- Industry: Oil & gas
- Number of terms: 8814
- Number of blossaries: 0
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A fine-grained detrital sedimentary rock formed by consolidation of clay- and silt-sized particles. Mudrocks are highly variable in their clay content and are often rich in carbonate material. As a consequence, they are less fissile, or susceptible to splitting along planes, than shales. Mudrocks may include relatively large amounts of organic material compared with other rock types and thus have potential to become rich hydrocarbon source rocks. The typical fine grain size and low permeability, a consequence of the alignment of their platy or flaky grains, allow mudrocks to form good cap rocks for hydrocarbon traps. However, mudrocks are also capable of being reservoir rocks, as evidenced by the many wells drilled into them to produce gas. <br><br>
Industry:Oil & gas
A fine paid to the host country for failure to attain specified production rates over a defined period of time.
Industry:Oil & gas
A feature on a sonic log caused by low signal amplitude that results in erroneously long traveltimes. Sonic logs that do not record waveforms measure the acoustic traveltime between transmitter and receiver by detecting the first signal at the receiver above a certain threshold (first motion detection). The threshold is small so that the signal is detected just after it crosses the zero signal baseline. However, if the threshold is set too high, or the signal is too small, the system will not trigger at the sharp zero crossing but at some later point on the waveform. This increases the apparent transmitter-receiver time. Delta-t stretch is more likely at the far receiver, where signals are weaker, so that the apparent traveltime calculated between receivers is too large. In the extreme case, the system triggers on the next cycle of the waveform, known as cycle skipping.
Industry:Oil & gas
A fault whose primary movement is in the strike direction (usually horizontal). This type of fault is usually caused by continents or tectonic plates moving laterally with respect to each other, as is happening in California today. The San Andreas fault is a strike-slip fault along which the western side is moving north relative to the eastern side.
Industry:Oil & gas
A fault whose primary movement is in the dip direction. Dip faults are also referred to as dip-slip faults.
Industry:Oil & gas
A facility consisting of many compressors, auxiliary treatment equipment and pipeline installations to pump natural gas under pressure over long distances. A compressor plant is also called a compressor station. Several compressor stations can be used to repressurize gas in large interstate gas pipelines or to link offshore gas fields to their final terminals.
Industry:Oil & gas
A dual-porosity reservoir in which flow to the well occurs in both primary and secondary porosity systems.
Industry:Oil & gas
A drillstem test performed in an openhole section of the wellbore. The test once was a popular method of assessing the productivity of exploration wells without the need to run casing or liner across the reservoir interval. Openhole testing now is less common because of the risks and limits associated with fluid flow from an unsupported formation.
Industry:Oil & gas
A drilling mud with a significant magnetic susceptibility. The magnetic susceptibility may affect the response of some logging measurements, mainly the induction X signal and nuclear magnetic resonance logs. The most common magnetic muds contain iron filings or magnetite. Other paramagnetic minerals such as hematite and ilmenite may contribute, although their magnetic susceptibility is considerably less.
Industry:Oil & gas
A downhole valve that operates by fluid velocity and closes when the fluid flow from the well exceeds preset limits. The forerunner to modern subsurface controlled safety valves, storm chokes were used in offshore applications as a contingency device in the event of a catastrophic failure of surface facilities during a storm or hurricane.
Industry:Oil & gas
