Natural gas hydrate is generally disseminated in tilted sediments. The inclination of hydrate reservoirs significantly affects the fluid migration behaviour and production potential. However, most of the current simulations ideally assume that the hydrate reservoir is horizontally distributed; resulting in the effect of the formation dip on the well deployment and corresponding gas production remains unclear. Here, we implement a real inclined alternating sand–clay hydrate reservoir model based on geological data from the Nankai Trough, Japan, to simulate the production performance of a single horizontal well and dual horizontal wells. Results show that the gas and water productions are enhanced when a single horizontal production well is deployed in the structural low of the reservoir. The gas and water production performance in upper sandy reservoir and the water extraction in the middle muddy reservoir are sensitive to the layout of the production wells, which can cause the daily difference is over 6%. The gas-to-water ratio is independent from the structural deployment positions of the horizontal wells in the same inclined layer. Compared to the single depressurization method, placing a horizontal thermal injection well in the structural high of the upper inclined sandy reservoir and a horizontal production well in the structural low of the same formation improves the gas recovery efficiency nearly twice, which is recommended for production enhancement. Our findings are useful for achieving effective and economic gas recovery from natural inclined layered hydrate reservoirs.

中文翻译：

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南开海槽倾斜层状甲烷水合物储层产气数值模拟

天然气水合物一般赋存于倾斜沉积物中。水合物储层的倾斜度显着影响流体运移行为和生产潜力。然而，目前大多数模拟都理想地假设水合物储层是水平分布的；导致地层倾角对井部署和相应产气量的影响仍不清楚。在这里，我们基于日本南海海槽的地质数据建立了真实的倾斜交替砂土水合物储层模型，以模拟单水平井和双水平井的生产动态。结果表明，在油藏构造低部部署单口水平生产井，可提高产气产水量。上部砂质油藏产气产水动态和中部泥质油藏抽水情况对生产井布置敏感，可导致日差超过6%。气水比与同一斜层水平井结构部署位置无关。与单一降压方法相比，在上部倾斜砂质油藏构造高位设置水平热注井，在同一地层​​构造低位设置水平生产井，采气效率提高近一倍，推荐用于增产。我们的研究结果对于从天然倾斜层状水合物储层中实现有效且经济的天然气回收很有用。