Hydraulic Fracturing of Polymer Injection Wells

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Abstract Polymer flooding is of strategic importance to Daqing Oil Field. At present, the oil production by polymer flooding is more than 12 million tons per year. However, some problems still need to be solved; fracturing in polymer injection wells is one of these problems. After fracturing more than 40 polymer injection wells by conventional methods, the results show that the effective period of fracturing is less than 3 months. This paper focuses on the reasons of this phenomenon (short effective period), how to solve this problem, what is the best operation procedure in the field and does it suit water injection wells also. From lab tests, it was found that under high injection pressure, the proppant in the fracture can propagate forward (especially when injecting high viscosity fluids), thereby causing the fracture near the well bore to close and the frac job to fail in a very short time. Lab and well site tests show that using resin coated sand (the proppant is adhesives together in the fracture to form a very porous pancake and cannot propagate forward) can greatly increase the effective period of the frac job in polymer injection wells (from 3 months to 30 months). The results in the field of 97 polymer injection wells fractured by this method are analyzed by using injectivity index curves and compared to that of conventionally fractured injection wells. The results of 13 water injection wells are also analyzed, showing that they are very good also, the effective period of the frac job increased from 6 months to more than 24 months. Now, most of the frac jobs on injection wells (both polymer and water injection wells) in Daqing are stimulated using the method described in this paper. This method should also be of reference value to injection wells that have a short effective period to a frac job.