Prediction of in-situ stress in the shale gas of the Lower Silurian Longmaxi Formation of Baima Area,Southeast Sichuan Basin

摘要

Baima Bolck is located in the Baima syncline,and the stress direction is complicated.This increases the difficulty of horizontal well placing and frature scheme design.In order to guide the shale gas exploration and production,it is necessary to predict stress value and direction.In the design process of shale gas horizontal well trajectory and construction work of hydrauic cracking,the maximum stress direction and the difference between the maximum and minimum stress are the important parameters which should be taken into consideration.They can directly affect on the postfracture response of shale bed,and the azimuth,dip,heigh and conductivity of hydrauic cracking.Aim to the Lower Silurian Longmaxi shale of Baima Area,Eastsouth Sichuan Basin,by using the stress prediction technology that combined the traditional structural mechanics simulation and the global periodically compressional pulse theory,take account of faults,folds and various rock physics factors,this paper concludes the corresponding strain on the maximum and minimum horizontal stress direction,that caused by the stress and compressional pulse on the fault and folds.It also estimates the maximum horizontal stress direction and the relative horizontal stress difference coefficient.Then use collapse,image logging data and FracPredictor horizontal well fracture simulation result of drilled borehole to verify.The result coincides with existing wells and thus be helpful for future horizontal wellbore design and hydro fracture operations.The result of stress prediction reveals that the maximum horizontal main stress direction is NWW-SEE.Compared with the actual measurement,there's close to an 80 percent coincidence.The result is helpful for future horizontal wellbore design and hydro fracture operations.High horizontal stress difference coefficient located in the bottom wall and the center of the study area.These area are the favorable zone for the deployment of horizontal wells.