- Industry: Oil & gas
- Number of terms: 8814
- Number of blossaries: 0
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A term that, in the past, referred to a mud containing bentonite clay, water, caustic soda and perhaps barite (as needed for density) usually with lignite or lignosulfonate present. Modern drilling does not necessarily recognize this as a conventional mud because polymer muds, special drill-in fluids and synthetic-base muds are now in common use. There may not be a "conventional mud" today.
Industry:Oil & gas
A term describing the application of a cloud point glycol or polyglycol as a shale inhibitor. The purported mechanism is that the glycol clouds out at the higher downhole temperatures, coating onto the surface of clays and preventing hydration.
Industry:Oil & gas
A term that is generally synonymous with drilling fluid and that encompasses most fluids used in hydrocarbon drilling operations, especially fluids that contain significant amounts of suspended solids, emulsified water or oil. Mud includes all types of water-base, oil-base and synthetic-base drilling fluids. Drill-in, completion and workover fluids are sometimes called muds, although a fluid that is essentially free of solids is not strictly considered mud.
Industry:Oil & gas
A temporary drilling site, usually constructed of local materials such as gravel, shell or even wood. For some long-drilling-duration, deep wells, such as the ultradeep wells of western Oklahoma, or some regulatory jurisdictions such as The Netherlands, pads may be paved with asphalt or concrete. After the drilling operation is over, most of the pad is usually removed or plowed back into the ground.
Industry:Oil & gas
A telescoping joint at the surface in floating offshore operations that permits vessel heave (vertical motion) while maintaining a riser pipe to the seafloor. As the vessel heaves, the slip joint telescopes in or out by the same amount so that the riser below the slip joint is relatively unaffected by vessel motion.
Industry:Oil & gas
A technique in nuclear magnetic resonance (NMR) logging based on a long echo spacing, specially chosen to enhance the diffusion of formation water. Echo spacings in standard NMR logs are too short to allow any significant diffusion relaxation from water. Long echo spacings, for example 3 s, cause diffusion relaxation to limit the maximum T<sub>2</sub> from water. They also limit the maximum T<sub>2</sub> from light hydrocarbons. However, there is a certain range of viscosity of medium oil that is less affected. The enhanced diffusion technique therefore permits the identification of some medium oils.
Industry:Oil & gas
A technique for displacing drilling mud from the annulus using a laminar-flow regime.
Industry:Oil & gas
A tapered, often bullet-nosed piece of equipment often found on the bottom of a casing string. The device guides the casing toward the center of the hole and minimizes problems associated with hitting rock ledges or washouts in the wellbore as the casing is lowered into the well. The outer portions of the guide shoe are made from steel, generally matching the casing in size and threads, if not steel grade. The inside (including the taper) is generally made of cement or thermoplastic, since this material must be drilled out if the well is to be deepened beyond the casing point. It differs from a float shoe in that it lacks a check valve.
Industry:Oil & gas
A system of identifying and categorizing the strength of casing materials. Since most oilfield casing is of approximately the same chemistry (typically steel), and differs only in the heat treatment applied, the grading system provides for standardized strengths of casing to be manufactured and used in wellbores. The first part of the nomenclature, a letter, refers to the tensile strength. The second part of the designation, a number, refers to the minimum yield strength of the metal (after heat treatment) at 1000 psi (6895 KPa). For example, the casing grade J-55 has minimum yield strength of 55,000 psi (379,211 KPa). The casing grade P-110 designates a higher strength pipe with minimum yield strength of 110,000 psi (758,422 KPa). The appropriate casing grade for any application typically is based on pressure and corrosion requirements. Since the well designer is concerned about the pipe yielding under various loading conditions, the casing grade is the number that is used in most calculations. High-strength casing materials are more expensive, so a casing string may incorporate two or more casing grades to optimize costs while maintaining adequate mechanical performance over the length of the string. It is also important to note that, in general, the higher the yield strength, the more susceptible the casing is to sulfide stress cracking (H<sub>2</sub>S-induced cracking). Therefore, if H<sub>2</sub>S is anticipated, the well designer may not be able to use tubulars with strength as high as he or she would like.
Industry:Oil & gas
A system that has reached equilibrium for the measurement or phenomenon concerned. In the case of permeability measurements on core samples, a steady state is reached when the flow rate, the upstream and the downstream pressures no longer change with time. At this point the permeability can be calculated from the flow rate and pressures and applying Darcy's equation. If gas is used, the inertial resistance and gas slippage (Klinkenberg effect) should be corrected for.
Industry:Oil & gas
