PetE 402 Reservoir Geosciences Midterms Reviewer PDF

PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 OUTLINE...

PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 OUTLINE CHAPTER 1 Chapter 1 Introduction to Reservoir Geosciences Introduction to Reservoir Geosciences Reservoir Geosciences o Importance in Petroleum Engineering o Application of Geosciences What is Reservoir Geosciences? Geology The study of the geological and geophysical o Major Branches of Geology characteristics of oil and gas reservoirs Chapter 2 Physical Geology Combines principles from geology, geophysics, and o Earth's Structure: Layers of the Earth petroleum engineering to understand behavior, Earth's Material o Minerals enhance exploration, and optimize production ▪ Classification of Minerals ▪ Physical Properties of Minerals Understanding of the geology of the reservoir o Rocks ▪ Classification of Rocks essential to its development, production, and ▪ Rock Cycle management Chapter 3 Geologic Process Includes both external geology of the reservoir (what Weathering created the hydrocarbon trap) and internal geology of o Types of Weathering the reservoir (the nature of the rocks in which Erosion o Agents of Erosion hydrocarbon exist) Transportation Deposition Field that integrates geology, geophysics, and Lithification engineering to understand and manage subsurface Sedimentary Structures Categories of Sedimentary Rocks reservoirs, typically for the extraction of of hydrocarbons (oil and natural gas), but also for water, Chapter 4 Introduction to Structural Geology geothermal energy, and other resources Structural Geology Continental Drift Importance in Petroleum Engineering o Supporting Evidences of Continental Drift Optimizing Resource Recovery Seafloor Spreading o Supporting Evidences of Seafloor Spreading Accurate Reservoir Characterization: for Theory of Plate Tectonics designing effective extraction strategies and Three Types of Plate Boundaries maximizing resource recovery. Tectonic Forces Three Types of Stress Predictive Modeling: predicts how fluids will Behavior of Rocks to Stress and Strain behave in the reservoir under different Fractures conditions. Faults o Classification of Faults Enhancing Exploration Success Folds o Types of Folds Identifying Prospective Areas: reduces risk and cost associated with exploration. Chapter 5 Geologic Mapping Seismic Interpretation: provide crucial infos Key Components of a Geologic Map that helps to locate and assess potential Tools and Techniques in Geologic Mapping reservoirs before drilling Importance of Geologic Mapping Guiding Drilling and Completion 1  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 Well Placement: helps in optimizing well Oil and Gas: exploring, drilling, and placement and drilling risks managing hydrocarbon resources Completion Design: selection of appropriate Water Resources: assessing groundwater equipment and techniques to maximize availability, quality, and sustainability, and production and longevity managing water supplies Improving Recovery Techniques Environmental Protection Enhanced Oil Recovery (EOR): helps in Pollution Control: tracking and mitigating implementing methods like water flooding, pollution sources gas injection, or chemical flooding, to Waste Management: managing hazardous improve recovery rates waste and finding safe disposal Reservoir Management: continuous methods/recycling options monitoring for adjustments Climate Change Studies: understanding and predicting climate patterns, assessing Economic and Environmental Efficiency impacts on ecosystems, and developing Cost Reduction: minimizing non-productive mitigation and adaptation strategies time and optimizing resource utilization. Environmental Impact: mitigate Hazard Assessment and Mitigation environmental risks and ensure more Earthquake Analysis: studying seismic sustainable extraction practices activity to predict earthquakes, improve building codes, and design earthquake- Integration with Other Disciplines resistant structures Cross-Disciplinary Collaboration: ensures Volcanology: monitoring volcanic activity that all aspects of reservoir management and Landslide Risk Assessment: evaluating and production are addressed managing landslide hazards Data Integration: data from seismic, well logs, and core samples, supports more Construction Engineering informed decision-making and enhances the Geotechnical Engineering: assessing soil overall efficiency of of petroleum operators and rock properties to ensure safe and stable foundation Innovative Technologies Site Selection: evaluating locations for Advancements in Data Analytics: uses data construction projects to avoid geological to improve modeling, simulation, and real- hazards and ensure optimal conditions time monitoring, leading to more effective and efficient reservoir management Education and Research Digital Twins: digital twins of reservoirs allow Academic Research: advancing knowledge for real-time simulation and monitoring, of earth processes, history, and dynamics helping optimize the production and respond Public Education: raising awareness about to changing conditions more effectively earth sciences and their relevance to everyday life and global challenges Application of Geosciences Natural Resource Management Agriculture Mineral Exploration: identifying and Soil Science: analyzing soil properties to extracting valuable minerals and metals improve agricultural productivity, manage soil health, and optimize land use 2  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 Resource Sustainability Stratigraphy: analysis of rock layers (strata) to Renewable Energy: exploring geothermal interpret history of sedimentary deposition energy and assessing sites for wind and and past environments solar power development Paleontology Sustainable Practices: implementing Fossils: study of ancient life forms preserved practices that reduce environmental impact in rocks and promote the sustainable use of earth’s Evolution: investigation of the history of life on resources earth and how organisms evolved over geological time Geology The scientific study of the earth, including its Environmental Geology materials, processes, history, and the forces that Human Interaction: examination of how shape it geological processes and materials impact Encompasses a broad range of topics, from the human activities and vice versa composition and structure of the earth’s interior to the Sustainability: study of how to manage interactions between geological processes and living geological resources (e.g. minerals, water) organism sustainably and mitigate environmental impacts Major Branches of Geology Physical Geology Economic Geology Earth Materials: study of rocks, mineral, and Resource Exploration: identification and soil extraction of valuable minerals, metals, and Processes and Landforms: examination of energy resources geological processes Mining and Production: methods for extracting and processing geological resources along Historical Geology with economic considerations and Earth’s History: reconstruction of earth’s past environmental impacts environments, climates, and life forms, using rock layers, fossils, and geological events Petroleum Geology Geological Time Scale: development of the application of geology to the exploration for timeline of Earth’s history and production of oil and gas dynamic and multidisciplinary field that plays Structural Geology a crucial role in the energy industry Rock Deformation: study of how rocks deform petroleum geologists contribute to the under stress efficient and sustainable exploration of and Tectonics: investigation of plate tectonics and production of oil and natural gas resources by the movement of earth’s lithospheric plates, understanding the formation, mitigation, and including the formation of mountains and accumulation of hydrocarbons such Sedimentology CHAPTER 2 Sediment Process: study of sediment formation, transport, and deposition. Introduction to Physical Geology Understanding sedimentary rocks and their environments 3  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 Physical Geology Building blocks of rocks and are essential to various branch of geology focused on understanding the geological and biological processes materials and processes that shape the earth’s Naturally occurring, meaning they form through structure and surface natural geological processes without human encompasses the study of rocks, minerals, and intervention landforms, and investigates the physical processes Inorganic, composed of elements and compounds driving geological change not associated with biological life Earth’s Structure: Layers of the Earth Solid at room temperature and have a crystalline Crust structure, which means they have an internal atomic Continental Crust: Thicker (about 30-70 km) arrangement that forms a crystal lattice, giving them and less dense than oceanic crust. Composed specific shapes and physical properties mainly of granitic rocks Oceanic Crust: Thinner (about 5-10 km) and Each mineral has a defined chemical formula that can denser than continental crust. Composed vary slightly due to impurities or substitutions primarily of basaltic rocks Many minerals come from magma, the molten rock Mantle beneath the earth’s surface. When magma cools, Upper Mantle: Extends to about 410 km below mineral crystals are formed. How and where magma the surface. Includes the lithosphere (rigid cools determine the size of the mineral crystals. outer layer) and the asthenosphere (partially When magma cools slowly beneath the molten and ductile layer) earth’s crust, large crystals form Lower Mantle: Extends from 410 km to about When magma cools rapidly beneath the 2,900 km. Composed of more solid, high- earth’s surface, small crystals form pressure minerals like perovskite and ferropericlase. Crystals may also form from compounds dissolved in a liquid such as water. When the liquid evaporates, or Core exchanges to a gas, it leaves behind the minerals as Outer Core: Liquid layer extending from about crystals. Halite, or rock salt, forms in this way. 2,900 km to 5,150 km. Composed mainly of iron and nickel, and is responsible for earth’s Classification of Minerals magnetic field. Major Mineral Groups Inner Core: solid layer at the center of the Silicates*** earth, extending from 5,150 km to about 6,371 Most abundant mineral group and characterized by km. Composed primarily of iron and nickel and the presence of silicon and oxygen. remains solid due to immense pressure. Examples: Earth’s Materials – Minerals and Rocks Quartz (SiO2) – composed of silicon and oxygen. major component of many rocks and Minerals is known for its hardness and resistance to Fundamental components of earth’s materials, weathering playing a crucial role in the composition, structure, Feldspar – group of minerals containing and processes of the planet aluminum silicates (orthoclase & plagioclase), which are important in granite Naturally occurring, inorganic solid with a specific and other igneous rocks chemical composition and crystalline structure 4  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 Mica – group of silicate materials with a Gold (Au) – a native metal, is used in jewelry, layered structure (muscovite & biotite), known electronics, and as a financial asset for their cleavage and use in electrical Silver (Ag) insulators. Copper (Cu) Carbonates*** Physical Properties of Minerals Minerals that contains carbonate ions (CO32-) Density Measure of the mass of a material divided by its Examples: volume Calcite (CaCO3) – found in limestone and marble, plays a significant role in the carbon Luster cycle and is used as a building material Used to describe how many mineral surface reflect Dolomite (CaMg(CO3)2) light and can be categorized as metallic, vitreous, pearly, etc. Oxides*** minerals where oxygen is combined with one or more Cleavage metals Refers to the flat, smooth planes, along which some minerals break and also to the shape of the resulting Examples: fragments Hematite (Fe2O3) – an iron oxide that is a primary ore of iron and is used in pigments and Color various industrial applications Refers to the hue of a mineral which can vary due to Magnetite (Fe2O4) impurities and exposure to environmental factors Sulfides Streak Minerals containing sulfur combined with metals Color of the residue produced by scratching a mineral on a non-glazed porcelain plate Examples: Pyrite (FeS2) – often referred to as “fool’s gold”, Fracture is an iron sulfide mineral with a metallic luster Tendency of mineral breaks unevenly or irregularly and is used in the production of sulfuric acid Hardness Chalcopyrite (CuFeS2) Measures a mineral’s resistance to scratching, often Halides assessed using Mohs scale Minerals that contain halogen elements like fluorine, Friedrich Moh’s, a German mineralogist, worked out a chlorine, bromine, or iodine scale of hardness. Geologists used Mohs hardness Examples: scale to describe mineral hardness. It has values from Halite (NaCl) – commonly known as “rock 1 to 10, with the hardest mineral, diamond, assigned salt”, is used for road de-icing and as a the hardness value of 10. These values are consistent seasoning in food with the scratch test. It is not an absolute scale. Fluorite (CaF2) Rocks Native Elements Fundamental to understanding geology Minerals composed if a single element Earth’s building blocks and provide insights into Examples: geological processes, history, and resource management 5  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 Naturally occurring aggregates of one or more and the quality of the oil or gas reservoir. Larger grains minerals, mineraloids, or organic materials = larger pores between them. It is easier for fluids, such as gas and oil, to flow through larger pores and They form through various geological processes and into a well are categorized based on their origin and composition Classification of Rocks Igneous Rocks Formed from the cooling and solidification of molten magma or lava. Texture can range from coarse-grained (granite) to fine-grained (basalt), depending on the cooling rate. Not typically source rocks for hydrocarbons but can serve as cap rocks due to their property such as impermeability. Two Types of Igneous Rocks Intrusive (Plutonic) Rocks: formed from magma that cools slowly beneath the earth’s Metamorphic Rocks surface, allowing crystals to grow From the Greek word meta = change and morphe = Extrusive (Volcanic) Rocks: formed from lava form that cools quickly at the earth’s surface, Result from changes to pre-existing rocks. These resulting in smaller crystals changes occur when the minerals that compose the Sedimentary Rocks rock are changed or rearranged or both. Formed from the accumulation and compaction of Formed from the alteration of pre-existing rocks sediments or from the precipitation of minerals from through heat, pressure, and/or chemical processes water. The changes can typically occur at temperatures in Often have a layered or stratified appearance due to excess of 200oC, which distinguishes metamorphic the accumulation of sediments. rocks from the lower-temperature weathering and Rocks that are drilled to find gas and oil. They are the lithification processes that form sedimentary rocks. source and reservoir rocks for gas and oil. Distinguished from igneous rocks because the Three Types of Sedimentary Rocks temperatures that change the former are not high Clastic Rocks: composed of fragments of enough to cause the rock to melt. other rocks or minerals that have been Texture can be coarse or fine-grained depending on cemented together the degree of metamorphism while the mineral Chemical Rocks: formed from the evaporation composition includes minerals like garnet, kyanite, of water and subsequent precipitation of and talc. minerals Organic Rocks: formed from the accumulation Can influence the structural framework of a region, of organic materials such as plant debris. affecting the distribution and mitigation of hydrocarbons. Due to their low permeability, Rock is often classified according to the grain size. The metamorphic rocks can act as cap rocks, trapping size of the grains controls the size of the pore spaces hydrocarbons in underlying reservoir rocks. 6  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 Two Types of Metamorphic Rocks material for rocks. Igneous rocks form both under the Foliated Rocks: have a layered or banded surface and above it when magma becomes lava. appearance due to the alignment of mineral Heat and pressure changes igneous and sedimentary grains under pressure rocks into metamorphic rocks. Erosion and Non-Foliated Rocks: do not exhibit layering weathering break igneous and sedimentary rocks up, and are more often formed from rocks that do which compact into sedimentary rocks. Sediments not have a significant alignment of mineral from organic sources also contribute to sedimentary grains rocks. Tectonic forces drive some rocks back below the surface where they can change forms or melt and Groundwater is described by salt content in parts per become magma once again. thousand (ppt). Freshwater contains so little salt (0-1 ppt) that it can be used for drinking water. Brines are CHAPTER 3 subsurface waters that contain more salt than seawaters (35-300 ppt). Brackish waters are mixture Geologic Processes of freshwater and brines. Two Categories of Geologic Processes Exogenous (external) Process Rock Cycle Occur on or near the surface of the earth. They it is the natural continuous process that forms, breaks are usually influenced or driven by gravity, down, and reforms rock through geological chemical water, wind, or organisms. Types of exogenous and physical processes. Through the cycle, rocks processes are weathering, erosion, mass convert between igneous metamorphic and wasting, and sedimentation. sedimentary. It is a dynamic system that recycles Earth's materials Endogenous (internal) Process in different forms, from molten magma deep below Takes place within or in the interior of the the surface, the solid rock formations and sediments. earth. Thermal energy of the mantle and crust is its driving force. These processes are responsible for earthquakes, development of continents, mountain building, volcanic activities, and other movements related to earth’s crust. Creates relief and responsible with large scale landform building and transforming processes. Weathering Process by which rocks and minerals are broken down into smaller particles by various physical, chemical, and biological mechanisms Essential in shaping the earth’s landscape and plays a critical role in soil formation. Impacts reservoir studies such as porosity and permeability, rock strength and stability, reservoir It is a continuous process through which rocks quality, outcrop analysis, environmental transform from one type to another over geological considerations, and impact on fluid dynamics. time scales. Molten rock called magma is the source 7  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 Types of Weathering Root Expansion: plant roots grow into cracks Physical (Mechanical) Weathering in rocks, expanding and causing the rock to The breakdown of rocks into smaller pieces without break apart changing their chemical composition or breakdown of Lichen and Moss: these organisms produce rocks by mechanical forces concentrated along rock acids that chemically weather rocks fractures. This occurs due to changes, whether Animal Activity: burrowing animals and other sudden or not, in temperature, pressure, etc. organisms disturb rock structure, leading to Frost Wedging: water enters cracks in rocks, mechanical breakdown freezes, expands, and eventually causes the rock to break apart Erosion Thermal Expansion: repeated heating and The process by which earth’s surface is worn away by cooling of rocks cause them to expand and wind, water, or ice. contract, leading to fracture The process of erosion moves rock debris or soil from Abrasion: rocks and sediment grind against one place to another. It takes place when there is each other, wearing down surfaces rainfall, surface runoff, flowing rivers, seawater Exfoliation: layers of rock peel away due to intrusion, flooding, freezing and thawing, hurricanes, pressure release or thermal stress wind, etc. Chemical Weathering Agents of Erosion The breakdown of rocks through chemical reactions Water that alter the mineral composition. Rock Rivers, steams, and rain can erode rocks and soil, decomposes, dissolves, alters, or weakens the rock carrying them downstream through chemical processes to form residual materials. Process by which rocks break down by Wind chemical reactions. Wind can transport fine particles over long distances, Hydrolysis: water reacts with minerals to form particularly in arid regions new minerals and soluble salts Ice Oxidation: oxygen reacts with minerals, Glaciers can erode large amounts of rock and soil as particularly iron, to form oxides, which can they move weaken the rock Carbonation: carbon dioxide in water forms Gravity (Mass Wasting) carbonic acid, which reacts with minerals like Landslides and rock faults result from gravity pulling limestone, dissolving them loose material downslope Solution: minerals dissolve directly into Transportation water, especially those susceptible to acids The movement of eroded material from one place to Biological Weathering another. The breakdown of rocks by biological activities. The The transportation of sediments is a key phase in the disintegration or decay or rocks and minerals caused process of erosion, where particles that have been by chemical or physical agents of organisms. eroded from their original location are moved to a new Happens by organic activity from lichen and algae, area by natural forces. Mechanisms of sediment rock disintegration by plant growth, burrowing and transportation are: tunneling organisms, and secretion of acids. Suspension is where fine particles like silt and clay are carried in the water column 8  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 Saltation is where small pebbles and sand weight of overburden, resulting to reduction of open grains are bounced along the bed of a river or pore space. by the wind Cementation is a process in which the precipitation Traction is where larger rocks and boulders of solid material called cement around sediment are rolled along the ground by water, wind, or grains bind them into a firm, coherent rock, resulting ice in further reduction of open pore spaces. Solution is where dissolved minerals are transported in water. Sedimentary Structures Physical features within sedimentary rocks that form Once sediments are transported, they are eventually during or shortly after sediment deposition. deposited when the energy of the transporting medium decreases. The deposited sediments can These structures provide valuable insights into the later form sedimentary rocks through compaction and environmental conditions prevailing at the time of cementation over geological timescales deposition. These structures are critical to reservoir studies because they provide insights into the Deposition depositional environment, which in turn influences The process by which transported material is laid the reservoir’s porosity, permeability, and overall down or settles in a new location quality. Plays a significant role in reservoir studies, particularly It may also reveal the original stratigraphic top, or in understanding the formation and distribution of upward direction of deposition which helps geologists reservoir rocks, which are crucial for hydrocarbon unravel the geometry or rocks that have been folded or exploration, groundwater management, and other faulted in tectonically active regions. subsurface resource evaluations. Categories of Sedimentary Rocks Sedimentation is highly relevant to reservoir studies Inorganic Sedimentary Structures because it directly influences the formation, Formed by physical or chemical processes without distribution, and characteristics of reservoir rocks. the direct involvement of biological activity Environment of deposition is the location which Bed forms and Surface Markings deposition occurs. Features which form on the surface of a bed of Examples: sediment River Deltas o Ripple Marks: Small, wave-like Sediments are deposited at the mouth of a structures formed by water or wind river as it enters a slower-moving body of water movement Sand Dunes ▪ Asymmetrical Ripples: form in Wind deposits sand in mounds or ridges unidirectional currents. Crests Glacial Moraines may be straight, sinuous, or Rocks and debris carried by glaciers are lobe-like, depending on water deposited as the glacier retreats velocity ▪ Symmetrical Ripples: Lithification produced in waves or The general term for a group of processes that convert oscillating water. Crests tend loose sediment into sedimentary rock. to be relatively straight, but Compaction is the process that packs loose may bifurcate sediment grains tightly together due to increasing 9  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 o Mud Cracks: Polygonal cracks formed “scoop-shaped” depressions. They in drying mud, indicating subaerial are commonly preserved as bulbous exposure or mammillary natural casts on the Internal Bedding Structures bottoms of sandstone beds. Because Stratification (layering) is the most obvious of their geometry, flute marks (aka feature of sedimentary rocks. The layers flute casts) can be used to determine (strata) are visible because of the differences paleocurrent directions. in the color or texture of adjacent beds. Strata Organic Sedimentary Structures thicker than 1 cm are commonly referred to as These structures result from the activities of living beds; thinner layers are called laminations or organisms, including both direct and indirect laminae; the upper and lower surfaces of biological processes. The organisms may be animals these layers are called bedding planes. which walk on or burrow into the sediment, they may o Beddings: most bedding is horizontal be bacterial colonies which trap and bind the because the sediments from which sediment to produce layered structures. the sedimentary rocks formed were Bioturbation: disruption of sedimentary originally deposited as horizontal layers by organisms such as burrowing layers animals, leading to a mixed or homogenized o Graded Bedding: result when a sediment sediment-laden current begins to slow Trace Fossils: indicators of biological activity, down. The grain size within a graded such as footprints, burrows, or feeding marks bed ranges from coarser at the bottom preserved in sediment to finer at the top. Hence, graded beds may be used as “up indicators” Reef Structures: organic buildup of skeletal o Cross-bedding: if the individual layers material from corals or other marine are thicker than 1 cm, the cross- organisms, creating significant depositional stratification may be referred to as features cross-bedding. Thinner inclined CHAPTER 4 layering is classed cross-lamination Sole Marks Introduction to Structural Geology These are bedding plane structures preserved on the bottom surfaces of beds. They generally Structural Geology result from the filling in of impressions made The study of rock units’ three-dimensional distribution into the surfaces of soft mud by scouring of the and deformation history. current, or by impacts of objects carried by the current It specializes with understanding how rocks respond o Tool Marks: produced as tools to tectonic forces as well as the processes that cause (objects such as sticks, shells, bones, formation to geologic structures like faults, faults and or pebbles) carried by a current joints. bounce, skip, roll, or drag along the The principal objective of structural geology is to sediment surface. They are commonly understand the history of deformation in the earths preserved on the lower surfaces of crust and predict the mechanical behavior of rocks sandstone beds as thin ridges. under various stress conditions. o Flute Marks: produced by erosion or scouring of muddy sediment, forming 10  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 Intense geologic activities occur at plate boundaries Sea-floor Spreading where plates move away from one another, past one It is a hypothesis that the sea floors form at the crest another, or towards one another. of the mid-oceanic ridge then move horizontally away from the ridge crest toward an oceanic. Continental Drift is the idea that continents move freely over the Earth's It is a continuous process where tensional forces on surface, changing their positions relative to one both sides of the plate cause them to constantly move another. apart. Researcher Abraham Ortelius (1527-1598) noted It is developed by Harold Hess (1895-1982) and Robert geographic fit of continents e.g. Africa and South Dietz (1914-1995). It suggests that seafloor moves America, Atlantic formed by separation of Africa from away from mid-oceanic ridge as a result of mantle South America, and speculates that earthquakes and convection. flooding may have the separation possible. Subduction is the sliding of the sea floor beneath a Seuss (1885), people supercontinent by studying continent or island arc. Hess Hypothesis was that sea fossils, rocks, and mountains. floor spreading is driven by deep mantle convection. Wegener and Taylor (1880-1930) proposed Convection It's a circulation pattern driven by the continental drift and Pangea and claimed that there rising of hot material and/or syncing of cold material. used to be only one super giant landmass where all Magma rises to the surface from the mantle. In time, continents came from. magma is cooled by sea water and forms the oceanic crust. New sea floor created the mid-ocean ridge and Arthur Holmes (1929-1965) suggested the idea of destroyed in deep ocean trenches. thermal convection as a driving force for the movement of continents. Supporting Evidences of Seafloor Spreading World Seismicity Supporting Evidences of Continental Drift Earthquake distribution matches plate boundaries. Fossils Similar distribution of fossils such as Mesosaurus Volcanism have been found in different regions and continents. Volcanoes March some plate boundaries; some are hot spots. Coals Seams Usually, coal is found in tropical areas because the Age of sea floor climate is warm and ideal for the propagation of Youngest sea floor is at mid-ocean ridge; oldest sea organisms. Coal would be found in polar regions such floor away from mid- ocean ridge. as North Pole and Antarctica. Paleomagnetism Mountains Because the ocean floor is mostly composed of Mountain ranges match across oceans (similar rock basalt, an iron-rich substance containing minerals layers and rock types). that align with the magnetic field, they record the alignment of the magnetic fields surrounding oceanic Glacial Deposits ridges. Places that are presently known to tropical and desert like, such as Africa, Madagascar, and India, finding ice Heat flow deposits would seem unreasonable if not for the Studies conducted with thermal probes, for example, concepts of drifting continents. indicated that the heat flows through bottom sediments is generally comparable to that through the 11  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 continents, except over the mid-ocean ridges, where plate; forms an active continental margin at some sites the heat flow measures three to four between the trench and the continent times the normal value. Continent to Continent Convergence: where plates collide crumble but neither is Theory of Plate Tectonics subducted Jogn Tuzo Wilson combined ideas of continental drift and seafloor spreading into “Plate Tectonics”. Transform Plate Boundaries is at which two plates move horizontally or laterally Plate is a large mobile slab of rock that is part of the past each other. Crust is neither created nor earth’s surface. Its interior is inactive tectonically. destroyed. Most common type of transform fault Plates interact with each other along their edges (plate occurs on fracture zones and connects two divergent boundaries) that has a high degree of tectonic plate boundaries (left lateral or right lateral). activities which causes the geologic processes such as earthquakes, etc. Earth’s outermost layer is Tectonic Forces composed of thin rigid plates moving horizontally. These are forces that tends to move or change the orientation of the plate (along earth’s crust). Where tectonic plates interact, they create different types of boundaries, each associated with distinct Deep within the earth’s crust, rock deformation geological processes. Uplift is the rising of the earth’s where rocks are constantly being squeezed, crust to higher elevations. Rocks that are uplifted may stretched, and sheared happen. It is driven by forces or may not be highly deformed. Subsidence is the that cause rocks to bend, break, or flow. sinking of regions of earth’s crust to lower elevations. Stress is referred to as the force per unit area or the Rocks that subside do not undergo deformation. force applied to a material divided by the area over Three Types of Plate Boundaries which it is applied. Divergent Plate Boundaries Stress produces strain which is when there’s a change The boundary between plates that are moving apart, in size (volume), shape, or both while an object is creating new crust. These boundaries are typically undergoing stress. found along mid-ocean ridges, where seafloor spreading occurs. As the plate separates, magma Three Types of Stress rises from below to fill the gap, creating new oceanic Tensional Stress crust. Caused by forces pulling away from one another from opposite directions. It causes stretching or Convergent Plate Boundaries extensional strain. Lies between plates that are moving toward each other. At these boundaries, plates collide. When two Compressive Stress plates of different densities meet (an oceanic and a Caused by forces pushing or squeezing towards one continental plate), the denser plate is forced beneath another in an opposite direction. It causes shortening the lighter one in a process called subduction. This strain. leads to the formation of deep ocean trenches and volcanic mountain chains Shear Stress Ocean to Ocean Convergence: where one Due to movement parallel to but in opposite directions plate dives or subducts under the other along a fault or other boundary. It causes shear strain. Ocean to Continent Convergence: where Behavior of Rocks to Stress and Strain dense oceanic plates under the continental Elastic 12  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 If the deformed body recovers its original shape after Reverse Fault: formed if the hanging wall the stress is reduced or removed. moves up along a dip-slip fault compared to the footwall and if the fault dips at an angle Elastic limit is the maximum stress or force per unit steeper than 45o. Rocks are compressed such area within a solid material that can arise before the that one plate moves up while the other onset of permanent deformation. descends below it. Ductile Thrust Fault: formed if the fault dips at an If it bends while under stress and does not return to its angles less than 45o original shape after relaxation of the stress. This type Strike-slip Faults of deformation occurs at higher temperatures and It is formed by horizontal movement along the strike pressures, deep within the earth. direction of the fault plane Brittle Left-lateral strike-slip fault: forms if features If it breaks or creates a fracture at stresses higher than appear shifted to the left from one side of the its elastic limit. This type of deformation is typical of fault to the other rocks in the upper crust, where temperatures are Right-lateral strike-slip fault: forms if lower and rocks are more rigid. features shifted to the right across the fault Fractures Oblique-slip Faults Fractures are natural breaks or cracks in rocks, often It is a combination of dip slip and strike-slip occurring due to tectonic stresses or rock movements in which diagonal motion occurs along deformation. Joints are fractures without significant the fault plane, both along the strike and dip. displacement. Faults Rift Valley or Graben is formed when two normal Faults formed when tension and compression faults occur parallel to each other and the land sinks associated with plate movement is so great that between the faults. Horst is the opposite of a rift valley blocks of rock fracture or break apart. where the land between the parallel faults is forced upward because the two faults are being pushed Strike of a non-horizontal bed, is the compass together. orientation of a line formed by the intersection of an imaginary horizontal plane with the inclined bedding Folds plane. Folds are bends or wave like features in layered rock. It occurs with convergent or compression motion. It is Dip of the inclined rock layer is the angle between the usually strained in a ductile way than elastic or brittle imaginary horizontal plane and the inclined rock layer strain. Perhaps folding took place when rock was Classification of Faults buried in a moderate depth where high confining Based on Direction of Movement Along Fracture pressure favors plastic behavior. Dip-slip Faults Formed from movement of rock along the dip of the Types of Folds fault plane Anticlines*** Normal Fault: forms when the hanging-wall Arched folds where limbs dip away from the hinge line. rock moves downward compared to the Oldest rocks are exposed along the hinge line. footwall. This occurs when rocks move away Synclines*** from each other due to the land moving apart. Trough-shaped folds where limbs dip toward the hinge line. Younger rocks are exposed along the hinge line. 13  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 Isoclinal Fold Rock Units (Lithologies) Limbs are parallel to each other, implying intense Distinct colors and patterns indicate different types of compressive stress. rocks or geological formations. Overturned Fold Structural Features Upper limb of the fold override the lower limb that Faults, folds, and fractures are represented using implies unequal compressive and/or shear stress. unique symbols. Recumbent Fold Geologic Contacts Type of fold that are overturned to such an extent that Lines demarcate boundaries between different rock the limbs are essentially horizontal and indicates units. compressive and/or shearing stress is more intense in Legend/Key one direction. Provides explanations for the map’s symbols, colors, CHAPTER 5 and patterns. Geologic Time Symbols Geologic Mapping Abbreviations and symbols on the map indicate the Geologic Map or Geological Map is a special- age of the rock formations. purpose map made to show geological features. Rock units or geologic strata are shown by using standardized color or symbols to indicate where they are exposed at the surface. It is an essential tool in geology, used to understand the composition, history, and structure of an area, providing critical information for various applications, including resource exploration, environmental assessments, and land use planning. Geologic maps, which represent rock formations and their structural links, aid in understanding a region’s tectonic and depositional history. It shows how rocks were folded, faulted, and eroded over millions of years. It also provides data to understand resource exploration. These maps are critical for discovering and evaluating natural resources such as minerals, oil, gas, and groundwater. Geologic mapping is critical for identifying areas vulnerable to natural disasters including earthquakes, landslides, and volcanic eruptions. Understanding the geological features and processes at work in these areas enables improved disaster preparedness and Tools and Techniques in Geologic Mapping risk reduction. Field Observations The foundation of geologic mapping is fieldworks. Key Components of a Geologic Map Geologists traverse the landscape, making direct 14  PetE 402 – RESERVOIR GEOSCIENCES Geron, Ghemory Karl PETE 2101 observations of rock types, structures, and Field Notebook, Masking Tape, and Marker Pens relationships. They measure the orientation of rock All important observations must be written down in a layers, collect samples, and note locations pf key concise, orderly, and legible manner features like faults and folds. Field data is compiled and synthesized into a geologic map. Importance of Geologic Mapping Identifying Reservoir Rock Units Remote Sensing and Aerial Imagery Understanding Trap Structures Modern geologists use satellite imagery, drones, and Assessing Reservoir Characteristics aerial photographs to map large, inaccessible areas. Planning Drilling Operations These tools allow for the rapid identification of broad- scale geological patterns and structural features, which can then be verified through fieldwork. Geophysical Methods Techniques such as seismic surveys, ground- penetrating radar (GPR), and magnetic surveys provide valuable subsurface information. These methods are particularly useful in areas where rock units are covered by thick layers of soil or sediment, as they can reveal the hidden structure and composition of the subsurface. GIS and Digital Mapping Geographic Information Systems (GIS) have revolutionized geologic mapping by allowing geologists to store, manipulate, and analyze geospatial data. Digital mapping platforms enable the creation of highly detailed maps that can be easily updated and shared. GIS also facilitates the integration of other datasets, such as topography, hydrology, and land use, providing a more comprehensive understanding of an area. Compass/Clinometer Compass is an instrument used for determining direction. Clinometer is an instrument used for measuring inclination, tilt, and elevation of rock outcrops. Geological Hammer Basic equipment for any geologist as it is the tool used for collecting samples. Handheld Lens Used to make the first analysis of rock samples in the field before further analysis is performed in the laboratories 15