A novel pore pressure prediction model of carbonate formation with fracture development

Key words:  carbonate  pore pressure  sonic transit time  fractures  effective stress

Abstract:

The fracture porosity was calculated by the difference of deep and shallow lateral resistivity quantitatively. Based on the effective stress theory, the integration of sonic velocity experiments was presented to imply the different responses to complex mechanisms of generating pore pressure. In addition, the correlation between sonic velocity and the effective stress was analyzed and a new pore pressure prediction model for carbonate formation was established by regression analysis method. The results show that the attitude of formation fractures can be justified by the difference of deep and shallow lateral resistivity. Moreover, the fracture porosity and fracture opening width can be also calculated quantitatively. When the porosity is an constant, both shear and compressional wave travel time increase with the rise of the effective stress. Otherwise, when the effective stress is an constant, both shear and compressional wave travel time decrease with the rise of porosity. The reliability and better accuracy are also testified compared with conventional methods.