Overpressure Prediction of Reservoirs Based on Multiple Regression of Geological Factors—A Case Study of Bohai Bay, Bozhong Depression, China

Accurate prediction of overpressure in deep reservoirs is critical for hydrocarbon ex-ploration and development. Conventional approaches, such as interpolation of sin-gle-well pressure data and seismic inversion, often produce considerable errors and uncertainty when predicting overpressure in undrilled or inter-well areas, potentially leading to misinterpretation of reservoir pressure-field distributions. To address these limitations, this study proposes a novel approach that integrates identification of overpressure origins with quantitative analysis of the geological factors controlling overpressure magnitude. Multiple regression analysis enabled accurate prediction of overpressure in undrilled areas, with relative errors of less than 5% compared with measured pressures. Based on the conventional classification of normal and overpressure systems in the Bozhong area, three pressure-system types were identified: (1) paleo-overpressure converted to present-day normal pressure, (2) paleo-normal pressure retained as present-day normal pressure, and (3) paleo-overpressure preserved as present-day overpressure. The first type, character-ized by present-day pressure coefficients of 1.0–1.1, occurs predominantly near first- and second-order faults and is attributed to vertical fault opening and subsequent pressure release. The second type occurs mainly on structural slope highs and is asso-ciated with slow sedimentation rates and the absence of high-quality source rocks. The third type, with pressure coefficients ranging from 1.2 to 2.0, is primarily distributed in slope lows and depressions. It exhibits complex origins involving individual mecha-nisms, including undercompaction, hydrocarbon generation, pressure transfer, and tectonic compression, as well as coupled mechanisms, particularly undercompaction combined with hydrocarbon generation. This complex pressure system is controlled by several geological factors, including burial depth, sedimentation rate, vitrinite reflec-tance (Ro), total organic carbon content, fault throw, fault dip angle, and distance from faults.