Stress Sensitivity Of Fractured Reservoirs

In this paper, the mechanism of fractured formations stress-sensitivity is deeply discussed in order to offer theory basis for developing this kind of formations with reason. Under the basis of fracture topography analysis and description, the micro-contact model of asperity and the contact process between two fracture surfaces have been studied. Through the CMS-300 experiment ,the relation between fracture permeability and applied stress can be gained directly and the relation can be expressed by negative exponent after regression analysis. The hydraulic behavior of fractures can be studies by use of plane models. On the basis of equivalent penetrate theory , the relation of fracture permeability and asperity .spacing is derived. An important character of fractured formations is that permeability takes on anisotropic sharply and permeability tensor describes this character exactly. This paper established an approach, based on the superposition principle, for providing models and solutions for arbitrarily oriented fractures. So the anisotropism of fractured formations is estimated quantitly. Because the different orientation fractures endures different in-situ stress, several models have been obtained to estimate normal stress and efficient stress. Based on the stress-sensitivity curve of single fracture and the in-situ stress state ,the stress- sensitivity of subsurface fracture can be analysised, including prediction of fracture aperture and permeability. Combined with the permeability tensors of fracture networks, the stress-sensitivity of fractured formations is then derived. This paper offers compute process. The stress distribution around hole will change after the hole is drilled. The secondly stress distribution will influent the fracture near hole wall. Elastic solutions have been made and the stress state of fracture is analysised . Then closure of fractures near hole wall is studied including the fluence of orientation, fluild pressure and well trace.