EXPERIMENTAL STUDY ON INFLUENCE FACTORS OF HOT-BRINE STIMULATION FOR DISSOCIATION OF NGH IN POROUS MEDIUM

A new one-dimensional experimental system for modeling natural gas hydrate (NGH) development has been designed to study the formation and dissociation process of NGH. In order to simulate the marine geological environment, NGH was made in a sand-packed tube, and then hot-brine was injected into the tube to study the thermal dissociation characteristics, and the injection parameters which will influence the thermal dissociation behavior and energy efficiency of NHG. The temperatures of the injected hot-brine were 60℃, 80℃ and 100℃, and the injection rates 12 mL/min, 15 mL/min and 18 mL/min respectively, and the time span for injection was 220 min to the maximum. The experimental results show that if the injection rate is fixed, the higher the temperature is, the larger releasing rate of gas from hydrate dissociation is and the lower energy efficiency becomes. Moreover; if the temperature of injected hot-brine is fixed, the higher the injection rate is, the larger releasing rate of gas from hydrate dissociation is and the lower energy efficiency becomes. As the injection time becomes longer,the energy efficiency of thermal stimulation decreases gradually. In this regard,the option of "hot brine slug + water flooding at normal temperature", or the combination of the thermal method and depressurization were proposed in this paper to improve the economic efficiency to develop NGH reservoirs.