- Branża: Oil & gas
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Antiquated term for a deviated wellbore, usually used to describe a well deviated accidentally during the drilling process.
Industry:Oil & gas
Another term for gel strength in a fluid. Shear strength opposes the movement of mud, whether by pumping or movement of pipe in a wellbore. Excessive shear strength can develop after a mud has been quiescent in the hole at high temperature for a period of time. Shear strength can be measured according to procedures published by the API.
Industry:Oil & gas
An oven into which mud-testing cells are placed. Ovens usually have a set of horizontal rollers inside and are also called roller ovens. Mud-aging cells are placed on the rollers. In pilot tests, rolling the cells allows a film of mud to continually contact the hot wall of the cell. Another type of oven tumbles cells end-to-end. Most ovens can also be used for static-aging tests.
Industry:Oil & gas
An uncontrolled flow of reservoir fluids into the wellbore, and sometimes catastrophically to the surface. A blowout may consist of salt water, oil, gas or a mixture of these. Blowouts occur in all types of exploration and production operations, not just during drilling operations. If reservoir fluids flow into another formation and do not flow to the surface, the result is called an underground blowout. If the well experiencing a blowout has significant openhole intervals, it is possible that the well will bridge over (or seal itself with rock fragments from collapsing formations) downhole and intervention efforts will be averted.
Industry:Oil & gas
An organic acid, properly called 2-Hydroxy-1,2,3-propanetricarboxylic acid, with formula C<sub>6</sub>H<sub>8</sub>O<sub>7</sub>. Citric acid is used to reduce the pH of drilling fluids and hence for treatment of cement contamination. It also acts as a polymer stabilizer.
Industry:Oil & gas
An opening in the rig floor near the rotary table, but between the rotary table and the vee-door, that enables rapid connections while drilling. The mousehole is usually fitted underneath with a length of casing, usually with a bottom. A joint of drillpipe that will be used next in the drilling operation is placed in the mousehole, box end up, by the rig crew at a convenient time (immediately after the previous connection is made). When the bit drills down and the kelly is near the rotary table, another piece of drillpipe must be added for drilling to continue. This next piece of pipe is standing in the mousehole when the kelly is screwed onto it. Then the kelly and the joint of pipe in the mousehole are raised to remove the pipe from the mousehole, the mousehole pipe screwed onto the rest of the drillstring, and the drillstring lowered, rotated, and pumped through to continue drilling. Another piece of pipe is put in the mousehole to await the next connection.
Industry:Oil & gas
An oil-base mud with diesel oil as its external phase. Diesel-oil mud is the traditional oil mud and has a history of excellent performance for drilling difficult wells. It has been used because the base oil is low-cost and widely available motor fuel. In-gauge holes can be drilled through all types of shales, salt, gypsum and other difficult strata using diesel-oil mud systems. It is often the mud of choice for drilling high-pressure, high-temperature zones. Diesel-oil muds usually contain from 5 to 40 vol. % emulsified brine water (except those that are specially designed to have none). The water phase usually contains 20 to 40 wt. % dissolved calcium chloride for shale control. Diesel-oil muds have been replaced in land drilling by mineral-oil muds and offshore by synthetic-fluid muds. These newer muds have fewer health, safety and environmental concerns compared to diesel oil.
Industry:Oil & gas
An oil-base mud in which the activity, or vapor pressure, of the brine phase is balanced with that of the formations drilled. Although long shale sections may not have a constant value for vapor pressure, a<sub>w</sub>, the oil mud will adjust osmotically to achieve an "average" a<sub>w</sub> value. Dynamic (autopilot) balance of mud salinity and drilled shales is maintained because as water moves into or out of the mud, it also moves out of or into the shale. As water transfer continues during drilling, the mud's water phase will be either diluted or concentrated in CaCl<sub>2</sub> as needed to match the average a<sub>w</sub> value of the shale section and cuttings exposed to the mud. <br><br>Reference:<br>Chenevert ME: "Shale Control With Balanced-Activity Oil-Continuous Muds," Journal of Petroleum Technology 33, no. 11 (November 1970): 1370-1378.
Industry:Oil & gas
An item of solids-removal equipment that removes fine and ultrafine solids. It consists of a conical drum that rotates at 2000 to 4000 rpm. Drilling fluid is fed into one end and the separated solids are moved up the bowl by a rotating scroll to exit at the other end. Centrifuges generally have limited processing capacity (50 to 250 gpm) but are useful for processing weighted drilling fluids and can remove finer solids than can a hydrocyclone or shaker screens. They can also be used for water clarification or for processing oily cuttings.
Industry:Oil & gas
