Measurement of hydraulic fracture growth in a naturally fractured orebody for application to preconditioning

Authors: Jeffrey, RG; van As, A; Zhang, X; Bunger, AP; Chen, ZR

DOI https://doi.org/10.36487/ACG_rep/1002_45_Jeffrey

Cite As:
Jeffrey, RG, van As, A, Zhang, X, Bunger, AP & Chen, ZR 2010, 'Measurement of hydraulic fracture growth in a naturally fractured orebody for application to preconditioning', in Y Potvin (ed.), Caving 2010: Proceedings of the Second International Symposium on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 647-662, https://doi.org/10.36487/ACG_rep/1002_45_Jeffrey

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Abstract:
Hydraulic fracturing is applied for the preconditioning of orebodies prior to cave mining. A major project at Northparkes Mines was carried out in 2006 to investigate hydraulic fracture interaction with shear zones in the E48 orebody. The fracture growth was remotely monitored by tiltmeter and microseismic arrays. The mined fractures were then physically mapped and their geometry was compared to that inferred from the remote monitoring. The fractures were found to be subhorizontal, which was consistent with the tiltmeter and in situ stress data. Shear zones, natural fractures, and veins were crossed by the hydraulic fractures, sometimes producing an offset or step in the fracture path at the crossing site. One hydraulic fracture terminated at a shear zone in close proximity to a lithological contact that may be a stress change boundary. Numerical modelling of hydraulic fracture growth with offsets reveals that such fractures require a higher pressure to propagate and grow more slowly than a straight fracture. Results from numerical modelling indicated that the E48 caveability would prove problematic. The E48 orebody was, therefore, preconditioned using hydraulic fracturing and the footprint of the cave was enlarged.

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