904 Oil and Gas Well Inspection

Glossary

A

Abandonment Plug. A cement or mechanical plug placed in a wellbore to seal and permanently isolate reservoir zones during well abandonment operations.
Acetic Acid. A weak organic acid commonly used in oil and gas operations for acidizing limestone or dolomite formations to increase permeability.
Acid Job. A treatment process where acid is pumped into a well to dissolve minerals and improve permeability or clean up wellbore damage.
Acidizing. The process of injecting acid into a formation to dissolve rock and improve flow paths for hydrocarbons.
Administrative Controls. Procedures and policies implemented to reduce risks to worker safety by managing how tasks are performed, such as safety training or shift scheduling.
Adjustable Choke. A device used to control the flow rate of fluids from a well by varying the size of the opening.
Ambient Temperature. The temperature of the surrounding environment, often considered during the planning and operation of oil and gas equipment.
Annular Safety Valve (ASV). A downhole safety valve designed to shut off flow through the annulus during workover operations or emergencies.
Area Open to Flow. The portion of a wellbore or reservoir that is exposed and allows fluid movement.
Artificial Lift. Methods used to enhance the flow of hydrocarbons to the surface when reservoir pressure is insufficient, such as beam pumps or gas lifts.
Atmospheric Corrosion. The degradation of metal caused by its reaction with oxygen and moisture in the air.
Axial Loading. The application of force along the axis of a structural component, such as tubing or casing in a well.

B

Bridge Plug. A mechanical device installed in the wellbore to provide a temporary or permanent seal, isolating specific zones during workover or abandonment.
Back Pressure Valve (BPV). A valve installed in the tubing to prevent backflow and maintain pressure control during workover operations.
Back Wash. The process of reversing the flow of fluid in a system to clean debris or contaminants.
Balanced Plug. A method of placing a cement plug in a well where the pressure above and below the plug is balanced.
Ball Catcher. A device used in the wellbore to catch balls used in ball-activated tools.
Ball Sealers. Small, spherical objects used to temporarily seal perforations in a wellbore during certain operations, such as acidizing.
Barite Plug. A dense mixture of barite and fluid used to plug a wellbore temporarily or permanently.
Beam Pump. A mechanical device used for artificial lift, consisting of a reciprocating pump and a surface beam system.
Blank Pipe. A solid section of pipe used in the wellbore to isolate zones or prevent fluid flow.
Blast Joint. A section of tubing installed in the wellbore to protect against erosion caused by high-velocity fluids.
Blast Sleeve. A protective sleeve installed in the wellbore to shield tubing from erosion or abrasion during high-velocity production.
Bleed-Off Line. A line used to safely vent or release trapped pressure from the wellbore or surface equipment during workover or abandonment.
Blowout Preventer (BOP). A critical safety device used to control well pressure and prevent uncontrolled flow of fluids during workover or abandonment operations.
Blow Down. The process of releasing gas or liquid from a well or pipeline to reduce pressure.
Bottomhole Choke. A restriction installed at the bottom of the well to control fluid flow rates.
Bottomhole Pressure. The pressure measured at the bottom of the well, used for reservoir evaluation and production optimization.
Bottomhole Sampler. A device used to collect fluid samples from the bottom of a well for analysis.
Breakdown Pressure. The pressure required to initiate the fracturing of the formation.
Bridge. An obstruction or intentional blockage within the wellbore, often formed by debris or as part of a well intervention.
Bridge Plug. A downhole tool used to isolate a section of the wellbore, commonly for testing or zonal isolation.
Bring In the Well. The process of initiating or restoring production from a well after drilling or workover operations.
Buttress Thread. A type of thread design on casing or tubing connections that provides high tensile strength and pressure resistance.
Bubble Flow. A two-phase flow regime where gas bubbles are dispersed in a continuous liquid phase, often observed in production tubing.
Buffalo Head. A slang term for a swivel fitting used in high-pressure lines during wellsite operations.
Bump the Plug. The act of landing the wiper plug against the float collar during cementing operations to complete the displacement of cement.
Buoyancy. The upward force exerted by a fluid that opposes the weight of an immersed object, affecting wellbore equipment and operations.

C

Cap the Well. The process of sealing a wellhead to prevent the escape of fluids, often done in emergencies or during well decommissioning.
Carbon Dioxide Corrosion. The deterioration of metal caused by the reaction of carbon dioxide with water to form carbonic acid, which corrodes steel.
Carrier Fluid. A liquid used to transport proppants, chemicals, or other materials into the wellbore during operations like fracturing or acidizing.
Casing. Steel pipe used to line the walls of a drilled well to prevent collapse and isolate different geological formations.
Casing Bowl. A component of the wellhead assembly that supports the casing string and provides access for pressure control.
Casing Burst Pressure. The maximum internal pressure a casing string can withstand before failing.
Casing Collar Locator (CCL). A logging tool used to detect casing collars, providing depth correlation in the wellbore.
Casing Completion. A well completion method where casing strings are installed and cemented in place before production begins.
Casing Hanger. A device used to suspend a casing string within the wellhead, supporting its weight.
Casing Pressure. The pressure inside the casing string, monitored to ensure safe operation and well integrity.
Casing Shoe Test. A pressure test performed at the casing shoe to verify the integrity of the cement job and formation.
Cement. A material used to secure casing strings, isolate formations, and maintain well integrity during drilling and production.
Cement Accelerator. An additive used to speed up the setting time of cement, particularly in cold environments.
Cement Additive. Chemicals or materials added to cement to enhance its properties, such as strength, density, or set time.
Cement Dispersant. An additive used to reduce the viscosity of cement slurry and improve its flow characteristics.
Cement Extender. A material added to cement to reduce its density and increase its yield, used in weak formations.
Cement Plug. A column of cement placed in the wellbore to isolate sections or permanently seal the well.
Cement Retainer. A tool used to control cement placement and prevent backflow during cement squeeze operations.
Centralizer. A mechanical device used to keep the casing or tubing centered in the wellbore to ensure proper cementing.
Charged Zone. A subsurface formation with significant hydrocarbon or fluid accumulation under pressure, often requiring special consideration during drilling or completion.
Check Valve. A valve that allows fluid to flow in only one direction, commonly used to prevent backflow in well operations.
Chelating Agent. A chemical compound used to bind and remove metal ions, often used to dissolve scale deposits or treat drilling mud.
Chemical Diverter. A chemical used to temporarily block certain flow paths in a formation, directing fluids to other zones during stimulation treatments.
Chemical Wash. A fluid treatment designed to clean wellbore surfaces by dissolving or removing deposits, mud, or residues.
Christmas Tree. An assembly of valves, spools, and fittings installed on the wellhead to control production and provide access for interventions.
Choke. A device used to regulate fluid flow from a well by restricting the flow area, often adjustable for changing conditions.
Choke Manifold. An arrangement of valves and chokes used to control well flow during testing, production, or well control operations.
Churn Flow. A two-phase flow regime characterized by irregular oscillations of gas and liquid phases, often occurring in vertical tubing.
Circulation Path. The flow path established for circulating fluids during workover operations to maintain well control and remove debris.
Cleanup. The process of removing drilling fluids, debris, or formation damage from the wellbore to restore or enhance production.
Clear Brine. A type of brine fluid without suspended solids, used in well operations to control pressure while minimizing formation damage.
Close In. To shut off flow from a well by closing the master valve or other flow control devices.
Combustible Gas Detector. An instrument used to detect the presence of flammable gases in the air to prevent explosions or fires.
Command Trailer. A portable unit used as a control center at a wellsite, providing monitoring and coordination during operations.
Commingled Flow. The production of hydrocarbons from multiple zones simultaneously, with fluids mixing in the wellbore or surface facilities.
Confined Space Entry. A safety procedure for accessing confined spaces, such as tanks or vessels, that involves atmospheric testing and using permits to protect workers.
Contingency Plan. A prepared strategy or set of actions designed to address potential problems or emergencies at the wellsite.
Continuous Gas Lift. A method of artificial lift where gas is continuously injected into the production tubing to reduce the hydrostatic pressure and increase flow.
Corrosion-Resistant Alloy (CRA). A type of material designed to withstand harsh environments, such as those with high levels of CO₂, H₂S, or chlorides, commonly used in well completions.
Cresting. The movement of water or gas into the perforated zone of a producing well, often caused by excessive production rates or reservoir conditions.
Crossover. A tool or fitting used to connect two pieces of equipment or pipe with different thread types or sizes.
Crossover Service Tool. A specialized tool used during well interventions to perform operations across different sections of the wellbore.
Crown Block Safety Device. A safety mechanism installed on the rig to prevent equipment from damaging the crown block during workover operations.
Crown Valve. The topmost valve on a Christmas tree, providing access to the wellbore for wireline or coiled tubing operations.
Crushed Zone. A damaged area around the wellbore caused by drilling or perforating, which may impair flow until treated.
Crystallization Temperature. The temperature at which dissolved salts begin to precipitate from a solution, critical in brine formulation and scaling prevention.
Crossflow. The movement of fluids between zones within a wellbore, typically through perforations or fractures, often unintended and requiring remediation.
Cut-and-Pull Operations. The process of severing and removing casing, tubing, or other equipment during well abandonment procedures.
Cuttings. Small pieces of rock or sediment produced during drilling operations, carried to the surface by drilling fluids.

D

Damaged Zone. A region around the wellbore where permeability is reduced due to drilling, completion, or production activities, often requiring remediation to restore flow.
Deadman Anchor. A buried anchor used to secure guy wires and maintain rig stability during workover operations.
Dead Oil. Crude oil that has lost most of its dissolved gas content, reducing its natural pressure and mobility.
Debris Sub. A tool placed in the drill string or wellbore to collect debris or loose materials during operations.
Depth Control. The process of accurately determining the position of tools or equipment within the wellbore during operations.
Depth Reference Point. A fixed point, such as the rotary table or wellhead flange, used as a basis for measuring depth in the wellbore.
Desander. A device used to remove sand and other solid particles from produced fluids or drilling mud to prevent equipment wear and formation damage.
Descaling. The process of removing scale deposits, typically calcium or other mineral buildup, from wellbore surfaces or production equipment.
Differential Pressure. The difference in pressure between two points, such as across a valve, choke, or formation.
Disposal Well. A well used for the safe injection of waste fluids, such as produced water or brine, into a designated subsurface formation.
Diverter. A tool or system used to redirect fluids during well control or drilling operations, often to protect the wellhead or crew.
Diverting Agent. A chemical or mechanical material used to temporarily block certain flow paths during stimulation to redirect fluids to other areas.
Downhole Gauge. A sensor installed in the wellbore to measure parameters such as pressure and temperature at reservoir depth.
Downhole Safety Valve (DSV). A fail-safe valve installed in the production tubing to shut off flow automatically in emergency situations, ensuring well control and safety.
Downhole Safety Valve (DHSV). A valve installed in the tubing string below the surface, designed to shut off flow in emergency situations.
Downstream. The segment of the oil and gas industry involved in refining, processing, and distributing petroleum products to end users.
Drainhole. A horizontal or near-horizontal section of the wellbore drilled to maximize contact with the reservoir and improve hydrocarbon recovery.
Drift. The tendency of a wellbore to deviate from its intended path, often monitored and controlled during drilling.
Drill Stem Test (DST). A procedure for evaluating the productivity and pressure of a formation by temporarily producing fluids through the drill string.
Driller's Depth. The measured depth recorded by the driller during operations, often used as the primary depth measurement on site.
Driller Packer. A mechanical packer designed for use in drilling operations to isolate wellbore sections temporarily.
Drilling Mud. A fluid used during drilling to cool the drill bit, carry cuttings to the surface, and maintain wellbore stability.
Drop Ball. A spherical object dropped into the wellbore to activate tools, such as packers or sliding sleeves, at specific depths.
Dry Gas. Natural gas that contains little or no condensate or liquid hydrocarbons, consisting mostly of methane.
Dual Completion. A well completion method that allows simultaneous production from two separate zones in the same wellbore.

E

Electric Submersible Pump (ESP). A type of artificial lift system that uses a multistage centrifugal pump, powered by a downhole electric motor, to lift fluids from the well to the surface.
Emergency Response Plan (ERP). A documented plan outlining the procedures and responsibilities for handling emergencies, such as spills, fires, or explosions.
Environmental Containment System. Equipment and procedures used to prevent spills and leaks during workover or abandonment operations, ensuring compliance with environmental regulations.
Equalizing Valve. A valve used to equalize pressure across a packer or other downhole tool to facilitate its removal or retrieval.
Erosion. The gradual wearing away of equipment or wellbore surfaces due to high-velocity flow of fluids containing solids.
Expandable Casing. A type of casing that can be expanded to fit tightly against the wellbore, enhancing zonal isolation and well integrity.
Expendable Plug. A temporary plug placed in the wellbore that is designed to degrade or be removed once its purpose, such as zonal isolation, is complete.
Expansion Joint. A device that allows for controlled movement and expansion of tubular components in the wellbore due to thermal or pressure changes.
Explosive Perforating. A method of creating holes in casing and formation using shaped charges to allow fluid flow into the wellbore.
External Pulling Tool. A specialized tool used to latch onto and retrieve equipment or debris from the wellbore.
External Upset. A thickened section at the ends of tubing or casing designed to strengthen the connection and improve tensile load capacity.

F

Fall Protection System. Safety equipment, such as harnesses and lifelines, used to prevent or arrest falls while working at heights.
Field Separator. Equipment used at the wellsite to separate oil, gas, and water from produced fluids before transportation or further processing.
Filtered Brine. A brine solution that has been treated to remove solids and impurities, commonly used in well completions and workovers to minimize formation damage.
Fire Watch. A safety procedure requiring a designated worker to monitor for fire hazards during hot work operations, such as welding or cutting.
Fishing Tools. Specialized tools used to retrieve lost or stuck equipment from the wellbore during workover operations.
Fixed Choke. A flow-control device with a fixed orifice size, used to regulate the production rate from a well.
Flag Joint. A marked section of tubing or pipe used as a depth reference or for identification during downhole operations.
Flange. A mechanical component with a flat, circular rim used to connect pipes, valves, or other equipment in a wellhead or pipeline system.
Float Collar. A device installed near the bottom of a casing string to provide a seal and support cement placement during cementing operations.
Float Shoe. A casing shoe equipped with a backpressure valve to prevent cement backflow during casing cementing operations.
Flow Assurance. The practice of ensuring the uninterrupted flow of hydrocarbons from the reservoir to the surface, addressing issues like hydrates, wax, and scaling.
Flowback. The process of recovering fracturing fluids and produced water from the well after a hydraulic fracturing operation.
Flow Check. A procedure to verify if the well is flowing or if pressure buildup is occurring, often performed during drilling or completion.
Flow Cross. A component of the wellhead or surface equipment with multiple outlets for directing fluid flow in various directions.
Fluid Invasion. The unintended entry of drilling or completion fluids into the formation, potentially causing damage or altering formation properties.
Fluid-Loss Additive. A chemical additive used in drilling or fracturing fluids to reduce fluid loss into the formation and protect reservoir integrity.
Flush Point. The depth at which fluids injected into the wellbore begin to displace reservoir fluids, often used in displacement or cleanup operations.
Formation Damage. A reduction in reservoir permeability near the wellbore caused by drilling, completion, or production activities.
Formation Fluid. Fluids naturally present in the reservoir, including oil, gas, and water.
Formation Fracture Pressure. The pressure at which the formation rock fractures, a critical parameter in hydraulic fracturing and well control operations.
Formation Pressure. The pressure exerted by fluids in the reservoir, influencing production rates and well control requirements.
Frac Balls. Spherical devices used in hydraulic fracturing to isolate zones and control fluid flow during multi-stage treatments.
Frac Fluid. A specially engineered fluid used in hydraulic fracturing to create and propagate fractures in the reservoir.
Frac Head. A piece of surface equipment installed at the wellhead during hydraulic fracturing to connect high-pressure fracturing lines to the wellbore.
Frac Iron. High-pressure piping and equipment used to transport fracturing fluid from pumps to the wellhead.
Frac Manifold. A system of valves and piping used to distribute fracturing fluid from pumps to multiple wells or fracturing zones.
Frac Stack. The assembly of valves, spools, and other equipment installed on the wellhead during hydraulic fracturing operations.
Frac Tree. A specialized Christmas tree used during hydraulic fracturing to control and monitor fracturing fluid injection.
Fracture. A crack or break in the reservoir rock created naturally or through hydraulic fracturing, providing pathways for hydrocarbons to flow into the wellbore.
Fracturing Fluid. A fluid used in hydraulic fracturing operations to create and propagate fractures in the reservoir, typically carrying proppants to hold fractures open.
Fracturing Mandrel. A downhole tool used during hydraulic fracturing to isolate and stimulate specific zones in the wellbore.
Fracturing Manifold. A surface system that directs fracturing fluids from the pumps to various wellhead or fracturing zones.
Froth Flow. A two-phase flow regime characterized by a mixture of gas and liquid resembling froth, often occurring in pipelines or production tubing.
Fullbore. A wellbore or tubular with no obstructions, allowing full diameter access for tools or fluid flow.

G

Gas Bearing. A formation or reservoir containing significant quantities of natural gas.
Gas-Bearing. A term used to describe formations with natural gas as the dominant hydrocarbon phase.
Gas Cap. A layer of natural gas that overlies oil in a reservoir, created by differences in hydrocarbon densities.
Gas Coning. The upward movement of gas into the oil-producing section of a reservoir due to excessive production rates.
Gas Drive. A reservoir drive mechanism where natural gas expansion forces oil to the wellbore.
Gas Injection. The process of injecting gas into a reservoir to maintain pressure and enhance oil recovery.
Gas Lift. A method of artificial lift that uses injected gas to reduce the hydrostatic pressure of the fluid column, aiding production.
Gas-Lift Valve. A valve installed in a gas-lift system to control the entry of gas into the production tubing.
Gas Lock. A condition where gas accumulates in a pump or system, preventing normal operation and causing a reduction in fluid flow.
Gas-Oil Contact (GOC). The subsurface boundary between the gas cap and the underlying oil column in a reservoir.
Gas-Oil Mandrel. A downhole tool used in gas lift or gas-oil separation operations.
Gas Separator. A tool used downhole or at the surface to separate free gas from liquids in the production stream.
Gas Well. A well drilled specifically for the production of natural gas.
Gasdrive. An alternative spelling for gas drive, referring to the same reservoir drive mechanism powered by gas expansion.
Gas Monitoring System. A system designed to continuously detect and alert workers to hazardous gases, such as H₂S, in oil and gas environments.
Gauge Pressure. The pressure measurement relative to atmospheric pressure, typically used in well operations.
Gauge Ring. A circular tool used to verify the internal diameter of tubing or casing.
Gat Valve. A colloquial term for gate valve, a type of valve used to isolate flow in a pipeline or system.
Goat Head. A fitting used on fracturing trees to connect high-pressure lines for hydraulic fracturing operations.
Gravel Pack. A completion technique where gravel is packed around a screen in the wellbore to prevent sand production while maintaining permeability.
Gravel-Pack Screen. A screen used in conjunction with a gravel pack to filter out sand while allowing hydrocarbons to flow into the wellbore.

H

H2S Safety Procedures. Specific protocols and equipment designed to protect personnel from hydrogen sulfide (H2S) exposure during workover and abandonment operations.
Hammer Union. A type of mechanical connection used to quickly and securely join high-pressure piping components, commonly found in wellhead and flowline equipment.
HF (Hydraulic Fracturing). A stimulation technique that involves injecting fluid at high pressure into a reservoir to create fractures, enhancing hydrocarbon flow.
Hazard Communication (HazCom). An OSHA-required program that ensures workers are informed about the chemical hazards they may encounter and how to handle them safely.
Hearing Protection Devices (HPDs). Equipment such as earplugs or earmuffs used to protect workers from hazardous noise levels in oil and gas operations.
Heat Stress Management. Procedures and controls used to protect workers from heat-related illnesses in hot environments, including hydration and breaks.
High-Pressure Manifold. A system of valves and piping designed to control and direct the flow of fluids under high pressure, often used in hydraulic fracturing or well testing operations.
Holdup Depth. The depth at which a tool or object becomes lodged or stuck in the wellbore during operations.
Hookwall Packer. A type of mechanical packer used to isolate sections of the wellbore, secured in place by a set of hooks that grip the casing wall.
Horizontal Tree. A type of Christmas tree installed horizontally at the wellhead, often used in subsea applications to facilitate flowline connections.
Horsehead. The curved arm or beam at the top of a pump jack (beam pumping unit) used in artificial lift systems. It is connected to the walking beam and facilitates the up-and-down motion of the sucker rod string, enabling the extraction of oil from the well.
Hot Oiling. The process of circulating heated oil into a wellbore or pipeline to remove paraffin, hydrate blockages, or other flow obstructions.
Hot Tapping. A method of connecting to a live pipeline or vessel without shutting it down, allowing for maintenance or the addition of new infrastructure.
Hot Work Permit. An authorization process required before performing tasks like welding or cutting in areas where flammable materials are present.
HUD (Heads-Up Display). A digital display system used on drilling rigs or at well sites to provide operators with real-time data, enhancing situational awareness and decision-making.
Hydraulic Fracture Monitoring. The process of observing and analyzing fractures created during hydraulic fracturing using tools such as microseismic sensors or pressure gauges.
Hydraulic Fracturing. A reservoir stimulation technique in which fluid is injected at high pressure to create fractures in the rock, increasing permeability and hydrocarbon recovery.
Hydraulic Packer. A type of packer activated by hydraulic pressure, used to isolate zones in the wellbore during production or injection operations.
Hydrogen Sulfide (H₂S) Safety. Procedures and equipment designed to protect workers from the toxic effects of H₂S gas, including gas monitors and breathing apparatuses.

I

ICD. Stands for **Inflow Control Device**, a tool installed in the completion string to regulate fluid flow into the wellbore, enhancing production uniformity.
ICV. Stands for **Inflow Control Valve**, an adjustable downhole valve used in intelligent wells to control inflow from various zones.
Inflatable Packer. A packer that expands by inflating with fluid or gas, used to isolate wellbore sections during testing or treatment.
Inflow Control Device (ICD). A completion tool designed to balance inflow from multiple reservoir zones by creating resistance to flow, mitigating water or gas coning.
Inflow Control Valve (ICV). A valve used to manage production or injection rates from different zones in a well, often operated remotely in intelligent well systems.
Inflow Performance Relationship (IPR). A mathematical relationship that describes the flow rate of fluids from the reservoir into the wellbore as a function of pressure drawdown.
Inhibitor. A chemical additive used to prevent or mitigate undesirable reactions, such as corrosion, scale formation, or hydrate plugging.
Injection Line. A pipeline or tubing string used to transport fluids, such as water or gas, into the reservoir for injection operations.
Injection Mandrel. A completion component used to direct injected fluids into specific zones in the reservoir.
Injection Pressure. The pressure required to inject fluids into the reservoir, a key parameter for injection operations like waterflooding or gas injection.
Injection Pump. A pump used to pressurize and inject fluids, such as water or chemicals, into the well or reservoir.
Injection Well. A well used to inject fluids, such as water, gas, or CO₂, into the reservoir to maintain pressure or enhance recovery.
Instrument Hanger. A device used to suspend instruments, such as sensors or gauges, in the wellbore to collect downhole data.
Intelligent Well. A well equipped with advanced downhole sensors, valves, and control systems, allowing for real-time monitoring and zonal production management.
Intermediate Casing. A casing string set between the surface and production casing to isolate problematic zones or provide wellbore stability during drilling.
Intermittent Gas Lift. A method of artificial lift where gas is injected into the wellbore in cycles to lift fluids intermittently, often used in wells with low productivity.
Internal Pulling Tool. A specialized downhole tool used to grip and retrieve inner components, such as tubing or plugs, from the wellbore.
Ion Stabilizer. A chemical additive used to control ionic activity in brines or other fluids, preventing precipitation or scaling in the wellbore or formation.

J

J-Slot. A design feature in mechanical tools that allows selective engagement or release of components by following a predetermined path, often used in packers or setting tools.
Jar. A mechanical tool used in the drill string or wireline operations to deliver an impact or shock force to free stuck tools or equipment in the wellbore.
Jet Pump. A type of artificial lift system that uses high-pressure fluid to create a jet, generating suction to lift hydrocarbons to the surface.
Job Safety Analysis (JSA). A systematic process used to identify potential hazards and implement controls before performing a specific task.

K

Kelly. A square or hexagonal steel pipe that connects the rotary table to the drill string, enabling the rotation of the drill bit.
Kelly Bushing. A device that fits inside the rotary table to drive the kelly and provide torque to the drill string.
Kick. An influx of formation fluids into the wellbore due to pressure imbalance during drilling, requiring prompt control to prevent a blowout.
Kickoff Point (KOP). The depth at which a deviated or horizontal well begins to deviate from the vertical trajectory.
Kill Fluid. A specially formulated fluid used to control or stop unwanted well flow during drilling or workover operations.
Kill Line. A high-pressure line connected to the wellhead or blowout preventer (BOP) stack for pumping kill fluid into the well during well control operations.
Kill Weight Fluid. A heavy fluid with sufficient density to overcome reservoir pressure, used to regain control of a well during a kick.

L

Landing Collar. A device installed in the casing string that provides a seat for the wiper plug during cementing operations, ensuring proper placement of the cement.
Landing Nipple. A profile machined inside the tubing string designed to receive and anchor downhole tools, such as plugs or flow-control devices.
Life of the Well. The entire operational lifespan of a well, from drilling and completion through production and eventual abandonment.
Lifting Sub. A tool or accessory attached to tubulars or equipment to enable lifting and handling operations with hoisting equipment.
Liner. A casing string that does not extend to the surface, typically hung from a liner hanger inside the previous casing string.
Liner Hanger. A device used to hang a liner from the casing string above it, allowing the liner to be secured in place without extending to the surface.
Live Oil. Crude oil containing dissolved gases under reservoir pressure, which expands when brought to the surface.
Lock. A downhole device used to secure tools or equipment, such as plugs or mandrels, inside a wellbore.
Lock Mandrel. A component installed in a landing nipple to hold or lock flow-control devices or plugs securely in place.
Lockout/Tagout (LOTO). A procedure for isolating energy sources to ensure that equipment cannot be started while maintenance or repairs are being performed.
Lubricator Valve. A valve installed on the wellhead to allow the safe insertion or removal of tools into the wellbore under pressure, often used in wireline or coiled tubing operations.

M

Matrix Acidizing. A stimulation technique where acid is pumped into the reservoir matrix at pressures below the fracture gradient to dissolve formation damage and improve permeability.
Mechanical Integrity. The condition of well components such as casing, tubing, and packers to maintain structural integrity and ensure well control.
Mechanical Packer. A downhole tool used to isolate sections of the wellbore, mechanically set by rotating or applying weight.
Mechanical Skin. A reduction in reservoir permeability caused by the invasion of drilling or completion fluids or the installation of completion equipment.
Memory Gauge. A downhole pressure and temperature gauge that records data for retrieval and analysis after it is pulled to the surface.
Microannulus. A small gap between the cement sheath and the casing or formation, often caused by thermal or pressure cycling, which may compromise zonal isolation.
Microfractures. Small, naturally occurring or induced fractures in the reservoir rock that may affect fluid flow and production rates.
Mill-Out. The process of using a milling tool to remove obstructions such as plugs, packers, or scale from the wellbore.
Minimum Allowable Pressure. The lowest pressure at which a well or system can safely operate without compromising integrity or production.
Monobore Completion. A well completion design with a single-diameter production path, simplifying intervention and production operations.
Multilateral Well. A well with multiple branches or laterals extending from the main wellbore to increase reservoir contact and production.
Multipacker Completion. A completion design using multiple packers to isolate and produce from different zones within the same wellbore.
Multiphase Flow Meter. A device used to measure the flow rates of oil, gas, and water simultaneously in a production stream without separating the phases.
Multistage Fracturing. A hydraulic fracturing technique performed in multiple stages along a horizontal or vertical well to maximize reservoir contact.
Mud Cake. A thin, low-permeability layer of drilling fluid solids that forms on the wellbore wall, helping to reduce fluid loss into the formation.
Multicycle Valve. A downhole valve that can be repeatedly opened and closed for various operations, such as injection, production, or isolation.

N

Natural Flow. The production of hydrocarbons to the surface solely due to reservoir pressure, without the need for artificial lift methods.
Nipple Profile. A specific internal shape or profile in a tubing string designed to allow tools to lock or seal for various downhole operations.
Nodal Analysis. A method used to optimize production by analyzing pressure and flow rates at various points (nodes) in the production system, such as the reservoir, wellbore, and surface facilities.
Non-Damaging Fluid. A fluid designed to minimize damage to the reservoir during drilling, completion, or workover operations, often used in sensitive formations.
Nonproductive Interval (NPI). A section of the wellbore that does not contribute to hydrocarbon production, often isolated during completion.
Normal Pressure. The pressure gradient in a reservoir or formation that corresponds to the weight of the overlying rock and fluids, often used as a baseline for comparison with abnormal pressures.
Neutral Zone. The region in a wellbore or completion system where pressures are balanced, minimizing the risk of fluid movement or mechanical damage.
Neutral Displacement. A completion technique where fluids are pumped in such a way that no pressure differentials are created, reducing the risk of formation damage.
Nipple. A short piece of pipe or tubing with threads on both ends, used to connect equipment or piping in a wellbore.
Nipple Down. The process of disassembling wellhead or blowout preventer (BOP) equipment, often performed during well completion or servicing.
Nipple Up. The process of assembling wellhead or blowout preventer (BOP) equipment onto a well, typically following drilling or maintenance.
Nitrogen Cushion. A column of nitrogen gas used to reduce hydrostatic pressure in the wellbore, typically to protect formations or enhance fluid removal.
Nitrogen Kickoff. The process of injecting nitrogen into the wellbore to initiate or restore production by reducing fluid density and increasing flow.
Nitrogen Lift. A method of artificial lift that uses nitrogen gas to reduce hydrostatic pressure in the wellbore, enabling hydrocarbons to flow to the surface.
Nitrogen Unit. Equipment used to generate or transport nitrogen gas to the wellsite for operations such as nitrogen lift, kickoff, or well stimulation.
No-Go Nipple. A specialized nipple with an internal restriction designed to prevent certain tools or equipment from passing through, used for depth control or zonal isolation.
NODAL Analysis. A systems approach used to optimize the performance of a well by analyzing pressure and flow at various points, or "nodes," in the production system.

O

Offset Well. A well drilled near an existing well to access the same reservoir or to provide additional data for development and production planning.
Oil Saver. A rubber or elastomeric device used on the wireline to minimize the escape of oil or gas during well interventions.
Oil String. A casing string designed to support the wellbore during production and provide a conduit for hydrocarbon flow to the surface.
Open-Flow Potential. The maximum rate at which a well can produce hydrocarbons without restrictions, determined by reservoir properties and well configuration.
Openhole Completion. A well completion method where the wellbore is left uncased or partially cased, exposing the reservoir directly to the wellbore.
Openhole Gravel Pack. A sand control method in which gravel is packed around a screen in an openhole section to prevent sand production while maintaining permeability.
Openhole Packer. A mechanical device used in openhole completions to isolate sections of the wellbore and control fluid movement during production or testing.
Openhole Test. A method of testing reservoir properties, such as pressure and fluid composition, in an uncased section of the wellbore.
Opening Bomb. A pressure-activated tool used to initiate flow in a well by rupturing a barrier or opening a valve.
Operating Gas-Lift Valve (OGLV). A valve in a gas lift system that regulates the injection of gas into the tubing to enhance production by reducing hydrostatic pressure.
Operating Envelope. The range of pressures, temperatures, and flow conditions within which well equipment is designed to operate safely and efficiently.
Orifice Plate. A flow control device with a precision-cut hole, used to measure and regulate flow rates in pipelines and surface facilities.
Orifice Valve. A valve designed with a fixed or adjustable orifice to control flow rates in well operations or production systems.
Oxygen Scavenger. A chemical added to well fluids to remove dissolved oxygen and prevent corrosion in pipelines, tubing, and other equipment.
Overbalanced Completion. A completion method where the pressure in the wellbore is higher than the reservoir pressure, often to control fluid movement and maintain well stability.
Overpull. An intentional application of additional pulling force on a tubing or tool string to overcome resistance or free stuck equipment.
Overshot. A fishing tool used to retrieve objects, such as stuck pipe or tools, from the wellbore by gripping them externally.
Oxidizer. A chemical used to break down certain compounds in well treatment fluids or to assist in the removal of organic deposits.

P

Packer. A downhole tool used to isolate sections of the wellbore, preventing fluid movement between zones during production or injection.
Perforation. The process of creating holes in the casing or liner to allow fluids to flow between the reservoir and the wellbore.
Perforating Gun. A tool used in perforation operations, containing shaped charges that create holes in the casing and reservoir rock.
Permeability. A measure of the reservoir rock's ability to allow fluids to flow through its interconnected pore spaces.
Permit to Work (PTW). A formalized system requiring authorization before beginning specific tasks, ensuring safety compliance during workover and abandonment activities.
Pipe Ram. A type of blowout preventer (BOP) component that seals around the drill pipe during well control operations.
Pigging. The process of using a device called a "pig" to clean or inspect pipelines, often used during pipeline maintenance.
Plug and Abandon (P&A). The process of permanently sealing a well with mechanical or cement plugs and decommissioning it.
Polished Bore Receptacle (PBR). A tubular device with a polished internal surface used to accommodate movement of the tubing string or packer seals.
Proppant. A material, such as sand or ceramic beads, used in hydraulic fracturing to hold fractures open and maintain fluid flow pathways.
Production Casing. The casing string installed after drilling is completed to enable production and isolate the wellbore.
Production Logging Tool (PLT). A tool used to measure and analyze production rates and fluid flow within the wellbore.
Production Tubing. A string of pipe installed in the wellbore through which hydrocarbons are produced to the surface.
Pressure Test. A procedure used to assess the integrity of well components or formations by applying and monitoring pressure.
Pressure-Drawdown Test. A well test used to evaluate reservoir pressure and productivity by measuring pressure changes during production.
Production Packer. A packer installed in the production tubing to isolate the production zone and control fluid movement.
Perforating Charge. A shaped explosive charge used in perforating guns to penetrate casing, cement, and reservoir rock.
Polished Rod. The uppermost rod in a sucker rod string, polished to provide a seal in the stuffing box.
Pressure Maintenance. A reservoir management practice of injecting fluids (e.g., water or gas) to sustain reservoir pressure and enhance recovery.
Pup Joint. A short section of pipe used to adjust the length of a tubing or casing string.
Positive Displacement Motor (PDM). A downhole motor used to rotate the drill bit during directional drilling or milling operations.
Pressure Test. A procedure to verify the integrity of well equipment and seals during workover and abandonment operations, ensuring safety and compliance.
Pressure Transient Analysis (PTA). The interpretation of pressure changes over time to assess reservoir characteristics and well performance.
Primary and Secondary Barriers. Layers of well control, such as blowout preventers and kill fluid, used to prevent uncontrolled flow during operations.
Process Safety Management (PSM). An OSHA standard aimed at preventing the release of hazardous chemicals through effective design, operation, and maintenance of processes.

Q

Quick Connect. A coupling mechanism used to rapidly connect or disconnect wellhead equipment, tools, or pipelines without the need for threading.
Quick Latch. A device used to securely and quickly connect or disconnect surface or downhole tools during well operations.
Quick Release Valve. A valve designed to quickly relieve pressure or disconnect flow lines, often used in emergency situations.
Quick Union. A fitting used to connect high-pressure piping or fracturing iron quickly, ensuring a secure and leak-proof connection.
Quill Shaft. A hollow rotating shaft in drilling and completion equipment, used to transfer torque or house internal components like wireline or coiled tubing.

R

Radial Jet Drilling. A method that uses high-pressure fluid jets to create small lateral holes extending from the wellbore into the reservoir, enhancing production.
Rated Working Pressure. The maximum pressure at which equipment or components, such as tubing or valves, are designed to operate safely.
Recompletion. The process of modifying a well's completion to access a new production zone or improve performance in the existing zone.
Reservoir Characterization. The analysis and modeling of reservoir properties, such as porosity, permeability, and fluid distribution, to optimize production strategies.
Reservoir Fluid. Fluids naturally occurring in a reservoir, such as oil, gas, and water, which are evaluated during completion planning.
Reservoir Fracturing. The process of creating fractures in the reservoir rock using hydraulic fracturing techniques to increase hydrocarbon production.
Reservoir Monitoring. The use of tools and techniques, such as downhole gauges or sensors, to track pressure, temperature, and fluid movement in the reservoir.
Respiratory Protection. Equipment such as respirators or SCBAs used to protect workers from inhaling hazardous substances like dust, fumes, or gases.
Reverse Circulation. A drilling or completion technique where fluid is pumped down the annulus and returns up the tubing, used to remove debris or condition the well.
Rig-Up Safety Checklist. A pre-operation checklist to ensure all safety equipment and procedures are in place before beginning workover operations.
Rod Pump. A type of artificial lift system that uses a surface beam and a subsurface pump connected by sucker rods to lift fluids to the surface.
Rotary Drilling. A method of drilling that uses a rotating drill bit to cut through the rock, commonly employed in well construction and completion.
Rotating Liner Hanger. A device used to suspend a liner in the wellbore and facilitate rotation to improve cementing.
Rupture Disc. A pressure-sensitive device designed to burst at a specified pressure to protect equipment or allow controlled wellbore communication.

S

Safety Data Sheet (SDS). A document that provides information about the properties, hazards, and safe handling of chemicals used in oil and gas operations.
Sanding. The production of formation sand into the wellbore during oil or gas production, often leading to equipment erosion and reduced productivity.
Sealing. The process of isolating zones in the wellbore to prevent fluid migration, typically achieved with packers, cement, or sealing elements in completion tools.
Sealing Element. A flexible component in downhole tools, such as packers, used to create a seal between the tubing and casing or wellbore.
Screen. A device installed in the wellbore to filter out sand and other solids from the production stream while allowing hydrocarbons to flow.
Scab Liner. A short section of pipe or liner used to repair or reinforce damaged casing or tubing in the wellbore.
Shale Shaker. Equipment used to separate drill cuttings from drilling fluids on the surface, ensuring the fluid can be reused.
Sliding Sleeve. A downhole tool with a movable sleeve that allows selective flow between the tubing and the annulus.
Slickline. A thin, non-electric wireline used for lowering and retrieving tools in the wellbore for maintenance or intervention operations.
Stimulation. Techniques, such as hydraulic fracturing or acidizing, performed on a well to enhance production by improving the flow of hydrocarbons.
Stage Cementing. A method of cementing a well in stages to improve zonal isolation and ensure proper placement of cement.
Stop Work Authority (SWA). A policy empowering any worker to halt operations immediately if they observe unsafe conditions or potential hazards.
Subsurface Safety Valve (SSSV). A downhole valve installed in the production tubing to shut off flow automatically in emergencies, ensuring well control and safety.
Surfactant. A chemical additive used in well operations to reduce surface tension, improve fluid mobility, and enhance well cleanup.
Squeeze Cementing. A process where cement is forced into specific zones in the wellbore to seal off unwanted fluid paths or repair casing leaks.
Swabbing. The process of using a swab tool to remove fluids from the wellbore to initiate or restore well flow.
Sand Control. Techniques used to prevent the production of formation sand, such as gravel packing or sand screens, during hydrocarbon extraction.
Sand Screen. A downhole device that prevents sand and other solids from entering the production tubing while allowing hydrocarbons to flow.
Sand Trap. A surface device or subsurface tool designed to collect and hold sand or debris produced during well operations.
Snubbing Unit. Equipment used to insert or remove tubulars in a pressurized wellbore during workover operations without killing the well.
Submersible Pump. A type of artificial lift system installed in the wellbore to pump fluids to the surface, often used in wells with low reservoir pressure.

T

Tag Line. A safety line attached to equipment to help guide and control it during lifting or placement operations, reducing risks of swinging or uncontrolled movement.
Temporary Abandonment (TA). The process of suspending a well’s operations temporarily while ensuring wellbore integrity and safety compliance.
Test Plug. A device used to temporarily seal a section of a wellbore or pipeline for pressure testing or maintenance.
Thief Zone. A formation or zone that readily accepts fluids during operations such as drilling or cementing, potentially leading to losses or operational challenges.
Thread Protector. A device used to protect the threads of casing, tubing, or other well equipment from damage during transportation or handling.
Tool Joint. A thickened section at the ends of drill pipe or tubing where threads are located, allowing for connection and disconnection during operations.
Top Drive. A drilling system that rotates the drill string from the top, replacing the traditional rotary table, and improving efficiency and safety.
Top Kill. A well control procedure involving the pumping of heavy fluids directly into the wellbore to counteract formation pressure during blowout scenarios.
Torque Wrench. A specialized tool used to apply precise torque to connections, ensuring proper tightening of equipment to prevent leaks or failures.
Tubing Hanger. A component of the wellhead that suspends the production tubing string and provides sealing and flow control.
Tubing Pressure. The pressure inside the production tubing, monitored to ensure safe and efficient well operation.
Twist-Off. A mechanical failure in the drill string or tubing caused by excessive torque, leading to a break and potentially requiring fishing operations.

U

Ultrasonic Testing (UT). A non-destructive testing technique that uses high-frequency sound waves to detect flaws, measure thickness, or assess material properties in well completion equipment.
Umbilical. A flexible line or bundle of lines used to convey hydraulic, electrical, or chemical control fluids to subsea wellheads or other equipment.
Underbalanced Drilling. A drilling method where the pressure in the wellbore is intentionally kept lower than the reservoir pressure to minimize formation damage and enhance safety.
Underreamer. A downhole tool used to enlarge the wellbore diameter below a restriction, improving completion efficiency and cement placement.
Upstream. The segment of the oil and gas industry involved in exploration, drilling, and production of hydrocarbons.
Upstream Safety Valve (USV). A type of safety valve used in wellhead systems to prevent uncontrolled flow by shutting off the well when necessary.
Unloading Valve. A valve used to assist in bringing a well into production by controlling the release of fluids or gas from the wellbore.
Unplanned Event. An unexpected incident or failure during well completion or production, requiring immediate safety or operational response.
Utility Line. A small-diameter line used to carry utilities such as chemicals, hydraulic fluids, or power to well completion or control systems.

V

Vacuum Pressure. A pressure lower than atmospheric pressure, often monitored during certain well operations to avoid formation damage or equipment failure.
Valve. A mechanical device used to control the flow of fluids or gases in well completion and production systems, including gate, ball, and check valves.
Vent Line. A pipe or conduit used to safely release gas or fluid from a system, preventing pressure buildup and ensuring safe operations.
Venturi Effect. A phenomenon where fluid pressure decreases as it flows through a constricted section of a pipe, utilized in flow measurement or certain downhole tools.
Vibration Monitoring. The practice of tracking vibrations in equipment and piping to detect potential issues like mechanical failure or structural instability.
Viscosity. A measure of a fluid's resistance to flow, critical in designing drilling, completion, and fracturing fluids.
Volatile Organic Compounds (VOCs). Organic chemicals that evaporate easily at room temperature, often monitored to ensure safety and environmental compliance at wellsites.
Volume Control. The process of managing the volume of fluids in circulation or production, ensuring system integrity and optimal operations.
Volumetric Efficiency. A measure of the effectiveness of pumps and compressors in moving fluids or gases, often monitored in well operations.
Volumetric Method. A technique used to estimate the amount of recoverable hydrocarbons in a reservoir based on volume calculations and fluid properties.

W

Walkway. A safe, designated path or platform used by personnel to access equipment and areas on a rig or well site.
Wall Cake. A thin layer of filter cake deposited on the wellbore wall by drilling mud to reduce fluid loss into the formation.
Washpipe. A tubular device used during wellbore cleanup operations to circulate fluids and remove debris from the wellbore.
Water Cut. The percentage of water in the total production stream, used to evaluate the water content of produced fluids.
Water Flooding. A secondary recovery process in which water is injected into the reservoir to maintain pressure and displace hydrocarbons toward production wells.
Water Hammer. A surge of pressure in a pipeline or tubing string caused by sudden changes in fluid velocity, which can damage equipment.
Water Injection Well. A well specifically drilled or converted to inject water into a reservoir to enhance oil recovery or dispose of produced water.
Wellbore Cleanout. The process of removing debris, scale, or other obstructions from the wellbore during workover or prior to abandonment.
Wellbore Cleanup. The process of removing debris, mud, or other contaminants from the wellbore before production or completion operations.
Wellbore Stability. The maintenance of structural integrity in the wellbore to prevent collapse or other issues during drilling, completion, or production.
Well Control. The set of procedures and equipment used to manage well pressure and prevent blowouts during drilling, completion, or workover operations.
Well Control Certification. A mandatory OSHA-compliant certification for personnel involved in workover operations, focusing on pressure control and blowout prevention.
Well Control Training. A specialized safety training program designed to equip workers with the knowledge to manage well pressure and prevent blowouts.
Well Integrity Management. A system of practices and tools ensuring that a well remains structurally sound and environmentally safe throughout its lifecycle, including abandonment.
Wellhead. The surface equipment at the top of a well that provides structural support and control for production, injection, or testing operations.
Well Integrity. The ability of a well to contain and control fluids within its constructed boundaries, ensuring safety and environmental protection.
Well Logging. The process of recording data about the geological formations and wellbore conditions to evaluate the well's potential and integrity.
Well Pad. A prepared surface location designed to support multiple wells and associated equipment, typically in unconventional oil and gas operations.
Well Test. A procedure to evaluate a well's productivity, pressure, and reservoir characteristics by temporarily producing fluids.
Whipstock. A tool used to deflect the drill bit or casing in a specific direction, often during sidetracking operations.
Wireline. A cable used to lower and retrieve tools in the wellbore for various operations such as logging, perforating, and setting packers.
Wireline Logging. The use of wireline tools to measure and record wellbore and formation properties, aiding in well evaluation and completion planning.
Workover. The process of performing major maintenance or remedial operations on a well to restore or enhance production.
Workplace Hazard Assessment. A formal evaluation of the work environment to identify risks and determine the appropriate safety measures.
Wiper Plug. A device used during cementing operations to separate the cement slurry from other fluids and clean the casing.

X

Y

Yield Point. A measure of the stress at which a material begins to deform plastically; in drilling fluids, it indicates the fluid's ability to carry cuttings.

Z

Zero Discharge. An environmental policy or practice aimed at preventing the release of fluids or materials from oil and gas operations into the environment.
Zero Flare Policy. A practice designed to eliminate routine flaring of natural gas during well completion or production, improving environmental compliance and reducing greenhouse gas emissions.
Zone Isolation. The process of isolating specific sections of the wellbore to prevent fluid communication between zones, often achieved using packers or cement plugs.
Zone Perforation. The targeted perforation of specific zones in a wellbore to allow fluid flow from selected intervals while isolating others.
Zone Testing. The process of evaluating the production potential, pressure, and fluid characteristics of individual reservoir zones during well completion.