface; (rb/stb) Oil FVF generally > 1.0 due to oil shrinkage by degassing). • • Solution GOR: The ratio between solution gas volume and oil volume within the oil (scf/stb) Solution GOR often ca. 100, meaning that 100 scf of gas are dissolved in each barrel of oil. Standard cubic feet Surface (“stock-tank”) Reservoir Black oil, or volatile oil reservoir (Dissolved gas at reservoir conditions) oil water OWC More about this in Practical 3… 36 36 GEOL 40310 Lecture A7 18