A Review of Geothermal Resource Estimation Methodology | |||
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| Authors: | Sadiq J. Zarrouk and Florida Simiyu | ||
| Keywords: | Resource Estimation, Recovery Factor, Stored Heat, Reservoir Modeling | ||
| Conference: | New Zealand Geothermal Workshop | Session: | |
| Year: | 2013 | Language: | English |
| Abstract: | The reliability of resource estimation methodology has become increasingly important due to the rapid developments in the geothermal industry. Several resource assessment methods are used at different stages of resource development to estimate resource potential. This work reviews the resource estimation methodology with particular focus on the volumetric (stored heat) method. The most contentious parameter in calculation of stored heat is the recovery factor. There is no agreed upon model in the industry that can be used to estimate this factor; different authors use analogy to existing fields or a preferred range of values. Several existing models were analyzed and a new model was suggested for relating the recovery factor and permeability to the types of geothermal systems based on enthalpy of the system. The reservoir size and temperature distribution have a very significant role in the calculation of the resource potential. Uncertainty in these parameters increases the inaccuracy of the stored heat estimation. Different values for the cut off temperature have been used in different geothermal fields. The value adopted depends on the type of geothermal resource, power conversion technology and the local electricity price. Resource sustainability has an effect on resource life. Many geothermal fields (e.g. Wairakei, Larderello and the Geysers) had constant production capacity long after their economic life of 25-30 years. Reservoir modeling is the most accurate resource estimation method. However, it has limited applicability in green fieldsdue to inadequate information of field parameters. The stored heat method is more suitable for green fields before field production to provide approximations of resource potential. Stored heat calculations was modified to account for the difference between hydrothermal and enhanced geothermal systems behavior by incorporating natural heat input into the reservoir. | ||
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