- المجال: Oil & gas
- Number of terms: 8814
- Number of blossaries: 0
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A downhole device that isolates wellbore pressure and fluids in the event of an emergency or catastrophic failure of surface equipment. The control systems associated with safety valves are generally set in a fail-safe mode, such that any interruption or malfunction of the system will result in the safety valve closing to render the well safe. Downhole safety valves are fitted in almost all wells and are typically subject to rigorous local or regional legislative requirements.
Industry:Oil & gas
A downhole device that enables circulation through the tubing string and associated annulus. As a completion accessory, a circulation valve is included to circulate fluid for well kill or kickoff. Circulation valves typically are operated by slickline tools and are generally capable of several opening and closing cycles before requiring service.
Industry:Oil & gas
A downhole device or assembly used to catch and retain balls used to actuate ball-operated tools or equipment. Following activation, some ball-operated tools incorporate a means of ejecting the activation ball to regain a fullbore flow path. In such cases, the ball can be retained in a ball catcher.
Industry:Oil & gas
A downhole device or tool component designed to catch debris or objects, such as balls, darts or plugs dropped to actuate downhole equipment or tools.
Industry:Oil & gas
A downhole completion component that enables injection of treatment chemicals or inhibitors into the production conduit. The injection mandrel is equipped with a port- and check-valve system to direct fluid pumped down the annulus or injection line into the production conduit.
Industry:Oil & gas
A downhole assembly or tool system used in the remedial repair of casing damage, corrosion or leaks. Casing patches are most frequently used as short- to medium-term repairs that enable production to be resumed until a major workover operation is scheduled. In some cases, such as in depleted wells nearing the end of viable production, a casing patch may be the only economic means of safely returning the well to production.
Industry:Oil & gas
A double logarithmic plot of a resistivity measurement on the x-axis versus a porosity measurement on the y-axis. The plot is named after G. R. Pickett. The plot is based on taking the logarithm of the Archie equation. Points of constant water saturation (S<sub>w</sub>) will plot on a straight line with negative slope of value m. Water zones define the lowermost line on the plot. Since S<sub>w</sub> = 1, the water resistivity can be determined from a point on the line. Once the water line is established, other parallel lines can be drawn for different S<sub>w</sub>, assuming a constant n (usually 2). Other data can then be plotted and interpreted in terms of S<sub>w</sub>. The same technique can be applied to the flushed zone, using flushed-zone measurements. <br><br>See Pickett GR: "A Review of Current Techniques for Determination of Water Saturation from Logs," paper SPE 1446, presented at the SPE Rocky Mountain Regional Meeting, Denver, Colorado, USA, May 23-24, 1966; SPE Journal of Petroleum Technology (November 1966): 1425-1435.
Industry:Oil & gas
A document prepared to list the sequence, type and volume of fluids to be pumped during a specific treatment.
Industry:Oil & gas
A distortion of the magnetic flux that has been introduced into a casing by a low-frequency electromagnet or permanent magnet. The principle of flux leakage is used to detect casing corrosion, since flux leakage is caused by rapid changes in the thickness of the casing and by pits and holes in either the internal or external wall. Flux leakage distorts the magnetic-flux lines and induces a signal into an electric coil moving past it. In-situ flux-leakage measurements make use of this effect by placing coils on or close to the casing wall, azimuthally distributed to cover the entire wall. The results are often combined with a high-frequency, eddy-current measurement, designed to detect flaws only on the inner wall.
Industry:Oil & gas
A distance that characterizes the ability of a logging tool to resolve changes parallel to the tool axis. The word vertical implies a vertical well, but the term is used at other wellbore deviations. The vertical resolution summarizes the vertical response of the measurement in one or more distances. Most quoted vertical resolutions assume a homogeneous formation with stated properties. Vertical resolutions can vary considerably in more complex conditions, and at different values of the properties concerned. They should be considered only a qualitative guide to tool response. <br><br>There are several different definitions of the vertical resolution distance. First, and most commonly, it is the interval within which a large percentage, typically 90%, of the vertical response occurs. Second, it is the minimum bed thickness needed for the measurement to read within a small percentage, typically 10%, of the true value at the center of the bed. Third, it may refer to the smallest bed thickness for which a significant change can be detected by the measurement. <br><br>For acoustic and electromagnetic propagation measurements, it is taken, with reasonable accuracy, as the span of the receiver array. For nuclear and nuclear magnetic resonance measurements, which must be acquired during a significant time interval, the vertical resolution also depends on the logging speed and the precision required.
Industry:Oil & gas
