Natural gas Glossary

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Abandoned well
  • A well that is permanently shut down because it was a dry hole or because it has ceased to produce crude oil or natural gas.
Abiogenic theory
  • A theory of petroleum formation in which petroleum is thought to have formed from hydrocarbons trapped inside the earth while the planet was forming.
Acid rain
  • Occurs when sulphur dioxide and nitrogen oxide gases react in the atmosphere with water vapor to form acidic compounds. These compounds can travel hundreds of kilometres before falling to the earth as rain, drizzle, snow or dry particles (this fallout is also known as “acid precipitation” or “acid deposition”).
  • A method of improving porosity and permeability of a reservoir by injecting acid under pressure to dissolve reservoir rock.
Alternative fuels
  • Fuels that can be used in place of fossil fuels, such as ethanol, biodiesel, biogas, hydrogen. In motor transportation, compressed natural gas is an alternative to gasoline.
  • The space between two concentric lengths of pipe or between pipe and the hole in which it is located.
  • Actions taken by staff or a third party to help measure a company’s compliance with legislation and internal requirements, and to identify opportunities for improvement. Audits can involve field inspections, interviews with management and document review.

  • A transaction that results in natural gas being “transported” in the opposite direction of the physical flow of a transportation system. This is usually achieved by redelivering the gas at a point upstream from the point of receipt.
  • A service that provides alternate supplies of natural gas in the event that a consumer's gas is not delivered.
  • Flammable, colourless to light yellow volatile aromatic hydrocarbon. A byproduct of cokemaking and other industrial processes, benzene is considered to be a carcinogenic (cancer-causing) substance.
  • Refers to the variety of ecosystems and animal, bird, fish and plant species.
Biogenic theory
  • A theory of petroleum formation in which the petroleum is thought to have originated from plant and animal matter that has undergone transformation by heat and pressure resulting from deep burial.
Blowout preventer (BOP)
  • Equipment that is installed at the wellhead to control pressures and fluids and to prevent uncontrolled fluid flow from the reservoir during drilling, completion and certain remedial operations to restore production.
  • An individual or independent corporation engaged in bringing together sellers and buyers of natural gas, assisting in negotiations, arranging transportation and delivery terms. Brokers usually do not buy or sell for their own account but act as an agent for the buyer and/or seller.
Bundled service
  • A service provided by a pipeline or a local distribution company which includes the natural gas as well as all the necessary services required for a consistent supply (backstopping, load balancing, storage).
  • The point of end-use consumption of a particular fuel, such as natural gas or residual fuel oil.
Burner-tip price
  • The price of natural gas (or other fuels) paid by the final consumer. For natural gas, this includes the price of the gas plus the cost of processing, gathering, transmitting and distributing it.
  • A component of natural gas consisting of four carbon atoms and 10 hydrogen atoms; condenses into a liquid at relatively low temperature and pressure

Cable-tool drilling
  • One of two principal methods of drilling for crude oil and natural gas. Cable-tool drilling is the older method and consists of raising and dropping a heavy drill bit, suspended from the end of a cable, so that it pounds and pulverizes its way through the subsurface structures. Water in the hole keeps the cuttings in suspension for removal at regular intervals by bailing.
Cap rock
  • Impermeable rocks such as shale, that overlies the reservoir rock and traps natural gas and crude oil in the reservoir. Also, impermeable rock overlying a geothermal reservoir. Also called sealing rock.
  • A group of compounds made up of carbon, hydrogen and oxygen.
Carbon dioxide (CO2)
  • A non-toxic gas produced from decaying materials, respiration of plant and animal life, and combustion of organic matter, including fossil fuels; carbon dioxide is the most common greenhouse gas produced by human activities.
Carbon monoxide
  • Colorless, odorless, poisonous gas produced by incomplete combustion of fossil fuels.
  • A type of pipe that is used to encase smaller diameter production pipe for installation in a well. Casing prevents the wall from caving in and protects against groundwater contamination and uncontrolled hydrocarbon releases.
Casing-head gasoline (naphtha)
  • A highly volatile liquid that is separated from natural gas at the wellhead and was once used as unrefined gasoline.
Centrifugal pump
  • A rotating pump, commonly used for large-volume oil and natural gas pipelines, that takes in fluids near the centre and accelerates them as they move to the outlet on the outer rim.
Christmas tree
  • The valve assembly at the top of tubing strings and casing ina natural gas well (or a free-flowing crude oil well) that provides primary pressure reduction, production rate control and shut-in capabilities.
Climate change
  • Term used to describe the view that the Earth’s temperature and climate will change, in part, due to the buildup of greenhouse gas emissions from human activities.
  • The process of burning natural gas in conjunction with another fuel. Cogeneration: The simultaneous production of electricity and steam from one energy source (e.g., natural gas, oil, biomass).
    Also the practice of burning biomass along with coal in coal-fired boilers
Coalbed methane
  • Natural gas generated during the coalification process and trapped within coal seams, commonly referred to as natural gas from coal
  • Technology that simultaneously produces power and thermal energy (heat and steam) from a single fuel source such as natural gas. An example is using steam generated for injection into reservoirs to also generate electricity.
Commingled gas
  • A homogeneous mix of natural gas from various physical (or contractual) sources.
  • Preparing a newly drilled well for production; usually involves setting casing – pipe that lines the interior of a well to prevent caving and protect against ground water contamination – and perforating the casing to establish communication with the producing formation
Compressed Natural Gas (CNG)
  • Natural gas in its gaseous state that has been compressed to about one per cent of its volume and stored at 20,000 to 27,500 kilopascals.
  • Increasing the pressure of natural gas to move it through pipelines or other facilities
  • A machine used to boost natural gas pressure to move it through pipelines or other facilities.
Compressor station
  • Permanent facilities containing compressors that supply the energy needed to move natural gas at increased pressures.
  • Liquids recovered during the production of natural gas, consisting primarily of pentane and heavier hydrocarbons.
  • End use of energy and energy sources, such as electrical energy, typically measured in kilowatt-hours; or natural gas, typically measured in thousands of cubic feet or millions of British thermal units, or crude oil and petroleum products, usually measured in litres or barrels.
Conventional gas
  • Natural gas that can be produced using recovery techniques normally employed by the oil and gas industry. The distinction between conventional and unconventional gas is becoming less clear. See also unconventional gas.
  • A cylindrical sample of rock cut by a special bit during the drilling process.
Cumulative effects
  • Changes to the environment caused by an activity in combination with other past, present and reasonably foreseeable human activities.
  • Small chips of rock from the formations through which the drill has bored, brought to the surface by the drilling mud.

  • A standard unit of measure of permeability. One darcy describes the permeability of a porous medium through which the passage of one cubic centimetre of fluid having one centipoise of viscosity flowing in one second under a pressure differential of one atmosphere where the porous medium has a cross-sectional area of one square centimetre and a length of one centimetre
  • The amount of natural gas a well, field, gathering, transmission or distribution system can supply in a given period of time.
  • The process of changing natural gas or electricity market regulations to allow a greater role for market forces to balance supply and demand and set prices. It does not mean the absence of regulation.
  • A load-bearing tower-like structure over a natural gas or crude oil well that holds the hoisting and lowering equipment for drilling, testing and reworking wells.
  • A liquid used to dilute bitumen to the point where it will flow. Condensate is the most commonly used diluent in the oilsands industry
Directional drilling
  • Drilling a wellbore at any angle other than vertical; used where the rig cannot be set up directly over the target, or to drill more than one hole from a single location.
Dispute resolution
  • Process to resolve conflicts in mutually beneficial ways, using techniques such as negotiation or third-party mediation instead of public hearings or courts
  • The refining and marketing sector of the petroleum industry.
Drill bit
  • The drilling tool that cuts through rock strata.
  • The operation that involves boring a hole through overlying geological horizons to the target zone(s) to determine if oil or gas is present in commercial quantities, and to convey oil and gas to the surface if found in commercial quantities.
Drilling mud
  • Specialized mud mixed at the drill site and pumped down the drillstring and up the annulus to prevent blowouts, remove cuttings and cool and lubricate the bit.
Dry gas
  • Natural gas from the well that is free of liquid hydrocarbons, or gas that has been treated to remove all liquids; pipeline gas.

Enhanced oil recovery (EOR)
  • Any method that increases oil production by using techniques or materials that are not part of normal pressure maintenance or water flooding operations. For example, natural gas or carbon dioxide can be injected into a reservoir to "enhance" or increase oil production.
Environmental assessments
  • Planning and decision-making tool used by industry and regulators to identify the environmental impacts and costs of proposed energy projects, and potential solutions. Power companies are potentially subject to environmental assessments for new power projects or changes to existing facilities.
Established reserves
  • Generally defined as proved reserves plus one half probable reserves.
  • A component of natural gas consisting of two carbon atoms and six hydrogen atoms, condenses into a liquid at relatively low temperature and pressure
Extraction loss
  • The reduction in volume of natural gas resulting from the removal of the natural gas liquid constituents at the processing plant. See also shrinkage.

Field pressure
  • The pressure of the natural gas as it is found in the underground formations from which it is produced.
  • An object left in the well bore during drilling or workover operations that must be recovered or bypassed before work can proceed.
  • Controlled burning of natural gas that cannot be processed for sale because of technical or economic reasons. The biggest portion is solution gas flaring, which involves the burning of natural gas produced along with crude oil and bitumen. Flaring contributes primarily to emissions of sulphur dioxide and greenhouse gases. Depending on the combustion efficiency of the flare, there may be other compounds produced in very small quantities, some of which are considered to be toxic.
Fossil fuel
  • Fuels sourced from plant and animal matter that have undergone transformation through heat and pressure.
Fracturing (or fracing)
  • A reservoir stimulation technique in which fluids are pumped into a potentially productive formation under high pressure to create or enlarge fractures allowing the oil or gas to flow from the zone at higher rates. In some operations proppants such as frac sand are injected with the frac fluid to help hold the rock fractures open.

  • One of the three states of matter: liquid, solid and gas. Gas is characterized by having neither shape nor specific volume: it expands to fill the entire container in which it is held.
Gas cycling
  • A petroleum recovery process that takes produced gas and condensate and injects it back into the reservoir to increase pressure and increase the production of natural gas liquids. See also repressuring.
Gas processing plant
  • Any facility which performs one or more of the following: removing liquefiable hydrocarbons from wet gas or casinghead gas; removing undesirable gaseous and particulate elements from natural gas; removing water or moisture from the gas stream.
Gas reservoir
  • A porous and permeable rock formation in which natural gas accumulates.
Gas transmission systems
  • Pipelines that carry natural gas at high pressure from producing areas to consuming areas.
  • The process of turning liquefied natural gas into a vapourous or gaseous state by increasing the temperature and decreasing the pressure.
Gathering system
  • A system of small-diameter plastic or steel pipes (gathering lines) transporting natural gas from producing wells to field facilities.
Geological trap
  • Any geological structure that stops the migration of natural gas, crude oil and water through subsurface rocks, causing the hydrocarbons to accumulate into pools in the reservoir rock.
Geophysical survey
  • Searching and mapping the subsurface structure of the earth's crust using geophysical methods to locate probable reservoir structures capable of producing commercial quantities of natural gas and/or crude oil.
Glycol dehydrators
  • Facility in which a glycol-based process removes water from produced natural gas, often in the field and before processing. The removal of water is needed to prevent corrosion and water freezing in pipelines.
Greenhouse effect
  • The warming of the Earth’s surface caused by the presence of carbon dioxide and other gases, known as greenhouse gases, in the atmosphere that trap the heat of the sun.
Greenhouse gases
  • Gases that trap heat near the Earth’s surface. These include carbon dioxide, methane, nitrous oxide and water vapor. These gases occur through natural processes (such as ocean currents, cloud cover, volcanoes) and human activities (such as the burning of fossil fuels).
  • Water accumulations below the earth’s surface that supply freshwater to wells and springs.

Horizontal drilling
  • Drilling horizontally through a reservoir to increase the exposure of the formation to the well.
  • A large class of liquid, solid or gaseous organic compounds, containing only carbon and hydrogen, which are the basis of almost all petroleum products.
Hydrogen sulphide (H2S)
  • A naturally occurring, highly toxic gas with the odour of rotten eggs.

In-line inspection tools
  • Cylinder-shaped devices, fitted with electronic sensors, that locate pipeline wall weaknesses before they can progress to the point of causing a leak
Injection (oil and gas)
  • Injection enhancement technique wherein water or other substances are injected into an oil field to improve production. Also, the reinjectiong of natural gas into an oil field to maintain reservoir pressure.

  • In the petroleum industry, "land" often refers to the oil and gas rights on a particular area of land. For example, in a "land sale," the oil and/or gas rights are "sold" (although in reality the rights are leased).
  • Site designed for disposal of solid or chemical wastes by burial. It may be an open pit or an engineered facility that includes special linings to prevent wastes from leaking into water supplies.
  • A male or female member of the exploration team whose primary duties are managing an oil company’s relations with its landowners and partners, including securing and administering oil and gas leases and other agreements. Other duties include helping to formulate exploration and developmkent strategies. Also known as a land agent or land person.
Lease agreement
  • The negotiated legal document giving an oil and gas company the right to utilize the surface lease site to drill for and produce oil or gas.
Liquefied natural gas (LNG)
  • Supercooled natural gas that is maintained as a liquid at or below -160°C; LNG occupies 1/640th of its original volume and is therefore easier to transport if pipelines cannot be used.
  • Detailed depth-related records of certain significant characteristics of an oil or gas reservoir; obtained by lowering measurement instruments into a well.
Low-impact seismic
  • Refers to site-specific seismic procedures that minimize environmental impacts during exploration.

Manufactured gas
  • A gas obtained by destructive distillation of coal, by the thermal decomposition of oil, or by the reaction of steam passing through a bed of heated coal or coke. Examples are coal gases, coke or oven gases, producer gas, blast furnace gas, blue (water) gas, or carbureted water gas. Also known as syngas.
Maximum efficient rate (MER)
  • The maximum rate at which natural gas and crude oil can be produced without excessive decline of reservoir energy or a loss in ultimate production.
Methane (CH4)
  • Methane consists of one carbon atom and four hydrogen atoms and is the largest component of natural gas. Methane remains in a gaseous state at relatively low temperatures and pressures. Methane is also produced when organic matter decomposes
  • Primarily the processing, storage and transportation sector of the energy industry.
  • The movement of natural gas, crude oil and/or water through porous and permeable rock.
Mineral rights
  • The rights to explore for and produce the resources below the surface. In the petroleum industry, mineral rights can also be referred to as “land.”

National Energy Board (NEB)
  • The federal regulatory agency in Canada that authorizes oil, natural gas, and electricity exports; certifies interprovincial and international pipelines, and designated interprovincial and international power lines; and sets tolls and tariffs for oil and gas pipelines under federal jurisdiction.
Natural gas
  • Gaseous petroleum consisting primarily of methane with lesser amounts of (in order of abundance) ethane, propane, butane and pentane, and heavier hydrocarbons as well as non-energy components such as nitrogen, carbon dioxide, hydrogen sulphide and water
Natural gas liquids (NGLs)
  • Liquids obtained during production of natural gas, comprising ethane, propane, butane and condensate.
Non-associated gas
  • Natural gas that is produced from reservoirs that contain only natural gas and therefore not associated with crude oil production.
Non-renewable resources
  • Natural resources that cannot be replaced after they have been consumed. This term applies particularly to fossil fuels such as coal, oil and natural gas, but also applies to other mineral resources found in the Earth's crust.

  • The company responsible for managing an exploration, development or production operation.
Organic theory
  • The most widely accepted theory explaining the origins of petroleum: as organic materials become deeply buried over time, heat and pressure transform them into hydrocarbons.
Orphan wells
  • Well sites for which the license operators have ceased to exist or cannot be traced.
  • Bedrock which is exposed at the earth’s surface


  • Expanding rubber diaphragms used to seal off portions of the wellbore.
Particulate matter
  • Dust, ash, soot, metals and other solid or liquid particles released into the air. Particulate matter comes from natural sources (such as forest fires and volcanoes) and human sources (such as burning of fossil fuels, dust from mining operations, road dust and wood stoves). Particulate matter can cause eye, nose and throat irritation and other health problems.
Pentane (C5H12)
  • A hydrocarbon compound consisting of five carbon atoms and 12 hydrogen atoms
  • Creating holes in the casing to allow hydrocarbons to flow into the wellbore for production; usually usually accomplished by shooting hardened metal rods powered by explosive charges through the casing using a perforating gun lowered down the well bore.
  • The capacity of a substance (such as rock) to transmit a fluid, such as crude oil, natural gas, or water. The degree of permeability depends on the number, size, and shape of the pores and/or fractures in the rock and their interconnections. It is measured by the time it takes a fluid of standard viscosity to move a given distance. The unit of permeability is the Darcy.
  • A naturally occurring mixture composed predominantly of hydrocarbons in the gaseous or liquid phase.
  • The process by which plants convert carbon dioxide and water into oxygen and carbohydrates.
  • The capacity od a reservoir to store fluids. The ratio of the aggregate volume of pore spaces in rock or soil to its total volume, usually stated as a per cent.
Potential resources
  • The volume of natural gas or crude oil that is thought to exist based on geological knowledge, but has not been proven to exist though geophysical techniques or drilling.
Probable reserves
  • Reserves believed to exist with reasonable certainty based on geological information.
Propane (C3H8)
  • A component of natural gas consisting of three carbon atoms and eight hydrogen atoms, condenses into a liquid at relatively low temperature and pressure
  • Sand, or ceramic or resin beads pumped into a wellbore at the end of the fracturing process to prop open newly induced fractures and enhance permeability.
  • A geographical area that exploration has shown contains sedimentary rocks and structures favorable for the presence of crude oil or natural gas.
Proved reserves
  • Reserves that can be economically produced with a large degree of certainty from known reservoirs using existing technology.
Public consultation
  • The process of involving all affected parties in the design, planning and operation of a seismic program, an oil or gas well, pipeline, processing plant or other facility.
Public interest
  • Usually intended to mean the interest of the public generally as opposed to the interest of an individual or company.

  • An energy quantity of one quadrillion BTUs (1,055 petajoules), which is approximately the energy equivalent contained in one trillion cubic feet of natural gas.

Raw natural gas
  • A mixture containing methane plus all or some of the following: ethane, propane, butane, condensates, nitrogen, carbon dioxide, hydrogen sulphide, helium, hydrogen, water vapour and minor impurities. Raw natural gas is the gas found naturally in the reservoir prior to processing.
Recoverable resources
  • Hydrocarbon reserves that can be produced with current technology including those not economical to produce at present.
Reforumulated gasoline/fuel
  • Fuel whose physical or chemical property specification has been changed.
Renewable energy
  • Naturally occurring energy sources that are continually replenished. Examples of renewable energy are wind, solar and water.
Reserve life index (RLI)
  • The reserve life index measures the length of time current proved or established reserves would last if current production rates were maintained and no new reserves were added. Essentially, it measures the "ready inventory" of crude oil or natural gas. Also known as reserves-to-production (R/P) ratio.
  • Recoverable portion of resources available for use based on current knowledge, technology and economics.
Reservoir (Oil and Gas)
  • A porous and permeable underground rock formation containing a natural accumulation of crude oil or natural gas that is confined by impermeable rock or water barriers, and is separate from other reservoirs.
  • The owner’s share of production or revenues retained by government or freehold mineral rights holders. The royalty is usually based on a percentage of the total production and the rate may vary according to the selling price.

Salt cavern
  • An underground natural gas storage cavern which has been developed in a salt dome by the solution mining process.
Sedimentary basin
  • A geographical area, such as the Western Canada Sedimentary Basin, in which much of the rock is sedimentary (as opposed to igneous or metamorphic) and is therefore likely to contain hydrocarbons.
Seismic method
  • A method of mapping subsurface structures using data derived from transmitting acoustic energy into the earth and recording the energy reflected back from subsurface geological boundaries.
Seismic surveys
  • Running one or more 2-D or 3-D seismic lines over a large area and using the acquired data to create detailed models of underlying geological formations and to find oil and natural gas reservoirs.
  • The reduction in volume of wet natural gas due to the extraction of some of its constituents, such as hydrocarbon products, hydrogen sulphide, carbon dioxide, nitrogen, helium and water vapour.
  • Brown summer haze that intermittently forms over some cities. It is comprised of ground-level ozone (nitrogen oxides, volatile organic compounds and fine particulates). Smog can be created by natural processes (such as forest fires and volcanoes) or human activities (such as the burning of fossil fuels). The name is derived from SMoke and fOG.
Solution gas
  • Natural gas that is disolved in crude oil in underground reservoirs. When the oil comes to the surface, the gas expands and comes out of the oil.
Sour gas
  • Raw natural gas with a relatively high concentration of sulphur compounds, such as hydrogen sulphide. All natural gas containing more than one per cent hydrogen sulphide is considered sour. About 30 per cent of Canada’s natural gas production is sour, most of it found in Alberta and northeastern British Columbia.
Source rock
  • The rocks in which hydrocarbons are created or sourced from carbohydrates through heat and pressure. Source rocks are often black shales.
  • Controlled or accidental release of a substance to land or water (oil, emulsion, produced water or other liquids).
  • People with an interest in industry activities that affect them. They may include nearby landowners, Aboriginal communities, recreational land users, other industries, environmental groups, governments and regulators.
  • Enhancing the production of a well; includes acidizing and fracturing the reservoir as well as removing wax and sand from the wellbore.
Straddle extraction plant
  • A gas processing plant located on or near a gas transmission line that removes natural gas liquids from the gas and returns it to the line.
Sulphur oxides (SOx)
  • Gases produced mostly from human activities (such as metal smelting, and fossil fuel combustion by factories, power plants and motor vehicles). Sulphur dioxide combines with water vapor to form sulphuric acid, a contributor to acid rain. Human exposure to sulphur dioxide emissions can also cause respiratory problems.
Sulphur recovery
  • Sour gas is processed at recovery plants to extract sulphur for sale to fertilizer manufacturers and other industries in Canada and overseas. The average rate of sulphur recovery at Alberta’s sulphur recovery plants has improved from 97.5 per cent in 1980 to 98.8 per cent in 2000.
Surface rights
  • The rights to areas of land used for well pads, batteries, gas plants and service roads
  • Ecosystem condition in which biodiversity, renewability and resource productivity are maintained over time.
Sustainable development
  • Development that meets the needs of the present without compromising the ability of future generations to meet their own needs (as defined by United Nations World Commission on Environment and Development).
Sweet gas
  • Raw natural gas with a relatively low concentration of sulphur compounds, such as hydrogen sulphide.
  • A fuel produced from solid hydrocarbons such as coal and petroleum coke. The process uses steam, air and controlled amounts of oxygen to break the solid down, and the resulting gas consists of vaying amounts of carbon monoxide and hydrogen.

Thermal electricity
  • Electricity generated from burning fossil fuels such as coal, natural gas and refined petroleum products; biomass such as wood, wood waste, pulping liquors and landfill methane; or other waste materials such as used tires.
Tight gas sands
  • Natural gas that is found in sandstone with low permeability.
  • The mechanism by which oil and gas are prevented from migrating out of the reservoir.
Trunk lines
  • Large-diameter pipelines that transport crude oil, natural gas liquids and refined petroleum products to refineries and petrochemical plants; some trunk lines also transport refined products to consuming areas.

Unconventional natural gas
  • In the case of natural gas from coal, natural gas from tight sands and shale gas, conventional gas found in unconventional reservoirs or reservoirs requiring special production methods or technologies; in the case of gas hydrates, conventional methane in an unconventional form occurring in a conventional reservoir
Underbalanced drilling
  • Drilling where the hydrostatic pressure of the fluids in the wellbore is lower then the reservoir pressure; commonly used in tight reservoirs to avoid reservoir damage
Upstream oil and gas industry
  • Refers to companies that explore for, develop and produce petroleum resources (in contrast, downstream refers to the refining and marketing components of the industry).

  • Energy for seismic surveys generated by massive, truck-mounted, vibrating plates.
Volatile organic compounds (VOCs)
  • Gases and vapours, such as benzene, released by petroleum refineries, petrochemical plants, plastics manufacturing and the distribution and use of gasoline; VOCs include carcinogens and chemicals that react with sunlight and nitrogen oxides to form ground-level ozone, a component of smog.

  • The assembly of fittings and valve equipment used for producing a well and maintaining surface control of a well.
Western Canada Sedimentary Basin
  • Canada’s largest region of sedimentary rocks; the largest source of current oil and gas production, covering all of Alberta and parts of Manitoba, Saskatchewan, British Columbia, and the Yukon.
Wet gas
  • Raw natural gas with a relatively high concentration of natural gas liquids (ethane, propane, butane, and condensates).
Wildcat well
  • A well drilled in a previously unexplored area.
Wire line logs
  • Charts derived from devices lowered into the wellbore on a cable or wire line that measure permeability, porosity and electrical properties of reservoir fluids.