Study About Thermal Front Of Natural Gas Hydrate By Heat Injection

Natural gas hydrate(NGH),as a new kind of clean,newly and large reserved energy resource,has been widely paid attention by governments and research institutions since successfully production in Japan,Nankai Trough.Heat injection is considered to be one of the efficient methods of NGH production,but its huge heat loss and low utilization made study of thermal front be the key task in urgent need.There are three kinds of theoretical model study on thermal front,namely heat conduction model,convective heat transfer model and energy conservation model.The different composition of the mathematical model is due to different consideration of models.From the view of integrity of consideration and mathematical model,Selim model、Macguire model and Front-sweep model are supposed to be better.Experimental study of thermal front could be divided into 1D experiment and 2D experiment,respectively.1D experiment result shows that,during hot water injection,the thermal front acts a likely linear relationship with time,while 2D experiment result shows a parabolic relationship with time.The moving of thermal front is influenced by the geological factors,as well as injecting factors,likely the more the saturation,the permeability of the hydrate is,the slower the front moves;the higher the initial temperature of the hydrate,the water temperature,the velocity,the salinity and the quantity of heat the hot water is,the faster the front moves,but not faster in a linear increment relationship,indicate that,there must be an optimum situation for production by heat injection,while under that situation,the heat will be taken full advantaged.The comparison results of theoretical model and experiment show that,the result of 1D model has large difference with experiment,the modified Selim model is proposed as a new theoretical model for thermal front calculation.The result of 2D model is in accord with experiment,especially the Front-sweep model,and the sensitivity regularity is as same as the experiment,so the recommended model is the Front-sweep model.