Growth of fractures with constricted opening
- 1University of Western Australia, Department of Mechanical and Chemical engineering, Crawley, Australia (elena.pasternak@uwa.edu.au)
- 2University of Western Australia, School of Engineering, Dept of Civil, Environment and Mining Engineering, Crawley, Australia (arcady.dyskin@uwa.edu.au)
Growth of real fractures is characterised by interruptions and local overlapping caused by rock heterogeneities. The interruptions and loci of overlapping can work as bridges distributed all over the fracture that connect opposite surfaces of the fracture [1]. These bridges constrain the crack opening and thus mitigate the dependence of the Mode I stress intensity factor of the fracture length (radius). In the case of hydraulic fractures, constraining the opening also affects the fluid (e.g. fracturing fluid) flow through the fracture.
The effect of bridges can be characterised by a characteristic length – the constriction length. When the fracture size is small compared to the constriction length, the fracture behaves similarly to a conventional Model I crack of the same configuration. Alternatively, when the fracture size is much greater than the constriction length both the average fracture opening and the Mode I stress intensity factor become constant. This restricts the ability of the fracture to growth in unstable manner or dynamically.
The effect of constriction is even more pronounced in the case when the fracture gets open in the displacement-controlled mode. In this case the dependence of the stress intensity factor of disc-like fracture on the fracture radius is no longer monotonic. The stage of decrease of the stress intensity factor with the fracture radius leads to the emergence of stable fracture growth when increase in the displacement is required to maintain fracture propagation. It is important that without taking the constriction into account the corresponding stage of stable fracture propagation can be taken for the effect of rock heterogeneity.
The theory developed is essential for predicting and monitoring growth of Mode I fractures, in particular hydraulic fractures.
- He, J., Pasternak, E. and A.V. Dyskin, 2020. Bridges outside fracture process zone: Their existence and effect. Engineering Fracture Mechanics, 225, 106453.
Acknowledgement. The authors acknowledge support from the Australian Research Council through project DP190103260.
How to cite: Pasternak, E. and Dyskin, A.: Growth of fractures with constricted opening, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4550, https://doi.org/10.5194/egusphere-egu22-4550, 2022.
