Definition - What does Oil Patch mean?
An Oil Patch is an oil producing region where large amounts of hydrocarbons are present and can be explored and extracted. In other words, it is an oil zone where a strata or formation or horizon of an oil or a gas well exists. The oil may have a gas cap on the top and water at the bottom or it can only exist as oil without gas or water.
Petropedia explains Oil Patch
Oil reservoirs usually extend over a large area and for full exploitation of oil it will entail multiple oil patches which are scattered across the area. Oil patch is an informal term used in the oil and gas industry to represent an area that produces large amounts of crude oil, natural gas, natural gas liquids and condensates. In the United States, some of the areas that produce large amounts of hydrocarbons falls under oil zone and can thus be called oil patch regions. Some of the regions where large amount of hydrocarbons are produced in the United States are Texas, Kansas, Oklahoma, etc.