Integrating the Fully Coupled Geomechanical with Thermodynamics Modeling for Accurate Pore Pressure Prediction in HPHT Wells
Authors: Ji Baoqiang , Zhou Wei , Wei Pu , Li Xiang , Fu Lei , Li Junfei , Li Zheng , Chen Jing , Zhu Ge , Jing Yadong , Huang Xingning 
Published: February 2024

There is a strong relationship between formation pressure and production capacity; high pressure often means high production. Accurate pressure prediction can provide a reference for good deployment and resource assessment; pre-drilling pressure prediction can effectively prevent well blowouts and other drilling accidents. The research on pressure prediction methods started in the 1960s and has been developed since then. However, due to the complexity of the overpressure genesis mechanism, a complete theoretical system has not been established yet. The existing pressure prediction models are mostly empirical relationships, which have applicability problems in different workings, and the accuracy of the velocity field used to calculate the pressure is not enough, which makes pressure prediction more difficult. In order to solve these problems, this paper takes SX block as the study area for pressure prediction work. The main contents are as follows: 1) Starting from the study of the basic theory of pressure prediction, comparing and analyzing the characteristics of the existing pressure prediction methods, and comparing and applying them in the work area, it is found that the method of calculating the pore pressure by relying only on the longitudinal wave speed will cause a large error in this work area. (2) Through the research on the characteristics of the type of compaction mechanism, the main overpressure mechanism in the work area is under compaction by using the acoustic wave density intersection method and combined with the tectonic characteristics of the work area, the tectonic extrusion also contributes to the overpressure to a certain extent. (3) For the establishment of the velocity field, which is the core parameter of pressure prediction, based on the combined velocity field proposed by the previous researchers, the results were improved to make the results more in line with the geologic law, and the results were applied in the work area, and the results were good. (4) Aiming at the problem that the contribution of tectonic stress to formation pressure cannot be ignored in the case of complex geological structures in the work area, a high-precision anomalous formation pressure prediction technique integrating logging, seismic and geologic data is proposed: the logarithmic Fillippone's formula, which only considers vertical stress, is changed to a three-phase stress combination. The method differs from the conventional one-dimensional calculation mode and introduces the horizontal ground stress fitting establishment related to the geological tectonic pattern. After comparing the prediction results of single wells in the SX Zone, the accuracy of this method is higher than that of the conventional pressure prediction method, and it is suitable for the SX Zone. It is proved by practical use that the improved pressure prediction model with combined velocity field and integrated logging-seismic-geological data for three-dimensional pressure prediction is successful in the SX work area, which points out the subsequent exploration area and has certain practical value.