Abstract: Oil and Gas in Reservoirs with Subnormal Pressures

Parke A. Dickey

It is common to find oil and gas in stratigraphic traps in structural basins, both at depth near the bottom and also along the flanks of such basins. In many, if not most cases, the initial reservoir pressures were subnormal. This indicates a lack of permeable connection to the outcrop. Maps drawn on the potentiometric (piezometric) surface from drill-stem test pressure data sometimes clearly show the location of the stratigraphic barriers which have trapped the oil. Many giant fields are in this geologic setting, but our current prospecting methods are not designed to look for them.

The cause of the low pressures appears to be removal of overburden, which has resulted in a dilation of the pore volume in the rocks, and a decrease in reservoir temperature.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC