页岩气藏压裂液返排理论与技术研究进展

页岩气藏的压裂实践表明,压后返排设计对页岩气藏压裂效果具有重要影响。近年来,压裂液返排理论与技术研究已成为页岩压裂领域的热点问题。基于国内外学者在页岩压裂液返排机理、模型、影响因素及工程工艺等方面的研究成果,系统总结和分析了页岩压裂液返排控制机制与设计方法。页岩压后压裂液在返排过程中的力学影响因素主要有毛管力、重力、化学渗透力、黏性力、气体解吸附效应等;针对压裂液是否渗吸进入基质以及压裂液的返排流动区域的研究存在争议,大多数学者认为压裂液并不渗吸进入基质中,返排流动区域主要是压后形成的水力裂缝;根据页岩气田现场生产数据分析得出早期返排过程主要为气水两相流动,目前针对页岩压后返排两相流动过程的数值模拟模型,考虑影响因素单一,应建立综合考虑影响返排过程中各类因素的模型;工程应用现状表明目前现场对返排制度的尝试还不能实现合理的返排控制,返排制度制定缺少正确的理论指导。研究成果对开展页岩压裂返排理论与工程设计研究具有一定导向作用,对提升页岩压裂改造效果具有重要指导意义。

Advances in the theory and technique of the fracturing fluid flowback in shale gas reservoirs

The fracturing practice of shale gas reservoirs shows that the flowback design after the fracturing has an important influence on the fractured effects of the shale gas reservoirs. In recent years, the researches on the theory and technique of the flowback of the fracturing fluid have become a hot issue in the shale fracturing field. Based on the research results at home and abroad of the shale fracturing fluid flowback mechanism, model, influencing factors, engineering process and so on, the flowback controlling mechanism and the design methods of shale fracturing fluid were systematically summarized and analyzed. After the fracturing, the main mechanical influencing factors of the fracturing liquid in the flowback process are the capillary force, gravity, chemical penetration, viscous force, gas desorption effect and so forth;in the light of the researches on whether the fracturing fluid will infiltrate into the matrix and flowback into the flow area, there are a few disputes, most scholars believe that the fracturing fluid doesn ’t penetrate and imbibe into the matrix, the flowback flow area is mainly the fractured hydraulic fractures;the analysis of the field production data of the shale gas field shows that the early flowback process is mainly gas-water two-phase flow, at present, the two-phase flowback numerical simulating model considers only single influencing factor, so the model considering comprehensively each factor in the flowback process;the current status of the engineering application shows that the attempt of the flowback system has not yet achieved a reasonable flowback control, and the flowback system lacks the correct theoretical guidance. The study results possess a certain guiding to the shale fracturing flowback theory and engineering design research, and moreover have important guiding significance for improving the fractured effect of the shale.