- Settore: Oil & gas
- Number of terms: 8814
- Number of blossaries: 0
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A category of clay minerals that have a three-layer crystalline structure (one alumina and two silica layers) and that exhibit a common characteristic of hydrational swelling when exposed to with water. Montmorillonite is a well-known smectite clay mineral to those working in drilling and drilling fluids. Its sodium form, bentonite, is a widely-used water mud additive. It is also used as an oil-mud additive when made oil-dispersible by surface treatment. Smectite clays that occur naturally in shales cause wellbore and mud-control problems due to their hydrational swelling and colloidal dispersion characteristics.
Industry:Oil & gas
A casing string that does not extend to the top of the wellbore, but instead is anchored or suspended from inside the bottom of the previous casing string. There is no difference between the casing joints themselves. The advantage to the well designer of a liner is a substantial savings in steel, and therefore capital costs. To save casing, however, additional tools and risk are involved. The well designer must trade off the additional tools, complexities and risks against the potential capital savings when deciding whether to design for a liner or a casing string that goes all the way to the top of the well (a "long string"). The liner can be fitted with special components so that it can be connected to the surface at a later time if need be.
Industry:Oil & gas
A calcium-based water mud system containing gypsum. Gyp mud can be used for drilling shales, but it is also well-suited for drilling gypsum, anhydrite and salt stringers. An advantage of gyp over lime muds is that the pH of gyp mud need not be so high because it contains more soluble Ca<sup>+2</sup> to inhibit shale swelling. Gypsum, CaSO<sub>4</sub>路2H<sub>2</sub>O, content is measured by an API test, and more can be added as needed. A calcium-tolerant clay deflocculant may be needed to control viscosity. Carboxymethylcellulose (CMC) and starch are used for fluid loss control along with a small amount of prehydrated bentonite.
Industry:Oil & gas
A brief influx of gas that is introduced into the drilling fluid when a pipe connection is made. Before making a connection, the driller stops the mud pumps, thereby allowing gas to enter the wellbore at depth. Gas may also be drawn into the wellbore by minor swabbing effects resulting from short movements of the drillstring that occur during the connection. Connection gas usually occurs after one lag interval following the connection. On a mud log, it will appear as a short peak above background levels. This peak often appears at 30-foot intervals, depending on the lengths of drillpipe being connected as the well is drilled.
Industry:Oil & gas
A blue dye with a cationic charge on the molecule used as the reagent for the methylene blue test used to estimate cation-exchange capacity (CEC) of solids in a water-base drilling mud.
Industry:Oil & gas
A branch of the US Lands and Mineral Management Department that supervises national resources. MMS has oversight of oil and gas leasing, royalty collection and other operations in US-owned areas. It closely monitors operations in Federal waters, oversees leasing of acreage, issues drilling permits and monitors operators for permit violations.
Industry:Oil & gas
A blowout preventer (BOP) closing element fitted with hardened tool steel blades designed to cut the drillpipe when the BOP is closed. A shear ram is normally used as a last resort to regain pressure control of a well that is flowing. Once the drillpipe is cut (or sheared) by the shear rams, it is usually left hanging in the BOP stack, and kill operations become more difficult. The joint of drillpipe is destroyed in the process, but the rest of the drillstring is unharmed by the operation of shear rams.
Industry:Oil & gas
A acidic salt, ZnBr<sub>2</sub>, which is used to prepare dense, clear (solids-free) brine for well completion and workover operations. The density of saturated zinc bromide is approximately 20 lbm/gal, but its pH is low and can cause acidic corrosion and handling problems. Its HSE problems must be weighed carefully against its advantages. Zinc bromide can be used to scavenge sulfides from a mud system in cases where the addition of that salt will not cause detrimental effects on mud performance, such as in a saltwater mud.
Industry:Oil & gas
A 20- to 50-gallon (3. 2- to 7. 9 m<sup>3</sup>) container for liquid mud additives, usually located above the suction pit on a drilling rig. The chemical barrel is used to slowly dispense various types of liquids into the active mud system. It has traditionally been used to add caustic (NaOH or KOH) solution at a slow and steady rate in order to maintain a uniform pH throughout a circulating mud system. Adding caustic solution is an especially risky operation and the proper design and use of the chemical barrel for safety is vitally important. Derrickmen must be informed of the dangers, proper protective clothing and safety rules to follow when using the chemical barrel.
Industry:Oil & gas
An extraordinarily poisonous gas with a molecular formula of H2S. At low concentrations, H<sub>2</sub>S has the odor of rotten eggs, but at higher, lethal concentrations, it is odorless. H<sub>2</sub>S is hazardous to workers and a few seconds of exposure at relatively low concentrations can be lethal, but exposure to lower concentrations can also be harmful. The effect of H<sub>2</sub>S depends on duration, frequency and intensity of exposure as well as the susceptibility of the individual. <br>Hydrogen sulfide is a serious and potentially lethal hazard, so awareness, detection and monitoring of H<sub>2</sub>S is essential. Since hydrogen sulfide gas is present in some subsurface formations, drilling and other operational crews must be prepared to use detection equipment, personal protective equipment, proper training and contingency procedures in H<sub>2</sub>S-prone areas. <br>Hydrogen sulfide is produced during the decomposition of organic matter and occurs with hydrocarbons in some areas. It enters drilling mud from subsurface formations and can also be generated by sulfate-reducing bacteria in stored muds. H<sub>2</sub>S can cause sulfide-stress-corrosion cracking of metals. Because it is corrosive, H<sub>2</sub>S production may require costly special production equipment such as stainless steel tubing. <br>Sulfides can be precipitated harmlessly from water muds or oil muds by treatments with the proper sulfide scavenger. H<sub>2</sub>S is a weak acid, donating two hydrogen ions in neutralization reactions, forming HS<sup>-</sup> and S<sup>-2</sup> ions. In water or water-base muds, the three sulfide species, H<sub>2</sub>S and HS<sup>-</sup> and S<sup>-2</sup> ions, are in dynamic equilibrium with water and H<sup>+</sup> and OH<sup>-</sup> ions. The percent distribution among the three sulfide species depends on pH. H<sub>2</sub>S is dominant at low pH, the HS<sup>-</sup> ion is dominant at mid-range pH and S<sup>2</sup> ions dominate at high pH. In this equilibrium situation, sulfide ions revert to H<sub>2</sub>S if pH falls. Sulfides in water mud and oil mud can be quantitatively measured with the Garrett Gas Train according to procedures set by API.
Industry:Oil & gas
