沧东凹陷孔二段页岩压裂套变原因分析及预防对策

Cause analysis and preventive countermeasures for casing deformation when fracturing shale in Kong 2 member in Cangdong sag

在页岩油藏开采中,多级分段压裂技术是增加页岩油水平井产量的关键技术之一。随着页岩油藏的大规模开发,在水平井多级分簇压裂过程中套管损坏问题频繁出现,极大影响了现场施工效率和经济效益。官东页岩油作业7口水平井有4口发现套变问题,对4口套变井进行了综合梳理后发现,该区域套变问题与固井质量和狗腿度等因素相关性较小,与钻遇断层情况联系紧密。其中GY2井区作业的3口穿过同一断层的水平井有2口发生了套变。结合断层激活理论,分析了压裂作业激活断层的相关因素,并对断层长度、压裂施工压力和断层走向等因素进行了敏感性分析。研究结果表明,GY2井区的GY2-1-2H井作业压力较低,钻遇断点过断层边缘和断层走向与最大主应力夹角较小是该井钻遇断点处未发现套变的主要原因。根据研究结果提出了控制套变的方法,为进一步防止套变发生提供了技术指导和参考经验。

When developing shale oil reservoirs,multi-stage fracturing technology is one of the key technologies to increase the shale oil production for horizontal wells.With the large-scale development of shale reservoirs,casing damage frequently occurs during the multi-stage fracturing process of horizontal wells,which greatly affects the field construction efficiency and economic benefits.In the Guandong shale oil operation,4 of the 7 horizontal wells were found with casing deformation problems.After comprehensively analyzing the 4 wells with casing deformation,it was found that the casing deformation problems in this area were less correlated with factors such as cementing quality and dogleg degree,and it is closely related to the faults drilling encountered.For example,2 of the 3horizontal wells that pass through the same faults in the GY2 well block were found with casing deformation.Combined with the theory of fault activation,the relevant factors that can activate the fault because of fracturing operation were analyzed,and the sensitivity analysis on the factors such as fault length,fracturing pressure,and fault strike was carried out.The research results show that the operating pressure of Well GY2-1-2 H in the GY2 well block is relatively low.For the Well GY2-1-2 H,the break point drilling encountered crosses the fault edge,and the angle between the fault strike and the maximum principal stress is small,which are the main reasons that no casing deformation is found at the breaking point drilling encountered.According to the research results,a method to control the casing deformation was proposed,which provides technical guidance and experience basis for further preventing the occurrence of casing deformation.