Lessons Learned from Applying Particle Gels in Mature Oilfields

As an effective conformance control method, gel treatments have been applied widely in mature oilfields to reduce excess water production by preferentially plugging the water thief zones after long-term water flooding. Performed particle gels (PPGs) are becoming more and more popular in China for this purpose because they overcome some of the inherent drawbacks of in-situ gel systems, including the lack of control over the gelation time, gelling uncertainty due to shear degradation, chromatographic fractionation or change of gelant composition, and dilution by formation water. However, the literature in this area remains limited, providing few case studies or data analyses regarding the use of PPG in oilfields. This paper reports field applications of particle gels in water flooding, polymer flooding and ASP flooding. In Chinese oilfields from 2001 to 2012, we treated 655 wells with 12,765.62 tons of particles; the injected dry particles typically weighed between 11.5 to 20.6 tons per well. The applications covered both sandstone reservoirs and naturally fractured reservoirs with different temperatures and formation salinities. Properties of the particles applied in oilfields, such as the particle size, swelling ratio, and thermal stability, were tested. Eight cases are reported in this paper as examples of how to design and evaluate gel treatment projects. The results showed that the oil production rate increased from 14.3% to 50% and that water production decreased to the range of 0.4% to 4.7% after treatment. Based on the case study, highlights of illustrative PPG field applications and results are presented. Criteria for well selection and PPG treatment design are provided to serve as a guide for the kinds of conditions under which PPG conformance control can be applied successfully