In situ stress determination in isotropic and anisotropic rocks and its application to a naturally fractured reservoir

Abstract Anisotropies exist in many sedimentary rocks, particularly naturally fractured reservoirs, causing horizontal stress anisotropies. Case studies indicate that when a rock formation contains high dip-angle fractures or factures (e.g. bedding planes), it has very distinguished stresses. In these cases, the conventional isotropic method for estimating stresses may give erroneous results. Using theory of anisotropy, vertical transverse isotropy (VTI) and (HTI) models are derived determining situ rocks. Comparing with model, VTI model predicts higher minimum maximum stress, which is suitable shales. contrast, HTI gives lower than model. A combined based on proposed containing natural different dip angles. Measured data Xujiahe gas reservoir China reveal breakdown pressures decrease as fracture angles increase, consistent to Natural can result by up 3 MPa/km reduction pressure 10 studied area. Combining anisotropic measured stresses, assessment their impact hydraulic fracturing proposed. study demonstrates good prediction reservoir.