Oil and Gas Terms Beginning with “D” — Page 8

The portion of movement of a downhole pump at which the rods are going down and the downhole pump is being filled with fluid. Read more →

A technique used to estimate the value of a potential field or seismic data at a surface beneath a measured surface. The method is risky because it assumes continuity of the field, so anomalies affect predictions,… Read more →

Pertaining to a technique in which a packerflowmeter is partially inflated and dragged up the hole to give a continuous flow log. This obsolete technique was introduced in the 1960s because the packer flowmeter could… Read more →

What Is Drainage in Reservoir Engineering? Drainage is the displacement process in which the wetting phase saturation decreases within a porous medium — oil (non-wetting) displacing water (wetting phase) during… Read more →

The reservoir area or volume drained by the well. The terms drainage area, reservoir area and drainage volume are often incorrectly used interchangeably. When several wells drain the same reservoir, each drains its own… Read more →

The portion of the volume of a reservoir drained by a well. In a reservoir drained by multiple wells, the volume ultimately drained by any given well is proportional to that well's production rate:Vi = Vt x qi/qt,where… Read more →

A hole or short conduit through which fluids can flow. In equipment applications, a drainhole is generally made to avoid the buildup of pressure within a nonpressure area, such as may occur in the event of a leak in a… Read more →

A configuration of layers of rock that has the appearance of a fold, but might form simply through sagging or differential compaction of layers around a preexisting structure (such as a reef) or on an uneven surface. Read more →

The difference in height between the static level and the dynamic level in a pumping well, expressed as hydrostatic fluid pressure. Read more →

The measurement and analysis of pressure data taken after a well is put on production, either initially or following an extended shut-in period. Drawdown data are usually noisy, meaning that the pressure moves up and… Read more →

What Are Drawworks? The drawworks hoists and lowers the drill string, casing strings, and completion equipment through a crown block and traveling block system by spooling and unspooling heavy steel wire rope on a… Read more →

An accurately machined device that is pulled through the casing, tubulars and completion components to ensure minimum-diameter specifications are within tolerance, as described in definition 2. While this tool is… Read more →

What Is a Drill Collar? A drill collar provides the weight on bit (WOB) and compressive stiffness needed to keep the bottom hole assembly on trajectory by placing the heavy, thick-walled pipe section directly above the… Read more →

A special fluid designed exclusively for drilling through the reservoir section of a wellbore. The reasons for using a specially designed mud are: (1) to drill the reservoir zone successfully, often a long, horizontal… Read more →

Formation solids contained in a mud system, generally considered to be detrimental to the drilling operation because they produce high plasticviscosity, yield point and gel strengths and build poor-quality filter cakes.… Read more →

A special fluid designed exclusively for drilling through the reservoir section of a wellbore. The reasons for using a specially designed mud are: (1) to drill the reservoir zone successfully, often a long, horizontal… Read more →

A technique using the noise of the drill bit as a source and receivers laid out along the ground to acquire a vertical seismicprofile (VSP). Acquisition and processing of a drill-noise VSP, also called a… Read more →

A packer assembly that can be removed from the wellbore only by drilling or milling. Drillable packers, and similar tools such as bridge plugs, are typically made from cast iron, aluminum, plastic or similar brittle… Read more →

The supervisor of the rig crew. The driller is responsible for the efficient operation of the rigsite as well as the safety of the crew and typically has many years of rigsite experience. Most drillers have worked their… Read more →

The depth of a well or features within the wellbore as measured while drilling. The measured length of each joint of drillpipe or tubing is added to provide a total depth or measurement to the point of interest.… Read more →

A sudden increase in the rate of penetration during drilling. When this increase is significant (two or more times the normal speed, depending on local conditions), it may indicate a formation change, a change in the… Read more →

The company that owns and operates a drilling rig. The drilling contractor usually charges a fixed daily rate for its hardware (the rig) and software (the people), plus certain extraordinary expenses. Under this… Read more →

Personnel who operate the drilling rig. The crew typically consists of roustabouts, roughnecks, floor hands, lead tong operators, motormen, derrickmen, assistant drillers, and the driller. Since drilling rigs operate… Read more →

A surfactant-type mud additive intended to prevent formation shales and clays from sticking to the drilling assembly and also to prevent gumboshale from agglomerating and plugging the annulus and flowlines. Some DDs are… Read more →

What Is Drilling Fluid? Drilling fluid (commonly called drilling mud ) is the engineered circulating fluid that a rig crew pumps down the drill string , through the bit, and back up the annulus during drilling… Read more →

The engineering plan for constructing the wellbore. The plan includes well geometries, casing programs, mud considerations, well control concerns, initial bit selections, offset well information, porepressure… Read more →

The speed at which the drill bit can break the rock under it and thus deepen the wellbore. This speed is usually reported in units of feet per hour or meters per hour. Read more →

A large-diameter pipe that connects the subsea BOP stack to a floating surface rig to take mudreturns to the surface. Without the riser, the mud would simply spill out of the top of the stack onto the seafloor. The… Read more →

Tubular steel conduit fitted with special threaded ends called tool joints. The drillpipe connects the rig surface equipment with the bottomhole assembly and the bit, both to pump drilling fluid to the bit and to be… Read more →

Pertaining to the use of drillpipe to move wirelinelogging tools up and down a borehole. In difficult conditions--high well deviation, rough hole--wireline logging tools cannot reach the bottom of the hole under their… Read more →