考虑热传导开采天然气水合物藏的可行性研究:以南海神狐海域为例

摘要

天然气水合物作为一种新型替代能源,如何有效开发成为当前研究的热点,热激发被认为是除降压法外天然气水合物开采的另一重要途径;然而,目前对于天然气水合物热开采效率及其经济可行性仍没有清楚的认识.本项研究构建了天然气水合物注热开采的模型,该模型经过理想简化,忽略了开采过程中热对流和压力差的影响,只考虑热作用对水合物分解的影响;进一步计算了水合物注热开采的热消耗效率和天然气的能量效益、可研究水合物开采的最大产出效率.通过对南海北部神狐海域天然气水合物藏特征以及钻井取心相关重要参数的研究,计算了天然气水合物的注热开发潜力,并通过相关参数的敏感性计算和分析研究,论证了神狐海域天然气水合物注热开采效率和可行性.研究结果显示,神狐海域水合物藏的单位长度生产井段3 a的最大累积产气量为509m3,远低于工业开发标准.水合物热激发分解速度缓慢,注热开采水合物生产成本较高,经济效益低下;因此,基于热传导开采南海神狐海域天然气水合物不具备工业应用的可行性.%How the gas to be effectively produced from hydrate deposits has become a hot research topic. Heat stimulation is regarded as another important way for producing; hydrate besides depressurization. However, the production efficiency and economic feasibility of gas production by heat stimulation have not been clearly understood. In this paper, a model for predicting gas production from hydrate deposits by heat stimulation was developed. The model was idealized and simplified by neglecting the effects of heat convection and pressure in sediment. We computed the heat consumption efficiency and gas energy efficiency of gas production by heat stimulation, only considering effect of hydrate dissociation. This model can be used to predict the maximum production efficiency. After thorough analysis of the charactenstics of hydrate reservoirs and significant parameters from drilling and sampling research, we calculated the production potential of Shenhu hydrate deposits and investigated the production efficiency and feasibility. The result shows that the maximum amount of cumulative gas production at Shenhu is about 509 m3 per meter in three years, and the production potential is much lower than the industrial criterion for marine production. Therefore, it is concluded that hydrate dissociation rate is very low,and production cost is high and economic value is low under the current production technology. Thus it is unfeasible to produce gas from Shenhu hydrate deposits only considering the thermal conduction.