The Law About Front Movement Of Natural Gas Hydrate By One Dimensional Heat Injection

Natural gas hydrate is widely considered as a kind of high quality and clean alternative energy,which has a bright prospect of development and utilization,and is regarded as the most promising strategic resource in the "post oil era".The main mining methods include depressurization method,thermal recovery method,injection inhibitor method and CO2 replacement method,among which thermal recovery method has strong practical operability and economy.The study of the front edge movement is the premise of defining the distribution of temperature and pressure in the process of thermal recovery,which provides a theoretical basis for the study of the influencing factors in the process of thermal recovery of natural gas hydrate and the optimization of heat injection conditions.Based on the actual distribution of gas hydrate saturation in China,three groups of hydrate samples with different saturation 0-30%,30-40% and 40-50% ere synthesized by intermittent gas injection method through the indoor hydrate formation kinetics device.The gas hydrate was analyzed from two aspects of development dynamic indexes(injection velocity and injection temperature)and geological factors(hydrate saturation)The sensitive factors and heat transfer law of one-dimensional heat injection mining front of complex.The conclusion is as follows:(1)A large number of experimental data show that there are obvious climbing wall effect and armor effect in the synthesis of hydrate,which restrict the uniform distribution and further synthesis of hydrate.Under the condition of intermittent flow,pressure disturbance can break the armor effect in the synthesis process,greatly increase the conversion of water,and effectively realize the incremental synthesis of hydrate.(2)The experimental results show that the decomposition front,the thermal front and the injection hot water front move forward along the central axis of onedimensional sand filling pipe at different moving rates,which are three non overlapping concepts.According to the movement rate from small to large,it is divided into decomposition front,thermal front and injection hot water front.Decomposition front is defined as the interface between decomposition area and non decomposition area.Thermal front refers to the surface where the initial temperature of hydrate reservoir begins to rise.(3)The energy utilization rate of hydrate exploitation is defined as the ratio of the heat consumed by hydrate decomposition to the total heat input.The law of gas production and energy utilization rate in the process of heat injection exploitation directly determine the exploitation benefit under different injection parameters.When the injection temperature is 80 ? and the flow rate is 6ml / min,the injection of hot water can achieve uniform propulsion,and the energy utilization rate changes little with time,about 0.22.(4)According to the theoretical model of the change of the position of the thermal front of the one-dimensional infinite hydrate layer by Tang Liangguang,Xia Xiran,Cao Wen and Selim,the hydrate layer is divided into the decomposition area and the non decomposition area,and the thermal front is the interface of the two,and the second generation of hydrate is not considered.It can be seen from the comparative analysis that the calculation results of different models are quite different,but the basic trend is the same,among which the caowen model is the closest to the experimental results.