Definition - What does Geopressured Shales mean?
Geopressured shales are reservoirs which contain shale gas (natural gas or methane) and shale oil. Shale is a fine grained detrital sedimentary rock composed mostly of consolidated clay, Silt or mud. Geopressured shale is usually black, brown, grey or red in color. Crude oil is also trapped in the geopressured shale; however, the quantities are not predominant like natural gas.
Petropedia explains Geopressured Shales
Unconventional sources of hydrocarbon reservoirs such as geopressured shales are composed in a way that the sedimentary rocks have very low permeability and high porosity. This means that drilling a well in a conventional way will not prove to be an economical method of extracting precious hydrocarbons from such shale formations. The method that is commonly practiced by E&P organizations in extracting shale gas and shale oil is horizontal drilling and hydraulic fracturing. Geopressured shales are the rich sources of natural gas in which the natural gas is trapped in the tight rock formations at high pressure enough that if a well is drilled, it will rise to the surface by itself.