Permeability Response of the Marine Hydrate Reservoir after the Invasion of a Novel Fracturing Slurry

Due to the difficulty in achieving commercial extraction from marine natural gas hydrate (NGH) reservoirs, hydraulic fracturing technology is employed for reservoir stimulation. Our research group has developed a novel fracturing fluid─a dual-enhanced stimulation slurry. However, the impact of this dual-enhanced slurry invasion on the permeability of the NGH reservoir, as well as the properties of the interfacial transition zone (ITZ) between the slurry and the reservoir, remains unclear. Therefore, this study conducted laboratory experiments to investigate the microstructure and permeability characteristics of the ITZ between the slurry and hydrate-bearing sediment (HBS) under various influencing factors. Using scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) technology, line scanning tests were performed on cemented interface samples. The thickness of the ITZ was calibrated based on differences in elemental content. It was found that an increase in effective pressure, sediment porosity, and the thickness of the slurry consolidation body (SCB) led to an increase in the thickness of the ITZ, reaching a maximum of 118 μm, which led to a reduction in sediment porosity at the interface, hindering gas flow. The porosity reduction at the interface ranged from 12.56% to 22.9%. Furthermore, pore diameters within the sediment were categorized, revealing that micropores (with diameters distributed between 0 and 2 μm) predominated. Due to the porosity reduction at the interface and the increased proportion of micropores, interface permeability was impaired. The permeability damage rate ranged from 37.9% to 90%.