Oilfield Glossary A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Nomenclature ABANDON- To cease efforts to produce oil or gas from a well, and to plug a depleted formation and salvage all material and equipment. ABSOLUTE PERMEABILITY- The proportionality constant in D’Arcy’s flow equation; a measure of the ease with which a fluid will flow through a porous medium. ABSOLUTE VOLUME- The volume per unit mass, reciprocal of absolute density. ABSORB- To accumulate or “drink in,” as a liquid into a porous solid, or a gas into a liquid. A sponge absorbs water. We pump fluid into a fractured formation and the fluid leaks off to the matrix permeability. The formation absorbs the leak-off fluid. ABSORPTION- The penetration or apparent disappearance of molecules or ions of one or more substances into the interior of a solid or liquid. For example, in hydrated bentonite, the planar water that is held between the mica-like layers is the result of absorption. ABYSSAL- Refers to the great depths of seas or lakes where light is absent. Greater than 6000 feet of water. ACID- Any chemical compound containing hydrogen capable of being replaced by positive elements or radicals to form salts. In terms of the dissociation theory, it is a compound that, on dissociation in solution, yields excess hydrogen ions. Acids lower the pH. Examples of acids or acidic substances are: hydrochloric acid, tannic acid, sodium acid pyrophosphate. A substance whose molecules ionize in a water solution to release the hydrogen ion from the constituent element. The strength of an acid is proportional to the concentration of hydrogen ions present. ACID RESISTANCE- The ability of a hardened cement slurry to withstand the softening and corrosive effects of organic or mineral acids, or water solutions of these acids and their salts having a pH lower than 7.0. ACIDITY- The relative acid strength of liquids as measured by pH. A pH value below 7. See pH. ACIDIZING- The practice of applying acids to the walls of oils and gas wells to remove any material which obstructs the entrance of fluids. Also used in carbonate formations, such as limestone, to increase porosity. ADAPTER- A device to provide connection between two other parts. ADDITIVE- A material other than cement and water which is added to a cement subsequent to its manufacture to modify its properties. 1 HRD Standards Glossary of Oilfield Terms ADHESION- The force which holds together unlike molecules. ADMIX- To add one material to another by mixing. NOTE: Admix should not be used replaceably with additive. ADSORB- The adhesion, in an extremely thin layer, of the molecules of a gas, a liquid or of dissolved substances on the surface of that which it is in contact. Generally, adsorption takes place on the surface of liquids or solids. Think of this like a paint film a few millionths of an inch thick. Our NE compounds adsorb on the face of a fracture in a formation. One theory about the action of scale inhibitors is that they are adsorbed on the face of the fracture. The molecules of the inhibitor are then slowly desorbed from the surface of the rock by the flow of produced fluids. The molecules of an emulsifier are adsorbed in a microscopic film on the surface of tiny globules of acid, holding them in the shape of a ball, and permitting them to be suspended in diesel oil or kerosene. This is emulsified acid. The same mechanism is responsible for the creation of unwanted emulsions of treating fluids with formation fluids. ADSORPTION- A surface phenomenon exhibited by a solid (adsorbent) to hold or concentrate gases, liquids, or dissolved substances (adsorptive) upon its surface, a property due to adhesion. For example, that water held to the outside surface of hydrated bentonite is adsorbed water. The accumulation of a thin layer of molecules of gas or liquid on a solid surface. AEOLIAN- An adjective applied to rocks formed of wind-borne sands. AERATE- Intimately admixing water and air. AERATION- The technique of injecting air or gas in varying amounts into a drilling fluid for the purpose of reducing hydrostatic head. Compare Air Cutting. AEROBIC- Bacteria that are active only in the presence of oxygen. Bacteria which requires free oxygen to degrade organic material. AGING- Natural or artificial maturing of cement, cement slurries, and hardened cement paste during which various physio-chemical changes take place. AGGLOMERATE- The larger groups of individual particles usually originating in sieving or drying operations. AGGLOMERATION- The grouping of individual particles. AGGREGATE- A group of two or more individual particles held together by strong forces. Aggregates are stable to normal stirring, shaking, or handling as powder or a suspension. They may be broken by drastic treatment such as ball milling a powder or by shearing a suspension. An essentially inert material of mineral origin having a particle size predominantly greater than 100 mesh, which forms a mortar or concrete when bound together with hardened cement paste. AGGREGATION- Formation of aggregates. In drilling fluids, aggregation results in the stacking of the clay platelets face to face. The viscosity and gel strength decrease in consequence. 2 HRD Standards Glossary of Oilfield Terms AIR CUTTING- The inadvertent mechanical incorporation and dispersion of air into a drilling-fluid system. Compare Aeration. AIR/GAS LIFT- Lifting of liquids by injection, directly into the well, of air or gas. AIR/OIL RATIO- The quantity of air required for injection to burn and displace a unit volume of oil in the in-situ combustion process. ALGAE- Cellular aquatic plants, mostly of marine habitat. They are found fossil, more or less, in every formation from the Pre-Cambrian to Recent. ALGAL- Pertaining to algae. ALIPHATIC- Those hydrocarbons which have straight or branched carbon chains in their molecular structure. The greater portions of the hydrocarbons in the crude oil are aliphatic in nature. Kerosene, diesel oil and gasoline are all mixtures of aliphatic or straight chain hydrocarbons. ALKALI- Any compound having marked basic properties. See Base. In chemistry, any substance having marked basic properties. In its restricted an common sense, the term is applied only to hydroxides of potassium, sodium, lithium, and ammonium. ALKALI FLATA- sterile plain, containing an excess of alkali, at the bottom of an undrained basin in an arid region. A playa. ALKALINITY- The combining power of a base measured by the maximum number of equivalents of an acid with which it can react to form a salt. In water analysis, it represents the carbonates, bi-carbonates, hydroxides, and occasionally the borates, silicates, and phosphates in the water. It is determined by titration with standard acid to certain datum points. See API RP 13B* for specific directions for determination of phenolphthalein (Pf) and methyl orange (Mf) alkalinities of the filtrate in drilling fluids and the alkalinity of mud itself (Pm). Also see Pf, Mf, and Pm. - *Standard Procedure for Testing Drilling Fluids, American - Petroleum Institute, Dallas, Texas, Nov. (1962) 1st Ed. ALLOCHTHONUS- Referring to limestone formed by the accumulation of transported organic matter or calcareous fragments, rhombs, colites, etc. ALLOGENIC- Originating elsewhere. The contrasted form is authigenic. ALLOWABLE- The amount of oil or gas that a well is permitted by state authorities to produce during a given period. ALLUVIAL- An adjective denoting that which is transported by running water. ALLUVIAL FAN- Sediments deposited by a swift stream flowing out onto a valley floor from higher land. ALUMINUM STEARATE- An aluminum salt of stearic acid used as a defoamer. See Stearate. 3 HRD Standards Glossary of Oilfield Terms AMBER- A hard, brittle, translucent, fossilized vegetal resin, of a clear yellowish- brown or light-yellow color. AMBIENT- We use this term to describe temperature. Strictly speaking, the term is defined as “completely surrounding.” Ambient temperature, then would be the temperature of the air surrounding us. We stretch this definition a little and refer to pumping fluids at ambient temperature. We mean we don’t heat or cool the fluid, but use it just like it is in the tank. Defined as “completely surrounding,” strictly speaking. Ambient temperature, then, would be the temperature of the air surrounding us. We stretch this definition a little and refer to pumping fluids at ambient temperature. We mean that we do not heat or cool the fluid, but use it at the temperature is in the tank. AMORPHOUS- Without form; applied to rocks and minerals having no definite crystalline structure. AMPHOTERIC- Anionic or cationic depending on outside conditions, pH for example. ANAEROBIC- Bacteria that do not require free oxygen to thrive. ANALYSIS, CORE- Laboratory examination of geological samples taken from the well bore. This examination is used to determine the capacity of the formation to contain oil and gas, the possibility of oil and gas passing through the formation, the degree of saturation of the formation with oil, gas, and water, and for other purposes. ANALYSIS, MUD OR DRILLING FLUID- Examination and testing of the drilling fluid to determine its physical and chemical properties and condition. ANDESITE- A very hard granite rock composed of granular feldspar. ANGULAR UNCONFORMITY- An uncomformity in which the beds below the unconformable contact had undergone movement and erosion before the upper beds were deposited. The lower beds are, therefore, not parallel to those above. ANHYDRITE- See Calcium Sulfate. Anhydrite is often encountered while drilling. It may occur as thin stringers or massive formations. CaSO4. ANHYDROUS- Without water. Destitute of water, especially water of crystallization. ANILINE POINT- The lowest temperature at which equal volumes of freshly distilled aniline and an oil that is being tested are completely miscible.