Oil and Gas Terms Beginning with “J”

What Is a J-Slot? A J-slot is a cam-and-track mechanism milled into downhole tools such as packers , bridge plugs, and tubing-retrievable safety valves that converts a specific sequence of surface axial and rotational… Read more →

A J-slot is a specially shaped slot or groove machined into the mandrel or body of a downhole tool — with a profile resembling the letter "J" when viewed as an unrolled flat surface — that works in conjunction with a… Read more →

The Joule-Thomson effect describes the temperature change that occurs when a gas expands through a restriction at constant enthalpy, meaning without any heat exchange with the surroundings and without performing… Read more →

A jacking frame is the structural hydraulic device mounted on top of a coiled tubing unit's injector head that provides the mechanical force necessary to push (inject) or pull (retrieve) the coiled tubing string into… Read more →

What Is a Jackup Rig? A jackup rig is a self-elevating mobile offshore drilling unit (MODU) that floats under tow or under its own power to the well location, then hydraulically or mechanically extends its steel legs… Read more →

A jar is a downhole tool installed in the drill string or fishing string that delivers a high-impact mechanical blow to free stuck pipe by storing energy in a compressed spring or hydraulic chamber that releases… Read more →

The jar test is a simple qualitative field procedure for assessing drilling fluid gel strength and thixotropic behavior by pouring a sample of mud into a glass jar, observing whether the fluid flows freely or holds its… Read more →

A small-diameter nozzle used to mix cement. Read more →

A jet cutter is a wireline-conveyed perforating gun configured specifically to cut through a tubular (casing, tubing, or drill pipe) by detonating shaped charges arranged circumferentially around the tool body to… Read more →

A jet mixer is a fluid mixing device used in oilfield cementing and drilling operations that uses the high-velocity flow of a liquid (typically water or drilling mud) through a narrow nozzle or jet to create suction and… Read more →

What Is Jet Perforating? Jet perforating is the process of creating flow channels through casing, cement sheath, and into the reservoir formation using shaped explosive charges mounted in a perforating gun. The Monroe… Read more →

A jet pump (also called a hydraulic jet pump or ejector pump) is a type of artificial lift device that operates on the principle of entrainment and momentum transfer between a high-velocity fluid jet and the surrounding… Read more →

The exit velocity of the drilling fluid after it accelerates through bit nozzles. Read more →

What Is a Joint? A joint refers to a single length of tubular goods, most often drillpipe , casing , or tubing , supplied as a discrete piece that threads to adjacent joints to assemble the full pipe string. Drilling… Read more →

(noun) An archaic oilfield slang term for a geophone, the ground-mounted sensor used in seismic acquisition to detect and convert reflected seismic wave energy into electrical signals. The term originated in early… Read more →

Jug hustler is the long-standing oilfield slang for a member of a seismic acquisition crew whose job is to lay out, plant, and later retrieve the geophones and connecting cables that record the ground motion in a… Read more →

What Is Junk? Junk is any unwanted object or debris inside a wellbore. It can be a dropped hand tool, bit cone, slips insert, broken wireline part, metal shavings, scale, cement, rubber, or failed tool piece. API RP 54… Read more →

A junk basket (also called a junk sub, debris catcher, or core catcher in some contexts) is a downhole fishing tool used in wellbore cleanup operations to retrieve metallic debris (junk), formation cuttings, and other… Read more →

A junk pusher is a downhole conditioning tool run on tubing, drillpipe, or coiled tubing to confirm that a section of casing is fully open to bore before a packer , bridge plug, or other fullbore device is set or run… Read more →

A junk sub (or junk basket) is a downhole tool placed above a mill, bit, or drill bit in the bottomhole assembly (BHA) that catches and retains metallic debris, junk, and cuttings generated during milling or drilling… Read more →