Laboratory study of methane hydrate formation kinetics and structural stability in sediments

Abstract

The natural gas hydrate deposits in the offshore of India are embedded in different sediments, namelyclay rich silts and sands, coarse grain sand and volcanic fly ash. The variations in gas hydrate concen-trations at different geological locations shows dependency on sediment mineralogy. It is also knownthat the particle size of the sediments plays an important role in hydrate formation and gas hydrateconcentrations in sediments. We carried out systematic studies on the methane hydrate formation ki-netics and methane hydrate volumetric yields, in stirred reactor experiments, using suspensions ofsynthetic silica and natural sediment from KrishnaeGodavari (KG) Basin. The hydrate formation behaviorin silica and KG basin sediment is also compared with the formation of methane hydrates in a “puresystem”without sediment or added silica grains. Our results show that the hydrate formation kinetics isfaster in 50mm silica system followed by that in natural marine sediment. Observed methane hydrateyield in the laboratory is higher (~39%) in both the pure (no sediment) and 1mm silica suspensions. Thegas intake is much quicker (~375 min) in the suspension of 50mm silica system, while the hydrate yield isnoticeably less (~29.38%). The methane hydrates are characterized by Raman spectroscopy and theyshow characteristic structure I (sI) methane hydrate signatures, with a hydration number in the range5.93e6.1