玛湖凹陷百口泉组砾岩储层泡酸后岩石损伤及压裂泵压下降机理

针对玛湖凹陷百口泉组砾岩储层水平井固井完井射孔后直接压裂施工存在泵压高、需借助长时间泡酸工艺来降低压裂启泵压力的问题,开展了储层射孔后酸损伤及降压机理研究:①通过玛湖1、玛131、玛18区块储层岩心及水泥石在模拟温度下的酸岩反应实验,得到了岩心及水泥石的宏观溶蚀率及其变化规律;②进行了玛湖1、玛131、玛18区块岩心及水泥石在酸岩反应前后的三轴力学实验,得到了酸作用前后岩石/水泥石力学特征及其变化规律;③采用扫描电子显微镜(scanning electron microscope,SEM)、能谱仪(energy dispersive spectrometer,EDS)、X-射线衍射仪(X-ray diffraction,XRD)分析了酸作用前后岩石孔/缝/面等微观结构的变化,从微观角度探索了酸岩反应机理;④综合玛湖压裂施工现状、酸反应前/后岩石及水泥石SEM/EDS/XRD分析结果、岩石/水泥石酸岩反应前后三轴力学性能,利用"七五"或组合弹簧模型及破裂压力公式分析了酸作用对地层破裂压力的影响规律,揭示了玛湖砾岩储层水平井固井完井射孔后酸损伤及降压机理.

Rock damage and fracturing pump pressure reduction mechanism of conglomerate Reservoirs in Baikouquan Formation of Mahu Sag after acidizing treatment

For the horizontal well cementing and completion of the conglomerate reservoir of the Baikouquan formation in the Mahu Sag after perforation, the direct fracturing construction has some problems in high pump pressure and need to long-time acid soaking technology to reduce the fracturing start pump pressure. The mechanism of acid damage and depressurization is studied after reservoir perforation in this paper. Firstly, the acid-rock reaction experiment of reservoir cores and cement stones in blocks of Mahu 1, Ma 131, and Ma 18 was carried out at the simulated temperature, and the macroscopic dissolution rate and the variation law of cores and cement stones were obtained. Secondly, the triaxial mechanical experiments on cores and cement in blocks of Mahu 1, Ma 131, Ma 18 before and after acid rock reaction were carried out, and the mechanical characteristics and changes of rock/cement stone before and after acid reaction were obtained. Thirdly, SEM, EDS and XRD were used to analyze the changes of pores/fractures/surfaces microstructure before and after acid treatment, and the mechanism of acid rock reaction was explored from the microscopic point of view. Finally, based on the Mahu fracturing construction parameters, the results of SEM/EDS/XRD analysis of rock and cement stone before and after acid reaction and the triaxial mechanical properties of rock/cement stone before and after acid rock reaction, the effect of acidizing treatment on formation fracturing pressure is analyzed by adopting seven-five model and fracture pressure formula, and the mechanism of acid damage and pressure reduction after perforation of horizontal well cementing and completion in Mahu conglomerate reservoir is revealed.