IWCF Glossary

The large, round frame (reel) on which coiled tubing is wound, deployed and stored.

A water-based fluid containing dissolved salts and inhibitors to increase density and prevent scales and corrosion in completion operations.

The tubing and associated accessories required to optimise well flow or injection, and to allow well intervention. Also known as ‘completion tubing’.

The tubing below the completion packer. Usually includes a wireline entry guide and nipple profiles.

A liquid-hydrocarbon mixture derived from natural gas with a density that is lower than oil.

A relatively short string of large diameter pipe that is set to keep the top of the hole open and provide a means of returning the up flowing drilling fluid from the wellbore to the surface drilling fluid system until the first casing string is set in the well.

Source: API STD 59

A small volume of gas that enters the wellbore due to a temporary decrease in bottomhole pressure (BHP) after stopping the pumps for a connection.

Hydraulic oil, water-based fluid, or gas that, under pressure, pilots the operation of control valves or directly operates functions.

Source: API STD 53

Where the control line that operates the surface controlled subsurface safety valve exits the wellhead.

A tool which connects two components of different sizes, threaded connection types or coupling designs.

A tool run into the well on a drillpipe that allows the wellhead and BOP arrangement to be tested on a drilling operation.

A tool which is dropped into the well to cut the slickline from a toolstring that is stuck.

Formation solids which enter the drilling-fluid system, whether produced by the drill bit or from the side of the borehole.

Source: API RP 13C

The fluid within a pressure gauge that protects the mechanism from shock. Also known as ‘dampening fluid’.

System designed to automatically shut in the wellbore in the event of a simultaneous absence of hydraulic supply and control of both subsea control pods.

Source: API STD 53

A vent line from a degasser that runs into the derrick.

Equipment that contains hydrocyclones that removes particles from the drilling fluid once it has passed through the shale shaker.

Equipment that contains hydrocyclones that removes particles from the drilling fluid once it has passed through the desander.

A well that is not vertical throughout.

Difference in pressure between any two points.

Source: API SPEC 16A

A valve that closes when there is a sudden decrease in the pressure downstream.

Slickline capable of digital two-way communication for data collection and tool functioning.

Gas which remains in solution until the pressure or temperature conditions change, at which time it may break out of solution to become free gas.

A tool placed in the flowline designed to remove metallic debris from the well.

A device that will divert well flow away from the rig when tophole drilling, or when handling gas in the marine riser. There are two types: annular and insert type.

An exercise to ensure the crew are ready to act appropriately if the drilling operation encounters a shallow gas reservoir.

Ensuring that two barriers are in place and available. If one barrier fails, the second barrier will prevent flow of well fluids.

A coiled tubing or snubbing tool which is part of the bottomhole assembly. There are always two valves. Also known as a dual flapper check valve.

A valve that will hold pressure from one direction. Usually on the end of a workstring.

A barrier element that has been installed to contain well fluids or pressure. Also known as ‘mechanical plug’.

Shutting off the flowline on the low pressure side of the choke.

A frictional force opposing movement of a fluid or solid.

A well intervention with a dummy toolstring to simulate a subsequent run where hazardous tools, such as perforating guns or radioactive charges, are deployed. This aims to ensure that the well geometry allows the toolstring to reach target depth and that the well is free of obstructions.

Thick-walled pipe or tube designed to provide stiffness and concentration of mass at or near the bit.

A two-circulation well kill method that removes the influx from the well before circulating kill weight fluid.

A change in the rate of penetration that may or may not be a result of penetrating a pressured reservoir.

Water or oil-based fluid circulated down the drillpipe into the well and back up to the rig for purposes including containment of formation pressure, the removal of cuttings, bit lubrication and cooling, treating the wall of the well and providing a source for well data. Also known as ‘mud’.

A measure of a fluid’s resistance to flow.

Pressure-containing component having end connections and outlets that is used below either between the BOP and casing head or between individual preventers of a BOP stack.

Drilling margin or drilling window or operating margin. The difference between the maximum pore pressure and the minimum effective fracture pressure. It is used while drilling and can be determined for any point within an openhole interval. Also known as ‘drilling margin’ or ‘operating margin’.

Source: API RP 96

The internal drillpipe volume for each unit of measurement, for example barrels per foot or litres per metre.

Full-opening valve located on the rig floor with threads to match the drillpipe connections or other tubulars in use. Note: This valve is used to close off the drillpipe to prevent flow and may be crossed over to fit other connections and sizes of tubulars being installed in the well.

Source: API STD 53

A device that can be dropped into the workstring that acts as a check valve, allowing drilling fluid to be circulated down the string but preventing back flow. This requires a full bore landing sub to be pre-installed in the workstring where it will landout when deployed and pumped down.

A valve that closes off the communication port in the side pocket mandrel between the tubing and the ‘A’ annulus.

A subsea well control term. The casing pressure minus the choke line friction (CLF) measured at surface while pumping.

Commonly used for stationkeeping on deep-water drilling rigs. These systems use information on the rig’s current location (for example, as determined by a global positioning system and acoustic sensors) to control thrusters, which act to restore the rig to a position over the well’s centre.

Source: API RP 96

The surface pump pressure observed when circulating at any given rate. It is the sum of all the pressure losses in the circulating system (surface lines, drillstring, bit nozzles, annulus).

A non-metallic sealing element.

A braided wireline with one or more electrical conductors. It is used to operate toolstring equipment from surface. Also known as an ‘e-line’.

A survey performed by analysis of certain electrical characteristics (such as resistivity and conductivity) of formations uncovered by the borehole. Also known as the ‘electric well log’ or ‘electric survey’.

System using electrical cables or fibre optics in a subsea umbilical such that, on each element, multiple distinct functions are independently operated by dedicated serialized coded commands. Note: Solenoid-operated valves in turn activate pilot-operated valves assigned to functions. Also known as ‘MUX systems’.

Source: API 17G

Part of the OWIRS system that allows rapid disconnect of the openwater riser from the subsea Xmas Tree.

Programmed sequence of events that operates the functions to leave the stack and controls in a desired state and to disconnect the lower marine riser package (LMRP) from the lower stack.

Source: API STD 53

Gas that is contained within the well, either drilling fluid returns or produced fluids in a completion string. See ‘background gas’ and ‘gas-cut drilling fluid’.

The pipework and valves within a hydraulic workover unit that allows equalisation of well pressure as the stripping rams are opened and closed to run and pull the workstring.

A device that operates to equalise the pressure across a pressure isolation barrier.

The effective density of the circulating fluid in the wellbore resulting from the sum of the hydrostatic pressure imposed by the static fluid column and the friction pressure (annulus pressure losses).

Source: API STD 65:2

The failure of elastomer sealing components due to rapid depressurisation in a live well.

A two-part completion accessory positioned above the packer that when stabbed together provide a seal. Allows the upper completion to be retrieved and replaced.

A valve that is opened by applying hydraulic pressure and will close when the hydraulic pressure is removed. For example, actuated Xmas Tree valves and surface controlled subsurface safety valves (SCSSSVs) are fail-safe closed.

The drillpipe pressure recorded at the surface after the kill fluid has been circulated down to the drill bit.

The mechanism in a toolstring or assembly that will activate an explosive charge. For example, an electrical detonator in a wireline perforating gun.

An operation required to retrieve equipment lost in the well.

A tool that is generally set in the BHA to prevent return flow into the drillstring when breaking connections on the rig floor. Also known as a float valve or ‘float (non-return) valve’.

A check valve assembly. The term is used broadly in drilling or casing operations. It is generally set towards the base of the string to prevent backflow into the casing or drillstring. This can be either a flapper type or plunger type of assembly which is not considered a tested barrier. Also known as float non-return valve or float flapper valve.

A rig that is used in deep water, such as a semi-submersible or drill ship.

A procedure carried out to monitor for the return of fluid at surface during drilling, completion and workover operations.

A heavier weight tubular placed within some completions either side of items that will see turbulent flow while the well is producing. The extra wall thickness prevents early failure due to erosion.

DWC: The piping that exits the bell nipple and conducts drilling fluid and cuttings to the shale shaker and drilling fluid pits.

Source: API RP 64

WIPC: The line attached to the Xmas Tree that carries well fluids into production.

A device that measures the fluid flow rate.

Volume of fluid or gas flowing in a unit of time. For example, bbl per minute (bbl/min), litres per hour (l/hr), metres cubed per day (m3/day).

The act of logging the well’s flowback characteristics to aid in detecting well flow. Fingerprinting can be applied to any repetitive operation to aid the detection of abnormal trends or other issues with well integrity and stability.

Mass of fluid per unit of volume, usually measured in lb/gal, kg/l or kg/m3.

The hydrostatic pressure per unit of vertical fluid column depth. Also known as ‘fluid pressure gradient’.

A tubular joint that has a consistent external diameter throughout its length.

The pressure at the reservoir that will cause the formation to start to fracture. This can lead to loss of drilling fluid and impact primary well control. Also known as ‘fracture pressure’ or ‘formation breakdown’.

The pressure that can be applied to a formation sufficient to inject fluids without causing breakdown or fracture. Also known as ‘leak-off pressure’.

A procedure used to establish if the formation can withstand a pre-determined pressure without initiating a fracture.

Pressure exerted by the fluids within the pore space of a formation. Also known as ‘formation pressure’ or ‘pore pressure’.

Source: API RP 59

The pressure that the formation can hold before it fractures.

Pumping down the workstring or completion and taking returns back through the annulus.

The operation of a piece of equipment or system to verify its intended operation (without subjecting it to pressure).

Source: API STD 53

When gas changes from dissolved in the well fluids to free gas. The pressure at which gas breakout occurs is also referred to as ‘bubble point’. Gas breakout is normally monitored at surface.

A light oil often produced with gas, a by-product of gas.

The process where a gas bubble travels upwards in a wellbore due to buoyancy.

Gas appearing within drilling returns at surface. Also known as ‘gas-cut mud’ or ‘gas cutting’.

A tool fitted within a side pocket mandrel that allows the flow of gas from the annulus into the tubing to assist in lifting produced fluids to surface.

A type of pressure isolation valve commonly used in Xmas Trees and wellheads.

The assembly attached to a coiled tubing injector head that guides the coiled tubing into the injector head.

A primary barrier element at the top of a braided line or electric wireline rig-up. Grease is injected through the flow tubes to allow the wire to be run through the head and back out without well fluids escaping to the atmosphere.

The operating limit of a piece of equipment.

When the weight of a portion of the drill string below a ram BOP is supported by a tool joint resting on the closed pipe ram or through the use of a special hang-off tool that lands in the wellhead.

Source: API STD 53

Pipe with thick wall used in the transition zone to minimize fatigue and as bit weight in directional wells.

Source: API RP 7G-2

A Xmas Tree design for subsea applications, configured with the master valves and flow-control equipment on a horizontal axis to minimize the assembly height.

Solid, crystalline compound of water and light hydrocarbons or CO2, in which the water molecules combine with the gas molecules to form a solid.

A small diameter pipe containing hydraulic fluid that is connected to a hydraulically actuated device such as a downhole safety valve or a BOP ram.

The panel that operates BOP equipment and hydraulically-operated valves. Also known as a ‘hydraulic control unit’.

Fluid that operates a hydraulic control circuit.

A high pressure flexible armoured hose used to function hydraulically operated equipment.

The pressure exerted by hydraulic fluid within a system.