欢北杜家台低渗透油藏增注技术研究与应用

Research and Application of Stimulation for Enhancing Water Injectivity in Low Permeability Reservoir of Dujiatai,Huanbei Block

欢北区块杜家台油藏由于低孔低渗,油层非均质性严重,泥质含量和碳酸盐含量较高,常规注水注不进,导致油藏未能实现注水开发,长期依靠天然能量开采,地层压力大幅下降,原始地层压力为24.94MPa,目前只有11.3MPa,区块处于低速开采阶段。为提高区块开发效果,根据储层综合评价标准,通过对孔隙度、渗透率、剩余可采储量、采油速度、开发方式等进行综合分析,对各区块进行评价分类,在注水开发可行性研究的基础上,开展了水质精细处理、高压增注等系列增注技术研究,实施温和注水、高压增注,加强增注工艺配套,实施分段压裂引效、高压分注等有效措施,实现了低渗油藏的正常注水,欢北注水区块视吸水指数由0.92～5.17m3/MPa,提高到0.97～14.33m3/MPa,目前已实现欢26块全面注水、欢50块一阶段注水开发。欢北杜家台油藏适合注水开发区块全面实施注水开发后,水驱采收率为29.4%,比天然能量开发提高17.6个百分点,预计最终可增产原油255×104t。

In Dujiatai oil reservoir of Huanbei block,water flooding development can′t be realized because of low porosity and low permeability,and serious heterogeneity of oil layers and high content of shale and carbonate.Long-term exploitation of natural energy has led to sharp drop in formation pressure： initial reservoir pressure is 24.94MPa and current pressure is 11.3MPa only.The block is at the low-speed stage of development.In order to improve the effect of development,each block is evaluated and classified through comprehensive analysis on porosity,permeability,remain recoverable reserves,oil recovery rate and development mode and so on based on synergistic reservoir evaluation criterion.Based on the research of feasibility on water flooding,stimulation for enhancing water injectivity is studied including fine treatment of water quality and enhancing water injectivity at high pressure.Moderate water flooding and stimulation for enhancing water injectivity at high pressure are carried out.The effective measures of segregated fracturing and injection at high pressure are taken,and then normal water injection is realized in the low permeability oil reservoir.Apparent water injectivity index of Huanbei block of water flooding increased from 0.92-5.17m3/MPa to 0.97-14.33m3/MPa.Now,Huan 26 block has full scale water injection,and Huan 50 block has been entered the first stage of water flood development.After that,water flood recovery factor is 29.4% in Dujiatai oil reservoir of Huanbei block,which is high 17.6 percent than that of natural energy development,and forecasted ultimate incremental oil is 255×104t.