Oil & Gas Glossary 1.0

An organic acid, H2CO2 or HCOOH, used for acidizing oilwells. It is stronger than acetic acid but much less corrosive than hydrofluoric or hydrochloric acid and is usually used for high-temperature wells.

An acid compound, HCI, commonly used to acidize carbonate rocks. It is prepared by mixing hydrogen chloride gas in water. Also known as muriatic acid.

Mixture of acids used for removal of mud from the wellbore. See mud acid.

A mixture of hydrochloric and hydrofluoric acids and surfactants used to remove wall cake from the wellbore.

A substance capable of reacting with an acid to form a salt. A typical base is sodium hydroxide (caustic), with the chemical formula MOH. For example, sodium hydroxide combines with hydrochloric acid to form sodium chloride (a salt) and water.

An acid that has been chemically treated before the acidizing or acid fracturing of a well to lessen its corrosive effect on the tubular goods and yet maintain its effectiveness. See acid fracture, acidize.

A crystalline acid derived from sulfuric acid that is sometimes used in acidizing.

A compound that is formed (along with water) by the reaction of an add with a base. A common salt (table salt) is sodium chloride derived by combining hydrochloric add with sodium hydroxide. The result is sodium chloride and water. Another salt is calcium sulfate, obtained when sulfuric acid is combined with calcium hydroxide.

A procedure by which acid is forced into a formation under pressure high enough to cause the formation to crack. The acid acts on certain kinds of rocks, usually carbonates, to increase the permeability of the formation. Compare matrix acidizing.

A method of stimulating production by opening new flow channels in the rock surrounding a production well. Often call a frac job. Under extremely high hydraulic pressure, a fluid (such as distillate, diesel fuel, crude oil, dilute hydrochloric acid, water, or kerosene) is pumped downward through production tubing or drill pipe and forced out below a packer or between two packers. The pressure causes cracks to open in the formation, and the fluid penetrates the formation through the cracks. Sand grains, aluminum pellets, walnut shells, or similar materials (propping agents) are carried in suspension by the fluid into the cracks. When the pressure is released at the surface, the fracturing fluid returns to the well. The cracks partially close on the pellets, leaving channels for oil to flow around them to the well. See explosive fracturing, hydraulic fracturing.

Salt of stearic acid that is a saturated, 18-carbon fatty acid. Certain compounds, such as aluminum stearate, calcium stearate, zinc stearate, have been used in drilling fluids for one or more of the following purposes: defoamer, lubrication, air drilling in which a small amount of water is encountered.

Oil containing hydrogen sulfide or another acid gas.

2. a salt or ester of phosphoric acid

A definite amount of oil, mud, acid, or other liquid in a tank or pipe.

Calcium oxide, used in certain oil-base muds to neutralize the organic acid.

A reaction in which the hydrogen ion of an acid and the hydroxyl ion of a base unite to form water, the other ionic product being salt.

Any substance or combination of substances that, when dissolved in water, produces a solution that resists a change in its hydrogen ion concentration on the addition of acid or base.

The active ingredient of quebracho and quebracho substitutes, such as mangrove bark, chestnut extract, and hemlock.

The procedure by which acid flow is confined to the natural permeability and porosity of the formation. Compare fracture acidizing.

The sodium or potassium salt of a high-molecular weight fatty acid. Commonly used in drilling fluids to improve lubrication, emulsification, sample size, and defoaming.

1. a charge of high explosive, usually nitroglycerine, detonated in a well to shatter the formation and expedite the recovery of oil. Shooting has been almost completely replaced by formation fracturing and acid treatments.

Organic acids of indefinite composition in naturally occurring leonardite lignite. The humic acids are the most valuable constituent.

Abbreviation: the phenolphthalein alkalinity of the filtrate, reported as the number of milliliters of 0.02 Normal (N/50) acid required per milliliter of filtrate to reach the phenolphthalein end point.

The half-neutralized sodium salt of carbonic acid, used extensively for treating cement contamination and occasionally other calcium contamination in drilling fluids.

Containing or caused by hydrogen sulfide or another acid gas (e.g., sour crude, sour gas, sour corrosion).

To pump a designated quantity of a substance (such as acid or cement) into a specific interval in the well. For example, 10 barrels of diesel oil may be spotted around an area in the hole in which drill collars are stuck against the wall of the hole in an effort to free the collars.

The methyl orange alkalinity of the filtrate, reported as the number of millimeters of 0.02 normal (n/50) acid required pr millimeter of filtrate to reach the methyl orange end point (pH 4.3).

2. substances in acid-base that, in solution, change color or become colorless as the hydrogen ion concentration reaches a definite value, these values varying with the indicator. In other titrations, such as chloride, hardness, and other determinations, these substances change color at the end of the reaction. Common indicators are phenolphthalein, and potassium chromate.

A unit of measure of the acid of alkaline condition of a substance. A neutral solution (such as pure water) has a pH of 7; add solutions are less than 7; basic, or alkaline, solutions are more than 7. The pH scale is a logarithmic scale. A substance with a pH of 4 is more than twice as add as a substance with a pH of 5. Similarly, a substance with a pH of 9 is more than twice as alkaline as a substance with a pH of 8.

A substance that consists of large molecules formed from smaller molecules in repeating structural units (monomers). In oilfield operations, various types of polymers are used to thicken drilling mud, fracturing fluid, acid, water, and other liquids. See micellar-polymer flooding, polymer mud. In petroleum refining, heat and pressure are used to polymerize light hydrocarbons into larger molecules, such as those that make up high-octane gasoline. In petrochemical production, polymer hydrocarbons are used as a feedstock for plastics.