Pore pressure prediction from bulk modulus in shale based on rock physics modeling

Accurate pore pressure prediction helps to prevent catastrophic incidents including well kicks and blowouts in situ, being of considerable importance in safety and costeffective well design and keeping away geologic disasters. The conventional forecasting methods for pore pressures generally utilize a relation between the vertical effective stress and physical parameters, and the theory of effective stress is usually involved. However, the normal compaction trend is inevitably required in the commonly used Eaton's equation, which cannot be estimated accurately. In this study, the normal compaction velocity and bulk modulus of shale are simulated by anisotropic shale rock physics modeling to improve the accuracy of the normal trend. Since the bulk modulus and the seismic wave velocity can be converted to each other, we have tried to propose a method for predicting pore pressures from bulk modulus. Firstly, the relation between pore pressure and bulk modulus is initially derived. Furthermore, the elastic impedance equation in terms of bulk modulus is given as forward solver for inversion. Prestack seismic inversion based on Bayesian theory is utilized and then the normal compaction velocity and bulk modulus are simulated through anisotropic shale rock physics modeling. Finally, the pore pressure predicted by the new method is compared with that by Eaton's velocity equation and the measured pore pressure in a work area of Sichuan Basin, and the difference are small, which verifies the feasibility of the bulk modulus approach. Presentation Date: Monday, September 16, 2019 Session Start Time: 1:50 PM Presentation Time: 2:40 PM Location: 221B Presentation Type: Oral