The open pit at the Lihir Gold Mine, Papua New Guinea, is planned ultimately to reach more than 200 m below sea level. Cooling and depressurization of the geothermal resource associated with the gold mineralisation is an essential part of the mining operation. This paper deals with the development of a numerical model of the resource capable of representing reservoir processes associated with shallow dewatering, geothermal development and providing sufficient detail for pit-wall stability calculations. Use was made of iTOUGH2 [Finsterle, 1999. iTOUGH2 User's Guide, Report LBNL-40040] running on a cluster of LINUX workstations to aid the fitting of some model parameters. Use of this program in a parallel computational environment was essential to complete the parameter fitting in an acceptable time. A detailed model containing almost 90,000 elements has been developed as an aid to pit-wall stability calculations and this has been run on a Cray and a LINUX cluster using a multiprocessor version of TOUGH2 recently developed at LBNL [Zhang et al., 2001. Parallel computing technique for large-scale reservoir simulation of multi-component and multiple fluid flow]. (C) 2004 CNR. Published by Elsevier Ltd. All rights reserved.