Geothermal Institute


Modelling of the Lihir System, Papua New Guinea


Newcrest Mining Ltd

Objective

The objective of the Lihir geothermal reservoir modelling project is to develop a tool capable of answering an evolving set of questions regarding the management and operation of both the mine and the geothermal energy resource.

In late 2014 a new phase of the project began targeted at converting the latest version of the model (Model V3) into a dual porosity model (Model V4). The immediate objective was to obtain more accurate predictions about the impact of a number of different reinjection scenarios. However the conversion to a dual porosity model was also in line with the overall model development plan.

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Model superimposed on a map of Lihir Island
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Deliverables

The model results will reduce the risk of implementing a reinjection strategy by providing more accurate estimates of the increased production and highlighting any potential negative impacts prior to implementation. The timeline for the proposed work is structured so that the results can be used by the Newcrest geothermal team to make decisions about how to implement the best reinjection strategy for increasing production at the start of 2015.

Detailed calibration of the shallow zone and the deep zones where there is currently no production was outside the scope of this phase of the project. However as the results show the calibration carried out in this phase of the project have resulted in a better match to the overall behaviour of the Lihir system which has also improved the matches to shallow field data.
While the changes implemented in this version of the model significantly improve upon the previous model there are several areas that still require work. The most important requirement is to update the field data and re-calibrate the model, particularly in the shallow mining zone. Other recommended work includes further refinement of the model grid, better representation of complex well behaviour and including the effects of salinity and NCG content. A systematic investigation of model uncertainty would also be very valuable. More accurate models will provide more information about the behaviour of the system and in particular provide insight into how best to manage production to protect the most productive and therefore most valuable wells. They also will more accurately capture the system behaviour that controls the shallow temperatures and pressures that affect mining operations.

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Typography and bathymetry fitted to the model grid
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