Numerical simulation of hydraulic fracture characteristics in gas hydrate bearing-sediments by using CDEM

Currently, gas hydrate exploitation suffers from problems such as low efficiency of production due to the low permeability of the reservoir and thermal conduction. As an effective technique for enhancing reservoir permeability in conventional oil and gas exploration, hydraulic fracturing is expected to be applicable for improving the permeability of natural gas hydrate reservoirs and increasing recovery efficiency. However, the research on the application of hydraulic fracturing of gas hydrate-bearing sediments (GHBS) is few. In this paper, the continuous-discontinuous element method (CDEM), which couples finite and discrete elements, is used to numerically simulate the hydraulic fracturing process in GHBS with different formation properties in a two-dimensional situation. The effect of reservoir properties and fracturing parameters on fracture generation in GHBS is investigated. The main conclusions are that among the fracturing parameters and sediment properties considered in this study, the smaller angle of internal friction angle and the higher injection flow rate are positive for fracturing. It is the most favorable condition for fracturing when the saturation and cohesion are in an appropriate range. The condition, when geostatic stress is equal in all directions, is the most favorable for fracturing but the least favorable for fracturing to extend farther.