Investigation on the fracture propagation for horizontal wells in hydrate reservoirs using a fluid-solid coupling discrete element method

Abstract

Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources, however, its application to gas hydrate reservoirs has been rarely studied. Currently, there is still limited understanding of the propagation and extension of fractures around the wellbore during the fracturing process of horizontal wells in hydrate reservoirs, as well as the stress interference patterns between fractures. This study simulates hydraulic fracturing processes in hydrate reservoirs using a fluid-solid coupling discrete element method (DEM), and analyzes the impacts of hydrate saturation and geological and engineering factors on fracture extension and stress disturbance. The results show that hydraulic fracturing is more effective when hydrate saturation exceeds 30% and that fracture pressure increases with saturation. The increase in horizontal stress differential enhances the directionality of fracture propagation and reduces stress disturbance. The distribution uniformity index (DUI) reveals that injection pressure is directly proportional to the number of main fractures and inversely proportional to fracturing time, with fracturing efficiency depending on the spacing between injection points and the distance between wells. This work may provide reference for the commercial exploitation of natural gas hydrates.

Keywords

Hydraulic fracturing technology / Gas hydrate reservoirs / Hydrate-bearing sediment / Discrete element method / Fluid-solid coupling / Hydraulic fracturing / Horizontal wells / Fracture propagation / Oil-gas exploration engineering

CRediT authorship contribution statement

Jia-Wei Zhang, Chang-Ling Liu and Yong-Chao Zhang conceived of the presented idea. Jia-Wei Zhang and YongChao Zhang carried out the experiment. All authors discussed the results and contributed to the final manuscript.

Declaration of competing interest

The authors declare no conflicts of interest.

Acknowledgements

This study was financially supported by the National Key Research and Development Plan (2023YFC2811001), the National Natural Science Foundation of China (42206233), and the Taishan Scholars Program (tsqn202312280, tsqn202306297). All financial supports are greatly appreciated.

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