- Branche: Oil & gas
- Number of terms: 8814
- Number of blossaries: 0
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A method of making hole that relies on continuous circular motion of the bit to break rock at the bottom of the hole. This method, made popular after the discovery of the East Texas Field by "Dad" Joiner in 1930, is much more efficient than the alternative, cable tool drilling. Rotary drilling is a nearly continuous process, because cuttings are removed as drilling fluids circulate through the bit and up the wellbore to the surface. Cable tool operations are discontinuous and cuttings removal is inefficient. This difference in efficiency becomes particularly significant as hole depth increases.
Industry:Oil & gas
A method of drilling whereby an impact tool or bit, suspended in the well from a steel cable, is dropped repeatedly on the bottom of the hole to crush the rock. The tool is usually fitted with some sort of cuttings basket to trap the cuttings along the side of the tool. After a few impacts on the bottom of the hole, the cable is reeled in and the cuttings basket emptied, or a bailer is used to remove cuttings from the well. The tool is reeled back to the bottom of the hole and the process repeated. Due to the increasing time required to retrieve and deploy the bit as the well is deepened, the cable-tool method is limited to shallow depths. Though largely obsolete, cable-tool operations are still used to drill holes for explosive charge placement (such as for acquisition of surface seismic data) and water wells.
Industry:Oil & gas
A method for recovering wireline stuck in a wellbore. In cut-and-thread operations, the wireline is gripped securely with a special tool and cut at the surface. The cut end is threaded through a stand of drillpipe. While the pipe hangs in the wellbore, the wireline is threaded through another stand of drillpipe, which is screwed onto the stand in the wellbore. The process is repeated until the stuck wireline is recovered. This technique, while dangerous and time-consuming, is known to improve greatly the chances of full recovery of the wireline and the tool at its end in the shortest overall time compared with trying to grab the wireline in the openhole with fishing tools.
Industry:Oil & gas
A metal strip shaped like a hunting bow and attached to a tool or to the outside of casing. Bow-spring centralizers are used to keep casing in the center of a wellbore or casing ("centralized") prior to and during a cement job.
Industry:Oil & gas
A mechanical device used downhole to deliver an impact load to another downhole component, especially when that component is stuck. There are two primary types, hydraulic and mechanical jars. While their respective designs are quite different, their operation is similar. Energy is stored in the drillstring and suddenly released by the jar when it fires. The principle is similar to that of a carpenter using a hammer. Kinetic energy is stored in the hammer as it is swung, and suddenly released to the nail and board when the hammer strikes the nail. Jars can be designed to strike up, down, or both. In the case of jarring up above a stuck bottomhole assembly, the driller slowly pulls up on the drillstring but the BHA does not move. Since the top of the drillstring is moving up, this means that the drillstring itself is stretching and storing energy. When the jars reach their firing point, they suddenly allow one section of the jar to move axially relative to a second, being pulled up rapidly in much the same way that one end of a stretched spring moves when released. After a few inches of movement, this moving section slams into a steel shoulder, imparting an impact load. In addition to the mechanical and hydraulic versions, jars are classified as drilling jars or fishing jars. The operation of the two types is similar, and both deliver approximately the same impact blow, but the drilling jar is built such that it can better withstand the rotary and vibrational loading associated with drilling.
Industry:Oil & gas
A mechanical device that must simultaneously suspend the weight of the drillstring, provide for rotation of the drillstring beneath it while keeping the upper portion stationary, and permit high-volume flow of high-pressure drilling mud from the fixed portion to the rotating portion without leaking.
Industry:Oil & gas
A mechanical device that keeps casing from contacting the wellbore wall. A continuous 360-degree annular space around casing allows cement to completely seal the casing to the borehole wall. There are two distinct classes of centralizers. The older and more common is a simple, low-cost bow-spring design. Since the bow springs are slightly larger than the wellbore, they can provide complete centralization in vertical or slightly deviated wells. However, they do not support the weight of the casing very well in deviated wellbores. The second type is a rigid blade design. This type is rugged and works well even in deviated wellbores, but since the centralizers are smaller than the wellbore, they will not provide as good centralization as bow-spring type centralizers in vertical wells. Rigid-blade casing centralizers are slightly more expensive and can cause trouble downhole if the wellbore is not in excellent condition.
Industry:Oil & gas
A measurement of the thickness of the filter cake, usually recorded in 32nds-inch. Under dynamic conditions, filter-cake thickness depends on rate of deposition versus erosion caused by fluid circulation and mechanical abrasion by the rotating drillstring. Typically, the filter cake will reach an equilibrium thickness in the wellbore. In laboratory tests, however, filter cake is built under static conditions with no erosion.
Industry:Oil & gas
A measurement based on the slowing down of neutrons between a source and one or more detectors that measure neutrons at the epithermal level, where their energy is above that of the surrounding matter, between approximately 0. 4 and 10 eV. The slowing-down process is dominated by hydrogen, and is characterized by a slowing-down length. By measuring the neutrons at the epithermal level, rather than the thermal level, the response is a purer estimate of hydrogen index, unaffected by thermal absorbers. On the other hand, the count rate is smaller for the same source and source-detector spacing. <br><br>Epithermal measurements have been made with both the compensated neutron technique and by using a pad pressed against the borehole wall with detectors focused into the formation.
Industry:Oil & gas
A measure of the total amount of hydroxyl ions in a solution as determined by titration with standardized acid. This test is a well-known water-analysis procedure to estimate hydroxyl, carbonate ion and bicarbonate ion concentrations. There are two pH endpoints, P and M, in this titration, corresponding to phenolphthalein and methyl orange indicators. The "P" endpoint is at pH 8. 3 and the "M" endpoint is at pH 4. 3. Each is reported in units of cm<sup>3</sup> acid/cm<sup>3</sup> sample. For water samples and very simple mud filtrates, P and M data indicate OH<sup>-</sup>, HCO<sub>3</sub><sup>-</sup> and CO<sub>3</sub><sup>-2</sup> concentrations, but an alkalinity test is unreliable for analyzing complex mud filtrates. The API has established standards for conducting alkalinity tests.
Industry:Oil & gas
