- Industry: Oil & gas
- Number of terms: 8814
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Analysis of a well that passes through a natural fracture or that has been hydraulically fractured. The fracture is treated as a slab of high permeability that is an effective extension of the actual wellbore. Flow is from the reservoir to the fracture and through the fracture to the well. The pressure-transient analysis for a fractured well can determine the fracture half-length and the fracture conductivity, as well as a fracture-face skin. The skin factor for the fracture is negative and usually ranges from -1. 5 to -5, with an absolute minimum of -6 in rare cases. For effectively infinite-conductivity fractures, the apparent wellbore radius is half the fracture half-length, or x<sub>f</sub>/2.
Industry:Oil & gas
Analysis of a geometrical system using fractal mathematics. This analysis is sometimes used in geostatistics to describe depositional systems and other geological phenomena.
Industry:Oil & gas
An upgoing and downgoing arrangement of transducers in a logging tool, largely to offset spurious changes in reading caused by variations in borehole size or sonde tilt. The technique is used for measurements that rely on the propagation of a wave, such as sonic, propagation resistivity and electromagnetic propagation measurement. <br><br>Propagation logs rely on measuring the difference in properties of a wave at two receivers. The borehole influences this difference if the tool is tilted or if there is a cave opposite one of the receivers. The effect can be compensated for by using two transmitters that radiate sequentially in opposite directions. In ideal conditions, the effect of a tilt or a cave is exactly opposite for the two transmitters, so that an average gives the correct result. Borehole compensation is different from borehole correction.
Industry:Oil & gas
An unmanned submersible vehicle controlled from surface. In deepwater operations, remotely operated vehicles are used to inspect subsea structures and equipment, and to control or manipulate valves. They can operate at depths from 1500 to 10,000 ft (457 to 3048 m). This term is commonly abbreviated as ROV.
Industry:Oil & gas
An unusual occurrence of hydrocarbon in which molecules of natural gas, typically methane, are trapped in ice molecules. More generally, hydrates are compounds in which gas molecules are trapped within a crystal structure. Hydrates form in cold climates, such as permafrost zones and in deep water. To date, economic liberation of hydrocarbon gases from hydrates has not occurred, but hydrates contain quantities of hydrocarbons that could be of great economic significance. Hydrates can affect seismic data by creating a reflection or multiple.
Industry:Oil & gas
An unfocused electrode device with small spacings, mounted on a pad and pressed against the borehole wall. The typical microlog has one current-emitting electrode and two measure electrodes in line above it, one at 1 in. (2. 5 cm), the other at 2 in. (5 cm). The potential at the 2-in. Electrode gives a 2-in. Micronormal log. The difference in potential between the two measure electrodes gives a 1-in. X 1-in. Microinverse log. The micronormal reads deeper than the microinverse. <br><br>Introduced in 1948, the microlog is used to detect permeable zones across which a mudcake has formed. Since the mudcake is usually less resistive than the invaded zone, the microinverse will read less than the micronormal opposite permeable zones. If the resistivity and thickness of the mudcake are known, it is possible to estimate the resistivity of the flushed zone. The log is usually presented on a linear scale, chosen to emphasize the lower readings often seen opposite permeable zones with mudcake.
Industry:Oil & gas
An underground rock formation from which oil, gas or water is produced. Any porous rock will contain fluids of some sort, and all rocks at considerable distance below the Earth's surface will initially be under pressure, often related to the hydrostatic column of ground waters above the reservoir. To produce, rocks must also have permeability, or the capacity to permit fluids to flow through them.
Industry:Oil & gas
An umbrella term for oil and natural gas that is produced by means that do not meet the criteria for conventional production. What has qualified as 鈥渦nconventional鈥?at any particular time is a complex function of resource characteristics, the available exploration and production technologies, the economic environment, and the scale, frequency and duration of production from the resource. Perceptions of these factors inevitably change over time and often differ among users of the term. At present, the term is used in reference to oil and gas resources whose porosity, permeability, fluid trapping mechanism, or other characteristics differ from conventional sandstone and carbonate reservoirs. Coalbed methane, gas hydrates, shale gas, fractured reservoirs, and tight gas sands are considered unconventional resources. <br>
Industry:Oil & gas
An ultrasonic logging device with a radially mounted rotating transducer that is used to scan the borehole wall. The transducer (in transmit mode) emits a high-frequency pulse that is reflected by the borehole wall back to the transducer (in receive mode). In openhole applications, it can be used to measure the borehole diameter (by measuring the acoustic transit time between transducer and borehole wall) and the amplitude of acoustic signals reflected by the borehole wall. The transducer is rotated to produce a cross section of the borehole size and images of the borehole wall. These are used to identify fractures, breakouts and other borehole features. In cased hole, they are used to identify internal corrosion.
Industry:Oil & gas
An operation to restimulate a well after an initial period of production. Refracturing operations attempt to bypass near-wellbore damage, reestablish good connectivity with the reservoir, and tap portions of the reservoir with higher pore pressure. Refracturing operations are also performed after a period of production that can alter the stresses in a reservoir due to depletion; the restimulation can allow the new fracture to reorient along a different azimuth. A successful refracturing operation restores well productivity to near original or even higher rates of production and extends the productive life of a well. <br>
Industry:Oil & gas
