Exploring structure and stress from depth to surface in the Wairakei Geothermal Field, New Zealand
McNamara, David D.
Milicich, Sarah D.
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McNamara, David D., Bannister, Stephen , Villamor, Pilar , Sepúlveda, Fabian , Milicich, Sarah D. , Alcaraz, Samantha, & Massiot, Cécile. (2016). Exploring Structure and Stress from Depth to Surface in the Wairakei Geothermal Field, New Zealand Paper presented at the 41st Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California.
Structures such as fractures and faults have an important role as fluid flow pathways in geothermal fields, as the reservoir rocks hosting geothermal resources can often have little to no intrinsic permeability. As such, understanding and characterizing this structural network is vital to developing reservoir models and field operation and development plans that will maximize the potential of a geothermal resource. Presented here are the preliminary results of three recent studies, micro-earthquake analysis, borehole logging, and active fault mapping, carried out in the Wairakei Geothermal Field to determine the structural character of the system, if and how it contributes to fluid flow, and how the structural observations from these studies inform and relate to each other. Across all three techniques a dominant NE-SW structure strike orientation is observed with lesser population of N-S, E-W and NW-SE, consistent with the broad Taupo Volcanic Zone observed trend. Further analysis of the data is required to resolve important structural questions around the Wairakei Geothermal Field including: whether the data supports the model of the Wairakei Geothermal Field being an expression of enhanced permeability due to its location in an inferred rift accommodation zone, how the links between observed structures at the surface and subsurface can be resolved, and what role to these structures play in geothermal fluid flow from depth to surface?