Oil and gas deposits are not found throughout the world, nor is the process of locating them random. Specific conditions must exist for oil and gas to become trapped in the Earth, and the process of finding them begins with defining where these conditions exist.

Exploration

Oil and gas deposits are not found throughout the world, nor is the process of locating them random. Specific conditions must exist for oil and gas to become trapped in the Earth, and the process of finding them begins with defining where these conditions exist.

Oil and gas (hydrocarbons) are normally found only in sedimentary rocks, formed by the accumulation of layers of small particles such as sand. Besides rock particles, this process also traps organic material. Over millions of years, deposition of successive layers can result in rock basins tens of thousands of feet deep. The buried organic material is subjected to high temperatures and pressures and, in certain conditions, changes to oil or gas.

Once formed, the oil or gas floats upward through the groundwater. It is estimated that 90% of the oil and gas formed migrated to the surface and evaporated. The remaining 10% collected in underground formations know as ‘traps.’

Oil and gas traps may form when an impermeable rock, such as shale, overlay a porous rock such as sandstone or limestone. Hydrocarbons can migrate upwards into the trap from below, but cannot migrate out. Traps are often associated with faults or folds in the rock layers. The search for oil and gas begins with identifying these traps within sedimentary basins.

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