Polymer Gel Profile Control In Low Temperature Reservoir System Research And Application

Water injection has been a primary technique to enhanced oil recovery for a century since it was proposed. However, for the heterogeneity of interlayer and horizons, strong absorbing ability of high-permeability zone, forming a water channel and ineffective water cycle, while the low-permeability zone is not injected by water in water injection.Polymer gel can be applied to block preferential path and control injection profile, finally, improve conformance factor and waterflood efficiency.This paper researches a low-temperature gel system,Most low temperature reservoirs are coming into late stages of waterflooding as FuYu oilfiled. During this period the water cut increases rapidly with the decreasing of the oil produ ction.The polymer gel system is synthesized and performance evaluation is made on it in this article that intended for the water controlling and oil increment for low-temperature reservoir. In this paper, the low-temperature gel system (DWJ) is crosslinked with chromium acetate that is compounded with adjuvant. The major goals of this paper is to investigate the factors, which mainly affect the conventional performances of the polymer gel, including the type of polymer(molecular weight, hydrolyzing degree)and concentration, the mass ratio of polymer and crosslinker, reaction time of crosslinker, salinity, adjuvant and stabilizer etc. Orthogonal experiments and single factor experiments were designed to evaluate the significance of these factors. The results demonstrate that there is a good agreement between orthogonal and single factor experiments, the concentration of polymer is the most significant one, followed by the ratio (polymer/crosslinker) and salinity. Finally, a gel system having a good compatibility with the injected water in the field is obtained through screening. The basic formulation decided in present study as follows:comb shaped polymer (molecular weight of25million, hydrolyzing degree of25%) which concentration is between2000-3000mg/L, the mass ratio of polymer and crosslinker ranging from8:1to10:1,the reaction time of crosslinker:one hour for60℃and3-8days for room temperature, the salinity is lower than1%. the concentration of adjuvant(DQ) is smaller than100mg/L, another adjuvant(DF) is50mg/L, and the concentration of stabilizer is in80mg/L. Furthermore, the other performances, for instance, the relationship of microstructure and gel strength, viscoelasticity, drag coefficient, residual resistance factor, displacement efficiency and the effect of profile modification were studied by several techniques such as ESME, HAAKE Rotational Rheometer and core flow test.On the basis of laboratory, this his system has been applied to D40-10block in Fuyu field. The results of field application show that this gel system can effectively block high permeability zone, divert the follow-injected water entering the low permeability zone. Consequently, swept volume of flood water can be improved greatly and higher oil production is achieved.