1. Acoustic
/ Relating to sound waves (synonymous with Sonic)
  1. Acquisition
/ Usually, in geophysics, the shooting of seismic data
  1. Alkanes
/ Naturally-occurring paraffin fractions in which the molecules are based on a "straight chain" of hydrogen - saturated carbon atoms.
  1. Alumino-silicates
/ Minerals consisting mainly of Aluminium, Oxygen and Silicon
  1. Amplitude anomaly
/ Anomalous seismic amplitudes which may be indicators of hydrocarbonor depositional geological features.
  1. Anhydrite
/ An evaporite mineral, CaSO4, found in sedimentary rocks; associated with gypsum.
  1. Appraisal
/ Activity, such as a well drilled to confirm the size or quality of a hydrocarbon discovery. Before development, a discovery is likely to need at least two or three such wells
  1. Architectural element
/ a genetic unit in fluvial sediments.
  1. Basin
/ 1.A syn-depositional depression in the earth's surface, typically, of a large size and
filled with sedimentary rocks.
2.Bowl-shaped synform in which layering dips inward towards a central point.
  1. Biogenic
/ A term applied to material produced by the action of living organisms
  1. Biomarker
/ Geochemical molecules, extracted from source rocks or oils that can be used as an indicator of the type of source organic matter (e.g., plant or animal) and as a tracer for oil-to- source rock correlations.
  1. Bitumen
/ A form of heavy, solid petroleum
  1. Borehole
/ A well, especially referring to the face of the rock outside or below the casing. Test boreholes are also sunk to examine the suitability of a site formajor foundation work, and to examine geological formations at points where no hydrocarbons are expected.
  1. Carbon Cycle
/ The cycle of carbon on the planet: Fixed in living organisms, burial of carbon in organic matter, cooking and release into hydrocarbons, discov ery through exploration, petroleum resource exploitation and release into the atmosphere before being fixed again in living organisms.
  1. Cavings
/ Large cuttings usually a sign of borehole instability
  1. Commercial well
/ A well capable of producing profitably
  1. Connate water
/ The original water content of a reservoir rock. Connate water reduces the pore-space (porosity) available to hydrocarbons. Sometimes called
Interstitial Water.
  1. Crude oil
/ An unrefined mixture of naturally-occurring hydrocarbons. Because it is essentially a mixture, the density and properties of Crude Oil vary widely. Light Crude normally has an A.P.I, gravity of 30° or more. Gravities of 20° to 30° include the medium gravity Crudes, while those below 20° are known as Heavy. Heavy Oils are found right down to the residual solid state. Sour crude has a significant sulphur content, low-sulphur crude is described as Sweet.
  1. Crystal
/ A three-dimensional material (usually natural), the bounding surfaces of which are arranged symmetrically and, for a given substance, with constant angular relationships, arising from the inherent regular atomic structure of the substance.
  1. Dead oil
/ Oil containing no natural gas
  1. Depth map
/ A relief map of a sub-surface geological structure where the contours relate to depths from the surface datum level, (i.e. sea level). This is a further interpretation of a seismic time map.
  1. DHI
/ Direct hydrocarbon indicators are seismic anomalies that may indicate the presence of hydrocarbons. Amplitude anomalies are often flat ("flat spots") or bright ("bright spots") and associated with gas. "Gas chimneys" are sometimes observed above oil fields and are expressed as a series of anomalies in a plume over the field attributed to gas leakage.
  1. Dilation
/ Increase in volume
  1. Dry gas
/ Natural gas, methane and ethane, without any significant content of heavierhydrocarbon fractions.
  1. Dry hole
/ A well in which no hydrocarbon is found.
  1. Erosion
/ That part of the process of denudation which involves the wearing away of the land surface by the mechanical action of transported debris. The agents of transportation are by themselves only capable of minute wearing action upon the rocks, but when they contain particles of weathered material they become powerful agents of destruction
  1. Evaporite
/ A deposit resulting from the evaporation of saline water
  1. Exploitation well
/ A development well e.g. an oil or gas producer, or gas or water injector to support production.
  1. Fat oil/Lean oil
/ Saturated or under-saturated oil. "Fat" Oil could, for example, be saturated with gasolines absorbed from a gas stream in a refinery. The oil is "lean" when the gasolines have been distilled out again, and the oil recycled to the process
  1. Fault
/ A fracture in rock along which there has been an observable amount of displacement. Faults are rarely single planar units; normally they occur as parallel to sub-parallel sets of planes along which movement has taken place to a greater or lesser extent. Such sets are called fault or fracture-zones.
  1. Fish/fishing
/ Any unwanted object down a well, commonly the lower end of a drill string which has broken off. "Fishing" is trying to recover the Fish, using various attachments to the drill stem or wireline, known as fishing tools.
  1. Gas Condensate
/ Light hydrocarbon fractions entrained in gas production which condense into liquid when brought to the surface. Changes in reservoir pressures as result of production may cause it to condense in the reservoir, when much of it may become irrecoverable.
  1. Gas oil
/ A middle distillate product fraction
  1. Gas/oil ratio (GOR)
/ The proportional amount of gas to oil liquid occurring in production from a reservoir, usually expressed as cubic feet per barrel.
  1. Geochemical Analysis
/ 1.Analysis of the hydrocarbon-bearing potential of an area by studying shallowcores and subsurface water for evidence of seepage or kerogens.
2.Analysis of cuttings for source rocks (e.g. Headspace gas and vitrinitereflectance)
  1. Geological modelling
/ Computer modelling of the subsurface geology, usually for input into the Reservoir simulator
  1. Geophones
/ Sound wave receivers employing a moving coil, used primarily for onshore seismic surveys. Geophones can also be clamped in wells.
  1. Heat flow
/ The rate of heat crossing a horizontal plane. Generally produced the inner zones of the Earth, but also by radiation processes in the crust. The average value is 65 mW/m2 per second, but higher values have been recorded in certain localities (especially in some areas of the ocean basins), which it is suggested may be due to uprising convection currents in the mantle.
  1. Heavy mineral, Heavy mineral separation
/ By use of a heavy liquid a mixture of mineral grains of different densities may be separated into two fractions: those which sink, the 'heavy minerals', and those which float, the 'light minerals'. Usually refers to minerals whose density is greater than 3.0gm/cc.
  1. Horizontal drilling
/ A technique for deviating wells through up to 90° from the vertical. While the main purpose of normal deviated drilling is to "reach" remote parts of a reservoir, with horizontal drilling the purpose is to keep the well bore within a given productive horizon or formation, to increase potential productivity
  1. Hydrocarbon minerals
/ A term usually taken to mean the naturally occurring solid varieties of carbon-hydrogen (sometimes also with oxygen) compounds, i.e. the natural 'organic' minerals. Two groups may be recognised - coal, and the bitumens, waxes and resins
  1. Hydrodynamic
/ Active movement of water in the earth's crust
  1. Improved Oil Recovery (IOR)
/ Any mechanism (e.g. Infill drilling, Horizontal drilling) that improves oil recovery.
  1. Inert gas
/ Chemically unreactive gases used to flood compartments where there is fire or imminent danger of fire. Inert gases are also used in the mixture breathed by divers.
  1. Inhibited mud
/ Mud containing chemicals to prevent loss of water which could damage surrounding formations, and cause build up of filter-cake in the well
  1. Interpretation
/ Picking the seismic lines, identifying key horizons and faults, generating maps. Generally refers to a process of synthesising a conceptual model.
  1. Isotopes
/ Chemical elements of same composition but different atomic weight. Isopoes differ by unit numbers of neutrons or protons.
  1. Jack-up
/ Drilling rigs, production barges, etc. which once floated onto location can raise themselves clear of the water by 'jacking' themselves up their legs. They then offer the operating advantages of fixed platforms but unlike piled steel structures, their stability and load capacity depends on the strength and stability of the sea bed, and closely underlying strata.
  1. Kerogen
/ A solid organic material (lipid rich) which yields petroleum-type hydrocarbons on heating and distillation. Kerogen has labile and refractory active proportions - the former sources oil, the latter gas.
  1. Log/logging
/ 1.Written chronological records such as shift logs, maintenance logs, tour sheets,and mud logs which also record the cuttings recovered from a well.Various devices (tools) for taking measurements of formations, physical conditions,and fluids encountered by a well, together with the records produced by them. Themain types of well logs are Electrical, Magnetic, Mechanical, Sonic, Nuclear, Image-
collectively known as Wireline logs. (Tools and Logs are usually recognized byinitials e.g. CNT and CNL - compensated neutron tool and log).
  1. Magnetic field
/ The Earth has a magnetic field, the poles of which are close to the North and South Poles. The magnetic field has reversed during the geological past, although the mechanism for this is not well understood.
  1. Magnetic survey
/ A preliminary exploration technique based on the relatively low-intensity magnetic fields associated with sedimentary rocks.
  1. Natural depletion
/ Producing a reservoir by means of its natural pressure - without pressure maintenance.
  1. Oil spill
/ Any accidental emission of liquid hydrocarbons, from general shipping, oil tankers, or operations onshore or offshore.
  1. Petroleum play
/ A perception or model of how a specific region of the Earth's sub surface may be an appropriate target for exploration drilling. Requires knowledge of source rock, maturity, timing, reservoir, migration, trap, seal. The play chance is the probability of a successful exploration well.
  1. Polarity
/ Positive (black) or negative (white) parts of a wave - used in the presentation of seismic sections, hence, reverse polarity.
  1. Pressure solution
/ Deformation mechanism that involves dissolution at grainboundaries under stress of soluble constituents such as calcite or quartz. Generally active at low to moderate temperature in the presence of water
  1. Production Logging Tool (PLT)
/ A combination of temperature log and spinner to locate the entry point of fluids into the bore hole.
  1. Production testing
/ Aproduction test concerns the capability to produce (productivity) of a well and its effects on the reservoir produced. A production test may continue for several months where extensive data is necessary prior to final commitment to development expenditures etc.
  1. Productivity/productivity index (PI)
/ The continuous productive capacity of awell. The Index is measured as volume produced (e.g. barrels per day) divided by the drop in pressure to achieve that flow rate starting with a "shut in" pressure.
  1. Profiling
/ Shallow seismic surveying by echosounder techniques
  1. Proprietary data
/ Primarily data obtained from the owner of a seismic survey record under confidentiality undertaking. It can also include all confidential information acquired as part of sole or joining operations
  1. Provenance
/ The source area or areas of the material making up a sediment, more especially the nature of the rocks from which the material has been derived. PST: Production Sample Taker - for accurate identification of fluids produced by a given zone in the well.
  1. PVT
/ Pressure/Volume/Temperature data usually related to a test of a reservoir formation or well.
  1. P-waves
/ Compressional, longitudinal pressure or primary waves
  1. Pyrolysis
/ Burning of rock in the lab to determine the oil yield of a rock as in the Rock Eval wellsite technique
  1. Quartz
/ a silicon mineral (Si 02) that makes up most of sand (see Sandstone, silicates)
  1. Radioactive decay
/ The natural decay of nucleides by the emission of atomic particles (e.g., Rubidium to Strontium). Used for Radiometric dating.
  1. Radiometric dating
/ Method for determining the absolute age of rocks (see Rub idium-Strontium) by the radioactive decay of nucleides.
  1. Radiocarbon dating
/ Age dating by the measurement of the decay of carbon isotopes (a form of Radiometric dating).
  1. Raw gas
/ Natural gas before removal of water, sand and other impurities
  1. Recrystallisation
/ The process whereby amass of crystals passes through a solution phase in developing a new set of crystals of the same kind
  1. Red beds
/ A term applied to an assemblage of sedimentary rocks formed in a highly oxidising environment, so that the iron present is in the form of red ferric hydroxide. The term has acquired a meaning almost synonymous with arid continental sediments, since most red beds were probably formed in such an environment. The meaning has also been extended not only to the typical red sandstones, red shales and red marls, but also to include associated evaporites, breccias, and cornstones (concretionary limestones).
  1. Remigration
/ Oil migrating out of a trap, due to breaching or tilting
  1. Reserves
/ Reserves are estimated volumes of crude oil, condensate natural gas, natural as liquids, and associated marketable substances anticipated to be commercially recoverable and marketable from a given date forward under existing ec onomic conditions, by establi shed operating practices, and under current go vernment regulations.
  1. PROVED RESERVES
/ Proved reserves are attributed to known reservoirs and are the least uncertain category. Proved reserves have only a 10% chance of not being met
  1. UNPROVED RESERVES
/ Unproved reserves may be subdivided into two classifications: (1) Probable and (2) Possible
1.Probable Reserves: Probable reserves are attributed to known accumulations andare based on geologic and/or engineering data similar to those used in estimates of
proved reserves; but technical, contractual, or regulatory considerations preclude suchvolumes from being classified as proved. Probable reserves are more uncertain than
proved reserves with a 50% chance of being met (P50).
2.Possible Reserves: Possiblereservesareassociatedwithknownaccumulationsand
are based on geologic and/or engineering data that are less complete andless conclusivethan the data used in estimates of probable reserves. In some cases, contractual orregulatory uncertainties may dictate the possible classification. Possible reserveshave a 90% chance of not being met (P90) or only a 10% chance of being present.
  1. Reservoir
/ A porous, fractured or cavitied rock formation with a geological seal forming a trap for producible hydrocarbons
  1. Residual oil
/ The dense, viscous "Heavy Ends" of the barrel, remaining after extraction of higher-value fractions
  1. Rig
/ A collective term to describe the permanent equipment needed for drilling a well. It has come to include the onshore and offshore vehicles, mobile platforms or vessels on which the equipment is installed
  1. Rock-forming minerals
/ Those minerals which occur in sufficient abundance and frequency as to constitute the major bulk of a rock. The main rock-forming minerals are the silicates (including silica), carbonates, and oxides, with sulphates, chlorides and phosphates in lesser proportions.
  1. Sedimentary rocks
/ An area which in a past geological era has been depressed, acquiring deposits of sedimentary rocks such as sandstones, siltstones or limestones. They are formed from detritus or erosion etc. of exposed formations and deposited in land or seabed depressions, or as e.g. wind-formed desert dunes.
  1. Seismic Method
/ Acquisition, Processing, Interpretation and Visualization
  1. Seismic reflection
/ Acoustic (sound) waves, generated by explosives or a mechanical vibrating truck (vibroseis), transmitted through the Earth, reflected where velocity changes, and recorded by an array of geophones.
  1. Tectonics
/ 1.The process of formation and evolution of the earth's solid surface crust. "Plate
Tectonics" relates to the formation and movement of the 'plates' of which the crust
is composed.
2.Study of large crustal ormantle features, such as mountain ranges, parts of continents,
trenches and island arcs, oceanic ridges, mantle plumes and entire continents and
ocean basins, and the relationships to stresses and tectonic plates.
  1. Thermal recovery
/ Enhanced Oil Recovery based on heating the oil in the reservoir by steam injection or subsurface combustion.
  1. Thief zone
/ A porous, fractured or vuggy formation in a well, into which drilling fluid escapes. It must be plugged or lined with casing.
  1. Transition zone
/ 1.Part of the Mantle
2.Nearshore between land and marine - for seismic acquisition
3.Above the OWC, the region where mobile water is present
  1. Trap
/ A structure in which oil and/or gas may collect
  1. Wash out
/ 1.Water leaks into the drilling mud downhole.
2.Mud short circulates through a hole in the drillstring.
3. Enlargement of the borehole to cavings