902 Well Site Preparation and Drilling Safety

Glossary

A

• Abandonment Plug. A cement or mechanical barrier placed in a wellbore to permanently seal it during well abandonment operations.
• Accumulator Unit. A hydraulic system that stores pressurized fluid to operate the Blowout Preventer (BOP) during well control events.
• Adjustable Choke. A device used to regulate and control the flow rate of fluids from the well, essential in managing pressure during drilling or production.
• Air Drilling. A method of drilling that uses compressed air instead of drilling mud to remove cuttings from the wellbore, commonly employed in certain types of formations.
• Annular Preventer. A component of the Blowout Preventer (BOP) stack designed to seal the wellbore around various sizes and shapes of equipment or the open hole. It uses a flexible rubber element that can be compressed to form a seal.
• Annular Velocity. The speed at which drilling fluids move through the annulus between the drill pipe and the wellbore, crucial for carrying cuttings to the surface.
• Annulus. The space between the wellbore wall and the casing, or between different strings of casing, used to circulate fluids or install barriers like cement.
• Angle Grinder. A handheld power tool used for grinding, cutting, and polishing materials such as metal, stone, and concrete.

B

• Bailer. A long, cylindrical tool used to retrieve debris, sand, or fluid from the wellbore during maintenance or cleanup operations.
• Bell Nipple. A large-diameter pipe located at the top of the BOP stack, directing drilling fluids and cuttings to the flowline or mud pits.
• Bit Breaker. A tool used to safely hold and loosen the drill bit from the drill string when changing the bit during drilling operations.
• Bit Nozzle. Openings at the base of the drill bit through which drilling mud is expelled, helping to clean and cool the bit while carrying cuttings to the surface.
• Blind Ram. A component of the BOP designed to completely seal the wellbore when no drill pipe or tubing is in the hole.
• Blowout. The uncontrolled flow of oil, gas, or other well fluids from a well, caused by a failure to control pressure during drilling, completion, or workover operations.
• Blowout Preventer (BOP). A safety device installed on the wellhead to prevent uncontrolled release of oil, gas, or fluids during drilling operations.
• Bottom Hole Assembly (BHA). The lower part of the drill string, including the drill bit, stabilizers, and other tools, designed to optimize the drilling process.
• Box and Pin Connections. The male (pin) and female (box) threaded ends of tubular equipment used to join sections of drill pipe or casing.
• Brake System. A mechanical or hydraulic system used to control the descent of the drill string and prevent excessive tension on the equipment during tripping and drilling operations.
• Bridge Plug. A downhole tool used to isolate sections of the wellbore temporarily or permanently, often employed during well workovers or abandonment.
• Brine. A saltwater-based fluid used in well control operations and as a completion or workover fluid to maintain wellbore stability.

C

• Catwalk. A platform used to stage and align tubulars and other equipment before they are hoisted onto the rig floor.
• Casing. Steel pipe placed in the wellbore to prevent the walls of the hole from collapsing and to isolate different subsurface layers.
• Casing Centralizer. A device used to keep the casing centered in the wellbore to ensure uniform cement placement around the casing.
• Cementing. The process of pumping a cement slurry into the annulus between the casing and the wellbore to secure the casing and prevent fluid migration between subsurface formations.
• Choke Manifold. A system of valves and chokes used to control and measure the flow of fluids from the well, particularly during well control operations.
• Circulating System. The system used to circulate drilling mud from the mud pits, down the drill string, and back to the surface, carrying drill cuttings to the shale shaker for removal.
• Circulation Sub. A specialized tool used to divert or control the flow of fluids within the drill string, often to aid in wellbore cleaning.
• Conductor Pipe. The first string of casing installed in a well to provide structural integrity to the wellbore and isolate shallow formations.
• Conventional Core. A cylindrical sample of rock extracted from the wellbore for detailed geological and petrophysical analysis.

D

• Degasser. A piece of equipment used to remove entrained gas from drilling mud to ensure safer and more efficient drilling operations.
• Directional Drilling. A technique used to drill non-vertical wellbores to reach reservoirs at specific locations, increase reservoir exposure, or bypass obstacles.
• Doghouse. A small structure on the rig floor that serves as an office or tool storage area for the driller and crew.
• Drift Tool. A cylindrical tool used to verify the internal diameter of casing or tubing, ensuring it is free of obstructions.
• Drill Collar. A heavy, thick-walled pipe placed above the drill bit to provide weight on the bit and keep the drill string under tension.
• Drill Mud. A specially formulated fluid used during drilling to lubricate the drill bit, remove cuttings, and maintain pressure in the well.
• Drill Pipe. Hollow steel pipes that make up the drill string and transmit torque and drilling fluids to the drill bit.
• Drill String Vibrations. Oscillations in the drill string caused by mechanical, hydraulic, or rotational forces, which can lead to equipment damage or inefficiency.
• Drilling Ahead. The process of extending the depth of the wellbore by rotating the drill bit and advancing the drill string.
• Drilling Fluids Engineer (Mud Engineer). A specialist responsible for designing, monitoring, and managing the properties of drilling mud to ensure it meets the operational and safety requirements.
• Drilling Jar. A downhole tool designed to deliver an impact force to free stuck equipment by generating a hammer-like effect in the wellbore.
• Dynamic Kill. A method of controlling a well kick by pumping heavy drilling fluids at high rates to overcome formation pressure.

E

• Electric Logging. A method of recording electrical properties of subsurface formations to determine characteristics such as porosity, water saturation, and lithology.
• Elevators. A clamping tool used to lift and lower drill pipe, casing, or tubing during tripping operations.
• Extended Reach Drilling (ERD). A drilling technique used to reach distant reservoirs from a single surface location by extending the horizontal reach of the wellbore.

F

• Fishing Magnet. A tool used to recover metal debris from the wellbore, such as broken drill bits or pieces of casing.
• Fishing Tools. Specialized tools used to retrieve lost or stuck equipment, such as drill pipe or bits, from the wellbore.
• Float Collar. A device installed near the bottom of the casing string to prevent cement from flowing back into the casing after it has been placed.
• Flowline. A pipe or conduit that transports drilling fluids and cuttings from the wellbore to the shale shakers or mud pits.
• Formation Integrity Test (FIT). A test conducted to determine the strength of the formation and its ability to withstand drilling pressures without fracturing.
• Formation Pressure. The natural pressure exerted by fluids within a geological formation, which must be managed to prevent blowouts.

G

• Gamma Ray Log. A type of well logging that measures natural gamma radiation to identify and analyze rock formations.
• Gas Kick. An influx of gas into the wellbore from the formation, often a precursor to a blowout if not controlled.

H

• Hook Load. The weight of the drill string, casing, or other equipment as measured by the derrick hook during hoisting operations.
• Hydraulic Fracturing (Fracking). A stimulation technique that injects high-pressure fluid into the formation to create fractures, enhancing the flow of oil or gas to the wellbore.

I

• Intermediate Casing. A string of casing set in the wellbore to isolate problematic zones, such as those with unstable formations or high-pressure fluids.

J

• Jar. A mechanical or hydraulic tool used to deliver sharp impacts to free stuck tools or equipment in the wellbore.

K

• Kelly. A long, square or hexagonal steel pipe that transfers rotary motion from the rotary table to the drill string.
• Kelly Bushing. A device that fits into the rotary table and allows the Kelly to rotate during drilling.
• Kick Tolerance. The maximum allowable influx of formation fluids that can be safely controlled without fracturing the weakest formation.
• Kickoff Point (KOP). The depth in a wellbore where directional drilling begins, deviating from vertical to reach a specific target.

L

• Liner Hanger. A device used to suspend a liner, which is a partial casing string, inside an existing casing to provide additional wellbore stability.
• Logging While Drilling (LWD). A process of collecting geological and formation data in real-time as the well is being drilled.
• Lost Circulation. The condition where drilling mud escapes into fractures or porous formations instead of returning to the surface, requiring remediation to maintain well control.

M

• Managed Pressure Drilling (MPD). An advanced drilling technique that uses precise control of drilling fluid pressure to mitigate risks and optimize wellbore stability.
• Measurement While Drilling (MWD). A system that collects real-time data on wellbore trajectory and drilling parameters, aiding directional drilling.
• Monkey Board. A platform located in the derrick where a derrickman handles and aligns drill pipe during tripping operations.
• Mudding. The process of circulating drilling mud through the wellbore to carry cuttings to the surface and maintain well pressure.
• Mud Pump. A high-pressure pump used to circulate drilling mud through the drill string, down to the bit, and back up the annulus to the surface.

N

• Neutral Point. The point in the drill string where the axial force transitions between tension and compression, critical for understanding string stability.
• Nipple-Up. The process of assembling and installing the Blowout Preventer (BOP) stack at the wellhead.
• Non-Productive Time (NPT). Periods during drilling or completion operations when no progress is made, often due to equipment failure or well control issues.

O

• Oil-Based Mud (OBM). A type of drilling fluid where oil is the primary continuous phase, used for its superior lubricating and temperature-stabilizing properties.
• Open Hole. A section of the wellbore that has not been cased or cemented, exposing the formation directly to the drilling environment.
• Overburden Pressure. The pressure exerted by the weight of overlying rocks and fluids on a formation, influencing drilling and completion operations.

P

• Pack-Off. A seal created in the wellbore to isolate fluid zones or control pressure, often using a packer or specialized sealing tools.
• Packer. A downhole tool used to create a seal in the annulus between the casing and the tubing or open hole, typically to isolate production zones or control pressure.
• Pill. A specially formulated volume of fluid, such as heavy mud or chemicals, used to address specific wellbore conditions, such as lost circulation or wellbore stability.
• Perforating Gun. A tool used to create holes in the casing and cement, allowing reservoir fluids to flow into the wellbore.
• Pipe Ram. A component of the BOP that seals around a specific size of drill pipe to control well pressure.
• Pilot Hole. A smaller, initial wellbore drilled to gather geological information or ensure proper positioning for the main well.
• Power Tongs. Hydraulic or pneumatic tools used to make up or break out threaded connections on drill pipe, casing, or tubing.
• Pore Pressure. The pressure exerted by fluids within the pores of a geological formation, critical for determining safe drilling parameters.
• Pressure Control Equipment. Devices such as BOPs, annular preventers, and choke manifolds that help maintain safe pressure in the wellbore and prevent blowouts.

Q

• Queen Post. A vertical support member in a derrick that provides stability to the structure during drilling operations.
• Quiescent Mud. Drilling mud that is at rest, often in the drill pipe or annulus, waiting to be circulated during well operations.

R

• Reaming. The process of enlarging or cleaning the wellbore by rotating the drill string and circulating drilling fluids.
• Reverse Circulation. A technique where drilling fluid is pumped down the annulus and returns up the drill pipe, often used for cleaning or special operations.
• Rigging Up. The process of assembling and setting up the drilling rig and associated equipment at the well site.
• Rotary Hose. A flexible, high-pressure hose used to deliver drilling mud from the mud pump to the standpipe.
• Rotary Steerable System (RSS). A tool used in directional drilling that allows continuous rotation of the drill string while controlling the direction of the wellbore.
• Rotary Table. A mechanical device on the rig floor that provides rotational force to the drill string during drilling.

S

• Safety Valve. A valve installed in the drill string to prevent backflow of fluids into the wellbore in emergency situations.
• Shale Shaker. A vibrating screen used to separate drill cuttings from the drilling mud.
• Shut-In Pressure (SIP). The pressure measured in the wellbore when the well is closed at the surface and no fluids are flowing, critical for assessing well control conditions.
• Sidetracking. The process of creating a new wellbore path by drilling out of the existing wellbore, often to bypass an obstruction or access a new reservoir.
• Spinning Chain. A chain used to rapidly spin sections of drill pipe to make or break threaded connections on the rig floor.
• Spudding. The initial phase of drilling a well, where the conductor pipe is driven into the ground to prepare for drilling operations.
• Stand. A section of drill pipe, typically consisting of two or three joints, racked vertically in the derrick during tripping operations.
• Stripper Rubber. A sealing element used in the stripper assembly of the BOP to maintain pressure control while allowing the drill string to move through it.
• Surface Casing. The first string of casing cemented into the well to protect freshwater zones and provide a foundation for BOP installation.
• Swivel. A device that allows the drill string to rotate while also enabling the circulation of drilling fluids through it.

T

• Torque Wrench. A specialized wrench used to apply precise torque to threaded connections, ensuring a proper seal and joint strength.
• Trip Tank. A small tank used to monitor fluid displacement during tripping operations to ensure proper well control.
• Tripping In. The process of lowering the drill string into the wellbore.
• Tripping Out. The process of removing the drill string from the wellbore.

U

• Underbalanced Drilling. A technique where the pressure of the drilling fluid is intentionally kept lower than the formation pressure to improve drilling efficiency and prevent damage to the reservoir.

V

• Volumetric Control. A method of managing a well kick by controlling the volume of fluids in the well to maintain pressure balance.

W

• Washout. An enlargement of the wellbore caused by high-velocity fluid flow, which can weaken wellbore stability and complicate drilling operations.
• Wellbore Stability. The condition where the wellbore maintains its structural integrity during drilling, completion, or production, preventing collapse or other issues.
• Well Control Operations. Techniques and procedures used to prevent or control the influx of formation fluids into the wellbore, ensuring safe drilling operations.
• Wellhead. The equipment installed at the surface of a well to control pressure and provide access to the wellbore.
• Wireline Logging. The use of electrically powered instruments lowered into the wellbore on a wireline to gather subsurface data.
• Workover Rig. A smaller rig used for maintenance, repair, or recompletion of an existing well to enhance or restore production.

X

• X-Mas Tree (Christmas Tree). A series of valves and fittings installed on a completed well to control production flow and provide access for maintenance or well intervention.

Y

• Yield Point. A measure of a drilling fluid’s ability to carry cuttings to the surface, defined as the stress required to initiate fluid flow.
• Yard. A storage area near the well site where drilling equipment, casing, and supplies are kept before being used in operations.

Z

• Zone Isolation. The process of isolating specific subsurface zones using casing, cement, or packers to prevent fluid migration between formations.
• Zero Discharge. An environmental policy or practice in which no waste or drilling fluids are discharged to the environment, requiring containment or recycling.