Simulation-based Research On Prediction For Tight Sandstone Reservoir’s Mechanical Parameters

Beach bar sandstone reservoir is a typical tight sandstone reservoir,especially in the shore-shallow lacustrine region.Sandstones are porous.Homogeneous and random distribution of pores lead to complicated mechanical properties and deformation of rock.The geomechanical behavior of naturally fractured reservoirs can be critical to both injection and production operations.Moreover,it is dominant to separate layer fracturing process and injection technology.Therefore,evaluating preliminary geomechanical data that will be used in further finely stratified fracturing constructions and simulations is very important.This paper is based on hydraulic fracturing of vertical well in tight beach bar sandstone reservoir.To study the relationship between property of pore and geomechanical parameters,some experimental and numerical studies of physical cores obtained by drilling sampling were carried out.A finite element analysis software RFPA2D(rock failure process analysis)is applied to build different numerical models with different porosities according to experiment results and geological logging data of an oilfield reservoir.The Young’s modulus,peak strength,residual strength and Poisson’s ratio of rocks with different porosities under uniaxial compression condition are discussed.Then prediction relationships of rock’s parameters and porosity based on all data including experiment tests and numerical tests were determined through linear regression analysis.Moreover,geomechanical parameters of different layers were predicted by these relationships.At last,the capabilities of a field-scale 3D hydraulic fracturing model whose parameters were determined by the proposed relationships were validated against on-site construction data by simulating.The research contents are as follows:i.Mechanical data of physical cores obtained by drilling sampling were gotten from experiment results and geological logging data of reservoir.Linear relationships between geomechanical properties and porosity were determined based on the data.ii.Numerical simulations with different porosities were run using RFPA 2D in which the heterogeneity of the rock materials and random distribution of pore were considered.In these simulations,the porosity’s influence on rock’s mechanical properties under uniaxial compression condition was discussed.iii.The Young’s modulus,peak strength,residual strength and Poisson’s ratio of rocks with different porosities under uniaxial compression condition were determined based on experimental and numerical studies of physical cores.According to these data,prediction relationships of geomechanical parameters of tight sandstone reservoir and porosity were determined through linear regression analysis.iv.A field-scale 3D hydraulic fracturing model whose parameters were determined by the proposed relationships was built to simulate the propagation of hydraulic fractures.The fracturing curve of numerical model was compared with hydraulic fracture operating curve in construction.It is shown that there is a good agreement between the numerical and the practical results.