Drilling Acronym Decoder

DRILLING ACRONYM DECODER

150+ OIL & GAS TERMS — INSTANT SEARCH

SHOWING 155 OF 155 TERMS

ACRONYM	FULL NAME	PLAIN ENGLISH	CAT
BHA	Bottom Hole Assembly	The collection of drill collars, stabilisers, and tools attached to the bottom of the drill string, directly above the bit.	DRILLING
BHP	Bottom Hole Pressure	The total pressure acting at the bottom of the well; must stay above pore pressure and below fracture pressure.	DRILLING
BHT	Bottom Hole Temperature	The temperature measured at total depth; governs elastomer selection and mud stability.	DRILLING
BIT	Bit — Drill Bit	The rotating cutting tool at the end of the drill string that actually grinds through rock.	DRILLING
DC	Drill Collar	Heavy, thick-walled pipe near the bit that provides weight-on-bit and stiffens the BHA.	DRILLING
DD	Directional Driller	The specialist on the rig floor who steers the wellbore to hit the target reservoir.	DRILLING
DP	Drill Pipe	The long, lightweight pipe that connects the surface to the BHA and transmits rotation and fluid.	DRILLING
ECD	Equivalent Circulating Density	The effective mud weight seen at the bit when mud is being pumped; always higher than static mud weight due to friction.	DRILLING
EMW	Equivalent Mud Weight	Any downhole pressure expressed as a mud density in ppg or sg for easy comparison to the mud window.	DRILLING
FIT	Formation Integrity Test	A pressure test applied to a new formation after setting casing to confirm it can hold the expected maximum wellbore pressure.	DRILLING
LOT	Leak-Off Test	A test pumped until the formation begins to fracture, establishing the upper pressure limit for that hole section.	DRILLING
WOB	Weight on Bit	The downward force applied to the drill bit, measured in thousands of pounds, that drives penetration rate.	DRILLING
RPM	Rotations Per Minute	How fast the drill string or bit is spinning; too fast or slow can damage the bit or cause vibration.	DRILLING
ROP	Rate of Penetration	How fast the bit drills through rock, measured in feet or metres per hour; the primary drilling efficiency metric.	DRILLING
SPM	Strokes Per Minute	The speed of the mud pump pistons; used to calculate flow rate and detect kicks by monitoring stroke count.	DRILLING
GPM	Gallons Per Minute	Flow rate unit for mud pumps; determines annular velocity and hole cleaning efficiency.	DRILLING
TFA	Total Flow Area	The combined nozzle area of the drill bit; determines jet velocity and hydraulic horsepower at the bit.	DRILLING
HSI	Hydraulic Horsepower per Square Inch	A measure of the cleaning energy delivered at the bit face; typically optimised between 1.0–1.5 HSI.	DRILLING
PDC	Polycrystalline Diamond Compact	A modern drill bit type using synthetic diamond cutters; faster and longer-lasting than roller-cone bits in many formations.	DRILLING
TIH	Trip In Hole	Running the drill string back down the wellbore after it was pulled for bit change or BHA maintenance.	DRILLING
POOH	Pull Out Of Hole	Pulling the drill string (or wireline tool) out of the well; often done to change the bit or run casing.	DRILLING
TD	Total Depth	The deepest point reached in a wellbore; declaring TD means drilling has stopped and logging or casing can begin.	DRILLING
KOP	Kick-Off Point	The depth at which a directional well begins to deviate from vertical; set by the wellbore design.	DRILLING
DLS	Dog-Leg Severity	The rate of change of wellbore direction, measured in degrees per 100 ft; high DLS risks pipe fatigue and stuck pipe.	DRILLING
TVD	True Vertical Depth	The straight-line vertical distance from surface to the point of interest; used for pressure calculations.	DRILLING
MD	Measured Depth	The actual length of wellbore along the borehole path; always ≥ TVD in a deviated well.	DRILLING
MW	Mud Weight	The density of drilling fluid, commonly in ppg or sg; the primary tool for controlling downhole pressure.	DRILLING
OBM	Oil-Based Mud	Drilling fluid with oil as the continuous phase; superior shale inhibition and lubricating properties but stricter disposal rules.	DRILLING
WBM	Water-Based Mud	Drilling fluid with water as the continuous phase; cheaper and easier to dispose of but less inhibitive than OBM.	DRILLING
SBM	Synthetic-Based Mud	Drilling fluid using synthetic (non-petroleum) base oil; performs like OBM but with lower environmental toxicity.	DRILLING
LCM	Lost Circulation Material	Fibres, flakes, or granules mixed into mud to plug thief zones and stop drilling fluid being lost into the formation.	DRILLING
MWD	Measurement While Drilling	Downhole tools that send wellbore direction, inclination, and pressure data to surface in real time via mud pulse.	DRILLING
RSS	Rotary Steerable System	An automated directional drilling tool that steers the bit while the entire drill string rotates, giving faster and smoother wellbores.	DRILLING
PDM	Positive Displacement Motor	A downhole mud motor powered by drilling fluid flow; used to rotate the bit independently of the surface drive.	DRILLING
JAR	Drilling Jar	A downhole tool that releases a sudden impact force to free a stuck drill string; either hydraulic or mechanical.	DRILLING
HWDP	Heavy Weight Drill Pipe	Intermediate-weight pipe between drill collars and standard drill pipe; reduces fatigue failures in the transition zone.	DRILLING
SCR	Slow Circulating Rate	The pump pressure recorded at a reduced, fixed stroke rate; a baseline used when displacing a kick or spotting pills.	DRILLING
SICP	Shut-In Casing Pressure	The pressure reading on the annulus side after shutting in on a kick; indicates the degree of underbalance.	DRILLING
SIDPP	Shut-In Drill Pipe Pressure	The pressure at the drill pipe after shutting in on a kick; used to calculate the kill mud weight needed.	DRILLING
BOP	Blowout Preventer	The pressure-rated valve assembly at the wellhead that can seal around or shear the drill string to prevent a blowout.	WELL CONTROL
BOPE	Blowout Preventer Equipment	The full stack of BOP components including annular preventers, rams, choke manifold, and kill lines.	WELL CONTROL
MAASP	Maximum Allowable Annular Surface Pressure	The highest surface casing pressure permitted before the weakest downhole formation would fracture; a hard kill-weight ceiling.	WELL CONTROL
KMW	Kill Mud Weight	The increased mud density required to balance reservoir pressure and stop influx; calculated from SIDPP.	WELL CONTROL
ICP	Initial Circulating Pressure	The pump pressure at SCR at the start of a well kill; kept constant while heavy mud reaches the bit (Driller's method).	WELL CONTROL
FCP	Final Circulating Pressure	The pump pressure at SCR when kill-weight mud fills the drill string; the target pressure for the second circulation.	WELL CONTROL
WC	Well Control	The discipline and procedures used to detect, manage, and stop unplanned influxes of formation fluid into the wellbore.	WELL CONTROL
IADC	International Association of Drilling Contractors	The global trade body that sets well control standards, rig classifications, and training certifications for the drilling industry.	WELL CONTROL
IWCF	International Well Control Forum	The body that manages the global well control certification exam taken by drillers, toolpushers, and company men.	WELL CONTROL
PIW	Pit Gain / Influx Volume	The volume of formation fluid that has entered the wellbore, monitored via the pit volume totaliser on surface.	WELL CONTROL
PVT	Pit Volume Totaliser	Instruments that continuously monitor active pit volumes; a sudden gain is the primary kick indicator.	WELL CONTROL
MPD	Managed Pressure Drilling	A closed-loop drilling technique that precisely controls annular pressure to stay within a tight pore-to-frac margin.	WELL CONTROL
UBD	Underbalanced Drilling	Drilling with wellbore pressure intentionally below reservoir pressure to improve ROP and reduce formation damage.	WELL CONTROL
H2S	Hydrogen Sulphide	A toxic, flammable gas encountered in sour wells; detectable by smell at low levels but immediately dangerous at high concentrations.	WELL CONTROL
LWD	Logging While Drilling	Sensors in the BHA that measure formation properties (resistivity, gamma ray, porosity) in real time as the well is drilled.	MWD/LWD
GR	Gamma Ray	A log that detects natural radioactivity; high values indicate shale, low values indicate clean sands or carbonates.	MWD/LWD
RT	True Resistivity	The electrical resistance of undisturbed formation away from the borehole wall; high values indicate hydrocarbons.	MWD/LWD
NPHI	Neutron Porosity	A porosity measurement from neutron bombardment of the formation; responds to hydrogen content, including bound water.	MWD/LWD
RHOB	Bulk Density	Formation density from a gamma-gamma tool; combined with NPHI to calculate porosity and identify gas zones.	MWD/LWD
APWD	Annular Pressure While Drilling	Real-time downhole annular pressure measurement from the MWD tool; the direct read of ECD and wellbore stability.	MWD/LWD
INC	Inclination	The angle of the wellbore from vertical; 0° is straight down, 90° is horizontal.	MWD/LWD
AZI	Azimuth	The compass bearing of the wellbore direction; combined with inclination to define the 3D trajectory.	MWD/LWD
EM-MWD	Electromagnetic MWD	An MWD transmission method using electromagnetic signals through rock instead of mud pulses; works in air- or foam-drilled wells.	MWD/LWD
AGS	At-Bit Gamma Ray / Steerable	A gamma-ray sensor positioned very close to the drill bit for faster geosteering response in thin reservoir layers.	MWD/LWD
NMR	Nuclear Magnetic Resonance	An advanced LWD measurement that directly measures pore size distribution and movable fluid volumes.	MWD/LWD
SWD	Seismic While Drilling	A technique using downhole geophones to receive seismic signals, providing look-ahead images of formations ahead of the bit.	MWD/LWD
UBIA	Ultrasonic Borehole Imager	An LWD tool using ultrasound to image the borehole wall; reveals fractures, dips, and breakouts in real time.	MWD/LWD
PWD	Pressure While Drilling	Any downhole pressure tool in the BHA; records both annular and internal pipe pressure for ECD management.	MWD/LWD
DWOB	Downhole Weight on Bit	WOB measured at the bit by the MWD tool; often differs from surface readings due to friction in deviated wells.	MWD/LWD
PERF	Perforation	Explosive charges that punch holes through casing and cement into the reservoir, creating a flow path for hydrocarbons.	COMPLETIONS
TCP	Tubing-Conveyed Perforating	A perforating system where guns are run on production tubing and fired downhole at the target interval.	COMPLETIONS
SCAB	Sand Control And Barrier	Gravel packs, screens, or chemical consolidation methods that prevent sand from flowing into the wellbore and damaging equipment.	COMPLETIONS
GPK	Gravel Pack	Sand control method that places sized gravel between the screen and formation to filter out reservoir sand.	COMPLETIONS
FRAC	Hydraulic Fracturing	High-pressure injection of fluid to crack the reservoir rock, creating fractures that dramatically increase well productivity.	COMPLETIONS
FDP	Field Development Plan	The engineering document that defines how a reservoir will be produced — well count, spacing, facilities, and schedule.	COMPLETIONS
PBTD	Plug Back Total Depth	The depth of a downhole plug set to isolate a lower zone; the effective new bottom of the wellbore above the plug.	COMPLETIONS
SSD	Sliding Side Door	A completion tool with a sliding sleeve that can be opened to allow selective communication between tubing and annulus or formation.	COMPLETIONS
SCSSV	Surface-Controlled Subsurface Safety Valve	A downhole valve held open by hydraulic pressure from surface; fails closed automatically if the line is cut or depressured.	COMPLETIONS
DHSV	Downhole Safety Valve	A generic term for any safety valve installed inside the production tubing, designed to isolate the reservoir in an emergency.	COMPLETIONS
WHP	Wellhead Pressure	The pressure measured at the top of the well at surface; reflects reservoir drive and tubing pressure losses.	COMPLETIONS
THP	Tubing Head Pressure	The flowing pressure at the tubing hanger at surface; a key parameter for production monitoring and choke management.	COMPLETIONS
CHP	Casing Head Pressure	The pressure reading on the annulus side at surface; monitored for signs of tubing leaks or barrier integrity issues.	COMPLETIONS
XMAS TREE	Christmas Tree	The surface valve assembly on top of a completed well that controls and monitors production flow.	COMPLETIONS
PLT	Production Logging Tool	A wireline tool run in a producing well to measure where fluid is entering and identify high-water or depleted zones.	COMPLETIONS
SWC	Sidewall Core	Rock samples collected from the wellbore wall during wireline logging; used to confirm fluid contacts and reservoir quality.	COMPLETIONS
WO	Workover	Any remedial operation on an existing well to restore or improve production — reperforating, squeezing, or plug-and-abandonment.	COMPLETIONS
GOR	Gas-Oil Ratio	Cubic feet of gas produced per barrel of oil; a rising GOR indicates a gas cap is coning into the wellbore.	PRODUCTION
WOR	Water-Oil Ratio	Barrels of water produced per barrel of oil; a rising WOR indicates water breakthrough from a connected aquifer.	PRODUCTION
BOPD	Barrels of Oil Per Day	The standard unit for measuring a well or field's oil production rate.	PRODUCTION
BWPD	Barrels of Water Per Day	The rate of water production from a well; drives disposal costs and can indicate reservoir depletion.	PRODUCTION
MMSCFD	Million Standard Cubic Feet per Day	The standard unit for gas production rates at surface conditions (60 °F, 14.7 psi).	PRODUCTION
API	API Gravity	A measure of crude oil density; light crudes (>31° API) are more valuable, heavy crudes (<22° API) require more refining.	PRODUCTION
ESP	Electric Submersible Pump	An electric pump lowered into the production tubing to lift fluids in low-pressure or high-watercut wells.	PRODUCTION
GL	Gas Lift	An artificial lift method that injects gas into the annulus to aerate produced fluids and reduce hydrostatic head.	PRODUCTION
FTHP	Flowing Tubing Head Pressure	Wellhead pressure measured while the well is producing; used to back-calculate flowing bottomhole pressure.	PRODUCTION
SBHP	Static Bottom Hole Pressure	Reservoir pressure when the well is shut in and pressure has fully built up; the best measure of reservoir energy.	PRODUCTION
PI	Productivity Index	Barrels per day per psi of drawdown; a measure of how easily a reservoir gives up its fluids to the wellbore.	PRODUCTION
IPR	Inflow Performance Relationship	A curve that plots well flow rate versus bottomhole flowing pressure; used to optimise artificial lift design.	PRODUCTION
VLP	Vertical Lift Performance	The pressure losses in the tubing as fluids travel from reservoir to surface; intersects IPR to find the natural flow rate.	PRODUCTION
WHFP	Wellhead Flowing Pressure	Surface pressure while the well is on production; monitored daily to track reservoir decline and line pressure changes.	PRODUCTION
EWT	Extended Well Test	A prolonged production test lasting weeks or months to gather reservoir data and process performance before permanent facilities are built.	PRODUCTION
DST	Drill Stem Test	A temporary completion run on drill pipe to flow a reservoir interval and gather pressure/fluid data before full completion.	PRODUCTION
PBU	Pressure Build-Up Test	A well test where flow is stopped and the pressure rise is analysed to determine permeability and skin damage.	PRODUCTION
AOF	Absolute Open Flow	The theoretical maximum flow rate of a gas well if wellhead pressure were zero; the benchmark for gas well deliverability.	PRODUCTION
FPSO	Floating Production Storage and Offloading	A ship-shaped vessel moored offshore that processes, stores, and offloads crude oil without a pipeline to shore.	PRODUCTION
TLP	Tension Leg Platform	An offshore production platform held in place by taut vertical tendons anchored to the seabed; suited to deepwater fields.	PRODUCTION
HSE	Health, Safety & Environment	The combined management discipline covering worker protection, process safety, and environmental stewardship on a rig or facility.	HSE
PTW	Permit to Work	A formal written authorisation required before any hazardous task begins; ensures hazards are identified and controls in place.	HSE
JSA	Job Safety Analysis	A step-by-step hazard identification exercise completed before a task; each step is assessed for risks and mitigations.	HSE
LOTO	Lock-Out / Tag-Out	Energy isolation procedure where equipment is physically locked off before maintenance to prevent accidental start-up.	HSE
PPE	Personal Protective Equipment	Hard hats, boots, gloves, glasses, and coveralls worn to protect workers from workplace hazards.	HSE
SIMOPS	Simultaneous Operations	Managing two or more hazardous operations happening at the same time on a rig or platform, requiring a formal risk review.	HSE
MSDS	Material Safety Data Sheet	A document describing the hazards, handling requirements, and emergency response for a chemical used on location.	HSE
TRIC	Total Recordable Incident Count	The total number of OSHA-recordable injuries and illnesses on a job site over a given period.	HSE
LTI	Lost Time Incident	An injury that results in a worker missing at least one scheduled shift; the key lag indicator for safety performance.	HSE
LTISR	Lost Time Incident Severity Rate	The average number of days lost per LTI; measures the severity of injuries rather than just their frequency.	HSE
NORM	Naturally Occurring Radioactive Material	Low-level radioactive scales and sludge that can accumulate in production equipment; requires special disposal procedures.	HSE
ERP	Emergency Response Plan	The documented procedures for evacuating, mustering, and responding to fires, blowouts, or medical emergencies on location.	HSE
HAZAN	Hazard Analysis	A systematic review of a process or task to identify all hazards and the likelihood and consequence of each.	HSE
HAZOP	Hazard and Operability Study	A structured team review of P&IDs using guide words (more, less, reverse…) to find deviations that could cause harm.	HSE
MUSTER	Emergency Muster Point	The designated gathering point where all personnel must report during an emergency so a headcount can be completed.	HSE
OIM	Offshore Installation Manager	The most senior person on an offshore platform; has legal authority over all personnel and operations on the installation.	HSE
ALARP	As Low As Reasonably Practicable	The UK/international risk management standard requiring risk reduction until the cost of further reduction is grossly disproportionate to the benefit.	HSE
MOC	Management of Change	A formal process to assess the safety implications of any change to people, processes, or equipment before it is implemented.	HSE
AFE	Authority for Expenditure	The approved budget document for a well or project; spending beyond the AFE requires formal re-approval.	GENERAL
NOC	National Oil Company	A state-owned oil company (e.g. Saudi Aramco, ADNOC, Petronas) that controls a country's hydrocarbon resources.	GENERAL
IOC	International Oil Company	A privately or publicly traded oil major (e.g. BP, Shell, ExxonMobil) that operates in multiple countries.	GENERAL
PSC	Production Sharing Contract	An agreement where an IOC recovers its costs from production then splits remaining profit oil with the host government.	GENERAL
JOA	Joint Operating Agreement	A legal contract between partners in a licence that defines decision-making authority, cost sharing, and operatorship.	GENERAL
WI	Working Interest	The percentage share of costs and production rights a company holds in an oil and gas licence.	GENERAL
NRI	Net Revenue Interest	The share of revenue a working interest owner receives after royalties are paid out.	GENERAL
OPEX	Operating Expenditure	Day-to-day costs of running a producing field — labour, maintenance, chemicals, and workovers.	GENERAL
CAPEX	Capital Expenditure	Large one-time investment costs — drilling wells, installing platforms, building pipelines — that appear on the balance sheet as assets.	GENERAL
NPV	Net Present Value	The discounted value today of all future project cash flows; the primary economic decision metric for new wells.	GENERAL
IRR	Internal Rate of Return	The discount rate that makes a project's NPV equal to zero; projects with IRR above the hurdle rate are sanctioned.	GENERAL
DP	Dynamic Positioning	A computer-controlled thruster system that holds a drillship or MODU precisely on location without anchors.	GENERAL
MODU	Mobile Offshore Drilling Unit	Any movable offshore rig — jackup, semi-submersible, or drillship — that can be repositioned between wells.	GENERAL
SEMI	Semi-Submersible Rig	A floating rig supported by submerged pontoons that dampen wave motion; used in deepwater where jackups cannot reach.	GENERAL
JU	Jackup Rig	A bottom-supported offshore rig with retractable legs that are lowered to the seabed; limited to ~150 m water depth.	GENERAL
DRLG	Drilling	Common abbreviation used in morning reports and well programmes to denote the drilling phase of an operation.	GENERAL
MR	Morning Report	The daily operational summary sent to company and government offices detailing progress, NPT, and next 24-hour plan.	GENERAL
NPT	Non-Productive Time	Rig time spent on problems rather than progressing the well — stuck pipe, equipment failures, waiting on weather.	GENERAL
PO	Purchase Order	The formal document authorising a supplier to deliver goods or services to a specific cost and specification.	GENERAL
WITS	Wellsite Information Transfer Standard	A data transmission protocol used to send real-time drilling parameters from the rig floor to offices and third parties.	GENERAL
WITSML	Wellsite Information Transfer Standard Markup Language	The XML-based successor to WITS; enables structured digital transfer of all well data between software systems.	GENERAL
DLIS	Digital Log Interchange Standard	The industry-standard file format for storing and exchanging wireline and LWD log data.	GENERAL
LAS	Log ASCII Standard	A simpler, widely-supported text file format for well log data; easier to read than DLIS but less feature-rich.	GENERAL
OWC	Oil-Water Contact	The depth at which oil transitions to water in the reservoir; defines the bottom of the oil column.	GENERAL
GOC	Gas-Oil Contact	The depth at which free gas overlies oil in the reservoir; defines the top of the oil column.	GENERAL
GWC	Gas-Water Contact	In a gas reservoir with no oil, the depth where gas transitions directly to water.	GENERAL
STOIIP	Stock Tank Oil Initially In Place	The total estimated volume of oil in the reservoir at surface conditions before any production begins.	GENERAL
GIIP	Gas Initially In Place	The total estimated volume of gas in the reservoir at surface conditions; the starting point for recovery factor calculations.	GENERAL
RF	Recovery Factor	The fraction of STOIIP or GIIP that can economically be produced; typically 20-60% for oil, higher for gas.	GENERAL
2P	Proved + Probable Reserves	The sum of proved and probable reserve categories; the most commonly quoted reserves figure in annual reports.	GENERAL
SPS	Subsea Production System	The complete set of seafloor equipment — trees, manifolds, flowlines — that ties subsea wells back to a production host.	GENERAL
SCM	Subsea Control Module	The electronic pod on a subsea tree that receives hydraulic and electrical commands from surface to operate valves.	GENERAL
P&ID	Piping and Instrumentation Diagram	An engineering drawing that shows all piping, valves, instruments, and control loops in a process system.	GENERAL
FEED	Front-End Engineering Design	The detailed engineering study completed before a final investment decision; defines scope, cost, and schedule with high confidence.	GENERAL
FID	Final Investment Decision	The board-level approval to commit capital and proceed with full project execution; a major project milestone.	GENERAL

ACRONYM

FULL NAME

PLAIN ENGLISH

CAT

BHA

Bottom Hole Assembly

The collection of drill collars, stabilisers, and tools attached to the bottom of the drill string, directly above the bit.

DRILLING

BHP

Bottom Hole Pressure

The total pressure acting at the bottom of the well; must stay above pore pressure and below fracture pressure.

DRILLING

BHT

Bottom Hole Temperature

The temperature measured at total depth; governs elastomer selection and mud stability.

DRILLING

BIT

Bit — Drill Bit

The rotating cutting tool at the end of the drill string that actually grinds through rock.

DRILLING

Drill Collar

Heavy, thick-walled pipe near the bit that provides weight-on-bit and stiffens the BHA.

DRILLING

Directional Driller

The specialist on the rig floor who steers the wellbore to hit the target reservoir.

DRILLING

Drill Pipe

The long, lightweight pipe that connects the surface to the BHA and transmits rotation and fluid.

DRILLING

ECD

Equivalent Circulating Density

The effective mud weight seen at the bit when mud is being pumped; always higher than static mud weight due to friction.

DRILLING

EMW

Equivalent Mud Weight

Any downhole pressure expressed as a mud density in ppg or sg for easy comparison to the mud window.

DRILLING

FIT

Formation Integrity Test

A pressure test applied to a new formation after setting casing to confirm it can hold the expected maximum wellbore pressure.

DRILLING

LOT

Leak-Off Test

A test pumped until the formation begins to fracture, establishing the upper pressure limit for that hole section.

DRILLING

WOB

Weight on Bit

The downward force applied to the drill bit, measured in thousands of pounds, that drives penetration rate.

DRILLING

RPM

Rotations Per Minute

How fast the drill string or bit is spinning; too fast or slow can damage the bit or cause vibration.

DRILLING

ROP

Rate of Penetration

How fast the bit drills through rock, measured in feet or metres per hour; the primary drilling efficiency metric.

DRILLING

SPM

Strokes Per Minute

The speed of the mud pump pistons; used to calculate flow rate and detect kicks by monitoring stroke count.

DRILLING

GPM

Gallons Per Minute

Flow rate unit for mud pumps; determines annular velocity and hole cleaning efficiency.

DRILLING

TFA

Total Flow Area

The combined nozzle area of the drill bit; determines jet velocity and hydraulic horsepower at the bit.

DRILLING

HSI

Hydraulic Horsepower per Square Inch

A measure of the cleaning energy delivered at the bit face; typically optimised between 1.0–1.5 HSI.

DRILLING

PDC

Polycrystalline Diamond Compact

A modern drill bit type using synthetic diamond cutters; faster and longer-lasting than roller-cone bits in many formations.

DRILLING

TIH

Trip In Hole

Running the drill string back down the wellbore after it was pulled for bit change or BHA maintenance.

DRILLING

POOH

Pull Out Of Hole

Pulling the drill string (or wireline tool) out of the well; often done to change the bit or run casing.

DRILLING

Total Depth

The deepest point reached in a wellbore; declaring TD means drilling has stopped and logging or casing can begin.

DRILLING

KOP

Kick-Off Point

The depth at which a directional well begins to deviate from vertical; set by the wellbore design.

DRILLING

DLS

Dog-Leg Severity

The rate of change of wellbore direction, measured in degrees per 100 ft; high DLS risks pipe fatigue and stuck pipe.

DRILLING

TVD

True Vertical Depth

The straight-line vertical distance from surface to the point of interest; used for pressure calculations.

DRILLING

Measured Depth

The actual length of wellbore along the borehole path; always ≥ TVD in a deviated well.

DRILLING

Mud Weight

The density of drilling fluid, commonly in ppg or sg; the primary tool for controlling downhole pressure.

DRILLING

OBM

Oil-Based Mud

Drilling fluid with oil as the continuous phase; superior shale inhibition and lubricating properties but stricter disposal rules.

DRILLING

WBM

Water-Based Mud

Drilling fluid with water as the continuous phase; cheaper and easier to dispose of but less inhibitive than OBM.

DRILLING

SBM

Synthetic-Based Mud

Drilling fluid using synthetic (non-petroleum) base oil; performs like OBM but with lower environmental toxicity.

DRILLING

LCM

Lost Circulation Material

Fibres, flakes, or granules mixed into mud to plug thief zones and stop drilling fluid being lost into the formation.

DRILLING

MWD

Measurement While Drilling

Downhole tools that send wellbore direction, inclination, and pressure data to surface in real time via mud pulse.

DRILLING

RSS

Rotary Steerable System

An automated directional drilling tool that steers the bit while the entire drill string rotates, giving faster and smoother wellbores.

DRILLING

PDM

Positive Displacement Motor

A downhole mud motor powered by drilling fluid flow; used to rotate the bit independently of the surface drive.

DRILLING

JAR

Drilling Jar

A downhole tool that releases a sudden impact force to free a stuck drill string; either hydraulic or mechanical.

DRILLING

HWDP

Heavy Weight Drill Pipe

Intermediate-weight pipe between drill collars and standard drill pipe; reduces fatigue failures in the transition zone.

DRILLING

SCR

Slow Circulating Rate

The pump pressure recorded at a reduced, fixed stroke rate; a baseline used when displacing a kick or spotting pills.

DRILLING

SICP

Shut-In Casing Pressure

The pressure reading on the annulus side after shutting in on a kick; indicates the degree of underbalance.

DRILLING

SIDPP

Shut-In Drill Pipe Pressure

The pressure at the drill pipe after shutting in on a kick; used to calculate the kill mud weight needed.

DRILLING

BOP

Blowout Preventer

The pressure-rated valve assembly at the wellhead that can seal around or shear the drill string to prevent a blowout.

WELL CONTROL

BOPE

Blowout Preventer Equipment

The full stack of BOP components including annular preventers, rams, choke manifold, and kill lines.

WELL CONTROL

MAASP

Maximum Allowable Annular Surface Pressure

The highest surface casing pressure permitted before the weakest downhole formation would fracture; a hard kill-weight ceiling.

WELL CONTROL

KMW

Kill Mud Weight

The increased mud density required to balance reservoir pressure and stop influx; calculated from SIDPP.

WELL CONTROL

ICP

Initial Circulating Pressure

The pump pressure at SCR at the start of a well kill; kept constant while heavy mud reaches the bit (Driller's method).

WELL CONTROL

FCP

Final Circulating Pressure

The pump pressure at SCR when kill-weight mud fills the drill string; the target pressure for the second circulation.

WELL CONTROL

Well Control

The discipline and procedures used to detect, manage, and stop unplanned influxes of formation fluid into the wellbore.

WELL CONTROL

IADC

International Association of Drilling Contractors

The global trade body that sets well control standards, rig classifications, and training certifications for the drilling industry.

WELL CONTROL

IWCF

International Well Control Forum

The body that manages the global well control certification exam taken by drillers, toolpushers, and company men.

WELL CONTROL

PIW

Pit Gain / Influx Volume

The volume of formation fluid that has entered the wellbore, monitored via the pit volume totaliser on surface.

WELL CONTROL

PVT

Pit Volume Totaliser

Instruments that continuously monitor active pit volumes; a sudden gain is the primary kick indicator.

WELL CONTROL

MPD

Managed Pressure Drilling

A closed-loop drilling technique that precisely controls annular pressure to stay within a tight pore-to-frac margin.

WELL CONTROL

UBD

Underbalanced Drilling

Drilling with wellbore pressure intentionally below reservoir pressure to improve ROP and reduce formation damage.

WELL CONTROL

H2S

Hydrogen Sulphide

A toxic, flammable gas encountered in sour wells; detectable by smell at low levels but immediately dangerous at high concentrations.

WELL CONTROL

LWD

Logging While Drilling

Sensors in the BHA that measure formation properties (resistivity, gamma ray, porosity) in real time as the well is drilled.

MWD/LWD

Gamma Ray

A log that detects natural radioactivity; high values indicate shale, low values indicate clean sands or carbonates.

MWD/LWD

True Resistivity

The electrical resistance of undisturbed formation away from the borehole wall; high values indicate hydrocarbons.

MWD/LWD

NPHI

Neutron Porosity

A porosity measurement from neutron bombardment of the formation; responds to hydrogen content, including bound water.

MWD/LWD

RHOB

Bulk Density

Formation density from a gamma-gamma tool; combined with NPHI to calculate porosity and identify gas zones.

MWD/LWD

APWD

Annular Pressure While Drilling

Real-time downhole annular pressure measurement from the MWD tool; the direct read of ECD and wellbore stability.

MWD/LWD

INC

Inclination

The angle of the wellbore from vertical; 0° is straight down, 90° is horizontal.

MWD/LWD

AZI

Azimuth

The compass bearing of the wellbore direction; combined with inclination to define the 3D trajectory.

MWD/LWD

EM-MWD

Electromagnetic MWD

An MWD transmission method using electromagnetic signals through rock instead of mud pulses; works in air- or foam-drilled wells.

MWD/LWD

AGS

At-Bit Gamma Ray / Steerable

A gamma-ray sensor positioned very close to the drill bit for faster geosteering response in thin reservoir layers.

MWD/LWD

NMR

Nuclear Magnetic Resonance

An advanced LWD measurement that directly measures pore size distribution and movable fluid volumes.

MWD/LWD

SWD

Seismic While Drilling

A technique using downhole geophones to receive seismic signals, providing look-ahead images of formations ahead of the bit.

MWD/LWD

UBIA

Ultrasonic Borehole Imager

An LWD tool using ultrasound to image the borehole wall; reveals fractures, dips, and breakouts in real time.

MWD/LWD

PWD

Pressure While Drilling

Any downhole pressure tool in the BHA; records both annular and internal pipe pressure for ECD management.

MWD/LWD

DWOB

Downhole Weight on Bit

WOB measured at the bit by the MWD tool; often differs from surface readings due to friction in deviated wells.

MWD/LWD

PERF

Perforation

Explosive charges that punch holes through casing and cement into the reservoir, creating a flow path for hydrocarbons.

COMPLETIONS

TCP

Tubing-Conveyed Perforating

A perforating system where guns are run on production tubing and fired downhole at the target interval.

COMPLETIONS

SCAB

Sand Control And Barrier

Gravel packs, screens, or chemical consolidation methods that prevent sand from flowing into the wellbore and damaging equipment.

COMPLETIONS

GPK

Gravel Pack

Sand control method that places sized gravel between the screen and formation to filter out reservoir sand.

COMPLETIONS

FRAC

Hydraulic Fracturing

High-pressure injection of fluid to crack the reservoir rock, creating fractures that dramatically increase well productivity.

COMPLETIONS

FDP

Field Development Plan

The engineering document that defines how a reservoir will be produced — well count, spacing, facilities, and schedule.

COMPLETIONS

PBTD

Plug Back Total Depth

The depth of a downhole plug set to isolate a lower zone; the effective new bottom of the wellbore above the plug.

COMPLETIONS

SSD

Sliding Side Door

A completion tool with a sliding sleeve that can be opened to allow selective communication between tubing and annulus or formation.

COMPLETIONS

SCSSV

Surface-Controlled Subsurface Safety Valve

A downhole valve held open by hydraulic pressure from surface; fails closed automatically if the line is cut or depressured.

COMPLETIONS

DHSV

Downhole Safety Valve

A generic term for any safety valve installed inside the production tubing, designed to isolate the reservoir in an emergency.

COMPLETIONS

WHP

Wellhead Pressure

The pressure measured at the top of the well at surface; reflects reservoir drive and tubing pressure losses.

COMPLETIONS

THP

Tubing Head Pressure

The flowing pressure at the tubing hanger at surface; a key parameter for production monitoring and choke management.

COMPLETIONS

CHP

Casing Head Pressure

The pressure reading on the annulus side at surface; monitored for signs of tubing leaks or barrier integrity issues.

COMPLETIONS

XMAS TREE

Christmas Tree

The surface valve assembly on top of a completed well that controls and monitors production flow.

COMPLETIONS

PLT

Production Logging Tool

A wireline tool run in a producing well to measure where fluid is entering and identify high-water or depleted zones.

COMPLETIONS

SWC

Sidewall Core

Rock samples collected from the wellbore wall during wireline logging; used to confirm fluid contacts and reservoir quality.

COMPLETIONS

Workover

Any remedial operation on an existing well to restore or improve production — reperforating, squeezing, or plug-and-abandonment.

COMPLETIONS

GOR

Gas-Oil Ratio

Cubic feet of gas produced per barrel of oil; a rising GOR indicates a gas cap is coning into the wellbore.

PRODUCTION

WOR

Water-Oil Ratio

Barrels of water produced per barrel of oil; a rising WOR indicates water breakthrough from a connected aquifer.

PRODUCTION

BOPD

Barrels of Oil Per Day

The standard unit for measuring a well or field's oil production rate.

PRODUCTION

BWPD

Barrels of Water Per Day

The rate of water production from a well; drives disposal costs and can indicate reservoir depletion.

PRODUCTION

MMSCFD

Million Standard Cubic Feet per Day

The standard unit for gas production rates at surface conditions (60 °F, 14.7 psi).

PRODUCTION

API

API Gravity

A measure of crude oil density; light crudes (>31° API) are more valuable, heavy crudes (<22° API) require more refining.

PRODUCTION

ESP

Electric Submersible Pump

An electric pump lowered into the production tubing to lift fluids in low-pressure or high-watercut wells.

PRODUCTION

Gas Lift

An artificial lift method that injects gas into the annulus to aerate produced fluids and reduce hydrostatic head.

PRODUCTION

FTHP

Flowing Tubing Head Pressure

Wellhead pressure measured while the well is producing; used to back-calculate flowing bottomhole pressure.

PRODUCTION

SBHP

Static Bottom Hole Pressure

Reservoir pressure when the well is shut in and pressure has fully built up; the best measure of reservoir energy.

PRODUCTION

Productivity Index

Barrels per day per psi of drawdown; a measure of how easily a reservoir gives up its fluids to the wellbore.

PRODUCTION

IPR

Inflow Performance Relationship

A curve that plots well flow rate versus bottomhole flowing pressure; used to optimise artificial lift design.

PRODUCTION

VLP

Vertical Lift Performance

The pressure losses in the tubing as fluids travel from reservoir to surface; intersects IPR to find the natural flow rate.

PRODUCTION

WHFP

Wellhead Flowing Pressure

Surface pressure while the well is on production; monitored daily to track reservoir decline and line pressure changes.

PRODUCTION

EWT

Extended Well Test

A prolonged production test lasting weeks or months to gather reservoir data and process performance before permanent facilities are built.

PRODUCTION

DST

Drill Stem Test

A temporary completion run on drill pipe to flow a reservoir interval and gather pressure/fluid data before full completion.

PRODUCTION

PBU

Pressure Build-Up Test

A well test where flow is stopped and the pressure rise is analysed to determine permeability and skin damage.

PRODUCTION

AOF

Absolute Open Flow

The theoretical maximum flow rate of a gas well if wellhead pressure were zero; the benchmark for gas well deliverability.

PRODUCTION

FPSO

Floating Production Storage and Offloading

A ship-shaped vessel moored offshore that processes, stores, and offloads crude oil without a pipeline to shore.

PRODUCTION

TLP

Tension Leg Platform

An offshore production platform held in place by taut vertical tendons anchored to the seabed; suited to deepwater fields.

PRODUCTION

HSE

Health, Safety & Environment

The combined management discipline covering worker protection, process safety, and environmental stewardship on a rig or facility.

HSE

PTW

Permit to Work

A formal written authorisation required before any hazardous task begins; ensures hazards are identified and controls in place.

HSE

JSA

Job Safety Analysis

A step-by-step hazard identification exercise completed before a task; each step is assessed for risks and mitigations.

HSE

LOTO

Lock-Out / Tag-Out

Energy isolation procedure where equipment is physically locked off before maintenance to prevent accidental start-up.

HSE

PPE

Personal Protective Equipment

Hard hats, boots, gloves, glasses, and coveralls worn to protect workers from workplace hazards.

HSE

SIMOPS

Simultaneous Operations

Managing two or more hazardous operations happening at the same time on a rig or platform, requiring a formal risk review.

HSE

MSDS

Material Safety Data Sheet

A document describing the hazards, handling requirements, and emergency response for a chemical used on location.

HSE

TRIC

Total Recordable Incident Count

The total number of OSHA-recordable injuries and illnesses on a job site over a given period.

HSE

LTI

Lost Time Incident

An injury that results in a worker missing at least one scheduled shift; the key lag indicator for safety performance.

HSE

LTISR

Lost Time Incident Severity Rate

The average number of days lost per LTI; measures the severity of injuries rather than just their frequency.

HSE

NORM

Naturally Occurring Radioactive Material

Low-level radioactive scales and sludge that can accumulate in production equipment; requires special disposal procedures.

HSE

ERP

Emergency Response Plan

The documented procedures for evacuating, mustering, and responding to fires, blowouts, or medical emergencies on location.

HSE

HAZAN

Hazard Analysis

A systematic review of a process or task to identify all hazards and the likelihood and consequence of each.

HSE

HAZOP

Hazard and Operability Study

A structured team review of P&IDs using guide words (more, less, reverse…) to find deviations that could cause harm.

HSE

MUSTER

Emergency Muster Point

The designated gathering point where all personnel must report during an emergency so a headcount can be completed.

HSE

OIM

Offshore Installation Manager

The most senior person on an offshore platform; has legal authority over all personnel and operations on the installation.

HSE

ALARP

As Low As Reasonably Practicable

The UK/international risk management standard requiring risk reduction until the cost of further reduction is grossly disproportionate to the benefit.

HSE

MOC

Management of Change

A formal process to assess the safety implications of any change to people, processes, or equipment before it is implemented.

HSE

AFE

Authority for Expenditure

The approved budget document for a well or project; spending beyond the AFE requires formal re-approval.

GENERAL

NOC

National Oil Company

A state-owned oil company (e.g. Saudi Aramco, ADNOC, Petronas) that controls a country's hydrocarbon resources.

GENERAL

IOC

International Oil Company

A privately or publicly traded oil major (e.g. BP, Shell, ExxonMobil) that operates in multiple countries.

GENERAL

PSC

Production Sharing Contract

An agreement where an IOC recovers its costs from production then splits remaining profit oil with the host government.

GENERAL

JOA

Joint Operating Agreement

A legal contract between partners in a licence that defines decision-making authority, cost sharing, and operatorship.

GENERAL

Working Interest

The percentage share of costs and production rights a company holds in an oil and gas licence.

GENERAL

NRI

Net Revenue Interest

The share of revenue a working interest owner receives after royalties are paid out.

GENERAL

OPEX

Operating Expenditure

Day-to-day costs of running a producing field — labour, maintenance, chemicals, and workovers.

GENERAL

CAPEX

Capital Expenditure

Large one-time investment costs — drilling wells, installing platforms, building pipelines — that appear on the balance sheet as assets.

GENERAL

NPV

Net Present Value

The discounted value today of all future project cash flows; the primary economic decision metric for new wells.

GENERAL

IRR

Internal Rate of Return

The discount rate that makes a project's NPV equal to zero; projects with IRR above the hurdle rate are sanctioned.

GENERAL

Dynamic Positioning

A computer-controlled thruster system that holds a drillship or MODU precisely on location without anchors.

GENERAL

MODU

Mobile Offshore Drilling Unit

Any movable offshore rig — jackup, semi-submersible, or drillship — that can be repositioned between wells.

GENERAL

SEMI

Semi-Submersible Rig

A floating rig supported by submerged pontoons that dampen wave motion; used in deepwater where jackups cannot reach.

GENERAL

Jackup Rig

A bottom-supported offshore rig with retractable legs that are lowered to the seabed; limited to ~150 m water depth.

GENERAL

DRLG

Drilling

Common abbreviation used in morning reports and well programmes to denote the drilling phase of an operation.

GENERAL

Morning Report

The daily operational summary sent to company and government offices detailing progress, NPT, and next 24-hour plan.

GENERAL

NPT

Non-Productive Time

Rig time spent on problems rather than progressing the well — stuck pipe, equipment failures, waiting on weather.

GENERAL

Purchase Order

The formal document authorising a supplier to deliver goods or services to a specific cost and specification.

GENERAL

WITS

Wellsite Information Transfer Standard

A data transmission protocol used to send real-time drilling parameters from the rig floor to offices and third parties.

GENERAL

WITSML

Wellsite Information Transfer Standard Markup Language

The XML-based successor to WITS; enables structured digital transfer of all well data between software systems.

GENERAL

DLIS

Digital Log Interchange Standard

The industry-standard file format for storing and exchanging wireline and LWD log data.

GENERAL

LAS

Log ASCII Standard

A simpler, widely-supported text file format for well log data; easier to read than DLIS but less feature-rich.

GENERAL

OWC

Oil-Water Contact

The depth at which oil transitions to water in the reservoir; defines the bottom of the oil column.

GENERAL

GOC

Gas-Oil Contact

The depth at which free gas overlies oil in the reservoir; defines the top of the oil column.

GENERAL

GWC

Gas-Water Contact

In a gas reservoir with no oil, the depth where gas transitions directly to water.

GENERAL

STOIIP

Stock Tank Oil Initially In Place

The total estimated volume of oil in the reservoir at surface conditions before any production begins.

GENERAL

GIIP

Gas Initially In Place

The total estimated volume of gas in the reservoir at surface conditions; the starting point for recovery factor calculations.

GENERAL

Recovery Factor

The fraction of STOIIP or GIIP that can economically be produced; typically 20-60% for oil, higher for gas.

GENERAL

Proved + Probable Reserves

The sum of proved and probable reserve categories; the most commonly quoted reserves figure in annual reports.

GENERAL

SPS

Subsea Production System

The complete set of seafloor equipment — trees, manifolds, flowlines — that ties subsea wells back to a production host.

GENERAL

SCM

Subsea Control Module

The electronic pod on a subsea tree that receives hydraulic and electrical commands from surface to operate valves.

GENERAL

P&ID

Piping and Instrumentation Diagram

An engineering drawing that shows all piping, valves, instruments, and control loops in a process system.

GENERAL

FEED

Front-End Engineering Design

The detailed engineering study completed before a final investment decision; defines scope, cost, and schedule with high confidence.

GENERAL

FID

Final Investment Decision

The board-level approval to commit capital and proceed with full project execution; a major project milestone.

GENERAL

[ NO MATCHING ACRONYMS FOUND ]

DRILLING ACRONYM DECODER

WHAT IS THIS PAGE?

This is a free, searchable reference for oil and gas acronyms used every day on drilling rigs, in operations centres, and across the upstream energy industry. Whether you are a brand-new roughneck on your first hitch or an experienced petroleum engineer reviewing well programmes, the alphabet soup of abbreviations can be overwhelming. This decoder covers more than 150 of the most important terms across seven disciplines: drilling operations, well control, MWD/LWD, completions, production, health and safety (HSE), and general industry terms.

WHY DO DRILLING ACRONYMS MATTER?

On a rig, communication must be fast, precise, and unambiguous. Acronyms exist because they compress long technical phrases into a handful of characters that every crew member can instantly decode on a morning report, over the radio, or in a drilling programme. When a driller shouts "BOP" or a company man queries the "ECD", there is no room for confusion — the wrong interpretation can mean the difference between a safe operation and a well control incident. Knowing your acronyms is therefore not just a career skill; in many situations it is a safety-critical one.

HOW TO USE THE SEARCH

Type any acronym, full name, or keyword into the search box above and results filter instantly. The category buttons let you narrow down to a specific discipline — useful when you know you're looking for a well control term but can't quite remember the letters. All 155 entries include the acronym, the full expansion, and a plain-English one-liner so even non-engineers can get the gist.

ABOUT DRILL-O-DORO

Drill-O-Doro is a free suite of retro-styled tools built for drilling engineers, wellsite geologists, and operations crews. Alongside this acronym decoder you will find a Pomodoro-style deep-work timer tuned to rig schedules, a comprehensive drilling unit converter, and a hydraulics and well-control calculator — all free, no sign-up required.