A simulation study of Class III hydrate production with a high efficiency through the depressurization recovery and thermal stimulation in horizontal wells

作者：Fan, Shuanshi^*; Yang, Shengwen; Wen, Yonggang; Wang, Yanhong; Lang, Xuemei

来源：Natural Gas Industry, 2013, 33(7): 36-42.

DOI：10.3787/j.issn.1000-0976.2013.07.006

• Alternative energy source
• Energy efficiency ratio
• Gas water ratio
• Hydrate dissociation
• Recovery rate
• Reservoir simulation
• Simulation studies
• Thermal stimulation

Natural gas hydrate is a potential and alternative energy source. For lack of the flowing layers underlain, the discovered hydrate reservoirs in China belong to Class III hydrate pools, which have top and bottom covered layers. However, most domestic scholars still doubt about the economic possibility and energy efficiency ratio (EER) of Class III hydrate production and no such literatures have ever been found yet. In view of this, the reservoir simulation tool HydrateResSim was adopted to simulate the production process of Class III hydrate through the depressurization recovery and thermal stimulation in a horizontal well, which aims to study the indicators such as EER, gas-water ratio, the gas recovery rate, etc. First, EER, defined by the ratio between energy output from hydrate and energy input to dissociate hydrate, was applied to evaluate the possibility of hydrate dissociation through the above two recovery methods in this case study. Then, the simulation conditions were as follows in the horizontal well: well temperature was 42°C;well pressure was 0.2 p0, 0.5 p0, 0.8 p0respectively. p0, the initial pressure of a hydrate reservoir, was equal to 1.383×107Pa. The following findings were concluded. a. At the early stage of hydrate production, there is huge energy consumption needed and a great volume of water produced. b. Only when the well temperature is 42°C and the well pressure 0.2 p0, the gas-water ratio will be kept above 100 for a long time, the gas recovery rate about 50%, and the EER up to 188, the indicators of which are all much bigger than those under the other two well pressures. Furthermore, through the analysis of other heat flow values in the case of 0.2 p0, it was found that only about 5.28% hydrate was dissociated by the thermal stimulation;and the others were all by the depressurization recovery. That could explain why the EER in this case is much higher. In conclusion, this study proves that the depressurization recovery and thermal stimulation in a horizontal well will be an economic strategy to achieve the hydrate production under a certain condition;and further studies are needed to demonstrate more than that.

• 出版日期2013-7
• 单位华南理工大学