Numerical simulation of productivity improvement of natural gas hydrate with various well types: Influence of branch parameters

The depressurization method and its modified scheme may be the best way to efficiently recover marine natural gas hydrate (NGH) from the reservoir. However, the capacity of existing engineering tests still poses considerable challenges to the industrial development of NGH. The complex structure wells can effectively promote the NGH contact area to enhance the exploitation efficiency, but the influence of branch parameters on gas production performance is not well sorted out for reference when performing well type optimization. Therefore, a geological model of an ideal hydrate reservoir and 65 wellbore models were established based on the geological data from station AT1 in Nankai Trough to analyze the influence of different branch parameters on the production capacity for various well types. Results indicate that the open hole section length is heavily constrained by the size of the reservoir for a single well. Compared to the corresponding single well, the multi-branch vertical wells can increase productivity by about 2.12%–51.18%, the multi-branch horizontal wells by about 0.99%–29.75%, and the cluster horizontal wells by about 54.36%–250.66% well. Moreover, the correlation coefficients of various branch parameters were analyzed as a reference when optimizing the well type and show that the cluster horizontal well has the highest sensitivity to branch parameters, which can significantly promote gas production efficiency, and is expected to break the threshold of industrial development.