Rock cuttings injection into subsurface is often considered as alternative for disposal of drilling waste, as it is both economical and environmental friendly. The repeated cuttings injection leads to the generation of secondary fractures after initial hydraulic fracturing. In this article, the Particle Flow Code (PFC) is used for a microscopic numerical system to simulate the interaction between the natural fractures, hydraulic fractures, and the fractures developed by re-injection of rock cuttings, due to the fact that PFC captures the dynamic mechanism of cuttings re-injection into fractured formation. In the model, a synthetic rock mass (SRM) with random distributed natural fractures is created, coupling with hydraulic fracturing, and apply drilling cuttings re-injection. Considerations on the influence of rock cuttings physical properties, injection pressure, and the stress regimes of SRM have been derived in this paper. The results demonstrate that the higher injection pressure helps generation of shear cracking; the fluid viscosity has not significant effect after propagation of fractures; taking advantages of natural fractures into stimulation treatment offers benefits to optimal conductivity with hydraulic fracturing.

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