Plugging Thief Zones in Water Injection Wells

Abstract

Standard Oil Co. of California its improving per@rm-ance of its California water flood.s by improving vertical coverage and reducing .watei cycling. This program is being achieved by selectively plugging thief zones irr waler injection wells with a mixture of silicic acid gel and either gilsonite or silica flour. Previous field trials over a pe. " iod of 10 years with tnany other materials and techniques had not achieved the desired results. This art[cfe discusses the theory and placement tech-niques of silicic acid gel and presents the results of suc-cessful plugging operations in unsegregated, multilayered reservoirs consisting of interbedded soft shales and uncon-solidated sands, The operations have been successfully con-ducted in slotted liner completions, gravel-packed Iiner completions and cemented gun -or jet-perforated liner completions, The silicic acid gel is prepared in the f?eid, and the entire operation can be conducted with a production hoist and cemen(truck. Results of this program show con-clusively that silicic acid gel in conjunction with proper placement techniques can be utilized to effectively plug thief intervals in water injection wells. This is expected to become a major factor in improving water ffooding ef)l-ciency with a resultant decrease in operating costs and in-crease in net profit.