Abstract: Petroleum Geology of Formation Waters

Saleh M. Billo

Some researchers have argued that most petroleum traps are hydrostatic and the potentiometric surface is a level plane, whereas others have emphasized the importance of hydrodynamic traps and that the potentiometric surface slopes. The Salt Creek oil field, Wyoming is a prime example of the large, anticlinal traps that has produced over 500 million barrels of oil, and was located by a large oil seep over the trap. The structure has five producing zones, all sandstones in the Cretaceous and the Sundance sand (Jurassic). Each has a separate oil-water contact and a transition zone, indicating a lack of permeable interconnection. The multiple oil-water contacts dip northward in pact with the hydraulic gradient of the region. The slope of the potentiometric surface determines hether the water is in a state of static or dynamic equilibrium. A hydrodynamic condition is usually dependent on the topography of the surface and/or the geology of the region. Knowledge of subsurface waters can help in the discovery and seismic mapping of hydrocarbon reservoirs through valuation of possible changes imposed on the waters in the presence of hydrocarbons by recognition of changes related to conducive development of traps; and eventually by defining condition of origin and migration of oil and gas.

AAPG Search and Discovery Article #90952©1996 AAPG Rocky Mountain Section Meeting, Billings, Montana