Oil & Gas Terms in Category H

Hydraulic centralizer

A downhole tool centralizer that is engaged by raising hydraulic pressure.


Absorbing or attracting moisture from the air

Hydrophilic-lipophilic balance (hlb)

An expressions of the relative attraction of an emulsifier for water and oil, determined largely by the chemical composition and ionization characteristics of a given emulsifier.

The hlb of an emulsifier is not directly related to solubilit5y, but it determines the type of emulsion that tends to be formed.

It is an indication of the behavioral characteristics and not an indication of emulsifier efficiency.

Hydraulic jar

See mechanical jar


The break down of a mineral by chemical reaction with water.

Hydrochloric acid

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.


A designation that is given for basic compounds containing the oh radical.

When these substances are dissolved in water, they increase the ph of the solution.

See base.

Hydrogen sulfide

A flammable, colorless gaseous compound of hydrogen and sulfur (h2s) , which in small amounts has the odor of rotten eggs.

Sometimes found in petroleum, it causes the foul smell of petroleum fractions.

In dangerous concentrations, it is extremely corrosive and poisonous, causing damage to skin, eyes, breathing passages, and lungs and attacking and paralyzing the nervous system, particularly that part controlling the lungs and heart.

In large amounts, it deadens the sense of smell.

Also called hepatic gas of sulfureted hydrogen.

Hydro-set tool

A wireline pressure setting tool for setting permanent downhole tools.

Hydrogen ion concentration

A measure of the acidity or alkalinity of a solution expressed as ph.

See ph.


Tending to absorb water.


Tending to repel water

Hydrofluoric-hydrochloric acid

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

See mud acid.

Hydro-trip pressure sub

A sub with a ball seat run on top of a hydraulically set packer to set the packer.

Hay pulley

A pulley that is normally attached to the wellhead at a convenient place for the wireline to pass through as it comes from the stuffing box sheave before being spooled onto the wireline reel.

The hay pulley prevents any lateral force from being exerted on the lubricator and the wellhead.