Experimental and prediction studies on methane cold seep development process through hydrate-bearing sediments

This is the authors' abstract. We don't add key points for this paper.

Methane breakthrough through hydrate-bearing sediment (HBS) layers plays a critical role in the evolution of marine cold seep systems. However, the evolution of methane breakthrough in water-saturated hydrate layers remains experimentally underexplored, and the underlying mechanisms and theoretical models are still unclear. This study employed 10 cases of hydrate-bearing sandy sediments with saturations ranging from 16.5% to 52.4%, subjected to a 6 MPa methane flow at 6 mL/min to evaluate the hydrate layer's sealing effect. Experimental results show that breakthrough pressures, indicating sealing strength, ranged from 0.7 to 3.2 MPa and positively correlated with sediment water content. Before breakthrough, water efflux dominated with negligible methane release; after breakthrough, methane efflux surged, reaching up to 5.2 times the displacement rate. Throughout the methane seep development process, from gas-water displacement to gas seepage, approximately 0.26∼0.47 moles of hydrate were formed from the residual water in the displacement zone. Based on experimental results and key parameter analysis, a predictive model coupling hydrate formation and gas-water displacement was developed and shows good agreement with the experimental results. This study reveals the dynamic evolution of methane breaking through HBS, offering valuable insights into cold seep development mechanisms.