An Analytical and Numerical Analysis for Hydraulic Fracture Propagation through Reservoir Interface in Coal-Measure Superimposed Reservoirs

Peibo Li, Jianguo Wang (), Wei Liang and Rui Sun
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Peibo Li: State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221116, China
Jianguo Wang: State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221116, China
Wei Liang: State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221116, China
Rui Sun: School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou 221116, China

Sustainability, 2023, vol. 15, issue 5, 1-34

Abstract: Hydraulic fracturing technology can be used to jointly exploit unconventional natural gas such as coalbed methane and tight sandstone gas in coal-measure superimposed reservoirs for the enhancement of natural gas production. Hydraulic fracturing usually induces mixed fractures of I and II modes, but existing studies have not considered the influence of reservoir lithology on the stress intensity factor of I/II mixed fractures in coal-measure superimposed reservoirs. This paper develops an analytical stress model and a seepage-mechanical-damage numerical model for the vertical propagation of I/II mixed fractures in coal-measure superimposed reservoirs. The variation of stress intensity factor of I/II mixed fractures is analyzed when the fractures are close to the interface of different lithologic reservoirs and the effects of elastic modulus difference, stress state, fracturing fluid viscosity, shear and tensile failure modes on the vertical propagation of hydraulic fractures are investigated. Finally, the ratio of elastic modulus of adjacent reservoirs is proposed as an evaluation index for the fracture propagation through reservoir interface. These investigations revealed that hydraulic fracture propagation through the reservoir interface is a process of multi-physical interactions and is mainly controlled by the injection pressure and the elastic modulus ratio of adjacent reservoirs. A critical line is formed in the coordinates of elastic modulus ratio and injection pressure. A fracture can propagate through the reservoir interface when the combination of injection pressure and the elastic modulus ratio is in the breakthrough zone. These results can provide theoretical support for the site selection of horizontal wells in coal-measure gas exploitation.

Keywords: stress intensity factor; coal-measure superimposed reservoir; hydraulic fracturing; vertical fracture propagation; rock damage (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (3)

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