Analysis And Countermeasures Of Casing Deformation Based On Fault Slip

Serious casing deformation occurred during hydraulic fracturing in ChangningWeiyuan shale gas block,Sichuan Basin.This not only decreases the number of viable fracturing stages,but also reduces the overall life cycle of the well,which in turn seriously restricts the efficient development of shale gas.Based on previous research,we take the H pad in Sichuan Basin as the research object.First,using the ant-tracking faults,microseismic events and treating pressure to analysis the correlation between casing deformation and faults,and concluded that the major cause of casing deformation might be the fault slip.On this basis,using the logs and seismic data to establish the fault model and in-situ stress model.The QRA method is used to identify the slip risk of faults.Finally,aiming at the medium and high slip risk faults,the optimization of treating parameters was carried out.The relationship between treating parameters and fault activation is established by hydraulic fracturing simulation,with which the sensitivity of treating parameters were analyzed.The results show that the slip probability of the faults intersecting the casing deformation section reaches 65% lowest,which proved that the casing deformation can be caused by fault slip.Reducing fluid volume is more effective for high slip risk faults,reducing pumping rate is more effective for medium slip risk faults.In conclusion,it is suggested that the borehole trajectory should avoid the high risk faults which identified by risk assessment.In the case of unavoidable,the fluid volume should be reduced in the fractured stages which near the high slip risk faults and the pumping rate should be reduced in the fractured stages which near the medium slip risk fault.The research has an important guiding significance for the prevention and control of casing deformation,and also has a positive role in promoting shale gas exploration and development.