- Settore: Oil & gas
- Number of terms: 8814
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A chemical that aids in breaking up solids or liquids as fine particles or droplets into another medium. This term is often applied incorrectly to clay deflocculants. Clay dispersants are various sodium phosphates and sodium carbonates aided by heat, mechanical shearing and time. Powdered polymers are dispersed by precoating the particles with a type of glycol to prevent formation of "fish-eye" globules. For dispersing (emulsification) of oil into water (or water into oils), surfactants selected on the basis of hydrophile-lipophile balance (HLB) number can be used. For foam drilling fluids, synthetic detergents and soaps are used, along with polymers, to disperse foam bubbles into the air or gas.
Industry:Oil & gas
A chemical that reduces the viscosity of a fluid by breaking long-chain molecules into shorter segments. Drilling fluids are commonly emulsified or contain long-chain molecules that have sufficient viscosity to carry cuttings to surface. After the drilling fluid has done its job, a breaker may be added to reduce the viscosity of the fluid by breaking down the long chain molecules into shorter molecules. A surfactant may be added to an emulsion to reduce its viscosity.
Industry:Oil & gas
A chemical property of an aqueous system that implies that there are more hydroxyl ions (OH<sup>-</sup>) in the system, or a potential to produce more hydroxyl ions, than there are hydrogen ions (H<sup>+</sup>), or potential to produce hydrogen ions.
Industry:Oil & gas
A chemical that reacts with dissolved oxygen (O<sub>2</sub>) to reduce corrosion, such as sulfite (SO<sub>3</sub><sup>-2</sup>) and bisulfite (HSO<sub>3</sub><sup>-</sup>) ions that combine with oxygen to form sulfate (SO<sub>4</sub><sup>-2</sup>). This is a redox reaction and requires a nickel or cobalt catalyst. Removal of air from a mud by defoaming and mechanical degassing is an essential first step before a scavenger can lower the dissolved oxygen content.
Industry:Oil & gas
A chemical that causes a dispersed colloidal system (such as clay) to coagulate and form flocs. Most flocculants are either multivalent cations such as calcium, magnesium and aluminum, or long-chain polymers. High pH, high salinity and high temperature can also cause clay flocculation.
Industry:Oil & gas
A chemical or isotopic marker that is uniformly distributed in the continuous phase of a drilling, coring, drill-in or completion fluid and used to later identify the filtrate in cores or in fluids sampled from permeable strata. A tracer must become a part of the filtrate, remaining in true solution and moving with the filtrate into permeable zones. It must not be a component in the strata that is expected to migrate, be adsorbed on clays, or degraded. It should be measurable in trace amounts and safe to handle. Examples of filtrate tracers include: (1) Radioactively tagged compounds (isotopes of elements). Tritium, a weakly-emitting radioisotope of hydrogen, can be a safe and effective tracer in both oil and water (as T<sub>2</sub>O) muds. It is measured by scintillation counts. (2) Bromide or iodide compounds are practical to use because they do not occur naturally in most muds or reservoirs. They are detectable in small amounts by electron-capture gas chromatography. (3) Fatty acids (or their derivatives) normally present in an oil-mud emulsifier can serve as oil-filtrate tracers and are analyzed by gas chromatography. (4) Nitrate (NO<sub>3</sub><sup>-</sup>) anion, added as sodium, potassium or calcium nitrate, is one of the earliest tracers used. It is limited by being difficult to analyze and lost by degradation.
Industry:Oil & gas
A chemical that acts as a surface active agent. This term encompasses a multitude of materials that function as emulsifiers, dispersants, oil-wetters, water-wetters, foamers and defoamers. The type of surfactant behavior, whether acting as an emulsifier or dispersant or otherwise, depends on the structural groups on the molecule (or mixture of molecules). Hydrophile-lipophile balance (HLB) number helps define the function that a molecular group will perform.
Industry:Oil & gas
A chemical system that resists a change in pH. It comprises three components: water, weak acid (or weak base) and salt of the weak acid (or salt of weak base). In a buffered system, the concentration of H<sup>+</sup> and OH<sup>-</sup> ions remain relatively constant because they are in equilibrium with one or more of the other two components, even with the addition of acids or bases.
Industry:Oil & gas
A chemical reaction between an acid and a base to form a salt and water. Neutralization is used in the manufacture of mud products, removal of acidic contaminants from muds and formation of emulsifiers in oil mud. Neutralization is used in the test for alkalinity of mud and mud filtrate.
Industry:Oil & gas
A cement system used to provide zonal isolation across generally nonproductive zones located above the zones of interest. The fill cement is also called the lead cement.
Industry:Oil & gas
