Analysis of Casing Deformation in the Changning-Weiyuan Block Based on Focal Mechanism

Casing deformation is a very serious problem in the Changning-Weiyuan Shale Gas Demonstration Area in Sichuan Province,where natural fractures(or faults)create problems,and in fact are the main controlling factor of casing deformation.In order to understand the effect of microseismic magnitude and fractures(or faults)and the scale which induces casing deformation,a study employed the source parameters of the circular fault model,and a mathematical model reflecting the relationships among parameters(e.g.fault radius,slip throw,seismic moment and moment magnitude)was developed.In practical application,the slip throw of fault(i.e.,casing deformation)is estimated by using 24-finger caliper logging data or the maximum diameter of grind shoe through the casing deformation position.Then the model is used to calculate the fracture or fault radius and the microseismic magnitude which can be related to the casing deformation.The calculated microseismic magnitude and fracture or fault radius related to casing deformation in Changning-Weiyuan Block are 2.0-3.5 and 100-400 m,respectively;the results are consistent with the measured data.The results also demonstrated a certain reliability and practicability of this model in the Changning-Weiyuan Block and verified the casing deformation mechanism.The research results can be used as references in wellbore trajectory optimization design,real-time microseismic monitoring during hydraulic fracturing and in the prevention and control of casing deformation.