Combination types and geological significance of natural gas transport system in the deformed front of the Makran accretionary prism

The Makran accretionary prism, as the world’s largest accretionary prism formed by low angle subduction of the Arabian Plate and the Eurasian Plate, contains abundant natural gas resources. Its deformation front is characterized by strong tectonic activity, with the development of thick sediments and complex structural combinations, such as imbricate thrust faults, small displacement normal faults, piggyback basins, gas chimneys, and décollement surface. These geological structures play an important role in the transportation and accumulation of natural gas. Based on seismic data and previous studies, we systematically categorized the natural gas migration systems of this region. Results indicate that natural gas is mainly transported through three types of transport systems: (1) deep transport systems in deformed zones: décollement and deep thrust faults act as primary vertical pathways, facilitating the upward transportation of deep fluids to shallow formations; (2) shallow lateral transport systems: after gas migrates along the thrust fault to the shallow part, it laterally migrates and accumulates in the high permeability turbidite sands in the piggyback basin, forming a natural gas reservoir under the stable domain of natural gas hydrates; (3) the transport system in the undeformed zone: it mainly consists of unconformities, small normal faults, and associated gas chimneys in hemipelagic sediments, which promote gas accumulation in shallow strata. This study revealed the complex natural gas transport network at the front edge of the Makran accretionary prism, and provided key geological evidence for the exploration and evaluation of potential and prospects of natural gas resources in the area.