Numerical Investigation on Mesoscale Evolution of Hydraulic Fractures in Hydrate-Bearing Sediments

Xiaowei Liang, Hui Zhao (), Yongchao Dang, Qihong Lei, Shaoping Wang, Xiaorui Wang, Huiqiang Chai, Jianbo Jia and Yafei Wang
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Xiaowei Liang: Shale Oil Development Branch, PetroChina Changqing Oilfield Company, Qingyang 745000, China
Hui Zhao: Shale Oil Development Branch, PetroChina Changqing Oilfield Company, Qingyang 745000, China
Yongchao Dang: Shale Oil Development Branch, PetroChina Changqing Oilfield Company, Qingyang 745000, China
Qihong Lei: Exploration and Development Research Institute, PetroChina Changqing Oilfield Company, Xi’an 710016, China
Shaoping Wang: Digital and Intelligentization Division, PetroChina Changqing Oilfield Company, Xi’an 710016, China
Xiaorui Wang: Shale Oil Development Branch, PetroChina Changqing Oilfield Company, Qingyang 745000, China
Huiqiang Chai: Shale Oil Development Branch, PetroChina Changqing Oilfield Company, Qingyang 745000, China
Jianbo Jia: Shale Oil Development Branch, PetroChina Changqing Oilfield Company, Qingyang 745000, China
Yafei Wang: College of Construction Engineering, Jilin University, Changchun 130026, China

Energies, 2023, vol. 16, issue 22, 1-19

Abstract: Hydraulic fracturing is widely recognized as a potential stimulation technology for the development of challenging natural gas hydrate. However, the fracturing behavior of non-diagenetic hydrate reservoirs has peculiar characteristics that are different from those of conventional oil and gas reservoirs. Herein, a fully coupled fluid-mechanical model for simulating hydraulic fracturing in hydrate-bearing sediments (HBS) was established based on the discrete element method, and the influence of hydrate saturation, in situ stress, and injection rate on the meso-fracture evolution was investigated. The results indicate that with the increase in hydrate saturation, the fracture morphology transitions from bi-wing to multi-branch, thereby enhancing fracture complexity. Both tensile and shear failure modes exist, and the tensile failure between the weakly cemented sediment particles is dominant. The tensile strength of HBS is an exponential function of hydrate saturation, with the breakdown pressure being governed by hydrate saturation and in situ stress, with the form being consistent with the classical Kirsch equation. Additionally, lower in situ stress and higher injection rates are conducive to the generation of microcracks, whereas an excessive injection rate reduces the fracture length. These findings contribute to understanding the meso-evolution mechanism of hydraulic fractures and guide the design of on-site hydraulic fracturing plans of natural gas hydrate reservoirs.

Keywords: natural gas hydrate; hydraulic fracturing; hydrate-bearing sediments; fluid and mechanical coupling; discrete element method (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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