Numerical Investigation on Propagation Behaviors of a Three-Dimensional Fracture Network Coupled with Microseismicity in Fractured Shale Reservoirs

Jianfa Wu, Haoyong Huang, Ersi Xu, Junfeng Li and Xiaohua Wang
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Jianfa Wu: Shale Gas Research Institute, PetroChina Southwest Oil & Gas Field Company, Chengdu 610051, China
Haoyong Huang: Shale Gas Research Institute, PetroChina Southwest Oil & Gas Field Company, Chengdu 610051, China
Ersi Xu: Shale Gas Research Institute, PetroChina Southwest Oil & Gas Field Company, Chengdu 610051, China
Junfeng Li: Shale Gas Research Institute, PetroChina Southwest Oil & Gas Field Company, Chengdu 610051, China
Xiaohua Wang: Department of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai 200092, China

Energies, 2021, vol. 14, issue 24, 1-19

Abstract: The formation mechanism and propagation behaviors of a three-dimensional hydraulic fracture network in fractured shale reservoirs remain unclear, especially when the scale of hydraulic fractures is much larger than that of natural fractures. In this study, taking the well XH in the Longmaxi shale reservoir in the Sichuan Basin, China as an example, we develop a fully three-dimensional numerical model for hydraulic fracturing coupled with microseismicity based on the discrete lattice method. We introduce a randomly generated discrete fracture network into the proposed model and explore the formation mechanism of the hydraulic fracture network under the condition that the hydraulic fractures are much larger than natural fractures in scale. Moreover, microseismic events are inversely synthesized in the numerical model, which allows the evolution of the fracture network to be monitored and evaluated quantitatively. In addition, we analyze the effects of injection rate, horizontal stress difference, and fluid viscosity on fracture propagation. Our results show that when the scale of hydraulic fractures is much larger than that of natural fractures, the fracture morphology of “main hydraulic fractures + complex secondary fractures” is mainly formed. We find that a high injection rate can not only create a complex fracture network, but also improve the uniform propagation of multi-cluster fractures and enhance far-field stimulation efficiency. Optimizing the horizontal wellbore intervals with low horizontal stress differences as the sweet spots of hydraulic fracturing is also beneficial to improve the stimulation efficiency. For zones with a large number of natural fractures, it is recommended to use an injection schedule with high viscosity fluid early and low viscosity fluid late to allow the hydraulic fractures to propagate to the far-field to maximize the stimulation effect.

Keywords: unconventional reservoir; hydraulic fracturing; microseismic events; multi-cluster fracturing; discrete fracture network; discrete lattice 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: 2021
References: View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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