Pore pressure modeling has proven and direct implications in oil and gas exploration and development. Abnormal pore pressure leads to drilling complexity and well control issues because of reduced mud window, contributing to major non-productive times and steep drilling cost. A comprehensive pore pressure–fracture pressure model plays a critical role in successful well drilling. This work caters to the pressure modeling of Panna area in Mumbai offshore basin, western India. Two offshore wells, drilled through 4 km of Tertiary sedimentary succession down to Cretaceous basaltic basement, were analyzed to interpret the vertical stress, pore pressure, fracture gradient and collapse pressure. Vertical stress profile was generated from density logs; pore pressure was estimated using Eaton’s method by employing resistivity and sonic logs. Calculated pore pressure was calibrated with various direct downhole measurements and various well events. Compaction disequilibrium was inferred as key mechanism for generating mild overpressure in Oligocene to early Miocene shales (14–15 MPa/km), while it increases sharply against early Eocene sediments, and hard overpressure with near-lithostatic gradient (22 MPa/km) was detected in the underlying Paleocene shales. The mid-Eocene Bassein formation, the primary hydrocarbon reservoir, reveals sub-hydrostatic condition (7.5 MPa/km) resulting from production-related depletion. Estimated fracture pressure was calibrated with available leak-off test data. Mohr–Coulomb rock failure criterion was employed to estimate collapse pressure and validated with the observations from caliper log to address the wellbore stability issues. This study provides insights on downhole pressure behavior across stratigraphy, to achieve optimum drilling mud designing as well as safe and successful operational planning.

中文翻译：

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印度西部帕纳海地区孔隙压力，断裂压力和塌陷压力梯度建模：对钻井和井眼稳定性的影响

孔隙压力建模已在油气勘探与开发中证明了直接的意义。异常的孔隙压力会导致泥浆窗口减少，从而导致钻井复杂性和井控问题，从而导致大量的非生产时间和陡峭的钻井成本。全面的孔隙压力-裂缝压力模型在成功钻井中起着至关重要的作用。这项工作适合印度西部孟买近海盆地潘纳地区的压力模拟。分析了两口海上油井，这些油井钻探了4 km的第三纪沉积演替层，直至白垩纪玄武质基底，以解释垂直应力，孔隙压力，裂缝梯度和塌陷压力。垂直应力分布由密度测井生成；使用伊顿方法通过采用电阻率和声波测井估算孔隙压力。通过各种直接的井下测量和各种井事件来校准计算的孔隙压力。压实不平衡被认为是在中新世至中新世早期页岩（14-15 MPa / km）产生轻度超压的关键机制，而对早始新世沉积物则急剧增加，而近静水梯度的硬超压（22 MPa / km）则是在下古新世页岩中发现。中始新世巴塞因地层是主要的油气储集层，揭示了与生产有关的消耗所致的亚静水压条件（7.5 MPa / km）。用可获得的泄漏测试数据校准估计的断裂压力。使用Mohr-Coulomb岩石破坏准则来估计坍塌压力，并用卡尺测井的观察结果进行了验证，以解决井眼稳定性问题。