Integrating Petrophysical, Geological and Geomechanical Modelling to Assess Stress States, Overpressure Development and Compartmentalisation Adjacent to a Salt Wall, Gulf of Mexico [dataset]

High pore fluid pressures exert a major influence on important geological processes such as subsidence, slope failure, faulting and folding. A quantitative understanding of pore fluid pressure also underpins the safe design of wellbore drilling operations, as well as the injection rates and maximum volume of subsurface storage of CO2 and H2 since resulting high pore pressures can lead to fracturing of the overburden. Here, hydro-mechanical forward models are used to understand the development and distribution of very high and spatially variable fluid pressures in channel sands within the Magnolia Field, which is located close to a salt dome on the continental slope of the Gulf of Mexico. Whilst the main contributor to high fluid pressures is loading due to the high rate of deposition of mud-rich sediments, tectonic loading related to salt dome movement contributes around seven percent of the observed overpressure. The models also show that linked to the high sedimentation rates, small variations in the permeability and connectivity of the mud-rich sections that bound channel sands result in highly compartmentalised pressure distributions in adjacent sand bodies; these are very hard to predict prior to drilling.

高孔隙流体压力（pore fluid pressure）对沉降、边坡失稳、断裂与褶皱等重要地质过程具有关键调控作用。对孔隙流体压力的定量认知，亦是井筒钻井作业安全设计以及CO₂与H₂地下注入速率、最大储存体积确定的核心依据——因为过高的孔隙压力会引发上覆岩层（overburden）破裂。本研究采用流固耦合正向模型（hydro-mechanical forward models），对位于墨西哥湾大陆坡盐丘（salt dome）附近的木兰油田（Magnolia Field）内河道砂体中极高且空间分布不均的流体压力的发育与分布特征展开分析。研究表明，高流体压力的主要成因是富泥沉积物快速沉积带来的载荷作用，而与盐丘运动相关的构造载荷仅贡献了约7%的观测超压（overpressure）。模型同时显示，受高沉积速率影响，约束河道砂体的富泥地层渗透率（permeability）与连通性（connectivity）的微小差异，会导致相邻砂体呈现高度分隔式的压力分布，这类分布在钻井前极难预测。