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PURPOSE The two primary purposes of drilling mud or drilling fluids are to: #Remove cuttings from the formation produced by the bit at the bottom of the hole and carry them to the surface. This is achieved by adjusting the Rheology of the mud system. #Maintain Hydrostatic Equilibrium so that fluids and gas from the formation do not enter the well bore causing the well to flow, kick or blow out. This is achieved by adjusting the mud weight ( Density ). High-density additives (barite, hematite) are used for preparation of kill-weight fluids, which create hydrostatic pressure that prevents water entering the well or hold the oil/gas inside and prevent Blowout , and to physically stabilize the formation. DETAILS OF USE On a Drilling Rig pumping it with mud pumps through the Drill String where it sprays out of nozzles on the Drill Bit , the mud then travels back up the annular space between the drill string and the sides of the hole being drilled, up through the surface ''casing,'' and emerges at the surface. Cuttings are then filtered out at the ''shale shaker'' and the mud enters the ''mud pits''. The mud is then pumped back down and is continuously recirculated and periodicaly treated to give it properties that optimize and improve drilling efficiency. COMPOSITION OF DRILLING MUD Water-based drilling mud may consist of Bentonite Clay with additives such as Barium Sulfate or Hematite . Various Thickener s are used to influence the Viscosity of the fluid, eg. Guar Gum , Glycol , Carboxymethylcellulose , polyanionic cellulose, or Starch . In turn, Deflocculant s are used to reduce viscosity of clay-based muds; anionic Polyelectrolyte s (eg. Acrylate s, Polyphosphate s, Lignosulfonates or Tannic Acid derivates (eg. Quebracho ) are frequently used. Red mud was the name for a Quebracho -based mixture, named after the color of the red tannic acid salts; it was commonly used in 1940s to 1950s, then was obsoleted when lignosulfates became available. One classification scheme for drilling fluids is based on their composition, and divides them to
MUD ENGINEER The slang name given to an oil field service company individual who is charged with maintaining a drilling fluid or completion fluid system on an oil and/or gas drilling rig. The work schedule of the mud engineer or '''Drilling Fluids Engineer''', as he or she is more properly called these days, is usually fairly strenuous, as are most jobs in this industry. Until a few years ago, the "mud engineer" rarely worked a set schedule and, if resident on an offshore installation, may have been on call for 24 hours a day, with few (if any) days off each month. With the advent some 15 years ago in Northern Europe, of having two mud engineers offshore due to Health, Safety and Environmental regulations and working hours restrictions in more advanced countries, the offshore mud engineer rarely works more than the normal 12 hour shift. On land, however, there usually still is only one mud engineer assigned, and most of the time, he is allocated to more than one drilling rig. The economics of land-drilling demands that the land-engineer spends a greater part of the day driving from rig to rig, testing the drilling or completion fluids, making recommendations for its maintenance, and then repeating the process at another rig(s). Offshore drilling, with new technology and high total day costs for the operation, have wells being drilled extremely fast and day rates for operations have increased. Any down time is frowned upon and two mud engineers makes economical sense, to sensible oil companies, to prevent down time due to drilling fluid difficulties. Two Mud Engineers also reduce insurance loading to oil companies for possible environmental damage that oil companies are responsible for during their license to drill and produce. The cost of the drilling fluid is typically about 10% of the total cost of well construction. This large cost overhead places a demand on the competency of the mud engineer. Large cost savings can result when the mud engineer adequately performs his job. Not to be confused with service personnel charged with monitoring gas from the mud and collecting wellbore samples is known as a Mud Logger . |
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