The pore-structure characteristics of foraminiferal shells and their relations with natural gas hydrate formation in the marine sediments

Abstract

Many marine hydrate reservoirs exhibit significant foraminifera abundance. These foraminifera alter the original properties of the sediments, potentially affecting the formation and accumulation of hydrates. This present study analyzed the pore-structure characteristics of foraminifera-containing sediments from the South China Sea and their influences on the hydrate formation process by using microscopic imaging techniques. Scanning electron microscopy (SEM) and X-ray computed tomography (X-CT) reveal the unique dual-porosity characteristics of these sediments, characterized by matrix pores and foraminiferal pores. These two types of pores diverge significantly in their size distribution, morphological attributes, connectivity, and other aspects. Further experiments show the formation and occurrences of tetrahydrofuran (THF) hydrate under different sedimentary conditions and solution concentrations. Foraminiferal shells are found to promote the formation of hydrate by increasing the volume fraction of hydrate-favoring pores, which is more pronounced under conditions of low hydrate saturation. These findings obtained may contribute to global hydrate resource assessments and enhance understanding of hydrate reservoirs.