Oil and Gas Terms Beginning with “H”

Hydrogen sulfide (H₂S) is a colorless, flammable, and acutely toxic gas with the characteristic odor of rotten eggs at low concentrations. It has a molecular weight of 34.08 grams per mole, is slightly heavier than air… Read more →

What Is a HAZOP? A HAZOP (Hazard and Operability Study) is a structured, team-based process safety technique that uses a systematic set of guide words to identify how deviations from design intent in a process or… Read more →

Abbreviation for held by production. Read more →

(noun) Chemical formula for hydrochloric acid. A strong mineral acid widely used in well stimulation and matrix acidising to dissolve carbonate formations, remove scale deposits, and improve near-wellbore permeability.… Read more →

Hydroxyethyl starch (HES, also abbreviated HE starch) is a chemically modified polysaccharide used as a fluid loss control additive in water-based drilling fluids, derived from natural starch (typically corn, potato, or… Read more →

HEC is the industry abbreviation for hydroxyethylcellulose, a non-ionic water-soluble cellulose ether polymer produced by the reaction of alkali cellulose with ethylene oxide, widely employed in oil and gas drilling,… Read more →

(noun) Chemical formula for hydrofluoric acid. A highly reactive acid used in combination with hydrochloric acid (mud acid) to dissolve siliceous minerals, clays, and fine particles in sandstone formations during matrix… Read more →

High-gravity solids (HGS) are dense solids added to drilling mud to increase its density, also known as weighting material — the principal HGS materials are barite (BaSO4, specific gravity 4.20 g/cm3, the standard… Read more →

HHP (hydraulic horsepower) in petroleum engineering is a measure of the power delivered by a flowing fluid, calculated as the product of pressure and flow rate divided by a conversion constant (HHP = pressure in psi ×… Read more →

What Is the HLB Number? The HLB (hydrophile-lipophile balance) number is a dimensionless scale from 0 to 20 that quantifies the relative affinity of a surfactant molecule for water versus oil, with low values (1-6)… Read more →

HP starch (high-pressure starch, also called HT starch for high-temperature starch) is a chemically modified starch product derived from potato, corn, or tapioca starch through esterification or etherification reactions… Read more →

HPHT (High-Pressure High-Temperature) designates wells, reservoirs, and associated equipment where pore pressure exceeds 10,000 psi (69 MPa) or bottomhole temperature exceeds 300 degrees F (149 degrees C), conditions… Read more →

The HPHT filtration test (High Pressure High Temperature filtration test) measures the static fluid-loss behavior of a drilling fluid under elevated temperature and pressure conditions that approach actual downhole… Read more →

An HPHT viscometer (High Pressure High Temperature viscometer) is a laboratory instrument designed to measure the rheological properties of drilling fluids under pressures and temperatures that simulate actual downhole… Read more →

HSE (Health, Safety, and Environment) in the oil and gas industry is the integrated management discipline and organizational function responsible for identifying, assessing, and controlling the hazards to worker health,… Read more →

Holdup depth (abbreviated HUD) is the measured depth in a wellbore at which a tool, drift mandrel, or gauge of a specified outside diameter can no longer pass freely through the casing, tubing, or open hole due to the… Read more →

HWDP (heavy weight drill pipe, also spelled heavy-wall drill pipe) is a specialized section of the drillstring that serves as a transition zone between the drill collars (the heavy, thick-walled tubulars immediately… Read more →

Hardfaced alloys welded onto drill pipe tool joints, collars, and heavy-weight pipe to protect the drill string from wear. Read more →

Like drill pipe, but with a heavier walled thickness and stiffer, used for a flexible transition between the drill collars and the drill pipe. Read more →

A Herschel-Bulkley fluid is a non-Newtonian fluid whose rheological behavior is described by a three-parameter model incorporating a yield stress, a consistency index, and a flow behavior index. Mathematically the model… Read more →

A Herschel-Bulkley fluid is a non-Newtonian fluid model that combines a yield stress (a minimum shear stress that must be exceeded before the material begins to flow) with a power-law relationship between shear stress… Read more →

The Horner slope is the gradient of the straight-line section selected from a Horner plot during pressure transient analysis. Denoted m , it quantifies the rate at which shut-in bottomhole pressure rises with the… Read more →

The Hough transform is a mathematical technique in image processing and pattern recognition that detects geometric shapes (particularly straight lines, circles, and ellipses) within digitized images by transforming the… Read more →

The Humble Formula is an empirically derived relationship between formation factor (F) and porosity (phi) developed by researchers at Humble Oil Company, now part of ExxonMobil. The original expression is F = 0.62 /… Read more →

Halite is the mineral name for sodium chloride (NaCl) in its crystalline rock form — the principal constituent of rock salt evaporite deposits that form when ancient seawater or saline lake water evaporates and… Read more →

An anomaly that occurs as a ring around a feature, such as electrical or geochemical rings around hydrocarbon accumulations. Read more →

Hard rock in the context of oil and gas drilling refers to formations with high compressive strength — typically consolidated sedimentary rocks (limestone, dolomite, anhydrite, chert), igneous rocks (granite, basalt,… Read more →

Water that contains hardness ions. Read more →

Hardbanding is the process of applying a wear-resistant alloy overlay to the tool joints and connection boxes of drillpipe, heavy-wall drill pipe, and drill collars to protect the base steel from abrasive wear caused by… Read more →

A hardground is a lithified, cemented seafloor surface formed when carbonate sediment is bound by the precipitation of calcite at or just below the sea floor, while sedimentation has slowed or paused long enough for… Read more →