Research and application of in-situ stress seismic data-based predic-tion approach of shale reservoirs based on fracture density inversion
In-situ stress seismic data-based prediction approaches of shale reservoirs usually apply the elastic pa-rameters to calculate differential horizontal stress ratios(DHSR).However,there are shortcomings.First,the anisotropy parameters(fracture weakness)are included in the prediction formula and cannot be solved easily,making it difficult to predict in-situ stress;second,parameters such as Young's modulus and Poisson's ratio in the prediction formula are obtained by indirect inversion,and the accuracy is low,which is difficult to meet the requirements of shale gas geoengineering integration.Therefore,an in-situ seismic data-based prediction ap-proach of shale reservoirs based on fracture density inversion is proposed.For enhancing the prediction accu-racy,a longitudinal wave azimuthal anisotropy AVO formula based on Young's modulus,Poisson's ratio,and fracture density is established to directly invert elastic parameters,and the DHSR formula expressed by Pois-son's ratio and fracture density is derived.The anisotropic petrophysical modeling of shale reservoirs is carried out according to well data,and pre-stack azimuthal anisotropy inversion is performed.The inverted Poisson's ratio and fracture density are applied to the estimated DHSR.The in-situ stress properties of shale reservoirs can be evaluated by the estimated DHSR.A real example verifies that smaller DHSR indicates that more or-thogonal and complex fracture networks will be generated by hydraulic fracturing in different directions,which is beneficial for modifying the physical properties and seepage channels of the reservoir.A larger volume of reservoir reconstruction is more conducive to reservoir fracturing.In addition,larger DHSR means that hydrau-lic fracturing will generate non-orthogonal plane fractures parallel to the maximum horizontal principal stress,forming isolated fractures that are not beneficial for volume transformation.Meanwhile,the estimated DHSR result agrees with existing well logging in-situ stress calculation,fracturing monitoring,and production testing,and it fits with the geology recognition,revealing that the approach is effective and reliable.
in-situ stressshale gas reservoiranisotropyfracture densityPoisson's ratiopre-stack inversion
万方数据
维普
