低渗油田水平井整体压裂技术实践与认识

Practice and Recognition of the Integral Fracturing Technology for Horizontal Wells in Low-permeability Oilfield

A油田P油层属低温薄差储层,同位素测井、井下及地面微地震监测结果及瞬时停泵压力梯度分析均表明,人工裂缝形态为水平裂缝。针对P油层试验区的地质特征,优选双封单卡分段压裂技术,优选新型压裂液和支撑剂,确定射孔方式,选取含油饱和度高的井段进行射孔,在油藏评价和压后产量预测基础上,建立裂缝数目优化模型。参照模拟结果,结合井身结构、地质特点和水平井井组注采对应关系等因素,对试验水平井水平裂缝参数进行优化。确定分段压裂平均砂比为21%,末期砂比在35%以上,施工排量为2.5～3.5m3/min。现场施工效果表明,双封单卡分段压裂管柱在承压性能及过砂量要求上,能满足要求;所选用的低温压裂液体系交联性能良好,能达到设计施工参数(砂比和排量)要求,8口井37个压裂层段工艺成功率达100%。投产井初期平均单井日产油6.0t/d,是同区块直井的4.0倍;投产3个月后,平均单井日产油4.0t/d,仍然是同区块直井的3.6倍。

Reservoir P in oilfield A is thin and poor at low temperature.Artificial fracture is horizontal according to the result of isotope logging,microearthquake monitoring at downhole and surface and the analysis of instant pump-off pressure gradient.According to the geological characteristics of pilot site at reservoir P,the technique of double-sealing and single-stick subsection fracturing and new-type of fracturing fluid and proppant agent are optimized.The interval with high oil saturation is perforated in certain casing perforation type.Optimization model of the number of fractures is built based on reservoir evaluation and production forecast after fracturing.Parameters of the horizontal fracture in tested horizontal wells are optimized according to the simulation results combined with the factors of hole structure,geological characteristics and injection-production corresponding relation of horizontal well group.Average proppant concentration is 21% when subsection fracturing and proppant concentration at last stage is above 35%.The discharge rate is 2.5-3.5m3/min in field application.Field application results show that the string of double-sealing and single-stick subsection fracturing can meet the demands of pressurization behavior and sand amount.The selected low-temperature fracturing fluid system has good cross-linking behavior,which can meet the demands of designed implementation parameters.Fracturing is successful completely for 8 wells in 37 layers.Average daily oil production of single well at early stage of the brought-in wells is 6.0t/d,four times of the straight wells of the same block.After three months,the average daily oil production of single well is 4.0t/d,3.6 times of the straight wells of the same block.