Predicting the True Reserve of a Steeply Dipping Deposit in a Multi-Deviation Angle Exploration Operation

Abstract

Borehole deviation is the most precise method of delineating ore bodies in hard rock exploration. In order to achieve a precise delineation and consequently a reliable reserve estimate, borehole trajectories should ideally intercept the ore bodies at 90°. However, because of rock mechanical properties and imperfectness in orientation of borehole trajectories and other factors, borehole trajectories hardly intercept the ore bodies at 90°. Consequently, the ore reserve estimated from borehole data are liable to differ from true values. This in-turn affects the value of the mineral projects and the entire investment profile. In this paper, we have studied the impact of borehole deviation on ore reserve for a range of deviation angles from 10°, 15°, 20°, 25°, 30°; using geometrical modelling. Most importantly, we have been able to develop a mathematical model relating the true reserve to the false reserve through coefficient of variation of the false reserves from their true values. This coefficient has been estimated for various ranges of deviation angles. We have also shown that this coefficient of variation depends on the angle of deviation only and not on ore body thickness or reserve. Consequently, they can be applied to estimate the true reserve from the false reserve for any deposit once the angles of deviation are known.

Publication Info:

Author: Nwosu, J.I. and Egesi, N.

Volume: 57

Issue: September

Published By: Journal of Mining and Geology, 2024-09-01