Gasbearing

Gasbearing refers to geological materials that contain natural gas within pore spaces, fractures, or adsorbed onto organic matter. Much of the world’s natural gas is found in gas-bearing sedimentary formations, particularly sandstone, limestone, and shale. The predominant hydrocarbon in gas-bearing rocks is methane, but gas can include ethane, propane, and butane, and, in some cases, carbon dioxide.

Natural gas originates mainly from thermal maturation of organic matter or from microbial, biogenic processes. Gas forms in source rocks or migrates from mature sources into reservoir rocks, accumulating in traps beneath impermeable seals. Gas-bearing reservoirs may store free gas in pore spaces or, in shales and coal, be largely adsorbed on organic matter or stored as gas in fractures.

Gas-bearing rocks have porosity and permeability that allow gas movement; in tight formations permeability is low, so gas is considered a tight gas resource. Gas often coexists with oil in mixed reservoirs. Gas hydrates occur where high pressure and low temperature stabilize methane in solid form, mainly on continental margins and in permafrost.

Evaluation relies on seismic imaging, well logs, core analysis, and pressure tests to determine gas saturation, composition, and recoverable volume. Terms include dry gas, wet gas, gas condensate, and gas saturation.

Handling gas poses explosion risk; methane is a potent greenhouse gas; extraction requires safety measures and environmental controls.