Open Pit Dewatering and Depressurisation of the Lihir Gold Mine, Papua New Guinea

Abstract

The open pit at Lihir Gold Mine is planned ultimately to reach more than 200 metres below sea level. Cooling and depressurisation of the geothermal resource associated with the gold mineralisation is an essential part of the mining operation. To investigate geothermal conditions beneath the mine pit, eight deep deviated geothermal wells were completed during 1999. Information from the deep well programme, together with information from the shallower mineral exploration wells drilled and tested in the 1980's has been used to develop a new numerical model which incorporates the development of the mine pit, shallow groundwater, interaction with the sea and the deep geothermal resource. This model has been calibrated using dewatering well information and is now being used to examine geothermal production scenarios required to rapidly depressurise and cool the shallow formations beneath the mine pit.