Department of Engineering Science


Geothermal, reservoir engineering and environmental fluids

Focusing on research, teaching and consulting activities related to geothermal energy, particularly on the numerical simulation of geothermal reservoirs.

A major focus of this group is carrying out research, teaching and consulting activities related to geothermal energy, with a particular focus on the numerical simulation of geothermal reservoirs.

The group is also active in research in petroleum reservoir engineering, coal bed methane extraction and carbon sequestration.

The environmental fluid research activities include computer modelling of tidal flows and the dispersal of pollutants in rivers and estuaries.

Research areas
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Wairakei geothermal field model

Geothermal modelling

  • Simulation of the Wairakei-Tauhara, Mokai, Ohaaki and Ngawha reservoirs.
  • Modeling of supercritical gethermal flows.
  • MCMC methods for model calibration.
  • Large-scale geothermal convection.
  • Subsidence in geothermal fields.

Geothermal engineering

  • Two-phase flow in geothermal pipelines.
  • Two-phase orifice plates.
  • Power station design and optimisation.
  • Automated analysis of geothermal well tests.
  • Direct use of geothermal energy.

Environmental fluids modelling

  • Tidal flow modelling.
  • Simulation of pollutant dispersal in rivers, estuaries and coastal environments.
  • Simulation of fish egg/larvae dispersal.

Petroleum reservoir engineering

Coal bed methane (CBM) production

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People

Academic staff

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Professor Rosalind Archer
Petroleum reservoir engineering; environmental fluid mechanics; geothermal energy, wind energy

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Dr John O'Sullivan
Computational fluid dynamics; modelling geothermal systems including inverse modelling and uncertainty quantification; turbulence modelling; modelling wind flow

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Dr Adrian Croucher
Geothermal reservoir modelling; rivers, estuaries and coastal environments (hydrodynamic and contaminant transport modelling; simulation of egg/ larvae dispersal)
 

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Professor Mike O'Sullivan
Computer modelling of geothermal fields; environmental fluid dynamics; computational fluids dynamics

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Dr Sadiq Zarrouk
Geothermal engineering (two flow, scaling, power production & direct use); reservoir engineering (geothermal & coalbed methane); modelling reacting flows in porous and fractured media

 

Professional staff

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Dr Eylem Kaya
Geothermal energy; geothermal reservoir engineering (reservoir simulation, inverse modelling, reinjection strategies); petroleum and natural gas engineering (reservoir engineering, well tests, fluid/rock properties)

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Angus Yeh
Geothermal reservoir modelling; subsidence modelling in geothermal fields; reservoir engineering.

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Postgraduate students

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Hafeza Abu Bakar
Proposed PhD thesis title: Reservoir characterisation and computer Simulation of Wastewater reinjection with reference to coal bed methane (CBM).

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Jem Austria
PhD thesis title: Dual porosity numerical models of geothermal reservoirs.

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Emily Clearwater
Interaction between the deep and shallow zones in geothermal systems.

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Jongchan Kim
Proposed PhD thesis title: THM geothermal modeling to predict potential man-made disasters in geothermal field.

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Ariel Vidal
Proposed PhD thesis title: Geostatistical models in well testing analysis for geothermal reservoirs, a data uncertainty approach.

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Charlie Zhang
PhD thesis title: Enhanced coalbed methane (ECBM) recovery using gas injection.

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Recent publications

The following are references to publications, sorted by year and author.

Croucher, A and O'Sullivan, M (2008)
Application of the computer code TOUGH2 to the simulation of supercritical conditions in geothermal systems
Geothermics, 37:622-634.

Abstract

At the high pressures and temperatures found in deep geothermal systems, supercritical conditions can occur. Current numerical geothermal simulators are either not capable of modelling these conditions, or can do so only at significantly reduced computation speed. This paper describes modifications to the TOUGH2 simulator to extend its applicability. It employs the updated IAPWS-97 thermodynamic formulation, and uses density and temperature as primary thermodynamic variables under supercritical conditions. Results from test problems are in agreement with results produced by other simulators, giving confidence that the simulator can be used for modelling deep geothermal reservoirs.

Zarrouk, S (2008)
Reacting Flows in Porous Media: Complex Multi-Phase, Multi-Component Simulation
VDM Verlag Dr. Müller . (ISBN: ISBN-10: 3639099850 ).

Abstract

Modelling of multi-component, multi-phase reacting flows in porous and fractured media is investigated with examples on spontaneous combustion of coal and the extraction of coalbed methane. Chemical reactions, adsorption, gaseous diffusion and changes in transport properties (porosity and permeability) are of particular importance. These matters along with numerical dispersion and stiffness are discussed in the first four chapters. A new power law model for representing the diminishing reaction effect during self-heating reactions was proposed, and compared with existing models. A modified version of the TOUGH2 simulator is used for modelling the adiabatic method for testing the reactivity of coal samples. The results agrees well with experimental measurements for coal samples from different mines in New Zealand and Australia. Moisture effect on the reaction rate was then introduced to TOUGH2 using a new two-phase equation of state (EOS) module. Finally the production of methane from low rank coalbeds was investigated. A new and versatile coalbed methane simulator was developed.

Zarrouk, S, O'Sullivan, M, Croucher, A, and Mannington, W (2007)
Numerical modelling of production from the Poihipi dry steam zone: Wairakei geothermal system, New Zealand
Geothermics, 36:289-303.

Abstract

The Poihipi power station utilizes dry steam from a shallow zone near the margin of the Wairakei geothermal reservoir. The station has been in operation for several years, with daily variations in the fluid production rate following variations in time-of-day pricing of electricity. The corresponding varying pressure history provides a good database for testing models of the geothermal reservoir.

Three different types of model were calibrated, namely, uniform porous medium, dual-porosity, fractured medium, and fractional dimension. The best match to the pressure data was achieved with the fractional dimension model.

Croucher, A and O'Sullivan, M (2005)
Source terms in Eulerian-Lagrangian contaminant transport simulation International Journal for Numerical Methods in Engineering, 62:682-699.

Abstract

Standard Eulerian treatment of source terms in Eulerian-Lagrangian numerical simulations results in poor performance at higher Courant numbers. To regain the customary high accuracy of Eulerian-Lagrangian methods under these conditions, a Lagrangian treatment of source terms is needed. It is also important to include the effects of fluid sources as well as contaminant sources. A new Lagrangian source formulation is presented, which has been implemented in a finite element simulator for contaminant transport in rivers and estuaries. Test problems demonstrate the high accuracy of the technique under a range of conditions, and its applicability to general multi-dimensional problems and unstructured grids.

O'Sullivan, M, Croucher, A, Anderson, E, Kikuchi, T, and Nakagome, O (2005)
An Automated Well Test Analysis System (AWTAS)
Geothermics, 34:3-25.

Abstract

Traditional methods of well-test analysis are of limited applicability to well-tests carried out in geothermal reservoirs. An automatic well-test analysis system (AWTAS) has been constructed that is based on fast numerical models, rather than the analytical (or semi-analytical) models used in traditional analysis. This approach makes it possible to simulate complex non-isothermal situations, including phase changes. It also allows the use of a broader range of model types. Examples are given which demonstrate the ability of the software to analyse geothermal well tests.

Croucher, A, O'Sullivan, M, Kikuchi, T, and Yasuda, Y (2004)
Eulerian-Lagrangian tracer simulation with TOUGH2
Geothermics, 33:503-520.

Abstract

Tracer simulations carried out using the TOUGH2 reservoir simulator are prone to numerical dispersion. This paper describes the development of a separate Lagrange–Galerkin finite-element tracer simulator, used in conjunction with TOUGH2, that introduces minimal numerical dispersion.

This approach raises the problem of converting the TOUGH2 flow fields to finite-element format. A new method is presented for carrying out this conversion using a quadratic minimisation technique.

Details are given of an initial implementation of the Lagrange–Galerkin method in a tracer simulator, together with example test results to demonstrate its low numerical dispersion.

Croucher, A and O'Sullivan, M (1998)
Numerical methods for contaminant transport in rivers and estuaries
Computers and Fluids, 27(8):861-878.

Abstract

A review is carried out of the wide range of numerical methods available for modelling contaminant transport in rivers and estuaries. Theoretical considerations indicate that Eulerian-Lagrangian methods (ELMs), particularly the Lagrange-Galerkin method, show the most promise for these problems. Such a method is implemented in a contaminant transport simulator flexible enough for modelling realistic problems. Test problems demonstrate the high performance of the simulator in comparison with other methods.

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Geothermal computing tools

Simulations are run on several geothermal packages developed at Lawrence Berkeley Laboratories and at The University of Auckland.

The main package used is AUTOUGH2, which is based on TOUGH2, developed by Karsten Pruess at Lawrence Berkeley Laboratories. Visualisation of the results are handled by the locally developed MULGRAPH package, as well as the open-source Paraview package. Mesh generation is performed using the locally developed MULGEOM.

We also use the package AUITOUGH2 which is based on ITOUGH2 developed by Stefan Finsterle at Lawrence Berkeley Laboratory. ITOUGH2 performs inverse modelling, or parameter optimisation by running a series of TOUGH2 models.

AUTOUGH2
AUTOUGH2 is a a modification of the TOUGH2 (Transport Of Unsaturated Groundwater and Heat) simulator developed at Lawrence Berkeley Laboratories. AUTOUGH2 contains some enhanced features for modelling geothermal reservoirs.

AUITOUGH2
AUITOUGH2 is an inverse modelling package for the AUTOUGH2 simulator, in the same way that ITOUGH2 carries out inverse modelling on TOUGH2 models. It is used to estimate the values of unknown parameters of AUTOUGH2 models, by matching model results with field observations using non-linear optimisation.

MULGEOM
MULGEOM is a graphical pre-processor for the AUTOUGH2 package. It is used for preparing AUTOUGH2 model grids.

Like MULgraph, MULGEOM was originally written for a different platform and later ported to MS Windows, so its user interface is non-standard.

MULgraph
MULgraph is a graphical interface for viewing the results of TOUGH2 and AUTOUGH2 models. It also has tools for creating AUTOUGH2 data files.

MULgraph was originally written in the late 1980s for the DEC VAX, and was subsequently ported to MS Windows. As a result, the interface is somewhat unfamiliar and not as user-friendly as a native application.

More recently, we have also started to use the Paraview open-source 3D visualisation package for visualising AUTOUGH2 models and results.

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Teaching

Postgraduate Certificate in Geothermal Energy Technology (PGCertGeothermTech )

The PGCertGeothermTech is a one semester course (60 points) aimed at training engineering and science graduates for work in the geothermal industry, and includes two (week long) field trips to the Taupo volcanic zone.

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