Occurrence characteristics of gas hydrates formed from seepage gas in sandy deposits

To better understand the process that hydrocarbon gas moves through permeable conduits into the gas hydrate stability zone, a hydrate formation system, mainly composed by a tube reactor, was designed and constructed. The influence factors, such as pressure, temperature, and gas flux, have been investigated. Here also providing a method to measure the induction time of hydrates formation in sandy sediments by analyzing the gas flow rate and pressure drop. Either increasing pressure or reducing temperature can shorten the induction time and improve hydrate formation rate. A percolation model was established to investigate the variation of physical properties of the sediments caused by hydrates formation from seepage gas. The results show that hydrate does not uniformly generate in the whole space of the sediments, but quickly nucleate and accumulate in part of the pore space. With the formation of hydrate, the channel of gas migration could be blocked, and the porosity and permeability of sediments would reduce accordingly.