Oil exploration - Definition and Overview

Oil Exploration is the search by petroleum geologists for hydrocarbon deposits beneath the Earth's surface. Oil and gas exploration are grouped under the science of petroleum geology.

When organic-rich rock such as oil shale is subjected to high pressure and temporature over an extended period of time, hydrocarbons form. Being less dense than the surrounding water table, these are expelled and forced upwards. Normally such hydrocarbons will seep to the surface, but particular formations of non-porous rock known as traps may allow them to accumulate. Such accumulations are known as reservoirs.

The objective of oil exploration is to find such reservoirs.

Visible surface features such as oil seeps, natural gas seeps, pockmarks (underwater craters caused by escaping gas) provides basic evidence of reservoirs (be it shallow or deep in the Earth); however, most exploration depends on highly sophisticated technology to detect and determine the extent of these deposits. Areas thought to contain hydrocarbons are initially subjected to a gravity survey or magnetic survey to detect large scale features of the sub-surface geology. Features of interest (known as prospects) are subjected to more detailed seismic surveys and those unlikely to be sealed traps are discarded. Finally, an exploration well is drilled to conclusively determine the presence or absence of oil or gas.

Oil exploration is an expensive, high-risk operation. Offshore and remote area exploration is generally only undertaken by very large corporations or national governments. Hundreds of smaller companies search for onshore hydrocarbon deposits worldwide, with some wells costing as little as $500,000 USD.