Origin of Hydrocarbons and Petroleum Theories.pptx
- 1. Origin of Petroleum Theories Geologist: Diana Helmy Mahmoud
- 2. What is Hydrocarbon ? • In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. • Hydrocarbons are examples of group 14 hydrides. Hydrocarbons from which one hydrogen atom has been removed are functional groups called hydrocarbyls.
- 3. Classification of Hydrocarbons 1. Saturated hydrocarbons are the simplest of the hydrocarbon species, composed of single bonds, and the basis of petroleum fuels (Alkanes). 2. Unsaturated hydrocarbons have one or more double or triple bonds between carbon atoms. - Double bond are called (Alkenes) - Triple bonds are called alkyne 3. Aromatic hydrocarbons, also known as arenes, are hydrocarbons that have at least one aromatic ring. • Hydrocarbons can be gases (e.g. methane and propane), liquids (e.g. hexane and benzene), waxes or low melting solids (e.g. paraffin wax and naphthalene) or polymers (e.g. polyethylene, polypropylene and polystyrene).
- 4. What is Petroleum ? • Petroleum is a Latin word of (Petra ‘‘rock’’ + Oleum ‘’ oil ‘’), also called as rock oil. • Naturally occurring, and the color varies from black to brown. • Either petroleum oil flows out itself (due to underground pressure) or it is pumped out mechanically.
- 5. Composition of Oil • Petroleum is a dark colored viscous oil found in deep Earth crust. Chemically it is a mixture of various types of • Hydrocarbons along with oxygen, nitrogen and sulphur containing compounds. The average composition of petroleum is : • C = 84 - 87% • H = 11 - 15% • O = 0.3 – 1.5% • S = 0.1 - 3% • N = 0.1 - 1.5
- 6. Origin of Petroleum Theories • Carbide Theory • Engler Theory • Modern Theory
- 7. Carbide Theory • Hydrocarbons present in petroleum are formed by the action of water or inorganic carbides • Inorganic carbides are formed by reaction of metal & carbon • under high temperature and pressure inside the earth Ca + 2C = CaC2 Al + C = Al4C3 • These carbides would react with underground water to form hydrocarbons CaC2 +2 H2O = Ca(OH)2 + C2H2 (acetylene) Al4C3 + 12 H2O= 4Al(OH)3 + 3CH3 (methane)
- 8. Cont. • Lower hydrocarbons then undergo hydrogenation and polymerization. C2H2 + H2 = C2H4 +H2 = C2H6 3C2H2 = C6H6 (benzene) 3C2H4 = C6H12 (cyclohexane) • Flaws In Carbide Theory: This theory fails to explain the following facts. presence of nitrogen and sulphur compounds. presence of chlorophyll. presence of optically active compounds • Due to these flaws this theory was rejected
- 9. Engler Theory • Suggested by Engler in 1900 that petroleum is of animal origin • Formed by the decay and decomposition of marine animals under high pressure and temperature • SO2 was given by volcano decide the sea-side kills the fish and other marine animals which go in to piling • Hundreds of year causes animal to decompose under high pressure and temperature to form petroleum.
- 10. Cont. • This theory was supported by the facts as destructive decomposition of fish, oil and other animals fats under high P & T, gives product similar to petroleum Presence of brine and sea water along with petroleum Presence of N and S compounds Presence of fossils in the petroleum areas. • However this theory fails to explain the presence of chlorophyll in petroleum as well coal deposit in the vicinity of oil field.
- 11. Modern Theory • According to modern theory Petroleum is believed to formed from the decomposition of marine animals as well as of plant organism of prehistoric forests. • Biogenetic origin of petroleum (Hydrocarbons) suggests that petroleum come from a long time decaying of died organisms such as planktons, zooplankton ad other form of biological species under a subjection of high temperature • High T & P in earth crust causes the degradation of biological matter in to petroleum • This theory has a wide acceptance and successfully explain the flaws present in previous theories like Presence of brine & coal in hype vicinity of petroleum Presence of chlorophyll & N and S compounds
- 13. The Origin of Oil & Gas • Petroleum was formed from organic matter. • The organic mater was deposited in a marine environment and remained buried under anoxic conditions for 100-400 millions years. • Over the years, layers of silt, sand and other sediments settled over the buried organic matter. • The increase of pressure and temperature slowly transformed the organic matter into hydrocarbons (kerogen, oil, gas). Also, over those millions of years various plate tectonics (continents drift over the underlying mantle) and other geological phenomena resulted in the rearrangement of oceans and continents; thus, we encounter oil in both onshore and offshore locations.
- 14. The Origin of Oil & Gas
- 15. The Deposition of Organic Matter Took Place as: • Marine organisms (zooplankton and algae) that settled to seabed at depths where oxygen concentration is very low to decompose the organisms. • Organic mater from nutrient-rich regions such as ancient river deltas. Those large amounts of organic material were covered by subsequent sediments faster that decomposition could take place.
- 16. Notes • Organic matter was buried before decomposition takes place. The lack of oxygen (anoxic conditions) is an essential factor since it prevents the decomposition of the organic matter which is then transformed to oil. • Subsequent layers cause the increase of pressure and temperature and the transformation of the organic matter to hydrocarbons (maturation)
- 17. Hydrocarbon Fluids • There are five main types of reservoir fluids: black oil, volatile oil, condensate (retrograde gas), wet gas, and dry gas • Each of these fluid types require different approaches when analyzing the reservoir • It is important to identify the correct fluid type early on in the reservoir's life • Laboratory analysis is our primary method for determining and quantifying fluid type, but production information such as initial production gas-oil ratio (GOR), gravity of the stock-tank liquid, and the color of the stock-tank liquid are also useful indicators
- 18. Hydrocarbon Fluids • Black oils are made up of a variety of components including large, heavy, and non-volatile hydrocarbons. • In the phase diagram, when the reservoir pressure lies anywhere along line 1 → 2, the oil is said to be undersaturated - meaning the oil could dissolve more gas if more gas were present. • If the pressure is at 2, the oil is at its bubble point, and is said to be saturated - meaning the oil contains the maximum amount of dissolved gas and can't hold any more gas. • A reduction in pressure at this point will release gas to form a free gas phase inside the reservoir. • Additional gas evolves from the oil as it moves from the reservoir to the surface. This causes some shrinkage of the oil. Black oil is often called low shrinkage crude oil or ordinary oil.
- 19. Hydrocarbon Fluids • Volatile oils contain fewer heavy molecules and more intermediate components (ethane through hexane) than black oils • Volatile oils generally have initial gas-oil ratios in the 2000 to 3300 scf/Bbl range, and the stock tank gravity is usually 40° API or higher • The color is generally lighter than black oil – brown, orange, or green • Gas associated with volatile oils tends to be very rich and similar to retrograde condensate gas
- 20. Hydrocarbon Fluids • The Condensate gas is very similar to volatile oils in terms of the color (green, orange, brown, even clear) and gravity (40° to 60° API) of the produced oil • However, the reservoir temperature of a condensate gas reservoir is greater than the critical temperature of the fluid, and so where a volatile oil is a liquid at original reservoir pressure and temperature, a condensate gas is a gas.
- 21. Hydrocarbon Fluids • Wet Gas (Rich Gas) Natural gas that contains significant heavy hydrocarbons such as propane, butane and other liquid hydrocarbons. The general rule of thumb is if the gas contains less methane (typically less than 85% methane) and more ethane, and other more complex hydrocarbons, it is labelled as wet gas. • Wet gas exists solely as a gas in the reservoir throughout the reduction in reservoir pressure. • The entire phase diagram of a wet gas will lie below the reservoir temperature. Note that the pressure path line does not enter the phase envelope, meaning no liquid is ever formed inside the reservoir.
- 22. Hydrocarbon Fluids • Dray gas Natural gas that occurs in the absence of condensate or liquid hydrocarbons, or gas that had condensable hydrocarbons removed • It is primarily methane with some intermediates. • The hydrocarbon mixture is solely gas in the reservoir and there is no liquid (condensate surface liquid) formed either in the reservoir or at surface. • The pressure path line does not enter into the phase envelope in the phase diagram, thus there is only dry gas in the reservoir. Note, the surface separator conditions also fall outside the phase envelope (in contrast to wet gas); hence no liquid is formed at the surface separator.
- 23. Reservoirs Classification • In general reservoirs are conveniently classified on the basis of the location of the point representing the initial reservoir pressure Pi and temperature T, with respect to the pressure-temperature diagram of the reservoir fluid. • Accordingly, reservoirs can be classified into basically two types. These are: Oil reservoirs: If the reservoir temperature T is less than the critical temperature Tc of the reservoir fluid, the reservoir is classified as an oil reservoir. Gas reservoirs: If the reservoir temperature is greater than the critical temperature of the hydrocarbon fluid, the reservoir is considered a gas reservoir.
- 24. Reservoirs Classification Depending upon initial reservoir pressure Pi, oil reservoirs can be subclassified into the following categories: • Undersaturated oil reservoir: If the initial reservoir pressure Pi, is greater than the bubble-point pressure Pb of the reservoir fluid, the reservoir is labeled an undersaturated oil reservoir. • Saturated oil reservoir: When the initial reservoir pressure is equal to the bubble-point pressure of the reservoir fluid, the reservoir is called a saturated oil reservoir. • Gas-cap reservoir: If the initial reservoir pressure is below the bubble point pressure of the reservoir fluid, the reservoir is termed a gas-cap or two-phase reservoir, in which the gas or vapor phase is underlain by an oil phase. The appropriate quality line gives the ratio of the gas-cap volume to reservoir oil volume.
- 25. Oil Trap Elements and Conditions • Source Rock is the rock where petroleum formed • Source rocks are sedimentary rocks and typically shales (90%). • The source rock was form along with deposition of the organic matter; thus, organic matter was abundant at the early age of a source rock • As mentioned earlier, hydrocarbons are created from organic matter buried in an anoxic marine environment. However, a few more conditions are required for hydrocarbons to accumulate and form a petroleum reservoir.
- 26. Oil Trap Elements and Conditions • Maturation is the conversion of organic matter to hydrocarbons • The first stage is the formation of kerogen. As the pressure and temperature is the source rock is further increase, kerogen converts to petroleum • If the temperature is raised above 130C for even a short period of time, crude oil will convert to gas. Initially the composition of the gas will show a high content of C4–C10 components (wet gas and condensate), but with further increases in temperature the mixture will convert to light hydrocarbons (C1–C3, dry gas) • An average geothermal gradient is about 3C per 100 m of depth • Oil window: 60–120 °C, 2-4 km • Gas window: 120–180 °C, 4-6 km
- 27. • Temperature, is the first most important factor for thermal maturation and determines the resultant hydrocarbon type. Time is the second most important factor for thermal maturation. Petroleum geologist use maturation indicators to evaluate potential hydrocarbon accumulations.
- 28. Oil Trap Elements and Conditions • Migration takes place after maturation. The hydrocarbons from the impermeable source rock move to the porous reservoir rock. • Reservoir Rock: is a porous rock that contains petroleum. Reservoir Rocks are typically sandstones and carbonates. Sandstone reservoir are of higher quality because the primary mineral, SiO2 (quartz) is strong and stable (hard to react). Carbonate reservoir are formed from coral, shell and other biogenic deposits. • Cap Rock: To locate and explore oil and gas prospects it is important to correctly assess the subsurface geology.
- 29. • To sum up, for a hydrocarbon reservoir formation it is necessary: 1. A basin were sedimentation took place 2. Deposition of organic matter in anoxic conditions, formation of source rock. 3. Through increase of temperature and pressure source rock must have reached maturation 4. Migration of the generated hydrocarbons into a porous type of sediment, the reservoir rock. 5. Creation of trap for the migrating hydrocarbons to accumulate. • Oil Shale: When kerogens are present in high concentrations in shale, and have not been heated to a sufficient temperature to release their hydrocarbons, they may form deposits.
- 30. Oil Traps • In petroleum geology, a trap is a geological structure affecting the reservoir rock and caprock of a petroleum system allowing the accumulation of hydrocarbons in a reservoir • Traps can be of two types: stratigraphic or structural
- 31. Oil Traps • Structure Traps: formed as a result of some structural deformation - a bend or dip - of rock. • These traps take on several forms and shapes as a result of different types of deformation, i.e. faults and folds. • This deformation tends to take place over tens or hundreds of millions of years after sediment that creates the seals and rocks themselves have been deposited. • In these traps, the pores of the reservoir rock contain oil, gas, or water. • Gas moves up in the trap as it is the lightest, with oil below it and water at the bottom. • The cap rock prevents upward migration of these fluids.
- 32. Oil Traps • Stratigraphic Traps: formed as a result of the deposition in sedimentary rocks. When the sediment that creates the reservoir rock is deposited in a discontinuous layer, the seals are created beside and on top of the reservoir. • In some cases, these seals are made of impermeable or low permeability shale deposited around the reservoir, blocking the oil and gas inside. The seals themselves may also be source rocks. • There are two main types of stratigraphic: Primary stratigraphic traps result from changes that develop during the sedimentation process. These are generally structural changes that arise as a result of discontinuous deposition of sediment. Secondary stratigraphic traps result from changes that develop after sedimentation has occurred. These changes can involve changes in porosity of the rock that lead to formation of a cap-like rock.
- 33. Oil and Gas Life Cycle • For more than a century, oil is well known as a good primary energy source competing coal, natural gas, nuclear energy and renewables in various regions and fields of the energy sector. • According to the last statistical reports, oil is dominant fuel in America and Africa, whereas natural gas dominates in Europe and Eurasia and coal in the Asia Pacific. • The use of oil and gas in the Middle East reach 98% of total energy consumption in this region.
- 34. Primary world energy consumption, million tons of oil equivalent
- 35. Oil and Gas Life Cycle
- 36. Oil and Gas Life Cycle • Exploration is a method used for searching potentially viable oil and gas sources through geological surveys and drilling exploration wells to identify areas of potential interest. During the drilling process, general information and samples are collected to know about the rocks, fluids to find out how much oil and gas may be available at the explored area and what is the depth of the oil and gas window. • The appraisal stage of the lifecycle starts after successful drilling exploration wells. The main purpose of this phase is to improve the field description through further data acquisition and to reduce the uncertainty or possibility of losses about the size, shape and marketability of the oil and gas reservoir.
- 37. Oil and Gas Life Cycle • The development stage occurs after successful appraisal and before production. The main activities are formation of a conceptual development plan (in order to develop the oil and gas field, to prepare design for the production wells, to decide what surface and subsurface facilities are required and to describe operating and maintenance principles) and construction of the facilities and production units. • The production phase starts with the first oil show in the wellhead. Oil and gas fields have a lifespan ranging from15 to 30 years (from first oil to abandonment) and may be extended up to 50 years or more for the largest deposits. After extraction, oil and gas transported for processing and distribution. • The abandonment phase when the oil and gas production is no longer cost-effective, wells are plugged and abandoned, production facilities are removed and this is the last stage of oil and gas fields’ life cycle.
- 38. Petroleum Exploration • The role of exploration is to provide the information required to exploit the best opportunities presented in the choice of areas, and to manage research operations on the acquired blocks • Exploration is responsible for handling the risk intrinsic in this activity, and this is generally achieved by selection of a range of options in probabilistic and economic terms
- 39. Petroleum Exploration The sequence of activities covered by an exploration permit is fairly uniform, and include: • The creation of a database • The analysis of available data • The programming of mapping, geological and photo-geological surveys • Seismic surveys and interpretation of seismic data • The choice of well locations, drilling • The analysis of results and the decision as to whether or not to proceed with the application for a lease or to release the area after fulfilling obligations
- 41. Thanks