The Chang 7 reservoir group in the Jingbian area of the Ordos Basin commonly exhibits abnormal overpressure. However, the pressure source and its spatial distribution remain poorly understood, and the lack of direct formation pressure measurements severely hinders further hydrocarbon exploration in this region. To address these issues, this study utilized well-logging and drilling data to systematically calculate formation overpressure using the balanced depth method, with the reliability of the results verified by the mud density method. The genetic mechanisms were determined through integrated log analysis, Bowers’ method, and acoustic velocity-density crossplots. Results show that the Chang 7 reservoir group is characterized by widespread weak overpressure, with an average residual pressure of 5.85 MPa and pressure coefficients ranging from 1.01 to 1.43. The residual pressure exhibits a "high in the west, low in the east" trend laterally and reaches its peak vertically at the base of the Chang 7 member. Genetic analysis reveals that undercompaction is the dominant overpressure mechanism, accounting for 79% of the total contribution, while hydrocarbon-generation expansion accounts for only 10%, with the remaining 11% attributed to their combined effect. This undercompaction-dominated origin significantly differs from the hydrocarbon-generation-dominated overpressure in the central basin, implying fundamentally different hydrocarbon migration processes and accumulation mechanisms in the Jingbian area. This understanding holds significant theoretical value for re-evaluating the hydrocarbon accumulation patterns in the northern slope of the basin and for establishing an appropriate exploration geological model for the Jingbian area. Furthermore, it provides direct scientific support for the next phase of hydrocarbon exploration deployment in this region.
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