Prediction and Application of Pore Pressure for Carbonate Reservoirs in Zhongjiang–Penglai of China

Abstract The Zhongjiang–Penglai block has a submitted reserve forecast of 20 billion m3 and is a vital guarantee for natural gas resources in the Sichuan Basin. However, the lower carbonate formations in this block have developed pores, caves, and fractures, with weak bearing capacity, frequent drilling leakage, and overflow, making it necessary to perform pore pressure prediction and research in the carbonate formations of the working area. First, a new effective stress model is proposed that comprehensively considers the impact of multiple factors, such as interval transit time, rock density, and formation resistivity. Based on this, a prediction model for pore pressure in carbonate rocks in the Zhongjiang Penglai block was established. Second, three-dimensional (3D) seismic velocity data establishes a 3D geological model of the primary carbonate formations in the Zhongjiang–Penglai block. The sequential Gaussian simulation method is used to obtain the distribution of 3D pore pressure in the primary carbonate formations, and the calculation results are visualized in three dimensions. The model is validated using field-measured data, and the calculated results of the single well prediction model for carbonate rock pore pressure were in good agreement with the measured and actual drilling results, with errors ranging from -7.35% to 5.87%. The 3D pore pressure model for the primary carbonate formations correlates well with the single well prediction model, and both have the same trend of change. The new pore pressure model established in this study can accurately predict the pore pressure of carbonate formations, providing strong support for the safe and efficient exploration of deep oil and gas resources in the Zhongjiang–Penglai block.