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

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 3 horizontal 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 GY2-1-2H in the GY2 well block is relatively low. For the Well GY2-1-2H, 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.