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basin: or sedimentary basin, a concave-upward shaped geologic feature into which sediments are deposited in great thicknesses.
cement: new material precipitated around sediments buried below Earth's surface.
crude oil: see petroleum.
downstream: relates to oil and gas refining, marketing and distribution activities. (see also upstream.)
geophysics: branch of science that applies physical principles to study of planet earth.
hydrocarbons: family of organic compounds, composed entirely of carbon and hydrogen (for example, coal, crude oil and natural gas).
impermeable: Rocks where cracks and pore spaces are very small or are blocked by mineral growth. Fluids cannot flow through clays, cemented sandstone or salt.
natural gas: a gas consisting mainly of methane produced by the burial and heating of organic matter in sediments.
oil: mixture of liquid hydrocarbons of different molecular weights, also called crude all.
permeable: rocks through which fluids can pass because of interconnected pores and fractures.
petroleum: generic name for hydrocarbons, including crude oil, natural gas and their products, contained in sedimentary rocks.
seal or cap: rocks (salt, clays or cemented sandstone) in right shapes and relative positions to form traps.
sedimentary rock: formed by consolidation of deposits formed by settlement of sand, silt, and other materials.
seismic surveys: measurements of seismic-wave travel. Seismic reflection surveys detect boundaries between different kinds of rocks; this detection assists in mapping of geologic structures.
source rocks: rocks containing sufficient organic substances to generate hydrocarbons.
stratigraphic traps: originate where suitable combination of rock types is deposited in a particular environment.
structural traps: formed by Earth movements that fold rocks into suitable shapes or juxtapose reservoir and sealing rocks along faults. Traps may also form when rocks are domed over rising salt masses.
upstream: oil and gas exploration, production and transportation activities up to refining. (see also downstream.)