Numerical simulation of hydraulic fracturing-assisted depressurization development in hydrate bearing layers based on discrete fracture models

A new simulation method for hydraulic fracturing-assisted depressurization development of hydrate bearing layers (HBLs) was developed, in which the mass transfers of matrix-matrix, fracture-matrix, and fracture-fracture are obtained based on discrete fracture models, and a perpendicular bisection (PEBI) grid was adopted to achieve accurate characterization of complex fracture shapes. Subsequently, a simulation model was established based on the parameters of an HBL in the South China Sea, and the influence of hydraulic fracturing on gas production was investigated. The results indicated that the permeability of the HBL has a significant influence on the stimulation performance of fracturing. For an HBL with a permeability of 7.5 millidarcy (mD), the fracturing case can increase the cumulative gas production by 115.5% compared to the case without fracturing. Moreover, the greater the number of fractures, the longer is the fracture length, the greater is the conductivity, and the greater is the increase in gas production. However, for an HBL with a permeability of 75 mD, the fracturing case can only increase the gas production rate during the early stage of depressurization. This limits the cumulative gas production increase to 3.2%.

Automated summary

A new simulation method was developed to study the hydraulic fracturing-assisted depressurization development of hydrate bearing layers (HBLs). The results showed that the permeability of the HBL has a significant influence on the stimulation performance of fracturing.