Prediction of casing critical buckling during shale gas hydraulic fracturing

Casing deformation during volume fracturing in shale gas horizontal wells is caused by both existing and induced stresses. These stresses jointly alter and compound the stress field around the casing leading to inefficient well stimulation as planned, lack of access into the well for recompletion, future workovers and present imminent danger of well integrity. Using two simulation scenarios, casing structural integrity was investigated in both radial and axial configurations under the mechanics of a combine system - casing, cement and formation rock. Results obtained show that time dependent rock slippage - creep during stimulation lead to an increase transverse displacement and corresponding stresses on the casing. In addition, the effect of combined loading results in significant increase in both displacements and stresses that can cause radial and axial permanent failure of the casing. This explains the lack of access into the casing during multi-stage hydraulic fracturing and future well intervention and recompletions and increased current understating of the downhole dynamics and casing structural integrity during volume fracturing. This new understanding is a major breakthrough in establishing casing health status during shale gas well stimulation.