Medium-Term Production Scheduling of the Lumwana Mining Complex

In this paper, we discuss our development of a life-of-mine production plan for Barrick Gold Corporation’s Lumwana operation, a large copper mining complex based on the Chimiwungo and Malundwe reserves. In our production plan, we maximize recovered copper metal based on a mixed-integer program (MIP) formulation with reserve aggregations that approximate those used in operational mine planning. We discuss the application of a MIP to medium-term planning based on a 60-month production schedule. Constraints on shovel placement, uranium levels in mill feed, stockpiling and mining, and processing capacity ensure that the resulting production schedules and resource allocation are operationally feasible. At Lumwana, our MIP solution strategies optimize the scheduling problem at two levels of time and production-volume granularity. A coarse solution based on annual production from aggregated reserve blocks sets the overall production strategy. This strategy is then imposed on a schedule of monthly production for the scheduling volumes used in actual production planning. This problem was not solvable as a single multiperiod monolith. Instead, we solved a sequence of overlapping multiperiod problems in which each subproblem advances the schedule horizon a given number of periods while fixing the solution to the initial periods of the previous subproblem. We solve multiple options relating to production capacity with a life-of-business optimization system (LOBOS) that we developed.