Analysis of competition and interference mechanisms of multiple hydraulic fractures in deep-sea hydrate reservoirs in the South China Sea

Improving the fundamental theory of hydraulic fracturing in deep-sea hydrate reservoirs is of great significance in enhancing the efficiency of gas hydrate mining. In this paper, a multi-cluster fracturing model for a horizontal well was established with a three-dimensional extended finite element method and the measured geo-mechanical data from hydrate reservoirs in the South China Sea. The performance, fracture initiation, and expansion mechanisms of multi-hydraulic fractures are investigated under different fracturing sequences, hydrate saturation and cluster deployment patterns. Some interesting results have been discovered: In the case of three-cluster, the fractures produced by sequential fracturing are notably more affected by pre-existing fractures. Furthermore, the effect of fracture interference between simultaneous and sequential fracturing is reflected in the middle fracture is compressed by the fractures on its left and right sides. The increase in hydrate saturation enhances the cementing ability of the sediments and results in an increased difficulty of fracture initiation for the five-cluster simultaneous fracturing. It also results in a decrease in the geo-stress field, where the interaction between fractures plays a dominant role in the process of fracture expansion, leading to non -uniform expansion.