Optimizing Long-Term Production Plans in Underground and Open-Pit Copper Mines

TLDR

Optimizing multiple mines in an integrated fashion is challenging because of the combinatorial nature of the problem. The study introduces a methodology for long‑term mine planning that optimizes several mines in an integrated fashion using a capacitated multicommodity network flow formulation. The approach models underground and open‑pit deposits sharing processing plants over a long horizon, solves a relaxed tight linear formulation, and rounds near‑integer solutions with a customized procedure, enabling scenario studies such as delaying the conversion of Chiquicamata. Implemented at Codelco, the system has been used regularly since 2001, raising the net present value of a single mine’s production plan by 5% and, when integrating multiple mines, by an additional 3%, while enabling planners to evaluate more scenarios.

Abstract

We present a methodology for long-term mine planning based on a general capacitated multicommodity network flow formulation. It considers underground and open-pit ore deposits sharing multiple downstream processing plants over a long horizon. The purpose of the model is to optimize several mines in an integrated fashion, but real size instances are hard to solve due to the combinatorial nature of the problem. We tackle this by solving the relaxation of a tight linear formulation, and we round the resulting near-integer solution with a customized procedure. The model has been implemented at Codelco, the largest copper producer in the world. Since 2001, the system has been used on a regular basis and has increased the net present value of the production plan for a single mine by 5%. Moreover, integrating multiple mines provided an additional increase of 3%. The system has allowed planners to evaluate more scenarios. In particular, the model was used to study the option of delaying by four years the conversion of Chiquicamata, Codelco's largest open-pit mine, to underground operations.