A practical reservoir fluid-flow control system based on colloidal silica gel was developed. Colloidal silica gel is an environmentally benign system that provides easy surface handling, reliable gel-time control at temperatures up to 250°F, and high in-situ performance. Extensive laboratory testing was completed and is discussed elsewhere. Colloidal silica gel has been used in II well workovers for water-injection-proftle modification (four wells), water-production control (three wells), and remedial casing repair (four wells). Only one of the four injection-well treatments was a clear-cut technical success, with failure typically caused by pressure parting the gel plug after the well treatment. Two of the three water-production-control jobs were technical and economic successes. Temporary success was achieved in three of the four casing-repair treatments.

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This paper describes a unified testing program to identify the best polymer gel systems for a particular field application. Beaker tests are used to rapidly screen gel systems.Coreflood tests are then employed for the final system selection.Results are presented from a full-scale laboratory evaluation of 15 commercially available polyacrylamide polymers with a Cr(III)-redox crosslinker for profile modification in a thick, multizone reservoir. Beaker tests showed that low levels of polymer hydrolysis were required to produce consistent gels at reservoir conditions.In addition, the pH of the gel solution in the buffered field brine had a large effect on the gel properties. Allied C~lloids Alcoflood®935L and American CyanamidCyanagel 150 were selected for further evaluation in coreflood tests.Either polymer gel maintained a permeability reduction of at least 97 percent after 50 days of static aging at reservoir conditions. The stability of an Alcoflood 9351 gel was evaluated during continuous injection and with exposure to near wellbore pressure gradients.

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe innovative application of