Pore pressure prediction using S-wave velocity based on rock physics modeling

Abstract

Pore pressure plays a critical role in improving drilling safety and exploring hydrocarbons. It is well known that the prediction of pore pressure is mainly based on P-wave velocity or acoustic transit time. However, due to the influence of various factors on P-wave velocity, it may not be sensitive enough to the perturbations of effective stress, which results in inaccurate pore pressure prediction results. To solve this issue, we perform a specialized analysis of rock physics data and find that S-wave velocity is more sensitive to the perturbations in effective stress than P-wave velocity. Therefore, in this study, we propose a new pore pressure prediction method based on shear waves to predict pore pressure more accurately. In order to obtain the normal compaction trend (NCT) required by the proposed method, an anisotropic rock physics model of mudstone is first constructed, and normal compaction porosity is added to the rock physics model. The difference between the obtained NCT and the measured S-wave velocity is then utilized for predicting pore pressure through the proposed method. In practical data application, the pore pressure predicted by the proposed method is highly consistent with the measured pore pressure points, which proves the advantages of S-wave velocity in predicting pore pressure.