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Glossary

Accumulation: The concentration of hydrocarbons in a trap or in a geological unit bounded by stratigraphic or structural rock boundaries.

ABEX: (Abandonment Expenditures): These are the expenses related to abandonment work

AFREC (African Energy Commission): A specialized agency of the African Union (AU), under the Department of Infrastructure and Energy, and responsible for the coordination, harmonization, protection, conservation, development, rational exploitation, marketing and integration of energy resources on the African continent

APPO (Organization of African Petroleum Producers): An African institution whose mission is to promote hydrocarbon cooperation among its member countries and other global institutions in order to foster fruitful collaboration and partnerships while using oil as a catalyst for energy security, sustainable development and economic diversification in Africa.

AVO (Amplitude Variation with Offset): Variation in the amplitude of seismic reflection as a function of the distance between the firing point and the receiver that indicates differences in lithology and fluid content in the rocks above and below the reflector. AVO analysis is a technique that allows geophysicists to determine the thickness, porosity, density, velocity, lithology, and fluid content of rocks.

Sedimentary basin: A depression within which sediment is deposited. It is a segment of the Earth’s crust that has undergone downward deformation, usually for a considerable period of time, but with intermittent elevations (hosts) and subsidence (grabens). The thickness of the sediment in these basins increases towards the centre of the basin.

Barrel: A standard unit of measurement used in the petroleum industry to quantify the volume of crude oil or crude oil products. One barrel is equivalent to 42 U.S. gallons, or about 159 liters. It is therefore a volumetric measurement, which is different from units of weight such as the ton. The barrel is mainly used to measure the production and marketing of oil on international markets.

Bitumen: Heavy oil residues used for road surfaces and roof waterproofing

Block: Geographical area delimited by a State and intended to be the subject of rights to prospect, explore, or even exploit hydrocarbon resources

Bright Spot (or Dim Spot): A seismic amplitude anomaly characterized by bright spots (or weak spots) of amplitude resulting from variations in lithology and pore fluids, sometimes observed in groups of superimposed reservoirs. It is a high-amplitude reflection on a seismic profile caused by the acoustic impedance contrast between rock layers and can indicate the presence of hydrocarbons. Bright spots result from large variations in acoustic impedance that occur when a gaseous sand lies under a shale, but can also be caused by phenomena other than the presence of hydrocarbons, such as a change in lithology.

Brent: A type of crude oil used as a standard or benchmark in the pricing of crude oil from Europe, Africa and the Middle East

CAPEX (Capital Expenditures): These are the capital expenditures represented by the funds used by an oil company to carry out exploration and development work.

Catalyst: A substance that increases the rate of a chemical reaction; it participates in the reaction but is not part of the products or reactants and therefore does not appear in the balance equation of this reaction.

ECOWAS (Economic Community of West African States): An intergovernmental body for West Africa whose purpose is to promote cooperation and integration with a view to achieving an economic union for West Africa, with a view to raising the standard of living of its peoples, maintaining and increasing economic stability, strengthening relations among member states and contributing to the progress and development of the African continent.

Oil field: An oil zone of variable extent giving rise to the production of natural hydrocarbons, constituting a single geological, structural, stratigraphic entity. It can be assimilated to a single deposit or to several distinct deposits, either in the vertical or in the horizontal direction, or in both at the same time, in the same geological and structural whole.

Gas Chimneys: A leak of underground gas from a poorly sealed accumulation of hydrocarbons, visible in seismic data as areas of poor quality because it causes a low rate of propagation in the overlying rocks. It is also a DHI.

Oil shock: A sudden and significant increase in the price of crude oil on the international market, often caused by a geopolitical crisis, a war, a strategic decision by producing countries, or a natural event disrupting supply while demand remains very high.

Condensate: Heavy components of natural gas accumulations from natural liquefaction when natural gas arrives at the surface. Otherwise, condensate is a condensation product sometimes known as distillate.

Conversion: Physico-chemical refining processes that include:

  • cracking that makes it possible to break the large molecules of the heavy fractions resulting from distillation (separation) into smaller molecules with higher added value, or

  • catalytic reforming that converts naphtha into high-quality gasoline and also produces hydrogen or

  • hydroconversion , which consists of converting refining residues by the addition of hydrogen into more usable products

  • coking by removing carbon from residues to obtain coke for use as fuel

DHI (Direct Hydrocarbons Indicator = Direct Hydrocarbons Indicator): A type of seismic amplitude anomaly or event that can occur in a reservoir containing hydrocarbons. These amplitude anomalies include Bright Spot or Dim Spot, Flat Spot, Gas Chimneys, etc. typically seen during AVO scans.

\mathbf{Densité\ API =}\frac{\mathbf{141,5}}{\mathbf{Densité\ à\ 15{^\circ}C}}\mathbf{- 131,5}

API density: A scale adopted by the American Petroleum Institute (API) that evaluates whether oil is light or heavy in relation to water. It is calculated by the formula:

  • Light oil (API > 30°) Light oil is highly prized on the world market because of its low viscosity and its ability to produce high-value-added refined products such as gasoline, kerosene and diesel. For example, West Texas Intermediate (WTI), mined in the United States, is a light crude widely used as a global benchmark. Similarly, Brent Crude, from the North Sea oil fields, is another emblematic example.

  • Medium oil (API between 20° and 30°) This type of oil is between light and heavy. Although it is less fluid than light oil, it is still relatively easy to refine. Examples include some crudes produced in the Middle East, such as Arabian Medium.

  • Heavy oil (API between 10° and 20°) More viscous and dense, heavy oil requires complex processes to be refined. For example, Venezuelan heavy oil, from the Orinoco Basin, is known for its technical challenges related to its transport and processing.

  • Extra-heavy oil (API < 10°) This type of crude oil is almost solid at room temperature and often contains bitumen. The tar sands of Alberta, Canada, are a major source of extra-heavy oil.

Well logs: Records obtained by lowering instruments into wells and continuously recording some physical properties of rocks.

Distillation: see Separation

Well Testing: Well testing performed with the drill string still in the hole, commonly known as Drill Stem Testing (DST). These tests are generally carried out using a closed down-the-hole tool allowing the opening and closing of the well at the bottom of the hole thanks to a valve operated on the surface. One or more pressure gauges are usually mounted on the DST tool and are read and interpreted after the test is complete. The tool includes a surface-actuated packer that isolates the formation of the annular space between the drill string and the casing, thus forcing the produced fluids to penetrate only the drill string. Closing the bottom of the well minimizes backflow and simplifies analysis, especially for low-flow formations. The drill string is sometimes filled with an inert gas, usually nitrogen, for these tests. In formations with low permeability, or when production consists primarily of water and the formation pressure is too low to bring water to the surface, surface production may never be observed. In this case, the volume of fluids introduced into the drill string is calculated and an analysis can be performed without obtaining surface production. Operators may want to avoid surface production for safety or environmental reasons and only produce the amount contained in the drill string. To do this, the surface valve is closed when the bottom valve is opened. These tests are called closed chamber tests.

Drill string testing is typically performed on exploration wells and is often essential to determine if a well has discovered a commercial hydrocarbon reservoir. The formation is often untubed prior to these trials, and the contents of the tank are often unknown at this stage. Fluid sampling is therefore usually a major concern. The most common test sequence consists of a short flow period of about five to ten minutes, followed by a pressure build-up period of about one hour, to determine the initial pressure of the tank. This is followed by a flow period of 4 to 24 hours to establish a stable flow to the surface, if possible, and finally a final shut-off or pressure rise test, to determine the thickness of the permeability and the potential for flow.

Recovery factor: See Reclaimability: The rate or proportion of crude oil or natural gas that can be extracted from the reservoir at the time of production to the surface relative to the amount originally in place and trapped in the reservoir.

R-Factor: A ratio determined by the ratio of revenues to costs and which is used as a trigger for the sharing of oil profit (profits) and in some cases for the determination of royalty rates

Flat Spot: A seismic amplitude anomaly that characterizes the contact between formation fluids (gas-oil, water-oil or gas-water), which can also indicate the dip of the reservoir in some cases.

Dissolved associated gas: Gas in contact with crude oil, either as a free gas layer or in solution with oil. It is the natural gas present in a reservoir in solution with crude oil, including the “gas cap”, which covers and is in contact with the crude oil.)

“Pipeline grade” gas: Marketed natural gas delivered to pipelines, typically in the range of 900 to 1,200 BTUs per 1,000 cubic feet and its general composition is as follows: Methane (CH4): 72.3%, Ethane (C2H6): 14.4%, Carbon dioxide (CO2): 0.5%, Nitrogen (N2): 12.8%

Natural gas: Hydrocarbons in a gaseous state under normal atmospheric conditions, including wet gases, dry gases, and residual gases produced singly or in combination after crude oil extraction.

Non-Associated Gas: Free gas that is not in contact with the crude oil in the tank.

Dry Gas: Gas composed almost entirely of methane

Gas pipeline: Pipelines that collect gas from a gas field and carry it to a remote location for use.

Field: see Oil Field

Commercial Deposit: An economically profitable field that can be developed and produced in accordance with the rules accepted in the international oil industry.

Generation: See Maturation

GIIP (Gas Initially In Place): The total volume of gas initially in place in the tank under standard surface conditions. It is divided into free gas and associated gas (dissolved in oil).

LNG = Liquefied Natural Gas: Natural gas condensed in a liquid state mainly methane. Natural gas is liquefied to facilitate its transportation when a pipeline is not possible. Less easily liquefiable than LPG, LNG must be subjected to low temperature and high pressure, or to an extremely low temperature (cryogenic) and close to atmospheric pressure to liquefy.

LPG (Liquefied Petroleum Gas ): A mixture of heavier paraffinic gaseous hydrocarbons, mainly butane and propane. These gases, which are easily liquefiable at moderate pressure, can be transported in liquid form and transformed into a gas once the pressure is released. Thus, liquefied petroleum gas (LPG) is a source of thermal energy as a fuel for internal combustion engines and has many industrial and domestic applications. Its main sources are natural gas and refinery gas, from which LPGs are separated by fractionation.

Gravimetric (surveying): Measuring changes in the Earth’s gravitational field using an instrument called a gravimeter, to understand variations in underground density and geological structures. It is therefore a geophysical method used in mining and oil exploration, groundwater assessment, geological mapping, etc.

Jet A1: Standard Aviation Fuel or Kerosene

Lead: A trap that may contain an accumulation of oil, but has not been mapped with a reasonable degree of certainty or whose contour is not precisely delineated.

NGL (NGL=Natural Gas Liquid): Hydrocarbons liquefied on the surface in field facilities or gas processing plants. Natural gas liquids include propane, octane and natural gasoline.

Magnetometry: An exploration method in which an instrument called a magnetometer measures the strength of natural magnetic forces in the Earth’s subsurface on land or at sea to detect changes in magnetic forces, which may indicate the existence of underground formations suitable for oil trapping.

Maturation: The process of generating hydrocarbons from source rocks under the effect of heat

Maturity: The thermal level required by a source rock to generate the hydrocarbon components normally found in oil.

Migration: The process by which hydrocarbons move from source rocks to reservoirs through openings in the rock. Migration falls into three categories:

  • Primary migration: movement of organic matter within the source rock to its boundary, where oil and gas leave the parent rock;

  • Secondary migration: movement from the bedrock boundary to the reservoir/trap, through permeable rocks (load-bearing beds), faults or fractures. For migration to be effective, the permeable pathways must be adequate and the trap must be present at the time of oil and gas migration (time).

  • Tertiary migration: migration of oil and gas from one trap to another or loss.

Naphtha: A fraction of straight-run gasoline used as a feedstock in conversion refining processes and also in the petrochemical industry, having a boiling point lower than that of kerosene

Pipeline: Pipeline carrying oil (“oléo” comes from the Latin oleum, meaning “oil”) and which allows the massive transport of oil. In practice, it can be crude oil or liquid fuel such as gasoline, diesel etc.)

OPEX (Operating Expenditures): These are the operating expenses that are the operating costs incurred by an oil company during the production phase and necessary to maintain the day-to-day operations and activities related to oil production

NATO: The North Atlantic Treaty Organization (NATO), or Atlantic Alliance, is a diplomatic and politico-military institution founded in 1949 by the Washington Treaty for the mutual defense and security of its 32 member countries, mainly in Europe and North America. It has expanded over time to Eastern Europe and is no longer considered a North Atlantic association.

Permeability: The ability of a porous rock to leak or transmit fluids when pores are interconnected

Crude oil: Crude mineral oil, asphalt, ozokerite, oil shale and all other liquid hydrocarbons in their natural state or obtained from natural gas by condensation or extraction, including condensates and natural gas liquids

Petrochemicals: A science that deals with the use of basic chemical compounds derived from petroleum to make other synthetic compounds that may or may not exist in nature; in the latter case, these compounds are said to be artificial. These manufactures are, in general, based on appropriate chemical reactions in the presence or absence of a catalyst.

Trap: A barrier or obstacle to migration that allows oil and gas to accumulate in a reservoir. These obstacles are usually impermeable rocks (cover rocks) located above, below and/or lateral to the reservoir rock. A trap must be of adequate size and seal. The filling of the trap corresponds to the volume of trapped hydrocarbons. The traps are of three categories:

  • Structural traps that result from folding, faulting, or other rock deformations. The most common trap is an anticline or faulted anticline.

  • Stratigraphic traps that result from lithological (facies) modifications, sometimes called “porosity and permeability pinching”.

  • Mixed traps that have both structural and stratigraphic aspects are called “combined traps”.

Play: A geographically delimited area or domain where several geological factors (presence of bedrock, reservoir rock and cover rock) are present, making it possible to prove the existence of oil. Play is said to be confirmed when oil is found there; the discovery is not necessarily profitable. If no finds have yet been found in an area, it is said to be unconfirmed.

Petroleum products: derivatives of the distillation of crude oil by refining or any other chemical transformation process in a liquid, solid or gaseous state including, but not limited to, all products such as: automotive fuels (petrol, diesel) and aviation fuels (Jet A1), LPG (commercial butane), kerosene, fuel oil, bitumen, lubricants, etc.

Preservation: Protection of trapped hydrocarbons from leaching, overcooking or biodegradation.

  • Leaching is washing of hydrocarbons with water.

  • Overcooking is the over-ripening of less desirable products.

  • Biodegradation is the decomposition by microorganisms.

Exploratory well: A hole drilled for hydrocarbons in a geological structure. It may also be referred to as a Wildcat well but sometimes includes the Evaluation wells.

Appraisal well: A hole drilled to delineate a new discovery**.** Also known as an appraisal well, it is used to determine the extent, limits, reserves and probable returns of a newly discovered hydrocarbon deposit.

Production well: A hole drilled to exploit a deposit. It is also called a development well

Dry well: Unproductive well

Porosity: Percentage of small free spaces in the overall volume of a rock;

Prospect: A trap that may contain an accumulation of oil, and is mapped in three dimensions.

Oil-producing province: A collection of sedimentary basins or geological structures that have the conditions necessary for the formation and accumulation of oil

Refining: any separation, conversion process that results in the transformation of crude oil into petroleum products including their chemical processing, storage and delivery to the appropriate point;

Retrievability: The ability to bring underground oil and gas to the surface. The factors that must be adequate are the permeability of the reservoir, the low viscosity (resistance to flow) of the oil, and the motive force of the reservoir (the driving force required for the production of hydrocarbons).

Reserves: Initially recoverable resources that licensees have decided to develop and for which the authorities have approved a development and operating plan. Reserves express the commercial and profitable nature of a discovered hydrocarbon deposit

Resources: New sources and potentially available reserves of hydrocarbons, including discovered and undiscovered sources.

Contingent Resources (Contingent Resources): Oil discovered that is potentially recoverable but is currently unmarketable.

Source rock: Sedimentary rock (usually deep buried shale/clay or limestone) whose organic matter has been naturally transformed into oil and/or gas by heat over time and burial. This transformation is called generation or maturation.

Cover rock: Clay or other impermeable rock acting as a barrier to the passage of oil migrating into the subsoil that covers the reservoir rock to form a trap.

Overburden rock: Sedimentary rock that overcoats, compresses and consolidates the source rock and contributes to its thermal maturation thanks to higher temperatures at great depths. It is an essential part of the petroleum system

Reservoir rock: A rock unit containing or potentially containing oil or gas that can be recovered from its small open spaces called pores. The reservoir rock must have adequate thickness, porosity and permeability.

Separation: The first basic step in the refining process or refining process, which consists of distillation, i.e. heating crude oil in a steel tower (fractionation column) in order to separate it into different components according to their volatility.

Seismic (acquisition): An exploration method by which strong, low-frequency sound waves are generated on land or in water to detect underground rock structures that may contain hydrocarbons. It provides information on the nature and succession of the rocks crossed as well as their fluid content. Seismic acquisition can be done in 2D (2 dimensions) or 3D (3 dimensions). 2D seismic acquisition provides less precise information than 3D, particularly with regard to the mapping of a hydrocarbon trap. There is also 4D seismic.

STOOIP (Stock Tank Oil Originally In Place): Total volume of oil originally in place in a tank under standard surface conditions

Chemical treatment: A refining process that consists of the removal of impurities by hydrotreating for light fractions or by hydrodesulphurization for heavy fractions

Flaring: The practice of the petroleum industry in which excess natural gas, usually methane, is burned in a controlled manner and cannot be stored or upgraded on-site. This produces a visible flame that escapes from a tall chimney called a flare.

VSP (Vertical Seismic Profil): This is a method of seismic logging carried out inside a single borehole. Instead of using surface sources and receivers as in conventional seismic surveys, VSPs use a seismic source positioned at the surface while the receivers are deployed downhole inside the well. This vertical configuration allows for a more accurate and detailed image of the subsurface directly below the borehole.

VSPs are used in a variety of geological applications, including:

  • Reservoir Characterization: Evaluate reservoir properties and fluid distribution

  • Seismic Interpretation: Improving Seismic Imagery and Understanding Subsurface Structure

  • Fracture detection: Identify natural fractures in the reservoir

  • Borehole integrity: Assess the stability and integrity of the wellbore

  • Geotechnical Applications: Studying the Earth’s Structure for Engineering Projects

AfCFTA (African Continental Free Trade Area): an African Union project that aims to establish a continental market with the aim of boosting intra-African trade.