Geological-engineering comprehensive evaluation model and application of feasibility of hydraulic fracturing in hydrate-bearing sediments

Natural gas hydrates (hereinafter referred to as hydrates) are a promising clean energy source. However, their current development is far from reaching commercial exploitation. Reservoir stimulation technology provides new approaches to enhance hydrate development effectiveness. Addressing the current lack of quantitative and objective methods for evaluating the fracability of hydrate reservoirs, this study clarifies the relationship between geological and engineering fracability and proposes a comprehensive evaluation model for hydrate reservoir fracability based on grey relational analysis and the criteria importance through intercriteria correlation method. By integrating results from hydraulic fracturing experiments on hydrate sediments, the fracability of hydrate reservoirs is assessed. The concept of critical construction parameter curves for hydrate reservoirs is introduced for the first time. Additionally, two-dimensional fracability index evaluation charts and three-dimensional fracability construction condition discrimination charts are established. The results indicate that as the comprehensive fracability index increases, the feasibility of forming fractures in hydrate reservoirs improves, and the required normalized fracturing construction parameters gradually decrease. The accuracy rate of the charts in judging experimental results reached 89.74%, enabling quick evaluations of whether hydrate reservoirs are worth fracturing, easy to fracture, and capable of being fractured. This has significant engineering implications for the hydraulic fracturing of hydrate reservoirs.