Numerical Research Of The Viscoelastic Behavior Of Shale Gas Rock And Its Influence On Fracturing

Over the past decade,the combination of horizontal drilling and hydraulic fracturing has allowed access to large volumes of shale gas that were previously uneconomical to produce.The productivity of shale reservoir is highly dependent on the design of hydraulic fracturing treatment.In order to successfully design the treatment,a good understanding of the shale mechanical properties is necessary.This thesis purposes that proppant embedment can be divided into two mechanisms,elastic deformation and creep deformation.The proppant particle has a negligible size in comparison with propped fracture face.Hence,in this thesis,we consider that the load distributed over a part of the boundary of a semiinfinite solid may describe the process.We developed a new model to perform a numerical parametric sensitivity analysis of proppant embedment into the shale reservoir rock by combining simplified physical process with elastic theory.We also develop an analytical model to estimate proppant embedment depth for a given conditions,making clear which factor is more important in embedding and improving understanding of the process.According to the results of analysis in this thesis,in shale formation,creep deformation of shale gas reservoir rock and proppant embedment are obvious during long term production stage and it may leads to the fracture closure.So,there will not be a fracture which sustain fracture width forever.Therefore,in soft formation like shale,propped fracture may heal due to embedment.This means re-frac is required after a period of production if the operators wants to maintain the production rate.The mechanisms described in this thesis provide a new understanding about embedment.It provides us a tool to determine how much the degree will be.