Origin

The origin of oil and gas is organic material - the remains of plants and animals, compressed in sedimentary rock such as sandstone, limestone and shale. As layers of sediment were deposited, decaying remains of plants and animals were integrated into the source rock. This organic material was transformed into oil and gas at a specific temperature and pressure deep within the earth's crust.

For oil and gas to accumulate, a petroleum system must be present in the ground. Source rock, reservoir rock, a migration route and cap rock are key elements of a petroleum system.

Because oil and gas are less dense than water, they migrate through relatively porous sedimentary source rock toward the earth's surface. When the hydrocarbons are trapped beneath relatively less-porous cap rock, an oil and gas reservoir is formed. These reservoirs, which are simply layers of rock containing relatively large quantities of oil and gas, are our source for crude oil and gas. By drilling into these reservoirs we source crude oil and gas.

Rock layers have different compositions and characteristics, such as porosity and permeability. Rocks with greater porosity can hold more liquid or gas, while rocks with greater permeability allow oil and gas to flow easily.

 

1. Origin               2. Exploration              3. Development              4. Production