Seismic Prediction for Formation Pressure Considering Diagenesis Effect

Accurate prediction for formation pressure is crucial for many practical scenarios in the field of oil and gas exploration, such as evaluating reservoir sweet spots. As formation depth gradually increases, the influence of diagenesis on formation pressure becomes more dominant. However, the diagenesis effect is still not well considered in the existing formation pressure methods. To address this issue, a seismic formation pressure prediction method incorporating the diagenesis effect is developed based on the depth-dependent diagenetic function. The proposed method concurrently incorporates the information of normal compaction trend, bulk modulus, and clay content. A diagenetic function is introduced into the classic effective stress theory to describe the diagenesis effect on depth dependency of formation pressure. The normal compaction trend is established using the rock physics model. The bulk modulus and clay content that are included in the prediction method are estimated from the pre-stack seismic data, respectively, with the linear Gray reflection coefficient equation and the proposed nonlinear reflection coefficient equation, where the Markov chain Monte Carlo (MCMC) method is used to obtain the optimal inversion results. Finally, the estimated normal compaction trend, bulk modulus, and clay content are employed to calculate the formation pressure. The proposed method has been applied in Xinjiang work area.