超临界CO2压裂技术现状与展望

Research status and prospects of supercritical CO2 fracturing technology

以水基压裂液开发非常规油气过程中所面临的问题为背景,总结了超临界CO2压裂技术的独特优势、技术特点、工艺流程及其作业机制。全面分析了超临界CO2压裂技术的起源、超临界CO2压裂岩石起裂机制、缝内携砂规律、井筒流动与控制、压裂设备及现场试验等研究发展现状,得到了当前阻碍该技术工业化应用的关键问题,并给出了相应对策。针对超临界CO2压裂岩石起裂机制的研究多为现象性描述,未来应重视理论分析与模拟实验相结合,给出定量评价方法;超临界CO2缝内携砂能力的研究除了加强增黏剂方向的攻关力度外,研发纳米纤维实现物理增黏、开发新型低密度支撑剂、提高施工设备技术参数等也是有益的工作。未来超临界CO2压裂技术将逐渐由直井单层压裂向水平井多级压裂发展并与连续油管拖动压裂相结合,逐渐满足页岩气、煤层气、致密砂岩气等非常规油气的规模化开发需求。

Based on the problems encountered in the development of unconventional oil and gas using water-based fracturing fluids,this paper summarizes the unique advantages,technical characteristics,technological processes and operating mechanisms of supercritical CO2 fracturing technology.Through comprehensively analyzing the current research and development status involving the origin of supercritical CO2 fracturing technology,fracture initiation mechanisms of rock during supercritical CO2 fracturing,proppant carrying laws in fractures,flow law and control mechanism of the wellbore,fracturing equipment and field tests,this paper puts forward the key issues for industrial application and further proposes corresponding countermeasures.The researches on the fracture initiation mechanisms of rock during supercritical CO2 fracturing are dominated by phenomenal descriptions.The future study should focus on the integration of theoretical analysis and simulation experiment,and set up the quantitative evaluation method.In research of the proppant carrying capacity during supercritical CO2 fracturing,in addition to strengthening the efforts in improving the adhesion performance of tackifiers,it is also useful to develop nanofibers for enhancing tackling ability by physical methods,develop newtype low-density proppants and optimize the technical parameters of equipment.Based on the single-layer fracturing of vertical wells,the supercritical CO2 fracturing technology will be gradually developed to achieve the multi-stage fracturing of horizontal wells;in combination with coiled tubing fracturing,it can gradually meet the demands for the large-scale development of unconventional resources,such as shale gas,coalbed methane,tight sandstone gas,and etc.