Modelling of gas production from hydrate reservoirs

人们正在对天然气水合物作为未来能源的潜力进行评估。为了促进这一评估，在过去的十年里，已经开发了一些数值油藏模拟器。这些模型相当全面，包括多相流、对流和传导的重要机制，以及水合物分解的本征动力学。目前，其中三个模拟器正在用于评估建议的开采方法的可行性，其中一个已经在我们小组开发。这个模拟器将作为这里提出的研究的一部分进行增强。基于最近使用我们的水合物模拟器进行的机理研究，我们已经确定了一些不影响水合物储集层产气率计算的近似公式，水合物储集层的底部包括游离气，顶部有水合物盖子。在这样的储集层中，一旦来自游离气区的天然气生产降低了储集层压力，顶部的水合物就会贡献所产生的天然气。在阿拉斯加已知的是这种类型的大型气藏，据信存在于西北地区的麦肯齐三角洲、加拿大和。目前，对这些储集层的规划不包括天然气水合物分解产生的额外天然气的影响。在这个项目中，我们引用上述近似公式并开发简单的模型来计算包括水合物在内的天然气产量。我们将使用我们的综合数值模拟器进行广泛的敏感性研究，以检验这些简化解决方案的适用范围，并评估气藏顶部的水合物对这些气藏的产能和寿命的影响。此外，解析解将被反转，以开发解释对水合物储集层进行的测试的方法，以确定水合物储集层的现场性质。热刺激技术也寻求类似的目标。作为这里提出的研究计划的一部分，将确定适合现场模拟的“等效”水合物分解反应参数。

Gas hydrates are being evaluated for their potential as a future energy source.  To facilitate this evaluation, a few numerical reservoir simulators have been developed over the past decade.  These models are quite comprehensive and include the important mechanisms of multi-phase flow, convection and conduction, as well as intrinsic kinetics of hydrate decomposition.  Currently, three of these simulators, one of which has been developed in our group, are being used to evaluate the feasibility of suggested production methods.  This simulator will be enhanced as part of the research proposed here.Based on recent mechanistic studies using our hydrate simulators, we have identified a number of approximations which do not affect calculation of the gas-production rate from a hydrate reservoir that includes free gas at the bottom and a hydrate cap at top.  In such a reservoir, hydrates at top contribute to the produced gas once the reservoir pressure is reduced by gas production from the free-gas zone.  Large gas reservoirs of this type are known in Alaska and are believed to exist in the Mackenzie Delta of the Northwest Territories, Canada and.  Currently, planning for these reservoirs does not include the effect of additional gas generated by the decomposition of the gas hydrate.In this project, we invoke the above approximations and develop simple models to calculate the rate of gas production including that from the hydrates.   We will conduct extensive sensitivity studies using our comprehensive numerical simulator to examine the range of applicability of these simplified solutions, and to evaluate the impact of the hydrate on top of the gas reservoirs on productivity and life span of these reservoirs.Furthermore, the analytical solutions will be inverted, to develop methods for interpretation of tests performed on hydrate reservoirs, for determination of the in-situ properties of the hydrate reservoir.  Similar objectives are sought for the thermal stimulation technique.  As part of the research program proposed here, "equivalent" hydrate decomposition reaction parameters will be determined that are suitable for field-scale simulation.