Book Description
Associated with their rich organic contents and laminated depositional environments, shales exhibit transverse isotropic (TI) characteristics. Ignoring TI nature of shale formations will lead to erroneous estimates of in-situ stresses and consequently to inefficient design of fracture geometry, which negatively affects the ultimate recovery. In this research, inclusion-based rock physics models were used to estimate the elastic properties of Tuwaiq Mountain Formation (TMF) using available petrophysical and XRD data. It was observed that the Young’s modulus and both mineral and elastic brittleness indices increase as the volume fraction of calcite increases while they reduce due to increased clay and kerogen volume. Following that, analytical modeling was performed to estimate fracture geometry and in-situ stresses in anisotropic medium. The results showed that the Young’s modulus anisotropy has a noticeable impact on fracture width, whereas the impact of Poisson’s ratio is minimal. The effect of stress anisotropy and other rock properties on stress shadow was also investigated and it was found that in presence of large stress anisotropy, the fractures can be placed close to each other, or theoretically, there is no concern regarding minimum fracture spacing. Finally, numerical modeling using ResFrac unconventional simulator was conducted to investigate the effect of shale TIV nature on hydraulic fracture development and spacing with a specific reference to Jafurah shale play. Results of numerical simulations show that larger anisotropic stiffness reduces the fracture width in TIV formations. It was found that stress anisotropy affects the development of fracture geometry and that tighter fracture spacing results in a higher magnitude of stress alteration around the fractures. This affects the geometry and propagation of the subsequent fractures where several fractures propagate asymmetrically in opposite directions which reduces the efficiency of hydraulic fracture treatments.