Reykjavík, Iceland
Reykjavík, Iceland

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Gunnarsson G.,OR Reykjavik Energy | Arnaldsson A.,Vatnaskil Consulting Engineers | Oddsdottir A.L.,OR Reykjavik Energy
Transport in Porous Media | Year: 2011

The Hengill Area is an important energy source for Reykjavík and surrounding area, both for electricity and district space heating. Two production fields are located in the area: Nesjavellir and Hellishei{eth}i. Two other potential production fields are believed to be in the area. We present a new conceptual model supported by numerical calculations for the entire Hengill Area. Calculations were performed using the TOUGH2 software suite. The model contains nine layers consisting of 966 elements each (total of 8,964). Geological survey data, down-hole measurements, and production histories from the fields have been used to calibrate the model. The model has been used to predict how production will affect the geothermal fields. Information gathered throughout the production history, such as drawdown and changes in enthalpy, have been used to re-evaluate the size and the production capacity of the production fields. Different production scenarios, such as different energy throughput, have been simulated. The model simulations have also been used to estimate the capacity of potential future production fields. © 2010 Springer Science+Business Media B.V.

Bjornsson G.,Reykjavik Geothermai | Arnaldsson A.,Vatnaskil Consulting Engineers | Akerley J.,Ormat Technologies Inc.
Transactions - Geothermal Resources Council | Year: 2014

The Steamboat project in South-Reno, Nevada, is among the most successful and long standing geothermai power projects in the US. Despite its shallow average well depth and very short distance between production and injection sectors, the reservoir is responding to the twenty-five years of massive flow with a negligible pressure drawdown and moderate cooling rates compared to other geothermai locations worldwide. The greater than 130 Steamboat wells drilled, large volume of downhole and production data, and structural information gathered comprise ideal circumstances for developing a high resolution numerical model. Additionally, advances in inverse modeling technology and rapidly increasing computer power move the task of modeling Steamboat from a forward model nightmare to a complex but rewarding inverse modeling exercise. The 20×40 km mesh area now developed is split into 14 layers of 2.5 km total thickness. About 40 thousand elements provided a sufficiently detailed mesh to capture the field data at hand, and 1270 datasets were calibrated against by the inverse technology. The deep and outer model elements are of less than 5 raD permeability and fracture zones are of several hundred mD while the shallow lower Steamboat permeability is as high as 10 Darcys. The model is heated by a deep 95 kg/s recharge of 236-250°C. A cold recharge occurs from the NW into the shallow model, imitating the hydraulic head of the Sierra mountain range. Around 160 kg/s exit the shallow model to the north as natural discharge into the Truckee Meadows alluvium and to the naturally occurring hot springs. Of this mass flow, two thirds are modeled as from the deep upflow and one third is outer boundary recharge. Systematic analysis of the calibrated model, assisted by splitting the reservoir into sectors and focusing on usable heat (>100 °C), shows that the Lower Steamboat sector has and will continue to sustain a large proportion of the early and current power production, later supplemented by heat and mass from the much hotter and deeper Steamboat Hills wells. As the heat reserve of Lower Steamboat is drained, the model is suggesting more dispersed injection and increased mass production from the Steamboat Hills wells as appropriate resource management strategy. Copyright © (2014) by the Geothermal Resources Council.

Arnaldsson A.,Vatnaskil Consulting Engineers | Berthet J.-C.,Vatnaskil Consulting Engineers | Kjaran S.,Vatnaskil Consulting Engineers | Sigurdsson S.T.,University of Iceland
Computers and Geosciences | Year: 2014

A new numerical scheme for fully tensorial treatment of anisotropic flow within model layers (2D) has been designed and implemented into the TOUGH family of simulators. The new scheme has been rigorously tested against a simple theoretical solution to Darcy's law as well as a more complicated example solved by numerical software packages with anisotropic flow capabilities. In all cases, a good agreement with the new scheme has been found. © 2013 Elsevier Ltd.

Plasencia M.,University of Iceland | Pedersen A.,University of Iceland | Arnaldsson A.,Vatnaskil Consulting Engineers | Berthet J.-C.,Vatnaskil Consulting Engineers | Jonsson H.,University of Iceland
Computers and Geosciences | Year: 2014

The objective function used when determining parameters in models for multiphase flow in porous media can have multiple local minima. The challenge is then to find the global minimum and also to determine the uniqueness of the optimized parameter values. A method for mapping out local minima to search for the global minimum by traversing regions of first order saddle points on the objective function surface is presented. This approach has been implemented with the iTOUGH2 software for estimation of models parameters. The methods applicability is illustrated here with two examples: a test problem mimicking a steady-state Darcy experiment and a simplified model of the Laugarnes geothermal area in Reykjavík, Iceland. A brief comparison with other global optimization techniques, in particular simulated annealing, differential evolution and harmony search algorithms is presented. © 2013 Elsevier Ltd.

Hjartarson A.,Mannvit Engineering | Arnaldsson A.,Vatnaskil Consulting Engineers
Transactions - Geothermal Resources Council | Year: 2010

HS Orka is the largest privately held geothermal company in Iceland. HS Orka is developing four high temperature geothermal fields located on the Reykjanes peninsula SW-Iceland, named Reykjanes, Svartsengi, Eldvorp and Krysuvik, and operating two power plants at Reykjanes (100 MWe and Svartsengi (75 MWe). Expansions are planned that will increase HS Orka's geothermal power production from the current output of 175 MWe by an additional 230 MWe, thus bringing total production capacity to 405 MWe by 2015. In 2009, Magma Energy Corp. acquired 43% stake in HS Orka. Mannvit Engineering prepared an independent technical report on the resources and properties of HS Orka on behalf of Magma as a part of Magma's due diligence exercise. In the independent technical report the geothermal resources and reserves of HS Orka were classified according to the Australian Geothermal Reporting code (2008). The results indicate that HS Orka has sufficient producing reserves and early stage development resources within its current operational and exploration portfolio in order to support its expansion plans of adding an additional 230 MWe to its current operational output of 175 MWe. The geothermal fields of HS Orka contain 175 MWe Proven Reserves and additional Indicated and Inferred Resources of 130 MW e and 500 MWe, respectively. This paper discusses the results of the classifications according to the Australian Geothermal Reporting Code and the methods used to assess the geothermal resources and reserves of HS Orka.

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