东营凹陷陆相页岩油CO2增能压裂裂缝形态研究

Study on Fracture Morphology of CO2 Energized Fracturing of Continental Shale Oil in Dongying Sag

  • 摘要: CO2增能压裂改造效果与生产效果评价受压裂裂缝分布的影响。为明确东营凹陷陆相页岩油CO2压裂造缝机理,通过试验确定了CO2浸泡下岩体破裂压力、天然裂缝剪切/张开应力和地应力随时间的变化;在此基础上,考虑CO2浸泡下的岩石应力参数,采用Pen-Robinson方程刻画CO2物性参数变化,结合试验和数模方法,形成了基于节点连接方法的CO2增能压裂裂缝扩展模拟方法,并对东营凹陷某油井进行了实例分析。研究结果表明,CO2比例对分支缝密度的影响较大,当CO2比例由0.1增加至0.3时,分支缝密度增加117%;应力差主要影响缝长及分支缝密度,水平应力差由5 MPa增至30 MPa时,缝长度增加了52%,分支缝密度下降了13.85%。裂缝形态模拟结果与实际监测结果具有较好的一致性,研究结果可以为陆相页岩油压裂方案的制定提供理论参考。

     

    Abstract: In the process of CO2 energized fracturing, the evaluation of fracturing stimulation effect and production effect is affected by fracture distribution. In order to clarify the fracture mechanism of CO2 fracturing of continental shale oil in Dongying Sag, the changes in rock mass fracture pressure, natural fracture shear/opening stress, and in-situ stress with time under CO2 immersion were determined by experiments. On this basis, by considering the rock stress parameters under CO2 immersion, the Pen-Robinson equation was used to describe the change of CO2 physical property parameters. In addition, combined with experimental and numerical methods, a simulation method for fracture propagation by CO2 energized fracturing based on node connection method was developed, and an example analysis of an oil well in Dongying Sag was carried out. The results show that the CO2 ratio has a great influence on the induced fracture density. When the CO2 ratio increased from 0.1 to 0.3, the induced fracture density increased by 117%. The stress difference mainly affects the fracture length and induced fracture density. When the horizontal stress difference increased from 5 MPa to 30 MPa, the fracture network length increased by 52%, and the induced fracture density decreased by 13.85%. The simulation results of fracture morphology are in good agreement with the actual monitoring. This study can provide a theoretical reference for the formulation of continental shale oil fracturing schemes.

     

/

返回文章
返回