Aiming at the defect that professional gas hydrate reservoir numerical simulator fails to accurately characterize mass and heat transfer laws in the matrix and reservoir stimulation areas.By adding PEBI unstructured grid division module and mass and the heat transfer calculation module for matrix and reservoir stimulation area in Tough+Hydrate software,a breakthrough is made in the numerical simulation of depressurization exploitation of natural gas hydrate reservoir assisted by reservoir stimulation.Firstly,the matrix and reservoir stimulation areas are modeled respectively,and the mass and heat transfer laws between the matrix and res-ervoir stimulation areas are characterized based on discrete fracture theory,thus establishing the numerical simulation method for de-pressurization exploitation of natural gas hydrate reservoir assisted by reservoir stimulation.Then,taking the reservoir stimulation by hydraulic fracturing as an example,the paper investigates the variation law of productivity and physical field during depressuriza-tion exploitation of natural gas hydrate reservoir assisted by hydraulic fracturing during trial production in Shenhu sea area of the South China Sea,and analyzes the influencing factors of productivity.Research results show that hydraulic fracturing can greatly ac-celerate the output rate and depressurization rate for gas-water mobile phase,so as to make full use of the reservoir heat and pressure to promote hydrate dissociation in the hybrid layer and hydrate layer.Compared with the case of no fracturing,the peak gas produc-tion and long-term cumulative gas production can increase up to 198.7％and 108.1％after hydrofracturing,respectively.However,being subject to the large consumption of heat,the hydrate dissociation rate and gas production will decrease significantly in the later stage of depressurization exploitation,and a large amount of undissociated hydrates still remain in the hydrate layer after depressur-ization.Fracture conductivity,fracture number and half length will have a great impact on gas productivity.The higher gas produc-tivity after depressurization exploitation is attributed to the stronger fracture conductivity,the larger amount of fractures,and the larger half length.
关键词
天然气水合物藏/水力压裂/离散裂缝/非结构网格/降压开发
Key words
gas hydrate reservoir/hydraulic fracturing/discrete fracture/unstructured grid/depressurization exploitation
维普
万方数据