基于膨胀管封堵的老井页岩油体积压裂技术研究

Research on Volumetric Fracturing Technology of Old Well Shale Oil Based on Expansion Tube Plugging

随着油气田开发的持续进行,油井采收率逐渐降低,采用压裂技术有效提高了油田效益。目前对于已经射孔的老油井,需要开发射孔段外的新油层,然而在对新的低渗油层或致密油层压裂施工时,因排量受限而不能实现目的储层体积压裂,储层改造效果不明显,影响老井产能。针对老井实现射孔桥塞联座压裂,提出了使用膨胀管封堵技术,对老井进行二次或多次压裂以提高采收率。膨胀管材料的选择和膨胀锥参数的设计对该技术的成功实施起着决定性作用,为此对固体膨胀管进行了选材、膨胀锥参数优化设计及橡胶环压缩量研究,并进行了室内试验评价。结果表明,膨胀管在膨胀时经历大塑性变形,材料应选择低屈强比、高延伸率的管材;膨胀锥的优化对固体膨胀管胀后残余应力、驱动力等参数有重要影响;膨胀管胀后抗内压60 MPa未发生泄漏,悬挂力至少为590 kN。在老井重复压裂中采用膨胀管封堵技术对降低油田开采成本、提高采收率具有重要工程价值。该研究结果为老井页岩油重复压裂提供了新的射孔封堵技术,也为提高老井采收率提供了新的思路和研究方向。

With the continuous development of oil and gas fields,oil well recovery has gradually decreased,and fracturing technology has effectively improved oilfield efficiency.At present,for old oil wells that have been perforated,it is necessary to develop a new oil layer outside the perforating section of the old oil wells.However,when fracturing new lowpermeability oil layers or tight oil layers,the purpose of reservoir volume fracturing cannot be achieved due to the limited displacement,and the reservoir transformation effect is not obvious,thus affecting the productivity of old wells.In view of how to realize the perforation bridge plug joint fracturing in the old well,the use of expansion tube plugging technology is proposed,and the old wells are subjected to secondary or multiple fracturing to improve oil recovery.The selection of the material of the expansion tube and the design of the expansion cone parameters play a decisive role in the successful implementation of the technology.The material selection of the expansion tube,the optimization design of the expansion cone parameters and the compression of the rubber ring were studied,and the indoor experiment evaluation was carried out.The results show that the expansion tube undergoes large plastic deformation when expanding,and the tube material with low yield ratio and large elongation should be selected.The optimization of the expansion cone has an important influence on the residual stress and driving force of the shock expansion tube.After the tube is expanded,the internal pressure is 60 MPa without leakage,and the suspension force is at least 590 kN.The use of expansion tube plugging technology in the repeated fracturing of old wells has important engineering value for reducing oilfield production cost and improving oil recovery.The results provide a new perforation plugging technology for repeated fracturing of old well shale oil,and also provide new ideas and research directions for improving the recovery rate of old wells.