热水吞吐开采水合物藏数值模拟研究

天然气水合物资源潜力巨大，高效的开采方法是实现水合物资源开发利用的关键。热水吞吐法广泛应用于石油工业，为加强对热水吞吐法开采水合物藏规律的认识，结合实际水合物藏参数，使用数值模拟方法，研究了水平井热水吞吐条件下水合物藏的开采动态规律，并与单纯降压与单纯注热的开发效果进行了对比。结果表明，热水吞吐开采水合物藏时，产气速率呈周期性变化，随周期数增加，周期生产时间变长，分解气速率整体呈上升趋势，开发效果变好，但分解气的采出比例偏低，需要采取合适措施提高其采出比例；水合物的分解以水平井筒为中心逐渐向外扩展，但受效范围主要在近井区域；热水吞吐开发水合物藏兼具降压和注热的作用，且开发效果比降压或注热单独作用时好，能够获得更高的产气量、分解气量和水合物分解程度。

Numerical Simulation of Mining from Hydrate Reservoir Using Huff-and-puff Hot Water Injection

Natural gas hydrate resources have great potential. The key to development and utilization of hydrate resources is an efficient mining method. Huff-and-puff hot water injection has been widely used in the petroleum industry. To better understand how huff-and-puff hot water injection is used to extract hydrate reservoirs, the mining performance of hydrate reservoirs during huff-and-puff hot water injection in a horizontal well are explored by numerical simulations, based on the actual hydrate reservoir parameters. The mining performance of huff-and-puff hot water injection is also compared with the simple depressurization method and simple heat injection methods. The results show that when extracting the hydrate resources using the huff-and-puff hot water injection method, the gas production rate changes periodically. With increasing number of cycles, the production time for one cycle becomes longer and the overall extraction rate of decomposition gas shows an increasing trend. These findings indicate a better extraction performance. However, the fraction of the decomposition gas in the output is relatively small, and proper approaches are required to enhance the production ratio. The decomposition of hydrates expands outwards gradually from the horizontal wellbore, but the most effective decomposition occurs in the region close to the well. The huff-and-puff hot water injection method can realize both depressurization and heat injection functions when used for extracting hydrate resources; it therefore exhibits a better extraction performance compared with only using either the depressurization or heat injection methods. In general, the huff-and-puff hot water injection method allows for a greater gas production rate, higher gas decomposition rate, and high decomposition level of hydrates.