Page 356 - Geology and Geochemistry of Oil and Gas

GLOSSARY 317
Histogram A graphical representation of class frequencies (or
relative frequencies) as rectangles against class
interval, the value of frequency being proportional to
the area of the corresponding rectangle.
Hydraulic fracturing Fracturing the formation by pumping in a specifically
blended liquid under pressure high enough to cause
the formation to crack open.
Hydraulic lift Use of hydraulic pressure to activate the downhole
pump.
Hydrocarbon Any organic compound, gaseous, liquid, or solid,
consisting solely of carbon and hydrogen. They are
divided into four specific groups: paraffin, cyclo-
paraffin or naphthene, olefin, and aromatic. Crude oil
is essentially a complex mixture of hydrocarbons.
Hydrocracking Method of cracking or breaking up of long-chain
hydrocarbons.
Hydrogen sulfide A toxic, corrosive gas, H 2 S, with a characteristic odor
of rotten eggs. It is emitted in natural decomposition
of organic matter and is present in many crude oils
and natural gases.
Hydrophilic Having strong affinity for water; said of colloids that
swell in water and are not easily coagulated.
Hydrophobic Lacking strong affinity for water; said of colloids
whose particles are not highly hydrated and coagulate
easily.
Hydrophone Waterproof microphone used to detect seismic echoes
at sea.
Hydrostatic head Pressure (p) exerted at the bottom of a column of
liquid, p ¼ gD, where g ¼ specific weight of liquid
3
3
(e.g., in lb/ft or kg/m ), and D ¼ depth (e.g., in ft or
m). Syn: Pressure head; Hydrostatic pressure.
Hydrothermal Alteration of rocks or minerals by the action of
heated waters.
Hypersaline Seawater salinity elevated beyond values of normal
salinity (e.g., greater than 34–38%); also used in
reference to environments of extensively high salinity.
Hypothesis testing The theory and methods used in statistics to test one
hypothesis (null hypothesis, H 0 ) about the probability
distributions of a sample population against another
(alternative or research hypothesis, H a ).
I
Igneous rock A rock mass formed by the solidification of material
poured (when molten) into the Earth’s crust or onto
its surface.