DOI: 10.15128/r14m90dv55b
title: Integrating Petrophysical, Geological and Geomechanical Modelling to Assess Stress States, Overpressure Development and Compartmentalisation Adjacent to a Salt Wall, Gulf of Mexico [dataset]

description: 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.
description: The data set loaded contains the results of the Thermo-Hydro-Mechanical models used in this paper.
description: Multi-well pressure data from the Magnolia Field, located on a flank of the salt-bounded Titan passive mini-basin in the Garden Banks area of the continental slope of the Gulf of Mexico, indicate remarkably high overpressures that vary, at similar depths, by up to 10 MPa between sand bodies 1 km apart. In the present paper, we integrate geological and geophysical analysis with 2D forward hydro-mechanical evolutionary modelling to assess the contribution of both disequilibrium compaction and diapir-related tectonic loading to the observed overpressure and to understand controls on pressure compartmentalisation. The 2D finite element evolutionary model captured the sedimentation of isolated sand channels bounded by mud-dominated sediments close to a rising salt wall which led to tectonic loading on sediments. Comparison of results from the 2D and 1D models shows that disequilibrium compaction can explain most of the overpressure as a result of very rapid deposition of mainly mud-rich, low permeability sediments; tectonic loading contributes around 7 % 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 the channel sands result in highly compartmentalised pressure distributions in adjacent sand bodies.
description: For this study, a set of well logs, a 3D seismic cube in time, check shots, pressure tests as well as core and drilling reports were used. Seismic interpretation, well correlation, lithofacies interpretation, pressure analysis and static model construction were performed with Petrel software (version 2022) and Techlog software (version 2018) was used for petrophysical interpretation. The Thermo-Hydro-Mechanical (THM) models were developed using the finite element geological modelling software ParaGeo (www.parageo.co.uk), which enable the prediction of basin structural development while capturing the evolutionary stress and strain tensors, pore pressure and temperature distributions during basin history.