Abstract: Disclosed herein in a method for determining the lithology of and the types of fluid contained within a subterranean formation. In the practice of this invention, high energy neutrons bombard the formation matrix and formation fluids. Induced gamma rays from inelastic scattering reactions are indicative of the type of fluid in the formation, and induced gamma rays from neutron capture reactions are indicative of the lithology of the formation matrix. Among other things, this technique permits differentiation between water-saturated limestones and oil-bearing sandstones. Also disclosed herein is a method for detecting the presence of natural gas within a subterranean formation.

Abstract: One embodiment includes an oil recovery process, more particularly a secondary or tertiary type crude oil recovery process utilizing a drive fluid to move a displacing fluid through a subterranean formation wherein the displacing fluid displaces crude oil therefrom and is driven through the formation by means of the drive fluid. The crude oil recovery process is improved by utilizing as the drive fluid a thickened, transparent, aqueous solution of a water-soluble sulfated, polyethoxylated C.sub.10 -C.sub.18 primary alcohol or alkylated phenol. The displacing fluid is generally an aqueous surfactant solution, a miscible displacing medium or most preferably a microemulsion. In a further embodiment, the water-soluble, polyethoxylated C.sub.10 -C.sub.18 primary alcohol or alkylated phenol is employed as a mobility control agent in a waterflood thereby increasing the sweep efficiency thereof.

Abstract: Disclosed herein is a method for recovering oil from a subterranean oil-bearing formation in which adjacent wells are subjected to steam stimulation to create a zone around each well which is initially heated to approximately steam temperature and which has a high water saturation following steam injection and oil production. Subsequently, a fluid having a relatively high electrical conductivity, such as a brine solution, is injected into the heated zone around the wells. Preferably the injected volume of high conductivity fluid is sufficient to displace the steam condensate from the zone and to fill the zone with the high conductivity fluid. The wells are then completed as electrodes and current is passed through the formation to heat the oil which was not heated to any significant amount by the steam. Following one or more cycles of steam stimulation and electrical heating, additional oil is recovered from the formation, preferably by line-drive steam displacement or by pattern steam flooding.