三塘湖盆地西山窑组砂岩油藏体积压裂技术研究与应用

Research and Application of Stimulated Reservoir Volume for Sandstone Reservoir in Xishanyao Formation in Santanghu Basin

三塘湖盆地西山窑组属于低孔隙度、低渗透率、低地层压力系数的复合圈闭＂三低＂砂岩油藏,天然产能低,开采难度大。前期直井常规压裂投产效果差,递减快,区块储量未取得有效动用。借鉴非常规油气藏＂体积压裂＂技术理念,以体积压裂适用的基本储层条件为依据,论证了西山窑组砂岩油藏水平井体积压裂的可行性。结果表明,三塘湖盆地西山窑组砂岩油藏具有石英含量高、岩石脆性指数高、天然裂缝发育等特征,易形成长宽主裂缝和分支裂缝的复杂裂缝网络,具备大规模体积压裂改造的基本要求。根据室内参数优化和现场先导性试验研究,形成了＂增加改造段数、减少改造簇数、高排量大规模注入＂的水平井＂细分切割＂体积压裂工艺技术。现场试验9口水平井,有效率达到100%,压后平均单井日产油23.46t/d,相比直井常规压裂提高了93.2%,平均单井累计产油2910.24t。

The sandstone reservoir in Xishanyao Formation belongs to the compound trap with low porosity,low permeability and low formation pressure coefficient.It is hard to be developed for low natural productivity.In the early stage,poor effect and sharp decline appeared in the process of conventional fracturing for the vertical wells,and the reserves of the block have not been produced effectively.Guided by the technology concept of stimulated reservoir volume for the unconventional reservoirs,the feasibility of the stimulated reservoir volume for the horizontal wells in the sandstone reservoir in Xishanyao Formation was discussed based on the basic reservoir conditions applicable to the stimulated reservoir volume.The results show that the sand-stone reservoir in Xishanyao Formation in Santanghu Basin has the characteristics of high quartz content,high rock brittleness index and developed natural fractures.It meets the demands of the large-scale stimulated reservoir volume for being easy to form a complex fracture network with broad main fractures and branch fractures.After laboratory parameter optimization and field pilot test,the stimulated reservoir volume with subdivision cutting for the horizontal wells was formed with increased reformed intervals,decreased reformed clusters,high discharge and large-scale injection.It was applied to nine horizontal wells in the field.The effective on-site implementation was 100%,the average daily oil production for the single well was 23.46 t/d raised by93.2% than the conventional fracturing for the vertical wells,and the average cumulative oil production for the single well was 2910.24 t.