Oil and Gas Terms Beginning with “G” — Page 4

The pressure within the Earth, or formation pressure. The common oilfield usage, however, is to indicate anomalous subsurface pore pressure that is higher or lower than the normal, predicted hydrostatic pressure for a… Read more →

The change in porepressure per unit depth, typically in units of pounds per square inch per foot (psi/ft) or kilopascals per meter (kPa/m). The geopressure gradient might be described as high or low if it deviates from… Read more →

The pressure of the weight of overburden, or overlying rock, on a formation; also called lithostatic pressure. Read more →

Techniques that are applied to reservoir characterization using various statistical approaches to estimate the geological characteristics of formations at a distance from known points, such as within wellbores. These… Read more →

The process of generating models of the subsurface using geostatistical methods. The methods derive a detailed model using only sparse data (such as logs and cores from a few wells in a large area) and a knowledge of… Read more →

The study of samples of data from a complete data set (or population) to attempt to estimate the behavior of the population. Typically, geostatistics is applied during the creation of high-resolution subsurface models… Read more →

The intentional directional control of a well based on the results of downhole geologicallogging measurements rather than three-dimensional targets in space, usually to keep a directional wellbore within a pay zone. In… Read more →

The natural increase of temperature with depth in the earth. Temperature gradients vary widely over the earth, sometimes increasing dramatically around volcanic areas. It is particularly important for drilling fluids… Read more →

A short-path multiple, or a spurious reflection that occurs when seismic energy initially reverberates upward from the shallow subsurface and then is reflected downward, such as at the base of weathering or between… Read more →

A trademarked product of American Gilsonite Co. Read more →

A lifting device, similar in function to a crane jib, that is used in a number of oilfield applications, such as for handling tubulars on a snubbing unit, tool strings on a slickline unit or on a winch truck, and for… Read more →

Pertaining to the environment of deposition by glaciers. Read more →

[(K,Na,Ca) 1.2-2.0(Fe+3,Al,Fe+2,Mg)4(Si7-7.6Al1-0.4O20)(OH)47nH20]A green silicatemineral found in sedimentary rocks and formed on continental shelves characterized by slow sedimentation and organic matter, such as… Read more →

A series of alcohols with general formula C2nH4n+2On+1. The simplest member is ethylene glycol C2H6O2, widely used as antifreeze. Glycols may be used in drilling fluids as gas hydrate inhibitors. Read more →

In a glycoldehydrator unit, the cylinder composed of various perforated trays in which wet gas and glycol are put in contact. Read more →

A unit used to remove minute water particles from natural gas if dehydration was not attained using separators. A glycoldehydrator unit is usually composed of an absorber and a reboiler.The wet gas enters at the bottom… Read more →

A diagram that displays multivariate data. A good choice of glyph design can aid the recognition of complex similarities or distinctions in a set of data. A well-known example of an oilfield glyph is the Stiff diagram,… Read more →

The assembly mounted on a coiled tubing injector head that guides the tubing string as it passes through an arc from the reel into a vertical alignment with the injector-head chains and wellbore. The radius of the guide… Read more →

The assembly mounted on a coiled tubing injector head that guides the tubing string as it passes through an arc from the reel into a vertical alignment with the injector-head chains and wellbore. The radius of the guide… Read more →

The total amount of revenue that a host government receives from production. This amount can include taxes, royalties and government participation. Read more →

A relatively low-standing fault block bounded by opposing normal faults. Graben (used as both singular and plural) can form in areas of rifting or extension, where normal faults are the most common type of fault.… Read more →

A device for measuring the average density of the fluid at different depths in a completed production or injection well to produce a fluid-density log. Knowing the density of the individual phases allows their holdups… Read more →

The density of the grains in a formation or core sample. As used in log and core analysis, the term 'grain' refers to all the solid material in the rock, since, when interpreting the measurements, no effort is made to… Read more →

A coarse-grained, plutonic or intrusive igneousrock of felsic composition having large crystals of quartz, feldspar and mica. In the oil field, "granite" is sometimes used incorrectly to indicate any type of hard rock. Read more →

A type of lost-circulation material that is chunky in shape and prepared in a range of particle sizes. Granular LCM is added to mud and placed downhole to help retard the loss of mud into fractures or highly permeable… Read more →

A type of lost-circulation material that is chunky in shape and prepared in a range of particle sizes. Granular LCM is added to mud and placed downhole to help retard the loss of mud into fractures or highly permeable… Read more →

A generic name given to tools that engage on the outer surface of a tubing string or tool assembly, generally for fishing purposes. Read more →

What Is a Gravel Pack? A gravel pack is a sand control completion technique in which a layer of precisely sized gravel — typically 16/20 or 20/40 mesh (0.4–1.2 mm) Ottawa or Brady sand — is placed between a production… Read more →

A perforating-gun system containing big-hole or gravel-pack charges. A gravel-pack gun usually has a large outside diameter to minimize standoff between the gun and casing. It is loaded to achieve a high shot density… Read more →

A record of the quality of a gravel pack and the quantity of solid particles it contains. The traditional logging technique uses a type of nuclear fluid densimeter, with a gamma ray source and a single detector. The… Read more →