Study On Rock Mechanical Parameters And In-situ Stress Characterization Methods Of Shale Reservoirs

The shale reservoir of the second member of Fu 2 in Jinhu sag in the eastern China exploration area in northern Jiangsu is difficult to mine,and it is difficult to evaluate rock mechanics parameters and in-situ stress.This paper uses geophysical logging methods to study it,and some breakthroughs have been made.The rock mechanics parameter models commonly used in logging are widely used in oil and gas engineering.However,due to the complex diversity of geological conditions in different regions on the earth,in order to improve the accuracy of the calculation results of each model in the second member of the Subei Basin,this paper combines XMAC logging Data and conventional logging data are used to optimize the commonly used models of rock mechanics parameters,which enhances the applicability of each model in the study area.At the same time,this paper proposes another method for calculating rock mechanics parameters,that is,analyzing the sensitive logging curve of each rock mechanics parameter,and using multiple linear regression to obtain a new model for calculating rock mechanics parameters,which is applied in the second member of the Subei Basin.At this time,the rock mechanics parameter model obtained by this method has a good effect.In the study,it was found that the Poisson's ratio parameter model has very high limitations.The presence or absence of measured shear wave data has a great influence on the application effect of the model.For this reason,a conceptual formula is proposed to invert the Poisson's ratio,and the calculation of the Poisson's ratio is established.When verifying its new model,it is found that its application effect is better than the commonly used model and the multiple linear regression model.Through the processing and analysis of logging data of the second member of Fu in the Subei Basin,it is found that the vertical in-situ stress of this interval exceeds 80 Mpa,indicating that the vertical in-situ stress has become a factor that cannot be ignored in later engineering development.When calculating the pore pressure,the Eaton method was used in this study to obtain a continuous pore pressure logging curve.According to the overburden pressure,pore pressure and other parameter values and the geological characteristics of the study area,the Huang's model was optimized to obtain a horizontal maximum and minimum in-situ stress calculation model suitable for the second member of the Subei Basin.Based on the Griffith criterion and the Coulomb-Navier criterion,the development of tensionshear fractures in the shale reservoir of the second member of the Fu 2nd Member of the Subei Basin was judged,and it is believed that the development of shear fractures in this reservoir is better than the development of tension fractures.The fracture pressure of the reservoir is obtained through the fracture pressure calculation model.Based on the relationship between the fracture pressure and the maximum principal stress(the fracture pressure is less than the maximum principal stress),it is inferred that the studied interval is a stress sweet spot,combined with logging oil and gas intervals.The data has been comprehensively evaluated.