The petroleum‐bearing Assam oil province, NE India, has a complex tectonic history resulting from the Cenozoic collision of the Indian Plate with the Eurasian and Burma Plates. Well data show that there are significant variations in the magnitude and stratigraphic occurrence of overpressures across the foreland basin. In areas which have not been affected by thrust tectonics, analyses of pore pressures in Upper Miocene to Eocene and underlying sequences indicate that overpressures are caused by disequilibrium compaction. Pore pressures were observed to be 25.8–28 MPa over a depth interval of 2259–2382 m and 43–45 MPa between depths of 3820 m and 3994 m. In the adjacent Schuppen (fold‐thrust) belt, multiple overpressure regimes are recognised and disequilibrium compaction is the main cause of the overpressures in both the supra‐thrust and the sub‐thrust successions. Unloading due to uplift and erosion in the supra‐thrust section of the Schuppen belt was quantified using velocity data and the normal compaction trend for shales; net uplift was estimated to total 1000–1600 m with a standard deviation of 250–476 m. Overpressure development in supra‐thrust strata in the Schuppen belt suggests the possible effects of normal burial prior to tectonic deformation, as well as of compaction related to high horizontal stresses resulting from thrusting and associated fold development. Pore pressures in the supra‐thrust section, over a depth interval of 700–1400 m which corresponds to the Oligocene to Upper Miocene succession, were observed to range from 9.6 to 19.5 MPa. The top of the overpressured zone in sub‐thrust strata was observed in the Upper Eocene to Oligocene succession at a depth of 3700 m, in the argillaceous Barail Formation, with pore pressures ranging between 48 MPa and 54 MPa. Pore pressures were estimated using acoustic log data calibrated to measured pressures from Modular Dynamic and Drill Stem Test data. The modelled pore pressures closely correspond to the measured data, supporting the robustness of the model. The numerical parameters defined in this study may be used for future exploration in the region.

中文翻译：

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压缩环境中的孔隙压力建模：以印度内蒙古阿萨姆邦为例

含石油的阿萨姆邦石油省，印度东北部，由于印度板块与欧亚板块和缅甸板块的新生代碰撞而形成了复杂的构造历史。井数据表明，前陆盆地超压的大小和地层发生率存在显着变化。在未受逆冲构造影响的地区，对上中新世至始新世以及下伏层序的孔隙压力分析表明，超压是由不平衡压实引起的。观察到的孔压为25.8–28 MPa，深度介于2259–2382 m和43–45 MPa之间，深度介于3820 m和3994 m之间。在相邻的Schuppen（推力）带中，认识到多种超压状态，超推演和次推演演算中不平衡压实是超压的主要原因。利用速度数据和页岩的正常压实趋势，对Schuppen带上冲断层中隆起和侵蚀造成的卸荷进行了量化。净隆升估计总计为1000–1600 m，标准偏差为250–476 m。Schuppen带上冲断层的超压发展表明，在构造变形之前正常的埋藏可能产生的影响，以及与冲动和相关褶皱发展引起的高水平应力有关的压实作用。在上冲断层的孔隙压力在700-1400 m的深度范围内，对应于渐新世至上中新世的演替，观察到的压力范围为9.6至19.5 MPa。在泥质Barail组中，始新世至渐新世的3700 m深度观察到了逆冲断层地层超压带的顶部，孔隙压力范围为48 MPa至54 MPa。使用根据标准动态和钻杆测试数据校准为测得压力的声波测井数据估算孔隙压力。建模的孔隙压力与测量数据紧密对应，从而支持了模型的鲁棒性。本研究中定义的数值参数可用于该地区的未来勘探。使用根据标准动态和钻杆测试数据校准为测得压力的声波测井数据估算孔隙压力。建模的孔隙压力与测量数据紧密对应，从而支持了模型的鲁棒性。本研究中定义的数值参数可用于该地区的未来勘探。使用根据标准动态和钻杆测试数据校准为测得压力的声波测井数据估算孔隙压力。建模的孔隙压力与测量数据紧密对应，从而支持了模型的鲁棒性。本研究中定义的数值参数可用于该地区的未来勘探。