Evaluation Of Wellbore Stability Of Stratified Shale Gas Reservoir

Today,shale gas has become the most reliable energy replacement type in the future.The completion of the Fuling shale gas field heralds the official opening of my country's shale gas market.Marching into shale gas fields and developing marine shale gas resources has become an inevitable trend in the development of my country's oil and gas industry.However,drilling operations in shale gas reservoirs still face various difficulties and challenges such as shale bedding and micro-fracture development,anisotropy,and heterogeneity.Many experts and scholars at home and abroad have carried out a lot of research on the wellbore stability of shale gas reservoirs with rational layers,and have made significant progress in wellbore stability analysis and control measures.However,the stability assessment of stratum shale gas reservoirs is not yet mature.Aiming at the wellbore stability problems of the rational shale gas reservoir in Block F,this paper takes Well J as an example to evaluate the wellbore stability of the rational shale gas reservoir.The research work mainly includes the following three aspects:(1)Combining geological data,logging data and laboratory test results to analyze the characteristics of shale gas reservoirs,bedding shale fabric characteristics,rock mechanical parameters,and bedding shale failure modes in Block F,and establish shale The relationship model between the cohesive force and internal friction angle of the body and the bedding surface determines the main reason for the wellbore instability of the rational shale gas reservoir in the block;(2)Established pore pressure and in-situ stress profiles based on logging data and experimental results;ignoring the influence of chemical factors,combined with the actual situation,optimizing the weak surface strength failure criteria,analyzing the wellbore shear failure area,and determining the rational shale gas storage of the well layer safe drilling direction of the layer;(3)Combining the Mohr-Coulomb weak surface strength criterion,the collapse pressure calculation model considering the influence of the weak surface is optimized,and the influence law of the bedding dip and the tendency of the bedding surface on the formation collapse pressure is analyzed,and the J Three pressure profiles of well-layer rational shale gas reservoirs.The research results show that the shale gas reservoir of Well J in Block F has developed shale bedding and graptolite fossils.The shale gas reservoir of this well has fractured leakage.Due to the influence of the bedding surface,the rock strength changes,and the rock along the layer Shear-slip failure occurred on the surface,causing the shaft wall to collapse and become unstable.When considering the influence of the bedding surface,the shale gas reservoir of the bedding surface of this well is drilled along the maximum horizontal principal stress,and the density of drilling fluid should be appropriately reduced.Therefore,the evaluation results provide an important reference for the design of drilling engineering and the use of mud density.