- Industry: Oil & gas
- Number of terms: 8814
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A wellbore that is not vertical. The term usually indicates a wellbore intentionally drilled away from vertical.
Industry:Oil & gas
A wellbore that is essentially the same diameter as the bit that was used to drill it. It is common to find well-consolidated sandstones and carbonate rocks that remain gauge after being drilled. For clays, it is common for the hole to slowly enlarge with the passing of time, especially if water-base muds are being used. Bit gauges, rings of defined circumference, are slipped around drill bits to detect and measure wear, which reduces the circumference of the bit during drilling.
Industry:Oil & gas
A wellbore that has not encountered hydrocarbons in economically producible quantities. Most wells contain salt water in some zones. In addition, the wellbore usually encounters small amounts of crude oil and natural gas. Whether the well is a "duster" depends on many factors of the economic equation, including proximity to transport and processing infrastructures, local market conditions, expected completion costs, tax and investment recovery conditions of the jurisdiction and projected oil and gas prices during the productive life of the well.
Industry:Oil & gas
A weighted, hollow glass bulb with a long, graduated tube attached for measuring the density of a liquid. A hydrometer is placed in the liquid and the bulb sinks according to the density of the liquid. Graduations on the tube indicate the density. Hydrometers are used in fluids that have no gel strength, such as brine, but are not reliable in drilling fluids because of gelation.
Industry:Oil & gas
A weak spot in the drillstring. Such a weak spot sometimes is intentionally put into the drillstring so that if tension in the drillstring exceeds a predetermined amount, the safety joint will part and the rest of the drillstring will be salvageable. A safety joint is commonly included in fishing strings and drillstem testing equipment, where the fish may be successfully caught by the fishing assembly, but tension to free the fish may prove insurmountable. By having the safety joint in the hole, the fishing company representative knows where the fishing string will part and what will be needed to latch onto the top of this additional fish.
Industry:Oil & gas
A water-soluble starch that has undergone irreversible changes by heating in water or steam.
Industry:Oil & gas
A water-base mud designed for offshore drilling whose make-up water is taken from the ocean. Sea water contains relatively low salinity, about 3 to 4 wt. % NaCl, but has a high hardness because of Mg<sup>+2</sup> and Ca<sup>+2</sup> ions. Hardness is removed from sea water by adding NaOH, which precipitates Mg<sup>+2</sup> as Mg(OH)<sub>2</sub>, and by adding Na<sub>2</sub>CO<sub>3</sub>, which removes Ca<sup>+2</sup> as CaCO<sub>3</sub>. Mud additives are the same as those used in freshwater mud-bentonite clay, lignosulfonate, lignite, carboxymethylcellulose or polyanionic cellulose and caustic soda. XC polymer may also be used in place of bentonite. Higher concentrations of each additive are required because of salinity effects. Bentonite (if used) should be prehydrated in fresh water.
Industry:Oil & gas
A water-base drilling fluid containing a high concentration of methylglucoside. The mud has been used to drill water-sensitive shales with less hole enlargement and fewer drilling problems. Methylglucoside is a polysaccharide containing methyl groups on the ring-like sugar structure. Being a rather large, nonionic molecule (resembling starch but highly water soluble), it ties up water molecules in concentrated solutions and it is thought to act as a low-efficiency osmotic membrane.
Industry:Oil & gas
A water-base drilling fluid that contains dispersed oil or synthetic hydrocarbon as an internal phase. Early emulsion muds used diesel or crude oil dispersed into alkaline water-base muds. Synthetic liquids are now being substituted for oils in emulsion muds. Water-base muds containing certain synthetic liquids can be discharged in the Gulf of Mexico because they are environmentally safe and pass the EPA static sheen test and mysid shrimp toxicity tests. <br><br>Reference:<br>Rogers WF: "Oil-in-Water Emulsion Muds," in Composition and Properties of Oil Well Drilling Fluids, 3rd ed. Houston, Texas, USA: Gulf Publishing Company, 1963.
Industry:Oil & gas
A water mud containing varying amounts of dissolved sodium chloride, NaCl, as a major component. Undissolved salt may also be present in saturated salt muds to increase density beyond 10 lbm/gal or to act as a bridging agent over permeable zones. Starch and starch derivatives for fluid-loss control and xanthan gums for hole-cleaning are among the few highly effective additives for saltwater muds. Attapulgite and sepiolite are used in saltwater muds only for cuttings lifting. The primary use of saltwater mud is to drill salt strata that are prone to dissolution when exposed to other types of drilling fluid. A saturated salt mud is used to drill salt to prevent hole enlargement. In hot, plastic, salt zones, the hole may close inward unless extremely high mud weight is maintained. As an alternative to high mud weight, maintaining undersaturation in the fluid allows controlled leaching to offset hole closure by plastic flow. Sized salt particles in saturated saltwater muds are used, along with polymers, to bridge over permeable production zones. The salt can be removed later with a water flush. Salt solids can increase density beyond 10 lbm/gal, up to about 13 lbm/gal, if needed.
Industry:Oil & gas
