Phase-field modeling of hydraulic fracture network propagation in poroelastic rocks
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ORIGINAL PAPER
Phase-field modeling of hydraulic fracture network propagation in poroelastic rocks Lin Ni 1 & Xue Zhang 2 & Liangchao Zou 3 & Jinsong Huang 1 Received: 30 June 2019 / Accepted: 10 March 2020 # The Author(s) 2020
Abstract Modeling of hydraulic fracturing processes is of great importance in computational geosciences. In this paper, a phase-field model is developed and applied for investigating the hydraulic fracturing propagation in saturated poroelastic rocks with preexisting fractures. The phase-field model replaces discrete, discontinuous fractures by continuous diffused damage field, and thus is capable of simulating complex cracking phenomena such as crack branching and coalescence. Specifically, hydraulic fracturing propagation in a rock sample of a single pre-existing natural fracture or natural fracture networks is simulated using the proposed model. It is shown that distance between fractures plays a significant role in the determination of propagation direction of hydraulic fracture. While the rock permeability has a limited influence on the final crack topology induced by hydraulic fracturing, it considerably impacts the distribution of the fluid pressure in rocks. The propagation of hydraulic fractures driven by the injected fluid increases the connectivity of the natural fracture networks, which consequently enhances the effective permeability of the rocks. Keywords Phase-field model . Poroelasticity . Hydraulic fracturing . Fracture network
1 Introduction Hydraulic fracturing is a process of fracture of rock formation induced by pressurized liquids. From the last decade, hydraulic fracturing has been attracting more and more attention because of its applications in the extraction of oil and gas from unconventional reservoirs [1] and the enhancement of geothermal energy systems [2]. In a process of hydraulic fracturing, high-pressurized fluids are injected into rock layers in order to widen the existing fractures and create new artificial fractures. The resulting fracture networks consequently provide high-permeability pathways for the recovery of oil, gas, and geothermal energy. Due
* Xue Zhang [email protected] 1
School of Engineering, University of Newcastle, Callaghan, NSW, Australia
2
Department of Civil Engineering and Industrial Design, University of Liverpool, Liverpool, UK
3
Department of Sustainable development, Environmental science and Engineering, Royal Institute of Technology, Stockholm, Sweden
to their complexity, analytical solutions to hydraulic fracturing problems are very rare, particularly for these practical problems in engineering which involve complicated geometries and boundary conditions. Thereby, predictions of hydraulic fracturing processes rely heavily on the available numerical techniques. In recent years, numerous computational methods have been developed to model hydraulic fracturing processes in rocks that can be roughly divided into discrete and continuous categories. The discrete approaches attempt to capture the exact topology of fract
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