Oilfield Glossary of Terms
The complexities of the oil and gas industry can make keeping up with all the terms and definitions related to drilling difficult. To simplify things, we’ve compiled a glossary of the most important terms related to drilling and to the oil and gas industry.
To pause or stop drilling operations or production from a well. Reasons for abandoning are if a well is a dry hole or if it’s not producing enough to be kept active.
This process allows a bidder to participate in an auction without being present. An absentee bidder will usually submit their offer before the auction and they need to follow the guidelines set in place by the auctioneer.
Also known as an auction without reserve, absolute auctions don’t have any limiting conditions or amounts. The property under auction will be sold to the highest qualified bidder.
Abstract of Title:
The historical ownership records for a property. These records include surface rights and mineral rights among other details.
When a person or institution is considered capable of understanding and affording the financial risks of unregistered securities, they are known as an accredited investor. The federal securities laws have more specific guidelines for who qualifies as an accredited investor in Rule 501 of Regulation D:
1. The institution is a bank, insurance company, registered investment company, business development company, or small business investment company.
2. An accredited investor can be an employee benefit plan if a qualified individual or organization (as identified above) makes the decision or the plan has assets over $5 million.
3. The institution is a charitable organization, corporation, or other partnership with assets over $5 million.
4. The person is an executive or partner of the company selling the unregistered securities.
5. The institution has equity owners that are accredited investors.
6. The individual has a personal, or joint net worth of over $1 million.
7. The individual has had a personal income of at least $200,000 for the past two years, or a joint income of at least $300,000. The income expectation for the next year must also be the same.
8. A trust with over $5 million in assets managed by a person capable of understanding the risks of unregistered securities is qualified. The trust’s original intent must not have been to purchase the securities offered.
A surface-based process where a substance’s atoms, ions, or molecules adhere to the adsorbent.
Also known as wash oil, this light liquid hydrocarbon is used in wet gas streams to absorb or remove heavier liquid hydrocarbons.
To increase the flow of oil or gas in drilling, hydrochloric acid can be pumped into the well. The acid works to break down limestone, reducing the restrictions the oil or gas was previously facing to increase flow.
AESC Association of Energy Service Companies:
This association provides training materials and represents the interests of energy service employees within the oil and gas industry.
Also known as caustic flooding, the alkaline flooding process involves injecting alkaline chemicals during polymer flooding or waterflooding. Sodium hydroxide, sodium carbonate, or other alkaline chemicals react with specific types of oils, and this reaction results in surfactants. These surfactants then increase oil production by reducing interfacial tension between oil and water. Alkaline flooding shouldn’t be used in carbonate reservoirs.
Aniline Point Test:
A test of oil mud to determine if the aniline point temperature (aninline point) of the oil will damage elastomers (rubber compounds). The aniline point corresponds to the amount and type of hydrocarbons found in an oil sample, so a low aniline point indicates higher aromatics, and vice versa.
An area between two concentric objects where fluid can flow. An example is the space between the wellbore and casing or the space between casing and tubing.
Anticlines are folds in the earth’s surface where at least 80% of the world’s oil and gas has be found. An anticline has strata that slope downward on both sides and usually has surface formations like hills, knobs, and ridges.
API American Petroleum Institute:
This oil and gas industry trade organization publishes standards and best practices related to the industry.
API – Monogram:
The logo of the American Petroleum Institute (API) is added to equipment that meets their minimum standards. API also provides industry-related publications about recommended practices and standards.
Used to describe any method for retrieving oil from a well and bringing it to the surface after the well ceases to produce.
Also known as “As Is, Where Is” and “In Its Present Condition”, “As Is” states there are no guarantees about the condition or usage of the property. The buyer is responsible for determining its condition and use cases.
The person who a property’s interests, like a working interest, royalty, or net profits interest, are assigned to.
The person who expresses interest in a particular assignment.
Natural gas that’s created with crude oil from the same resevoir.
Auction With Reserve:
The opposite of an absolute auction, auctions with reserves have minimum buying prices that may not be disclosed to the bidders. The seller also has the ability to deny a bid for any reason.
Authorization for Expenditure:
Abbreviated as an AFE, this is a proposal given to each stakeholder that estimates the cost of drilling and completing a proposed well. The proposal will contain dry hole costs, completion costs, and the total cost. Dry hole costs are the spend needed to drill to the casing point, while completion costs are the funds needed to complete the well.
Typically used to describe the payout to investors for their initial well investment, a back in is a type of interest in a well or property that becomes effective at a future time or after a future event.
The part of a separation vessel used to temporarily slow the flow of fluids; needed when attempting to separate oil and water.
A steel bar that supports the swivel and connects it to the hook; resembles the handle of a bucket.
A cylindrical container with a valve used in cable-tool drilling; used to remove oil, water, sand, and mud from a well.
Barrel of Oil Equivalent (BOE):
The amount of oil barrels produced from a site each day.
Simply put, base oil is the continuous phase in oil-based drilling fluids (water-in-oil emulsions where water is in the dispersed phase and oil is in the continuous phase).
BBL is simply the abbreviation for barrel. For context, a barrel of oil is 42 US gallons.
A steel bar that supports the swivel and connects it to the hook. Resembles the handle of a bucket.
An extremely viscous form of crude oil that contains sulfer and other metals; to be produced, bitumen must be heated or combined with lighter hydrocarbons.
An oil and gas limited partnership that has not comitted to a single lease or property yet.
Occurs when down-hole pressure gas is not properly balanced with the weight of the drilling mud; the uncontrolled flow of gas, oil, or other fluids.
As a noun, a bore is the inside diameter of a pipe or drilled hole. As a verb, bore means to penetrate a surface with a rotary tool.
Also known as the wellbore, a borehole typically refers to the openhole or uncased portion that is created in well drilling.
As the name suggests, the bottomhole is the deepest part (the bottom) of the well.
In this situation, brokers will register potential bidders for properties being sold at an auction. The brokers are paid through commission by the property owner or auction firm.
An acronym for British Thermal Unit, BTU is a measurement to describe the amount of heat generated from burning oil or gas.
There are two instances where burner valves are used. The first is in a dehy unit or line heater where it maintains a constant temperature in the process bath by controlling the flow of gas to the fire tube. The second is on a heater treater where constant temperatures are maintained in the vessel by the burner valve.
A rope, wire or braid of strong fibers.
A well that has the casing already inserted. The opposite of a cased hole is an open hole.
A steel pipe that’s placed in an oil or gas well after drilling is completed to prevent the well hole from caving in. Casing also prevents fluids from moving from one formation (like groundwater) to another and helps in well control.
Drill Rig: The machinery that’s used to drill oil and gas wells. There are two types of drill rigs: rotary and cable tools, with rotary drill rigs being more efficient.
A large wrench used for turning casing tubulurs when making up or breaking out casing.
Describes the continous pumping of mud from surface-level mud tanks, down the drill pipe, out the drill bit nozzles, and through the gap between the drill pipe and the borehole to the surface. This movement carries rock cuttings via the shale shaker to the mud system.
The stub attached to a check that includes relevant information like the well name, production month, total volume produced, price received, and the net decimal interest of the payee.
Caused by quick changes in pressure, cavitation is the creation of vapor cavities within a low-pressure liquid. Cavitation can cause severe wear through cyclic stress on metal surfaces as they implode.
A long, but small in diameter pipe that is used to replace jointed pipes in certain types of drilling, completion, and workover operations.
A well that produces enough to pay for it’s production costs and leave enough oil and gas to be sold for revenue.
Used to describe all activities between drilling to casing point and putting the well to production. Includes cleaning out the well bore, setting the casing and tubing, adding surface equipment, and perforating the casing.
An engine that is used to increase natural gas pressure so that it can more easily flow through the pipeline.
A government grant awarded to oil and gas companies to explore and produce oil and gas – usually on government-owned property. Typically, the government receives a bonus or license fee and a portion of the production.
Hydrocarbon accumulation within highly permeable rocks that tend to have high-recovery factors.
Used to describe the legal transfer of property from one owner to another via a deed or bill of sale.
Specified in the production sharing contract, cost oil is applied annually by the operator to recover costs.
As the name suggests, a counterbalance weight is used to balance an existing weight. Often used in oil production pumping units to balance the weight of the upstroke (fluids and the column of the sucker rod) and downstroke (rods) of the pump.
Oil’s form as it comes directly from the ground; it’s a mixture including naturally occurring liquid hydrocarbons.
Thick oil or residue that’s at such a low pressure that no dissolved gas or volatile elements are present.
A legal document used to transfer a property’s title from a person (or organization) to another.
Paid to the lessor by the lessee, this consideration extends the oil and gas lease terms when there is no operations or production. The payment typically gives the lessee another year, however, if no payment is made and operations cease, the lease is considered abandoned.
This radioactivity contact log responds to variations in the specific gravity of formations by emitting neurtrons and measuring the secondary gamma radiation from the detector to the instrument. This is particularly helpful when measuring porosity in shaley sands.
The loss in mineral deposits as the well is produced.
Depletion (Gas) Drive:
An income tax deduction that can be taken advantage of for exhausting a natural resource.
The loss in mineral deposits as the well is produced.
A well that’s drilled in a proven oil or gas reservoir at the depth of proven productivity.
A removable, steel, serrated piece that fits into the jaws of tongs. Die inserts grip drill pipes, drill collars and casing while the tongs are making up or breaking out pipe.
A tool used to shape, form, or finish other tools or pieces of metal.
An internal-combustion engine frequently used for powering drilling rigs. A diesel engine is a high-compression engine that draws air into its cylinders and compresses the air to very high pressures; ignition then occurs as fuel is injected into the compressed, hot air. Combustion takes place in the cylinder above the piston; the combustion then powers the piston.
Also called a dip meter or dip log, this surveying method determines the direction and angle of a formation dip in relation to the borehole to provide geological structure of the formation.
Drilling in the opposite direction of a wellbore from the vertical. Directional drilling uses rotary steerable tools to move around rocks or other obstructions to continue drilling.
A document used to describe the property owner’s interests in drilling operations to the property operator. The Division Order also details the owner’s personal information like their tax ID.
The industry that includes: oil refineries, petrochemical plants, petroleum products distributors, retail outlets and natural gas distribution companies. The Downstream operates anywhere oil, plastics and natural gases are used.
The cutting or boring element used to access oil or gas in the drilling process. Not only are most bits roller-cone bits, but the drill bit also typically includes both the cutting element and the circulating element.
A heavy steel tube that’s placed between the drill pipe and the bit in the drill stem. Drill collars are used to add weight to the bit to make drilling easier.
A piece of seamless tubing used to rotate the bit and circulate the drilling fluid. The pipe joints are usually about 30 feet long and are joined together by tool joints.
The machinery that’s used to drill oil and gas wells. There are two types of drill rigs: rotary and cable tools, with rotary drill rigs being more efficient.
Transmits fluid and rotational power from the kelly bushing to the drilling collar. As the name suggests, the drill string is a column, or string, with attached tool joints.
Describes a well that does not produce oil or gas at commercial volume; typically is a producing well, but does not have enough resources to justify production.
Electronic Flow Meter:
Monitors the amount of oil and gas flowing from a wellhead; measurements are expressed in real time, actual flow, cumulative flow, and historical data.
Used by geologists to determine the nature of rocks, a special tool is used in an uncased hole that outputs electrical current into the rock and records the rock’s resistance.
A drilling rig – typically powered by diesel – where the original energy source is converted to electricity via generators. Electricity is then pumped through electrical conductors to electrical motors.
Cylindrical bars used to attach elevators to the hooks and support the weight of the elevator.
Hinged steel devices with manual operating handles that are attached to rotary and top drive rigs. Crew members latch elevators onto tool joints to operate them.
Enhanced Oil Recovery:
This oil recovery process that restores formation pressure and improves oil displacement can be used at any point of the productive life of an oil reservoir. There are three major types of enhanced oil recovery: chemical flooding, miscible displacement, and thermal recovery. Each recovery type alters the original properties of oil, but the specific type used is dependent on the temperature, depth, and other traits of the reservoir.
Estimated Ultimate Recovery (EUR):
An estimation of the cumulative volume of reserves that will be discovered in a specific reservoir.
A well created for the purpose of finding oil or gas in a previously unproductive area.
Used to describe the area holding reservoirs grouped on the same geological structural feature or stratigraphic condition. Can also describe the area holding a single reservoir.
A well that produces oil and gas using its own reservoir pressure as opposed to pumps or other production methods.
Forces oil into producing wells by injecting gas and liquids into the reservoir.
Also known as heavy oil, this substance contains dispersed gas bubbles that were created at the wellhead of a heavy oil reservoir. The bubbles in foamy oil stay small, keeping the oil viscosity low, while still creating the energy needed to drive the oil to the producing well.
The process of a fluid (usually crude oil, diesel or water) being pumped into the reservoir to break the reservoir rock open.
A liquid, typically water, oil, or an acid, that’s used in hydraulic fracturing. Fracturing fluid assists in the hydraulic fracturing process by carrying propping agents that hold open formation cracks after hydraulic pressure dissipates.
Free Water Knockout (FWKO):
A vertical or horizontal separator used to separate gas, oil and water. The water is removed to prevent corrosion and the formation of hydrates or tight emulsions.
Used to prevent gas lock, this tubular and perforated device works by allowing the lighter gas to rise, while the fluids make their way to the pump. It works like this: fluids first enter the anchor, while gas rises and exits the anchor through the perforations at the top. The rest of the fluids enter the anchor through a mosquito bill which allows all the gas to escape before fluids enter the pump.
The energy created by expanding compressed gas within a reservoir. Also called a depletion drive, this energy moves crude oil to a wellbore.
The process of injecting gas into a reservoir to maintain the pressure created by the gas drive. This process also reduces the decline rate of the original reservoir drive. There are two main types of gas injection: non-miscible oil and miscible oil injection.
Gas Oil Contact:
Used to describe the surface where the above gas and below oil make contact. This contact is transitional, forming a mix of gas and oil.
In well testing this refers to the ratio of produced gas to produced oil (also known as GOR); in production, this is the volume ratio of gas vs. oil that comes out of solution at standard conditions.
A well that primarily produces gas.
The person who received the land or mineral grant.
The person responsible for granting or conveying land, minerals, and other resources.
Developed by the American Petroleum Institute, this standard measures the density of liquid as expressed by degrees. The lower the degree, the heavier the liquid.
Crude oil with an API gravity of 20 degrees or less. It tends to have a high viscosity and hinders an easy flow of oil.
High Pressure Control Valve:
As the name suggests, the high pressure control valve is used to control fluids up to pressures of 6000 psig. The valves range from 2 to 10 inches long and are used to release fluid from areas of natural gas production.
A drilling technique that consists of vertical drilling down to a particular depth, and then involves turning at a right angle to drill horizontally within a specified reservoir.
Reserves oil, mineral, or gas rights at specific geologic depths.
Hot oiling is used to dissolve or move paraffin deposits from production tubing by circulating heated oil.
Operated, moved, or effected by water or liquid.
A low-viscosity fluid used in a liquid-based system.
High-pressured liquid is pumped into a formation to force the formation open and create passages for oil to flow into the wellbore.
A pumping method that uses a downhole pump without sucker rods. Specifically, two reciprocating hydraulic pumps are used; the first pump powers the second, production pump. Single and double tubing strings can both be used to pump multiple wells from a main source. When a single string is used, power oil travels down the string to the pump, and a mix of power oil and fluid is returned through the casing tub annulus. When two strings are used, power oil travels down one string, while the other returns the exhaust and produced fluid.
Improved Oil Recovery:
Generally speaking, improved oil recovery is any activity that increases oil production and recovery factor. However, in the restricted sense, it’s a process (like water flooding or gas flooding) that adds energy to the reservoir to increase oil production and recovery factor. Improved oil recovery allows further oil extraction beyond typical methods.
In this electric well log, the conductivity of a formation is measured. In other surveys, the resistivity is measured. Conductivity measurements work because oil-bearing formations are less conductive than water-bearing formations.
Injects coiled tubing into a well to seal the tubing and provide a pressure tight connection.
As the name hints, an injection well is a well where fluids are injected into an underground stratum. Also called an input well, this process increases reservoir pressure and displaces oil.
Intangible Drilling Costs:
Abbreviated as IDC, these costs are inclusive of everything needed to drill and prepare wells for oil and gas production. Includes costs associated with ground clearing, construction of derricks and pipelines, and wages, among a plethora of other costs.
A weighted float created to sink in oil and float in water; used as a testing tool.
A single section of drill pipe, casing or tubing that’s usually about 30 feet long.
Joint Operating Agreement (JOA):
A written agreement between multiple land operating partners that details how the land will be developed, who will pay for the exploration and development, and when this development will happen.
A phrase to describe an oil and gas investment project.
This steel piece turns the drill stem as the rotary table turns; typically suspended from the swivel through the rotary table and then connected to the top joint of the drill pipe.
A long hollow steel bar that’s used to connect the upper end of a drill string. Kelly bushing is a sleeve in the rotary table that allows the Kelly to freely move up and down during drilling. Kelly bushing also plays a part in the measurement of well depth, as well depth is measured from the Kelly bushing, down to the bottom of the well.
Occurs when water, gas, oil, or other fluid enters the wellbore during drilling when the pressure created by the column of drilling fluid is lower in comparison to the pressure created by fluids in the drilled formation. When not addressed, kicks may cause blowouts.
Any combination of fluids (including oil, gas, and water) that enters the borehole from a permeable formation.
The person who manages land leasing and land damages for oil and gas companies.
The individual who owns the property where minerals are found. Oftentimes the ownership is limited to the ground-level of the property.
The agreement formed by the owner of the property and the interested exploration and development party. The property owner gives the lessee exclusive rights to search for and extract any minerals found on the property.
The person who acquires the rights to drill for oil or gas on a piece of land.
The landowner who grants access for drilling for oil or gas on their land, known as a mineral lease.
The person who acquires the rights to drill for oil or gas on a piece of land.
The most common definition of a liner is a pipe used below existing casing to case an open hole. A liner extends from the setting depth up into another string of casing above the lower end of the oil string. Other types of liners include: a short type of perforated pipe that’s placed opposite of a producing formation to prevent loose sand from entering the well; liners in jet perforating guns are conically shaped and are used to increase the efficiency of the charge by improving the jet penetrability; cylinder liners are replaceable tubes created to fit inside the cylinder of an engine or a pump.
Low Pressure Control Valve:
A diaphragm used to control the flow of liquid and gas; often found in oil and water dump valves. Used in systems with working pressures up to 300 psig.
Also known as the master gate, the master valve is located on the Christmas tree and used to control gas and oil flow.
The acronym that represents one thousand barrels of oil equivalent.
Mechanical Oil Valve:
Also known as a Mechanical Liquid Valve or a Dump Valve, it is designed to work together with a trunnion assembly to remove liquids from the vessel. It’s controlled by a mechanical level.
The sector within the industry between oil production and the consumers that processes, stores and markets crude oil and natural gas.
The movement of oil and gas within layers of rock deep within the earth.
The owner of the gas, oil, or other minerals when they’re naturally occuring in a reservoir. Frequently, mineral owners will contract a oil or gas lease with a third-party to extract the minerals.
A unit of measurement to describe a million barrels of curde oil, bitumen, natural gas liquids, or condensate.
A mixture of hydrocarbons and non-hydrocarbons (like Hydrogen Sulfide or Nitrogen) in the same gaseous space or in a mixture of crude oil in underground preserves
Net Oil Production:
The amount of oil produced minus the injected oil (also known as the power oil).
The extracted natural gas from a reservoir that doesn’t contain notable amounts of crude oil.
Oil and Gas Lease:
A contract between the mineral owner and the company interested in drilling that gives the interested company rights to explore and produce oil and gas for a specified term. The lease is usually given for royalty payments in return.
A type of drilling mud where the oil is in the continuous phase. Oil-base mud is frequently used where it is difficult to drill with waterbase mud.
A compartment of the separator that gathers oil skimming over the oil weir.
The surface area, reservoir, wells and production equipment overlying oil reservoirs.
The pipe that directs oil out of the treater.
Similar to a dam, this vessel compartment allows oil to skim over into the oil chamber.
Any costs associated with operating a well or similar venture.
The party or person responsible for the drilling and operation of a well, and the maintenance of the leased land. All of the operator’s responsibilities will be detailed in the JOA.
Over Balanced Drilling:
Used to describe instances where the pressure used to drill (from the drilling fluids) is more than the pressure of the oil or gas within the reservoir.
An oil and gas lease that’s paid to the Lessor through the first term at the lease signing.
Paraffin Base Crude Oil:
Used for motor oil or kerosene, this crude oil contains a lot of paraffin wax, but minimal asphaltic materials.
A hollow steel tube that transports fluids. Pipes used in oil fields are: casing, drill pipes, tubing, and line pipes.
A type of oil acceptable for pipeline shipment because it’s free water, sediment, and emulsion (BS&W) content is low enough.
The part of the sucker rod pump that pulls well fluids into the pump.
This type of crude oil is used to energize the bottom pump in hydraulic pumping through surface pressurization.
Term used to describe the process of extracting, preparing, storing, and delivering well oils.
After deducting the expenses from the oil production, the amount of production that’s left is known as profit oil. This oil will be shared among participating parties and the host government based on the production sharing contract.
Processing plant where crude oil is turned into a variety of more useful oils like gasoline and diesel.
The amount of oil and gas in a reservoir that can be extracted. Measured in terms of barrels of oil or million cubic feet (MCF)
Simply put, a reservoir is the rock body in which oil or gas is stored. Common reservoir rocks are limestones, dolomites, or sandstones – all rocks that are porous, permeable, or naturally fractured. A reservoir can be filled with oil, volatile oil, dry gas, and gas condensate.
When fluids are flowing through rock by way of primary recovery, secondary recovery, and invasion, residual oil does not move.
The machine used to drive rotational power to the drill stem while still allowing vertical movement of the pipe for rotary drilling. Most moden rotary machines have a rotary or master brushing used to turn the kelly bushing, which then allows vertical movement of the kelly while the stem is turning.
A percentage of the profits made from the development of mineral resources. Royalties are paid to the property owners.
Funds given to the lessor from the production of oil and gas excluding production costs, taxes, and transportation fees.
Salt Water Disposal Well:
Oilfield salt water is drained into these wells.
Once a reservoir has been fully extracted using the primary production method, the well or field moves into secondary recovery. Secondary recovery methods frequently include gas injection or water flooding – the goal being to repressurize the reservoir for additional oil recovery.
Closing the valves on a well to stop production. Can also refer to a well on which the valves were closed to stop production.
Spring Loaded Back Pressure Regulator:
Controls the gas pressure and water level in the vessel of a free water knockout.
Steam Oil Ratio:
Also known as SOR, steam-oil ratio is used to rate the efficiency of steam injection oil production. The ratio measures the volume of steam needed to create one unit volume of oil and the lower the ratio, the more efficiently the steam is being used.
A type of improved recovery method used to restore formation pressure, improve oil displacement, or improve reservoir fluid flow. Can also be used to extract additional oil after the secondary recovery.
A floatless level control valve, typically installed with the water leg and oil leg of a heater treater.
A pipe with a small diameter or a tube threaded at both ends. Tubing is lowered into a completed well so that oil and gas can be produced through the string of tubing.
A type of fixed price drilling contract where a drilling contractor is required to drill to a specific depth and provide ample equipment so the operator only needs to turn a valve to see oil or gas flow.
A horizontal, vertical, or spherical vessel that separates well fluids into gas and total liquid. The oil leaves the vessel through the bottom, while gas leaves through the top.
Ultra Heavy Oil:
The US Department of Energy classifies a hydrocarbon fluid as an ultra heavy oil when it has a gravity of 10 degrees API or lower.
A type of sand formation where the grains of sand don’t stick to each other. When an unconsolidated sandstone produces oil, it frequently is mixed with sand unless properly controlled.
When multiple oil companies are involved in field production, the unit operator is the company in charge of development and production.
The sector within the oil and gas industry that finds and produces crude oil and natural gas; often called the exploration sector.
Used as a safety device to control flow within a line by opening or shutting a line completely.
In geophysics, velocity is described as medium-distance divided by traveltime. Velocity can be measured vertically, laterally, and azimuthally and measured with laboratory measurements, acoustic logs, vertical seismic profiles, and velocity analysis of seismic data.
Used to describe a fluid’s resistance to flow. For example, a highly viscous fluid won’t flow as easily as one with a low viscosity.
A heavy crude oil with a viscosity above 10 cp, a gravity below 22.3 degrees API, and low hydrogen-to-carbon ratios. Viscous oil also boasts higher acid numbers as well as high nitrogen and heavy-metal content.
The production of oil due to the expansion of underlying water and rock, which then forces oil into the wellbore. Both bottom water drive and edgewater drive are commonly used. Bottom water involves oil that’s totally in contact with water, whereas with edgewater, only a small portion of the oil touches water.
Water in Oil Emulsion:
A type of drilling fluid that consists of an external phase of oil with water or brine droplets.
Also knowns as WOR, water oil ratio is the ratio of produced water to produced oil.