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目前水平井段井壁失稳是制约页岩气资源钻探开发进程的主要技术难题之一。针对上述技术难题,采用低压氮气吸附与高压压汞实验,分析了硬脆性页岩的微纳米孔隙结构特征,探讨了微纳米孔隙结构特征对页岩气地层井壁稳定性的影响。利用压力传递实验,开展了页岩微纳米尺度裂缝封堵评价实验。研究表明,页岩气地层的井壁失稳与其自身的微纳米孔隙结构特征具有密切关系,微纳米尺度裂缝发育是导致页岩气地层井壁失稳的内在主要因素;在此基础上,提出了页岩气协同稳定井壁钻井液技术对策,其中强化封堵页岩微纳米尺度裂缝是解决页岩气地层井壁失稳的关键技术措施。进一步优选了新型微纳米封堵剂,其粒径在80~200 nm之间呈“单峰”分布,能够有效封堵页岩微纳米尺度裂缝,阻缓压力传递与滤液侵入,增强裂缝性页岩井壁稳定性。
At present, the failure of wellbore in the horizontal well section is one of the major technical problems restricting the development of shale gas resources. In view of the above technical problems, the micro-nano pore structure characteristics of hard and brittle shale were analyzed by using low-pressure nitrogen adsorption and high pressure mercury intrusion experiments, and the influence of micro-nano pore structure characteristics on the wellbore stability of shale gas formation was discussed. Using pressure transfer experiment, the micro-nano-scale crack plugging evaluation experiment was carried out. The research shows that the instability of the shaft wall in shale gas formation is closely related to its own micro-nano pore structure characteristics. The development of micro-nano scale cracks is the inherent major factor leading to the instability of the shaft wall in the shale gas formation. On this basis, The shale gas synergistic stability of the borehole drilling fluid technology measures, including strengthening the closure of micro-scale cracks in shale micro-scale shale gas formation is to solve the key technical measures of instability. A new type of micro-nano plugging agent was further optimized. Its particle size distribution was “unimodal” between 80 and 200 nm, which could effectively block micro-nano-scale cracks in shale, retarding pressure transmission and filtrate intrusion and strengthening cracks Shale wall stability.