二次加砂压裂理论模型及应用

二次加砂压裂作为一项针对特殊储集层发展起来的应用工艺技术,在形成短宽缝、避免裂缝穿层方面优势明显,在现场得到了成功应用。但由于未针对二次压裂开展相关理论研究,导致现场设计存在极大的盲目性。在考虑砂堤高度随时间不断变化对流体压降影响的基础上,建立了适用于二次加砂压裂的裂缝延伸模型;考虑支撑剂的对流影响建立了支撑剂沉降运移模型,采用界面追踪求解支撑剂运移分布。编制程序对比分析了二次加砂压裂与常规压裂的裂缝参数。计算结果表明,二次压裂和常规压裂相比,支撑裂缝长度和高度减小,宽度明显增加,裂缝导流能力显著提高。根据油田实际物性特征,优化了二次加砂压裂工艺,实施后增产效果理想,具有推广应用价值。

Theoretical Model and Application of Secondary Sand Fracturing

As a kind of applied technology for special reservoir development, the secondary sand fracturing is of obvious advantage in shaping short and wide fracture and avoiding fracture penetrating interlayer, which has been successfully applied in fields. However, for the lack of relevant theoretical research, the field design of it is still in great blindness. This paper presents the fracture-extending model for secondary sand fracturing considering the impact of sand bank height change with time on fluid pressure drop; the proppant sedimentation and migration model considering the proppant convection impact, by which the proppant migration and distribution is gained by interface tracing; and proposes related program for correlation and analysis of fracture parameters from both secondary sand fracturing and conventional fracturing. The calculated results indicate that the secondary san fracturing is characterized by decreases of the length and height, and obvious increases of the width and conductivity of proppant fractures. According to the real reservoir petrophysical properties, the optimized secondary sand fracturing technology has satisfactory effect for stimulation, being worthy of popularization and application.