Petroleum Geology 01 - Lecture notes 1 PDF

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Petroleum Geology. Lecture #1 What is Petroleum Geology? - Is the branch of economic geology that relates to the origin, migration and accumulation of oil and gas and to the discovery of their commercial deposits. - It refers to the specific set of geological knowledge that is applied to search for hydrocarbon (Gas & Oil exploration). Formation Water: it is found with oil sometimes. Petroleum System: It’s a relation between accumulation “Surrounding places of generation” and place of generation. Or Elements and processes related to generation, migration and trapping. Oil Kitchen: Pod of active source rocks. Hydrocarbon Potentiality = ‫إحتمالية وجود الهيدروكاربون‬ Trap: Something stop the migration of Oil/Fluids. Lecture #2 Relation between Geology and Petroleum Geology - Geology, Is the science that deals with the history and structure of the earth and its life forms, especially as recorded in rock record. - A basic understanding of its concept and processes is essential in the petroleum industry, for it is used to predict where oil accumulations might occur. - It is the job of the petroleum geologist to use his knowledge to reconstruct the geologic history of an area to determine whether the formations are likely to contain petroleum reservoirs. - It is also the job of the geologist to determine whether the recovery and production of these hydrocarbons will be commercially profitable. Energy Resources of the World, - Coal 21%, Oil 32%, Natural Gas 23%, Nuclear Power 6%, Hydropower/Geothermal/Solar/ Wind 7% Oil Shales: Enriched in Organic matter “fine grained” Shale Oil: petroleum oil we get from Oil shale “Tight oil = Crude oil” Kerogen: Solid mixture of organic chemical compounds. Tar Sands: type of unconventional petroleum deposits. Wild Cat Well: Exploratory well. API gravity: American Petroleum Institute.

What is Petroleum? - Legally, petroleum has been called a mineral, but their usage does not satisfy the common geologic definition of a mineral as an inorganic substance. - It has also been called a mineraloid a term also applied to chalcedony and amber on the ground that it is not definite enough in chemical composition. Mineraloid is a naturally occurring, usually inorganic substance that is not considered to be a mineral because it I amorphous and lacks characteristic crystal form. - Amber is a fossilized tree resin, which has been appreciated for its color and natural beauty since Neolithic. - Chalcedony is a cryptocrystalline form of silica, composed of very fine intergrowths of the mineral’s quartz and moganite, these are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. What is Petroleum? - It is frequently called mineral fuel, along with peat and coal. - Petroleum is a fossil fuel, because it was formed from the remains of tiny sea plants and animals, that died millions of years ago. The Development of Petroleum Geology, 1. The Oil Seepages. “First to be discovered” - Place where oil or gases escape to the surface through bedding planes, fractures, folds. - They are quite common in California “Thousands” - How Oil Seepage was Formed? 2. The Anticlinal Theory. - The theory was that because oil is lighter than water it would seek the highest part of an underground structural fold. Thus, an anticline is a more favorable place to drill for oil than syncline. - Collector = Reservoir rock = Bed contains oil. - Closure: Distance between spill point to crest. - Spill point: Point of migration of Oil if reached. 3. Subsurface Geology. - The study of the information revealed by the bore-holes already drilled and from the study of the sedimentary story as revealed in well and surface sections showed that oil accumulations could be found by tracing lateral changes in rock composition, locating breaks in deposition and other ways. - Techniques for the presentation of structural and stratigraphically information improved greatly during this time.

4. Geophysics. - The torsion balance for gravity measurements had been introduced in 1920 and the seismograph in 1923. - The chief advantage of the geophysical tools is that they allow the operator to look below breaks in the geological sequence, which masks the formations at depth from surface geological inspection. Notes, - Subsurface geology and geophysics are related to each other. - Basement rock: Igneous or Metamorphic (+V) - Salt Dome: (-V) “Mass/Density less than sedimentary” Selling is perfect, Good cooking for organic matter. 5. New Methods. “Direct detection of Hydrocarbon” I. Bright Spots. - It is one of the pattern classes in a seismic section and the indicators of gas (hydrocarbon) accumulation. - In the past, detection of bright spots depended primarily upon visual examination and the experience of a geophysicist. - Due to acoustic embidance difference. - Good indication of Hydrocarbon. - Fluid contact in reservoir coinciding with a velocity/density contrast that is enough to generate a seismic reflection. The gas has a lower density and lower P-wave velocity than the brine pore fill. The amplitude anomaly corresponds to a bright spot. The flats spot is the result of the change in pore fill, it corresponds to the gas/water interface. - Carbonate build-up with several seismic facies’ units. The high-energy reef front is characterized by lower amplitude chaotic reflections. Note that the gas containing reservoir section is represented by a high amplitude seismic facies unit. II. 3D Seismic. - A technology that has significantly changed energy exploration. III. 4D Seismic - Time represents the fourth dimension. - A more precise term is repeated seismic; because that is what is done: a seismic survey over a given area (oil/gas field) is repeated in order to monitor production changes. - The acquisition of 4D or time-lapse seismic has opened new horizons for monitoring reservoir properties such as fluids, temperature, saturation and pressure changes during the productive life of a field.

- Seismic Acquisition: Is the artificial generation and recording of seismic data.

IV. Seismic Stratigraphy - It is the study of stratigraphy and depositional facies as interpreted from seismic data. - The primary exploration objective in the use of seismic stratigraphy is its assistance in the tracing of facies across wide areas. Lecture #3 The Story of Petroleum - Petroleum has been known and used since very old times, from the earliest times recorded by man, petroleum is frequently mentioned as having an important part in the religious, the medical and even the economic life of many regions. - Gushers: ‫آبار ذات إندفاعات بترولية‬. - Drill rigs: ‫بريمة الحفر‬. The importance of petroleum - Oil is the major supplier of energy. “more than 60,000,000 barrels per Day” Some Numbers, - Number of oil and gas wells drilled to date: ~ 7 million - Producing wells worldwide: ~ 1 million - Total number of producing fields: ~ 40,000 - Total number of petroleum geologists: ~ 100,000 (exc. China) - Total number of drill rigs worldwide: ~ 5,000 What is Petroleum? - It is a general term for all naturally occurring hydrocarbons, whether gaseous, liquid or solid. - Liquid petroleum, which is called crude oil to distinguish it from refined oil, is the most important commercially. - It consists chiefly of the liquid hydrocarbons, with varying amounts of dissolved gases, bitumen and impurities - It has an oily appearance and feel; in fact, it resembles the ordinary lubricating oil selling at filling stations. - Crude oil is measured by American Barrel = 42 American Gallons = 158.9 liters. - Crude oil is measured in France and Germany by m³ = 6.28 barrels.

Measurement Units, - 1 barrel = 159 liters - 1 cubic meter = 6.37 barrels - 1 metric ton = 6.8 to 7.6 barrels (dep. on gravity) - Gas is expressed in millions of Cubic feet: 1 MMcf ≈ 3x10⁴ m³ - Energy-wise, gas can be expressed in oil equivalents: - 1 boe ≈ 6000 to 6500 cf What is Petroleum? - Petroleum gas, commonly called natural gas “not manufactured gas” it is consists of the lighter paraffin hydrocarbons, of which the most abundant is methane gas (CH4). - Natural gas is measured by cubic feet, which is small for production of gas, so we used thousand cubic feet. Natural gas - Natural gas is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, with up to 20% concentration of the other hydrocarbons (usually ethane) as well as small amounts of impurities such as carbon dioxide. - Natural gas usually consists mostly of methane (CH4) but may contain variable amounts of higher-order paraffins (ethane, propane and butane). - “Dry gas” is predominantly methane and ethane, while “Wet gas” contains more than 50% propane and butane. Top 5 countries in gas production - They are USA, Russia, Iran, Canada, Qatar. What is Petroleum? - The semisolid and solid forms of petroleum consist of the heavy hydrocarbons “more than 15 Carbon atoms” and bitumen. They are called asphalt, tar, pitch or by any one of many other terms, depending on their individual characteristics and local usage. - The general term “Bitumen” has long been used interchangeably with petroleum for both the liquid and solid forms. - Hydrocarbon is a term often used interchangeably with petroleum for any of its forms. This is not strictly correct, since hydrocarbon consists of only hydrogen and carbon, whereas petroleum contains many impurities. Caustobiolithes “Combustible Rocks” Group - e.g. Oil, Natural gas, Coal, Combustible oil shale and other natural organic rock. - The term consists of three Greek words: Caustic = hot; bios = life and litho = stone. - This term points to the organic origin of these inflammable rocks.

Acaustobiolithes “Non-Combustible Organic Rocks” - Oil shale = kerogen shale is an organic rich fine-grained sedimentary rock containing kerogen (a solid mixture of organic compounds) from which liquid hydrocarbons called shale oil can be produced. What is sapropel? ‫فحم وقاد‬ - Sapropel is jellylike ooze or sludge composed of plant remains, most often algae, putrefying in an anaerobic environment on the shallow bottoms of lakes and seas. - It may be a source material for petroleum and natural gas. - A mud rich in organic matter formed at the bottom of a body of water. - A fluid slime found in swamps as a product of putrefaction. - Sapropel (means in ancient Greek sapros = putrifaction and pelos = mud) is a term used in marine geology to describe dark-colored sediments that are rich in organic matter. - Organic carbon concentrations in sapropels commonly exceed 2% in weight. Chemical properties of petroleum - Ratio between Carbon and Hydrogen is very important. - There is no two identical chemical composition in two types pf crude oils. - The chemical composition of this oil will vary, especially in hydrocarbon type, as well as its physical properties such as color, gravity and viscosity. 1. Elemental composition. Main Elements: Hydrogen/Carbon. Minor Elements: Sulfur, Nitrogen and Oxygen. Trace Elements: e.g. Phosphorus, Vanadium and Nickel. Chemical Composition, Gas: 1-4 carbons, Liquid: 5-15 carbons, Solid: above 15 carbons Element

Crude Oil

Carbon 82-87 Hydrogen 11-14 Sulfur 0.1-5.5 Nitrogen 0.1-1.5 Oxygen 0.1-4.5 Petroleum Fluid Classification

Asphalt 80-85 8-11 2-8 0-2 0-2

Natural Gas 65-80 1-25 Trace-0.2 1-15 -

Kerogen 79 6 5 2 8

Phase

Fluid Type

Gas/Oil ratio

Liquid

Black Oil

0 - 2000

Liquid

Volatile Oil

1700 - 3300

Liquid/Gas

Condensate

3000 - 150000

Gas

Wet Gas

150000

Gas

Dry Gas

No oil produced

2. Molecular size variation - The elements carbon and hydrogen are combined as hydrocarbons that vary both in the size and in type of the molecules. - Hydrocarbons form homologous series, which is a family of molecules whose members have similar properties and differ in size by a CH 2 group.

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Hydrocarbon series The hydrocarbons have been divided into various series, differing in chemical properties and relationships. The four that comprise most of the naturally occurring petroleum are: The Normal paraffin (or alkanes) series. CnH2n+2 They are the second most common constituents of crude oil next to naphthene’s. Paraffins dominate the gasoline fraction of crude oil, and they are the principal hydrocarbons in the oldest, most deeply reservoirs. The Iso-paraffin series (or branched-chain paraffin). The Naphthene (or cycloparaffin) series. CnH2n The most common molecular structures in petroleum. Sour crudes: % of Sulfur is H=high. The Aromatic (or benzene) series. CnH2n-6 Benzene is a colorless and a volatile liquid, is the parent and most common member of the series found in petroleum. While aromatics are present in all petroleum, the percentage is generally small.

The percentage of aromatics is usually small (...