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Summary

After the success of polymer flooding in Daqing, two alkaline/surfactant/polymer (ASP) floods were conducted to increase oil recovery further, to study the feasibility of ASP flooding, and to provide technical and practical experience for expanding the ASP pilots. The crude oil of both pilots has a high paraffin content and low acid value. After extensive screening, an ASP system with very low surfactant concentration and wide range of ultralow interfacial tension (IFT) with any concentration change of the three components was determined for each pilot. Coreflooding and numerical simulation show more than 20% original-oil-in-place (OOIP) incremental recovery by ASP over waterflooding for both pilots. The ASP flood pilot tests are technically successful and, on the basis of preliminary evaluation, economically feasible; therefore, much larger-scale ASP-flooding field tests are planned in Daqing oil field in the near future.

Introduction

A polymer-flooding pilot test and a commercial field test have been conducted successfully in the Daqing oil field, and large-scale commercial application is now in process. To improve oil recovery and displacement efficiency further, surfactant/polymer- and micellar/polymer-flooding pilot tests have been conducted. All the tests achieved good technological results. Because of the high cost of use of large quantities of surfactants, this technology has not been expanded. ASP flooding can enlarge swept volume, improve the water/oil mobility ratio, and greatly improve displacement efficiency. Pilot tests of ASP flooding have been conducted, and good results achieved for high-acid-value crude oil; however, no pilot tests have been reported in reservoirs with low-acid-value crude oil. The acid value of crude oil in Daqing oil field is 0.1 mg/g KOH. We conducted ASP flooding research in laboratory and obtained good results. On the basis of the specific reservoir characteristics in north and south of Daqing oil field, two ASP-flood formulations were selected and pilot tests were conducted.