- Industri: Oil & gas
- Number of terms: 8814
- Number of blossaries: 0
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An eight-carbon alcohol. Iso-octanol is used as a defoamer for water muds.
Industry:Oil & gas
An average or baseline measure of gas entrained in circulating mud. This baseline trend pertains to gas that is liberated downhole while drilling through a uniform lithologic interval at a constant rate of penetration. The gas is typically obtained from a suction line above the gas trap located immediately upstream of the shale shaker screens, where the gas evolves out of the mud. <br> Oil-base mud systems tend to produce higher background gas values than do water-base muds. Deviations from the background gas trend likely indicate changes in porosity or permeability, or changes in drilling conditions; any of which merits further investigation. A drift or gradual shift of the background gas trend toward higher values may indicate a slow gas influx into the mud column, which can eventually lead to a kick or blowout. When annotated on mud logs, background gas is usually abbreviated as BGG.
Industry:Oil & gas
An asphaltic mud additive that has been reacted with sulfite to add anionic sulfonate groups to the complex molecular structure. Sulfonate groups make an additive water dispersible, depending on the extent of sulfonation. Such an additive is used to stabilize wellbores and as a filter-cake additive for water- and oil-base muds.
Industry:Oil & gas
An assembled length of steel pipe configured to suit a specific wellbore. The sections of pipe are connected and lowered into a wellbore, then cemented in place. The pipe joints are typically approximately 40 ft (12 m) in length, male threaded on each end and connected with short lengths of double-female threaded pipe called couplings. Long casing strings may require higher strength materials on the upper portion of the string to withstand the string load. Lower portions of the string may be assembled with casing of a greater wall thickness to withstand the extreme pressures likely at depth. <br><br>Casing is run to protect or isolate formations adjacent to the wellbore. The following are the most common reasons for running casing in a well:<br><br>1) protect fresh-water aquifers (surface casing)<br><br>2) provide strength for installation of wellhead equipment, including BOPs<br><br>3) provide pressure integrity so that wellhead equipment, including BOPs, may be closed<br><br>4) seal off leaky or fractured formations into which drilling fluids are lost <br><br>5) seal off low-strength formations so that higher strength (and generally higher pressure) formations may be penetrated safely<br><br>6) seal off high-pressure zones so that lower pressure formations may be drilled with lower drilling fluid densities<br><br>7) seal off troublesome formations, such as flowing salt<br><br>8) comply with regulatory requirements (usually related to one of the factors listed above).
Industry:Oil & gas
An aromatic hydrocarbon molecule containing a benzene ring with two methyl side chains, formula C<sub>6</sub>H<sub>4</sub>(CH<sub>3</sub>)<sub>2</sub>. Xylene is an excellent solvent, especially for aromatic solids such as asphaltic materials. It is used as a solvent and emulsion breaker in workover operations to clean up reservoirs. In drilling mud testing, a 50/50 xylene/isopropanol (IPA) mixture had been used to break oil-mud emulsions prior to titrations to measure alkalinity, chloride and calcium. However, the xylene mixture has been replaced by a single material, propylene glycol normal propyl ether (PNP), to break oil mud emulsions.
Industry:Oil & gas
An anion with formula CO<sub>3</sub><sup>-2</sup>. Carbonate chemistry involves a pH-dependent equilibrium between H<sub>2</sub>O, H<sup>+</sup>, OH<sup>-</sup>, CO<sub>2</sub>, HCO<sub>3</sub><sup>-</sup> and CO<sub>3</sub><sup>-2</sup>. At low pH, carbon dioxide (CO<sub>2</sub>) dominates. As pH rises from acidic toward neutral, HCO<sub>3</sub><sup>-</sup> ions dominate. As pH rises above neutral, CO<sub>3</sub><sup>-2</sup> ions dominate. If no component is lost from the system (such as CO<sub>2</sub> gas evolving), changing pH up and down continually reverses the relative proportion of the carbonate species. Carbonates play several important roles in water mud chemistry. One role is the corrosion of metals by acidic CO<sub>2</sub>. A second is the formation of calcium carbonate (CaCO<sub>3</sub>) scale on surfaces by carbonate and calcium ion reactions. Another role is in the chemistry of deflocculated mud, where bicarbonate ions prevent attachment of deflocculants such as lignosulfonate, onto clay edge charges.
Industry:Oil & gas
An aqueous solution of sodium, calcium or zinc bromide salt or mixtures of these salts. These dense aqueous solutions are used for well completion and workover purposes.
Industry:Oil & gas
An analytical procedure to determine the concentration of carbonate species using the Garrett Gas Train (GGT) when performed to API specifications. A water mud filtrate sample is put into the GGT. N<sub>2</sub> or N<sub>2</sub>O is the carrier gas. A CO<sub>2</sub> Drdger tube is used to measure the total carbonates released as CO<sub>2</sub> when sulfuric acid is added to the chamber containing the sample. Total carbonates are measured by the amount of CO<sub>2</sub> evolved in the test. <br><br>Reference:<br>Garrett RL: "A New Field Method for the Quantitative Determination of Carbonates in Water-Base Drilling Fluids," Journal of Petroleum Technology 30, no. 7 (July 1978): 860-868.
Industry:Oil & gas
An all-inclusive term to describe various progressive interactions between clay minerals and water. In the dry state, clay packets exist in face-to-face stacks like a deck of playing cards, but clay packets begin to change when exposed to water. Five descriptive terms describe the progressive interactions that can occur in a clay-water system, such as a water mud. <br><br>1) Hydration occurs as clay packets absorb water and swell. <br><br>2) Dispersion (or disaggregation) causes clay platelets to break apart and disperse into the water due to loss of attractive forces as water forces the platelets farther apart. <br><br>3) Flocculation begins when mechanical shearing stops and platelets previously dispersed come together due to the attractive force of surface charges on the platelets. <br><br>4) Deflocculation, the opposite effect, occurs by addition of chemical deflocculant to flocculated mud; the positive edge charges are covered and attraction forces are greatly reduced. <br><br>5) Aggregation, a result of ionic or thermal conditions, alters the hydrational layer around clay platelets, removes the deflocculant from positive edge charges and allows platelets to assume a face-to-face structure.
Industry:Oil & gas
An additive used in preparation of foam used as a drilling fluid. Drilling foam is water containing air or gas bubbles, much like shaving foam, and it must withstand high salinity, hard water, solids, entrained oil and high temperature. Foaming agents are usually nonionic surfactants and contain polymeric materials.
Industry:Oil & gas
