Oil Reservoir Gas Cap

For a massive oil reservoir the intermediate casing may be run to the top of the oil reservoir and then open hole completion is applied after drilling the weathering crust.

Oil reservoir gas cap. This recovery level is considerably greater than the nonsegregating gas cap or solution gas drive reservoirs 74 9 and 52 3 respectively. In saturated oil reservoirs the free gas forms a gas cap portion of the reservoir overlain by free gas due to gravity segregation. The reservoir rock is the porous permeable rock layer or layers that hold the oil and gas. The cap rock seals the top and sides so that the hydrocarbons are trapped in the reservoir while water often seals the bottom.

A gas cap present at the time of the discovery of the oil reservoir is known as a primary gas cap. Certain oil reservoirs are discovered with an initial reservoir pressure below the bubble point pressure where a primary gas cap forms long before the reservoir is discovered and produced. The segregating gas cap reservoir terminates at a pressure of 508 psia. For example the red colored region of the numbi field in figure 3 01 is a gas cap.

In conventional reservoirs the naturally occurring hydrocarbons such as crude oil or natural gas are trapped by overlying rock formations with lower permeability while. For a reservoir to exist oil and gas from the source rock must migrate into the reservoir rock which takes millions of years. The segregating gas cap reservoir recovers 91 1 of the oil leg ogip. 5 shows the gas recovery history.