Physical and Mechanical Properties of the Rotokawa Andesite from Production||wells RK 27_L2, RK 28 and RK 30

Abstract

Mighty River Power’s geothermal production wells of RK 27_L2, RK 28 and RK 30 were spot cored within the Rotokawa Andesite during the drilling of the wells. Core recovery was nearly 100% from the three cores and these were analyzed and logged by GNS Science at Wairakei Research Centre. Subsequently, the cores were transferred to the University of Canterbury to determine alteration mineralogy and physical properties, and were subjected to rigorous mechanical testing to determine strength and stiffness properties. The Rotokawa Andesite ranges from mildly altered andesite lavas and breccias to a complete replacement by alteration products where host fabric can no longer be easily identified. Density, porosity, and acoustic velocity measurement were measured and samples were subjected to strength testing including uniaxial compressive strength and Brazilian tensile strength. Results are presented here with preliminary correlations between results of mechanical strength testing to physical parameters.