Benchmarking and Experiments with Waiwera, A New Geothermal Simulator

Abstract

The Geothermal Supermodels project was a four-year New Zealand-based research programme, a major part of which was the development of a new open-source, parallelized geothermal reservoir flow simulator, called Waiwera. This paper describes progress on Waiwera, presents the results of benchmarking tests and discusses experiments carried out on full-scale geothermal reservoir models. Waiwera features modern modular object-oriented code design, parallelized assembly and solution of equations, leverage of established numerical libraries, improved input and output and improved convergence of natural state models. Thermodynamic behaviour has also been improved by implementing more sophisticated algorithms for phase transitions and for non-condensable gas energy of solution. Work has also been done to increase the efficiency of linear equation assembly and also solution, via improved pre-conditioning techniques. The performance of Waiwera has been assessed using a suite of benchmark tests. The results are presented and the benchmark test models are included with the Waiwera installation. Waiwera has also been used to carry out a number of experiments on natural state simulations of full-scale geothermal reservoir models using different equations-of-state. Models of Ngawha (CO2-water) and an air-water system are presented and the findings discussed.