煤储层无水压裂技术现状及展望

Research Status and Prospects of Waterless FracturingTechnology in Coal Reservoir

中国煤层气产业已迈入全新发展阶段,水力压裂技术不断创新的同时,也面临着水资源消耗量巨大,煤储层伤害严重,裂缝扩展不充分等问题,寻求一种可替代的无水或少水压裂技术势在必行。文章研究总结出三种当前适用于煤储层的无水压裂技术(超临界二氧化碳压裂、液态氮气压裂、泡沫压裂),对其作用机理、理论创新以及国内现场应用的现状进行分析阐述。对各项压裂技术的优缺点特性开展了评价,结果表明无水压裂技术能减轻煤储层伤害,避免黏土膨胀和水锁效应,有效促进复杂缝网生成,缩短见气时间,实现产量显著提升,可很好应用于煤储层二次压裂改造,具备良好的环境效益和技术可行性;但同时也存在支撑剂携带困难,设备运维成本较高等问题。最后对煤储层无水压裂技术的发展提出展望,建议逐步开展煤储层无水压裂技术现场先导性试验,优化施工参数,研发地面—井下低温特殊工艺设备,推进开展低密度支撑剂和压裂液增稠剂的优选实验,巩固提升泡沫压裂液体系在高温高压环境下的稳定性能。

The coalbed methane industry in China has entered a new stage of development.With the continuous innovation of hydraulic fracturing technology,it is also faced with problems such as huge consumption of water resources,serious damage to coal reservoirs,and insufficient fracture expansion.Therefore,it is imperative to find an alternative waterless fracturing technology.Three kinds of waterless fracturing technologies suitable for coal reservoir are summarized(supercritical CO_(2) fracturing,liquid N_(2) fracturing,foam fracturing)in this paper,and the mechanism of its action,theoretical innovation and the development status of domestic field application are deeply analyzed.The advantages and disadvantages of each waterless fracturing technology are compared and evaluated.The results show that waterless fracturing technology can effectively reduce the damage of coal reservoir,avoid clay swelling and water locking effect.At the same time,it can promote the formation of complex fracture network,shorten the gas detection time,and achieve significant increase in production.Waterless fracturing technology can be well applied to the reconstruction of coal reservoir secondary fracturing,which has good environmental benefits and technical feasibility.However,it also has problems such as difficulty in carrying proppant and high equipment operation and maintenance cost.Finally,this research put forwards the prospect of the future development of waterless fracturing technology.It is suggested that field pilot tests of waterless fracturing technology for coalbed methane blocks should be gradually carried out in the future,and relevant operation parameters should be optimized and determined.Strengthen the research and development of special surface-underground process equipment and facilities such as low temperature cooling circulation system.It is suggested to carry out optimization experiments of low density proppant and fracturing fluid thickener.Further find ways to improve the stability of N_(2)/CO_(2) foam fracturing fluid system under high temperature and pressure environment.