Oil and Gas Terms Beginning with “D” — Page 3

A graph that shows the effects of environmental factors on the ideal response of a measurement. The name comes from the departure of the actual response from the ideal. The term is used most commonly in relation to the… Read more →

In a nuclear magnetic resonance (NMR) measurement, the loss of synchronization of hydrogen atoms precessing at different speeds about the static magnetic field. When the signals from individual atoms are not… Read more →

An isolated section of reservoir in which the pressure has dropped below that of adjacent zones or the main body of the reservoir formation. Read more →

The drop in reservoirpressure or hydrocarbon reserves resulting from production of reservoir fluids. At times, a strong waterdrive will maintain reservoir pressure to a substantial degree so that reserves diminish… Read more →

An assembly of pressure-control equipment that enables the running and retrieval of long tool strings on a coiled tubing string in a live wellbore. The deployment system is configured to provide two barriers against… Read more →

The area of thickest deposition in a basin. Read more →

The action of moving sediments and laying them down. Read more →

The relative kinetic energy of the environment. A high-energy environment might consist of a rapidly flowing stream that is capable of carrying coarse-grained sediments, such as gravel and sand. Sedimentation in a… Read more →

The area in which and physical conditions under which sediments are deposited, including sediment source; depositional processes such as deposition by wind, water or ice; and location and climate, such as desert, swamp… Read more →

The three-dimensional array of sediments or lithofacies that fills a basin. Depositional systems vary according to the types of sediments available for deposition as well as the depositional processes and environments… Read more →

The practice of ensuring that all measurements taken in a borehole are matched to the "base depth," normally the depth determined with the resistivity log. Read more →

A device used in acquisition of marineseismic data that keeps streamers at a certain depth in the water. Read more →

The process of transforming seismic data from a scale of time (the domain in which they are acquired) to a scale of depth to provide a picture of the structure of the subsurface independent of velocity. Depth… Read more →

The process of comparing and fixing measured depths with known features on baseline logs of the wellbore tubulars and the surrounding formation. Read more →

(noun) A fixed reference elevation from which all depth measurements in a well are calculated, typically the kelly bushing, rotary table, drill floor, or mean sea level. Establishing a consistent depth datum is… Read more →

A two-dimensional representation of subsurface structure with contours in depth that have been converted from seismic traveltimes. Read more →

A magnetic mark placed on a loggingcable as a reference for depth measurements. The marks are placed on the cable at regular intervals, usually 100 ft [30 m] or 50 m [164 ft], under a certain tension in a workshop. The… Read more →

Pertaining to two or more logging curves that have been aligned in depth. Logs recorded on different runs will not be exactly aligned at all depths because of the difficulty of perfect depth control. If the two logs are… Read more →

The practice of shifting depths of various data sets to a measurement that is known to be on depth. The general standard that is usually used is the first resistivity logs run, because those logs usually underwent the… Read more →

A step in seismic processing in which reflections in seismic data are moved to their correct locations in space, including position relative to shotpoints, in areas where there are significant and rapid lateral or… Read more →

The distance from the borehole wall that the mudfiltrate has penetrated into the formation. The depth of invasion affects whether a log measures the invaded zone, the undisturbed zone or part of each zone. The term is… Read more →

What Is Depth of Investigation? Depth of investigation (DOI) is the radial distance from the borehole axis at which a wireline or LWD logging tool is primarily sensitive to formation properties. It defines how far into… Read more →

A point on the surface for which the depth to a horizon has been calculated in a refractionseismic survey. The term is commonly misused as a synonym for common depth point. Read more →

The point in a well from which depth is measured. Alternatively, the depth reference is the point at which the depth is defined as being zero. It is typically the top of the kelly bushing or the level of the rig floor… Read more →

A point within the wellbore from which accurate depth measurements can be made, such as the end of the tubing string, or a nipple or similar completion component. Read more →

A display of seismic data with a scale of units of depth rather than time along the vertical axis. Careful migration and depth conversion are essential for creating depth sections. Read more →

A calibrated wheel used to drive the depth recording system in wirelinelogging. The wheel is pressed against the logging cable as the cable is spooled onto the drum and therefore turns as the cable is run in and out of… Read more →

Referring to a borehole-compensation scheme for sonic logs that combines measurements taken when the logging tool is at two different depths in the borehole. In normal borehole-compensation schemes, the effects of caves… Read more →

Logs that have been calculated from other logs to find the rate at which a log is changing with depth. For example, the derivative caliper (rugosity) calculates the rate at which the caliper is changing from one depth… Read more →

The structure used to support the crown blocks and the drillstring of a drilling rig. Derricks are usually pyramidal in shape, and offer a good strength-to-weight ratio. If the derrick design does not allow it to be… Read more →