Experimental Study On The One Dimensional Of Natural Gas Hydrate By Depressurization

The reported results from laboratory and field exploration indicate that hydrates in nature always accumulate in the certain region of the stratum,and present as layer or ribbon pattern.To obtain the production behavior of gas and water during the depressurization of these kinds of hydrate deposits,sets of experimental runs were carried out in a one dimensional hydrate simulator.The effects of scales of hydrate deposits(thickness and width)and production pressure on the efficiency were studied.The main contents are as following:With the increasing of hydrate scales,the maximum temperature drop at the different sites of sediments were increasing gradually.When the hydrate scales was smaller,the temperature at the site close to the production port dropped more remarkably.And when the whole reactor was filled by hydrate bearing sediments,the maximum temperature drops in sediments were very close.But for the enhancing of gas and water migration during depressurization,the sites close to the production port present higher temperature in some runs.Higher water and gas recovery rations were obtained with the lower production pressure,which didn’t monotonously increase with the increase of hydrate scales.The depressurization of hydrate deposits with larger volumes obtained higher gas to water ratios.As water can migrate to the production port much more easily in the vertical direction,the mass of produced water in the runs with vertical hydrate distribution was much higher than that in the runs with horizontal hydrate distribution,which decreased the gas production ratio and gas to water volume ratios in the runs with vertical hydrate distribution.The remarkable migration of water in the sediments brought extra heat to the sediments close to the production port,therefore temperature close to the production port in the runs with vertical hydrate distribution was slightly higher than that in the runs with horizontal hydrate distribution.After the water production,gas was dominated in the pores of sediments,the thermal conductivity decreased with the increase of gas saturation,so that the rates of temperature decrease was slowed down,which was much more obvious in the hydrate free sediments.