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In the oil industry, mud weight is the density of the drilling fluid and is normally measured in pounds per gallon (lb/gal) (ppg) or pound cubic feet (pcf) . [1] In the field it is measured using a mud scale or mud balance. Mud can weigh up to 22 or 23 ppg. A gallon of water typically weighs 8.33 pounds (or 7.48 ppg).
Drilling fluids also support portion of drill-string or casing through buoyancy. Suspend in drilling fluid, buoyed by force equal to weight (or density) of mud, so reducing hook load at derrick. Weight that derrick can support limited by mechanical capacity, increase depth so weight of drill-string and casing increase.
Mishandling mud at the surface accounts for many instances of insufficient fluid weight. Such as opening the wrong valve on the pump suction manifold and allowing a tank of lightweight fluid to be pumped; bumping the water valve so more is added than intended; washing off shale shakers; or clean-up operations. All of these can affect mud weight.
See mud log for an example of the corrected d-exponent plotted on a mud log. The parameter is an extension ("correction", hence the "c" notation) to the d-exponent method previously used for estimating formation pore pressures. The extension consists of a correction for the mud weight in use, compared to "standard" mud for the region.
This mud type can be used as a completion and workover fluid, a spotting fluid to relieve a stuck pipe and as packer or casing fluid. They are very good for "Gumbo" shales. The mud weight can be controlled from 7–22 lbs/gal. It is sensitive to temperature but does not dehydrate as in the case of water based mud as mentioned before.
When underbalanced drilling is used, mud pulse telemetry can become unusable. This is usually because, in order to reduce the equivalent density of the drilling mud, a compressible gas is injected into the mud. This causes high signal attenuation which drastically reduces the ability of the mud to transmit pulsed data. In this case, it is ...
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Mud logging technicians observe and interpret the indicators in the mud returns during the drilling process, and at regular intervals log properties such as drilling rate, mud weight, flowline temperature, oil indicators, pump pressure, pump rate, lithology (rock type) of the drilled cuttings, and other data.