Abstract: In a method of radioactive tracer logging, two slugs of tracer material are ejected. The slugs are ejected either sequentially from a single location or simultaneously from two spaced-apart locations. The distance between the tracer slugs is measured by moving a detector through the tracer slugs as they move down the borehole. The distance between the two slugs of tracer material are repeatedly measured as a function of depth, and from the measurements the amount of fluid exiting the wellbore is calculated to provide an injection profile of the well.

Abstract: A polymer gel is formulated by adding a cross-linking agent containing a polyvalent metal cation to an aqueous solution of undried partially hydrolyzed polyacrylamide. The resulting gel is dissolved or suspended in an aqueous medium and injected via a well into a subterranean hydrocarbon-bearing formation to improve oil recovery from the formation.

Abstract: A reducing agent is added to an aqueous medium containing a mixture of undried partially hydrolyzed polyacrylamide and an oxidizing agent. The reducing agent and oxidizing agent act as a redox catalyst system to cross link the polymer and form a polymer gel. Gelation time is controlled by maintaining the components of the gel-forming mixture at predetermined concentrations, reaction ratios and pH. The gel-forming mixture is applied to a porous matrix such as a subterranean hydrocarbon-bearing formation where the mixture gels in situ at a controlled rate to reduce the permeability of the porous matrix.

Abstract: The fluid flow profile in an underground reservoir having a well borehole is determined by placing in the well borehole an instrument capable of detecting the velocity of an interface moving in the well borehole. The well is shut-in to allow oil and water to separate and form an interface. A fluid miscible with the oil and less dense than the water is injected into the well borehole and forces the interface to move down the well borehole. The fluid flow profile is determined by analyzing the data obtained from the instrument.

Abstract: A treating fluid is selectively injected into a portion of subterranean formation by creating a fluid interface within a well bore penetrating and communicating with the formation. The fluid interface is created by injecting preflush fluids of differing densities into the well bore, and is maintained at a vertical location within the well bore adjacent the portion of the subterranean formation to be treated while treating fluid is injected into the well bore.