Hydrological and Thermal Aspects of Petroleum Occurrence

Abstract

This paper presents a study of the problem of oil occurrence from the point of view of the hydrology and geochemistry of subterranean waters as well as of the geothermal environment of an area. The principles which are developed in the present article take into consideration: (a) the genetic types of subterranean waters, (b) their salinity, and (c) hydrodynamics. Three types of waters have been determined as typical for oil pools in the world: (a) chloride (brines), (b) bicarbonate, and (c) sulphate. The recharge-discharge cycle of subterranean waters (accumulation, movement, metamorphism, and drainage) is a basic concept of the problem. Hydrodynamics of subterranean waters takes account of the rate of exchange of dissolved salts and the rate of movement of waters: (a) zone of active water exchange, (b) zone of delayed water exchange, and (c) zone of stagnant waters. The optimum geothermal gradient for the oil-field areas has been found to equal 55.2 feet per 1°F. The ratio between the gradient observed in an area and the typical (optimum) gradient in the oil-field areas is accepted as one of the criteria for oil prospect.