An Injection Study Of The Copahue Geothermal Field In Argentina
Engineering Honours Degree, 2011
University of Adelaide
The objective of this project was to develop an injection strategy enabling sustainable long-term production from upper section of the vapour-dominated, geothermal reservoir in Copahue, Argentina, with the aim of determining the optimal operating conditions. To achieve this, the project was broken down into several major components, consisting of research, data review and evaluation, and lastly, model construction and simulation.
A detailed literature review was performed, encompassing the current energy breakdown of Argentina and its utilization of geothermal energy. A history of geothermal energy, a summary of the operation of geothermal power plants, and the need for geothermal and other renewable was also included. Lastly, a review of the findings from other analogous fields provided a detailed compilation of problems which are likely to arise in geothermal, and more specifically, vapour-dominated reservoirs; as well as numerous flawed management strategies which are best avoided, if possible.
The review and evaluation of the available data on the project area provided by Earth Heat yielded the complication of lack of quality data, which was the limiting factor for this project. The available data consisted of a description of the energy situation in Argentina, a detailed description of the project area, an assessment of the geothermal resource, a preliminary design of the proposed power plant, substation and transmission lines, and an environment and sustainability assessment. Despite a large amount of data being available, the majority of the data was qualitative and unclear, significantly limiting its usefulness. Several important conclusions were drawn from this data. Firstly, that the area of interest had, even from the most conservative estimates, significant heat reserves, and secondly, the reservoir had proven to be commercially producible from the last two wells and that this project would form a valuable part of the detailed feasibility study on the reservoir for the construction and operation of a 15 MW geothermal power plant.
The final component of the project was to build a 3D model of the reservoir in the specialized geothermal software, TOUGH2. This required extensive specialized training in Auckland, New Zealand. In order to build this model, it required the amalgamation of the findings of both the literature research and evaluation of available data discussed previously. It became apparent at this stage how limiting the data was, with much being assumed to be typical values from analogous reservoirs or significantly extrapolated, meaning that the accuracy of the results and any strategies and predictions drawn from them are likely to be poor.
It was concluded from running the various production and injection simulations of the reservoir model that injection is preferable higher in the reservoir’s structure as this results in the maintenance of higher enthalpies over the production life, with a higher injection rate for the long term maintenance of both pressure and production rate of the reservoir. However, the injection temperature has a negligible impact on the reservoir and that the optimal production rate for the COP-5 well is 25 kg/s whilst the optimal production rate is 10 kg/s for COP-4.