Natural gas hydrate represents an environmentally friendly alternative energy. However, the low-permeability hydrate reservoirs pose significant challenges to commercial production. To optimize hydrate production, reservoir stimulation methods like hydraulic fracturing, gas fracturing, and explosive fracturing are potential. In the investigation of the fracturing effect on hydrate dissociation behavior, we developed a three-dimensional model that comprehensively incorporates the arrangement of fracture planes, encompassing fracture permeability, spacing, and height. The model was implemented using a self-developed hydrate simulator which was validated at multiple scales. We firstly conducted a comparative analysis, contrasting the conventional depressurization method in horizontal wells with a combined depressurization and fracturing method. The comparison suggested that fracturing brings significant promotion (113.5%) on hydrate dissociation. Sensitivity analysis revealed fracture permeability and fracture height evidently exhibit an optimal value that facilitates the dissociation behavior. The optimal value of fracture permeability is dependent on the geological background. The optimal value of fracture height occurs just before penetrating the hydrate-bearing sediment layer and the overlying/underlying formations, i.e., near the thickness of the hydrate-bearing sediment layer. The impact of spacing on gas volume is limited while decreasing the spacing leads to more evident localized dissociation and differential subsidence of hydrate reservoir. It is necessary to balance production and geological risks when selecting the fracture spacing. The conclusions suggest that the fracturing operation need to be optimized by controlling the injection rate and the fracturing interval. It is not advisable to blindly pursue the effectiveness of reservoir stimulation but rather to consider the geological conditions. Additionally, we have found that it is preferable to establish barriers between the reservoir and overlying/underlying formations near the hydraulic fracturing section before reservoir stimulation, to prevent excessive early water production. In conclusion, this study would provide valuable insights for the optimization of fracturing techniques in stimulation of hydrate reservoir.

中文翻译：

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优化压裂技术以增强低渗透油藏中水合物的解离：数值模拟的见解

天然气水合物代表了一种环保的替代能源。然而，低渗透水合物储层给商业生产带来了重大挑战。为了优化水合物产量，可以采用水力压裂、气体压裂和爆炸压裂等储层增产方法。在研究压裂对水合物解离行为的影响时，我们开发了一个三维模型，该模型全面考虑了裂缝面的排列，包括裂缝渗透率、间距和高度。该模型是使用自主开发的水合物模拟器实现的，并在多个尺度上进行了验证。我们首先进行了对比分析，将水平井常规降压方法与降压压裂联合方法进行了对比。对比表明，压裂对水合物解离有显着的促进作用（113.5%）。敏感性分析显示，裂缝渗透率和裂缝高度明显表现出有利于解离行为的最佳值。裂缝渗透率的最佳值取决于地质背景。裂缝高度的最佳值出现在刚好穿透含水合物沉积层和上覆/下伏地层之前，即接近含水合物沉积层的厚度。间距对气体体积的影响有限，而减小间距会导致水合物储层的局部解离和差异沉降更加明显。选择裂缝间距时需要平衡生产和地质风险。结论表明需要通过控制注入量和压裂间隔来优化压裂作业。不宜一味追求油藏改造效果，而应考虑地质条件。此外，我们发现，在储层增产之前，最好在水力压裂段附近的储层和上覆/下伏地层之间建立屏障，以防止早期过度产水。总之，这项研究将为水合物储层增产压裂技术的优化提供有价值的见解。