致密砂岩薄层压裂工艺技术研究及应用

摘要

针对致密砂岩薄层压裂面临缝高难控、改造体积小、裂缝支撑效率低及导流能力保持较差等难题,从压裂工程角度出发,通过压裂工艺参数优化模拟研究了不同黏度压裂液在不同的压裂施工参数下对裂缝延伸参数的影响规律,分析了薄层体积压裂存在的问题及难点,得出了主控因素,并在此基础上提出了薄层压裂控缝高措施及提高裂缝支撑效率工艺方法.研究表明:压裂液黏度是影响裂缝扩展、延伸的主要因素,其次是排量、液量;薄层压裂应以控缝高为前提,充分利用天然裂缝的作用,提高改造体积及裂缝支撑效率;低黏度压裂液能兼顾薄层压裂控缝高及造缝长的作用,有利于开启及扩展天然裂缝,进一步降低储层伤害,适宜作为薄层体积压裂的前置液;施工不同泵注阶段采用多黏度组合的压裂液体系,既可以扩大有效造缝体积及形成多尺度的裂缝系统,又能兼顾前置液阶段控缝高及携砂液阶段加砂的要求;采取变密度支撑剂结合多尺度组合加砂方式可实现不同粒径支撑剂与不同尺度裂缝系统的匹配,提高多尺度裂缝系统及远井地带裂缝的支撑效率.研究成果在龙凤山薄层气藏及江陵凹陷薄层油藏的多口井进行了试验,压裂后增产及稳产效果显著高于常规改造工艺,且稳产有效期明显增长,提高了该类储层压裂的有效性.%In order to solve the fracturing problems in the thin layer of tight sandstone reservoir,such as difficul-ty of controlling fracture height,low stimulated reservoir volume, low proppant supporting efficiency,the main-taining of flow conductivity etc.,the difficulties of fracturing in such reservoir were analyzed by the means of simulating how different kinds of fracturing fluid under different fracturing construction parameters affect the fracturing parameters,and the main controlling factors were obtained. On this basis,a fracturing technological method for controlling fracture height and improving fracture supporting efficiency was formed. The result shows that the main factors affecting the expansion and extension of the fracture are the viscosity of fracturing fluid,followed by the construction displacement and the liquid quantity. The thin layer fracturing should be based on the controlling of fracture height,make full use of the natural fracture,and improve the construction volume and the supporting efficiency. Low viscosity fracturing fluid is suitable for thin layer volume fracturing for it can take into account the role of controlling fracture height and making long fracture length in thin layer fracturing,which is beneficial for opening and expanding natural fractures,and further reducing reservoir damage. The combination of multi-vis-cosity fracturing fluid system at different stages of pump construction can not only expand the effective fracture volume and form multi-scale fracture system,but also take into account the requirement for controlling fracture height in the front fluid stage and carrying proppant in the carrying stage. Variable density proppant combined with multi-scale proppant adding method can match different size proppant with different scale fracture system, and improve the supporting efficiency of multi-scale fracture system and fractures in far well zone. The research result was successfully used in many wells in Longfengshan thin layer gas reservoir and Jiangling thin layer oil reservoir. According to the testing result,the production was far better than that of conventional fracturing method and the stable production period was improved effectively. This method improved the effectiveness of thin layer fracturing.