Prediction of overpressure in carbonate formation is still a difficult problem in overpressure researches. Commonly, the method to predict overpressure in clastic formation is empirical, which is based on Terzaghi effective stress theory. And there always exist a parameter (mostly p-wave velocity) which have clear response to overpressure. These empirical methods are not suitable to predict overpressure in carbonate formation with dense lithology and extremely inhomogeneous physical property. By analyzing the effects on saturated carbonate rocks under the action of stress and pore pressure, a theoretical method has been established based on poroelasticity theory, which can reflect the quantitative relationship between pore pressure and rock elastic parameters. In this study, the established method is applied in northeastern Sichuan basin to predicate overpressure in carbonate formation. The basic physical parameters (e.g., rock component and porosity) needed in application are obtained by well-logging comprehensive interpretation model in carbonate formation. Besides, we establish a rock physical model for carbonate rock to calculate S-wave velocity and rock elastic parameters, which are also used in the application. Finally, overpressure in carbonate rock is predicted by the quantitative poroelasticity model with basic physical parameters and rock elastic parameters. The prediction result shows that the predicted pressure is highly consistent with the drill-stem-testing pressure and the monitoring pressure while drilling. Therefore, the quantitative model, established in this study, could be a new approach to solve the problem of overpressure prediction in carbonate rocks.
Presentation Date: Monday, October 15, 2018
Start Time: 1:50:00 PM
Location: Poster Station 5
Presentation Type: Poster