Oil and Gas Terms Beginning with “T” — Page 6

Transit time, almost always written as the interval transit time and symbolized DT or delta-t, is the duration required for a compressional acoustic wave, a P-wave, to travel a fixed unit of distance through a… Read more →

Transition flow (also called churn flow) is a multiphase flow regime in which gas and liquid are mixed in a violently unstable, chaotic pattern with no clear continuous phase. It occurs at gas velocities higher than… Read more →

The transition zone in formation evaluation refers to the volume of formation between the flushed zone (the immediately near-wellbore region from which mud filtrate has displaced essentially all moveable formation… Read more →

Transmission tomography in oilfield geophysics is an imaging method that reconstructs the spatial distribution of subsurface acoustic or electromagnetic properties by analyzing the travel times, amplitudes, or waveforms… Read more →

Transpression is a structural geological deformation regime in which oblique convergence (movement of tectonic plates or crustal blocks toward each other at an angle to the boundary between them) produces a combination… Read more →

Transtension is a tectonic regime that combines oblique extension with a component of strike-slip displacement, occurring where two crustal plates or blocks move apart at an angle that is oblique to the boundary between… Read more →

Transverse electric mode (TE mode) in electromagnetic theory is a wave propagation mode in which the electric field vector is oriented entirely perpendicular to the direction of wave propagation — with no component of… Read more →

The transverse magnetic (TM) mode is a specific configuration of an electromagnetic field in which only one component of the magnetic field exists alongside two components of the electric field perpendicular to it — for… Read more →

Transverse relaxation is the loss of coherent precession energy by hydrogen protons in a rock sample while the protons precess about a static magnetic field during a nuclear magnetic resonance (NMR) measurement —… Read more →

What Is a Trap in Oil and Gas? A trap in petroleum geology is a geometric configuration of reservoir rock and impermeable seal rock that prevents migrating hydrocarbons from escaping and causes them to accumulate into… Read more →

Trapped oil is the fraction of crude oil that remains immobile in pore spaces of a reservoir rock after primary depletion and waterflood operations because of capillary forces that prevent its displacement by the… Read more →

(noun) A section of tubing with a polished bore receptacle or seal assembly that permits relative axial movement between the tubing string and a downhole packer, accommodating thermal expansion, contraction, and… Read more →

The traveling block is the movable assembly of sheaves (pulleys) that hangs on the drilling line in the derrick and travels up and down as the drill string and casing are run into and out of the wellbore — paired with… Read more →

The traveling valve is one of the two ball-and-seat check valves at the heart of a subsurface sucker-rod pump, the beam-driven pump that artificially lifts oil from wells whose reservoir pressure can no longer push… Read more →

Travelling slips are the gripping element mounted at the top of the hydraulic jack assembly on a snubbing unit, also called a hydraulic workover (HWO) unit, and they are the component that physically moves a tubular… Read more →

Travelling snubbers are the hydraulic gripping and stroking assemblies in a snubbing unit that clamp onto the drill pipe or tubing string and move it up or down through the wellbore under live well pressure, functioning… Read more →

Traveltime in reflection seismology is the elapsed time it takes a seismic signal to leave a source, propagate down through the Earth, reflect off a subsurface boundary where acoustic impedance changes, and return to a… Read more →

A treater (also called heater treater or emulsion treater) is a process vessel used to treat oil-water emulsions in the produced fluid stream so that the resulting separated oil meets pipeline transport specifications… Read more →

The temporary surface piping, valves and manifolds necessary to deliver a fluid treatment to the wellbore from the mixing and pumping equipment. Read more →

A treatment fluid is any fluid pumped into a wellbore or formation during a stimulation, completion, workover, or well intervention operation to achieve a specific engineering objective — the term encompasses acid (for… Read more →

Used synonymously with the term play to describe an area in which hydrocarbons occur, such as the Wilcox trend of the Gulf Coast. Read more →

Trip gas is the increase in hydrocarbon gas concentration measured in the drilling fluid returns when drill pipe is pulled out of (tripped out of) a wellbore — arising from the swabbing action of the drill string as it… Read more →

A triplex pump is a positive-displacement reciprocating pump with three cylinders arranged in parallel that discharges fluid in three offset pressure pulses per revolution of the crankshaft, producing a smoother and… Read more →

Tripping pipe is the operation of pulling the drillstring out of the wellbore and running it back in, and a complete out-and-in cycle is called a round trip. The most common reason to trip is a dull or damaged bit that… Read more →

In petroleum geoscience and engineering, trough refers to several related concepts that share the common characteristic of a low point or elongated depression, each with distinct technical meanings depending on the… Read more →

True resistivity (Rt) in formation evaluation is the electrical resistivity of the undisturbed formation in the reservoir zone beyond the reach of mud filtrate invasion, representing the resistivity of the rock matrix,… Read more →

True stratigraphic thickness (TST) is the actual thickness of a rock layer measured perpendicular to its bedding planes. The number is what a geologist would get if they could lay the rock layer flat and measure across… Read more →

What Is True Vertical Depth? True vertical depth (TVD) is the vertical distance from a reference datum — typically the kelly bushing (TVDKB) or mean sea level (TVDSS) — to a specific point in a wellbore, calculated from… Read more →

True vertical thickness, abbreviated TVT, is the thickness of a bed or rock body measured straight down along a vertical line at a single point in the subsurface. It is the thickness you would record if you dropped a… Read more →

True amplitude recovery (TAR) is a sequence of seismic data processing steps designed to compensate for the amplitude decay of seismic waves caused by spherical divergence, intrinsic attenuation (anelastic absorption),… Read more →