Exploration Technique: Conceptual Model
|Exploration Technique Information|
|Exploration Group:||Data and Modeling Techniques|
|Exploration Sub Group:||Modeling Techniques|
|Parent Exploration Technique:||Modeling Techniques|
|Information Provided by Technique|
|Lithology:||Rock types, rock chemistry, stratigraphic layer organization|
|Stratigraphic/Structural:||Location and shape of permeable and non-permeable structures, faults, fracture patterns|
|Hydrological:||Hydrothermal fluid flow characteristics, up-flow patterns|
|Thermal:||Temperature and pressure extrapolation throughout reservoir, heat source characteristics|
AIn geothermal exploration a conceptual model is a geologic representation of the subsurface to help visualize the characteristics of the geothermal reservoir. A conceptual model of a geothermal reservoir is an integration of data sets across many disciplines to develop a physical model. Information from field observations, geophysical surveys, geochemical sampling, drilling efforts, and temperature and pressure data are combined to generate an overall picture of the processes and conditions within the reservoir. An ideal conceptual model will show the heat source for the reservoir, the size and shape of the reservoir, the locations of recharges zones, general flow patterns, the main flow channels, permeable and impermeable structures, temperature and pressure conditions, and two-phase and steam dominated zones within the reservoir.  Not all conceptual models will incorporate all of the data listed but as more information is learned and added to the model it will become more comprehensive and useful.
A well-constrained conceptual model can help guide decisions when designing an exploration plan and aid in interpreting the results of the collected data. A good conceptual model is very important for selecting locations and targets for drilling. Most conceptual models of geothermal reservoirs are represented as cross sectional views or plane view maps. The cross sectional view is most useful for interpreting how the buoyant flow of geothermal fluids will interact with the permeable formations in the geothermal reservoir. Conceptual models are an important basis for geothermal resource assessment and are ultimately the basis for developing an exploration plan. Conceptual models provide a unified picture of the nature of a geothermal system and play a key role from the beginning of exploration until after development and utilization of a geothermal resource.
Conceptual models come in many forms from very simplified 2D drawing to more complex 3D interpretations.
A conceptual model should integrate data from surface mapping, subsurface data, remote sensing data, geophysical surveys, chemical and isotopic analysis of fluid from surface manifestations and samples from wells, temperature and pressure data, and any other relevant data collected.
To develop an effective geothermal conceptual model, it is important to integrate all gathered information (e.g., geochemistry, geophysics, hydrological, structural, and petrological) into a consistent model to answer questions like: Does a reservoir exist? If it exists, how big is it? Is the reservoir sufficiently permeable? What are the controls on permeability? What is the probability of development and expected value? What is the lowest cost drilling strategy to discover, prove, and develop the resource? A fully developed conceptual model will illustrate reservoir fluid and rock properties that affect production performance, such as temperature, permeability, volume, pressure, porosity, and chemistry. Conceptual models should be revised continuously during exploration, development, and utilization to improve and keep the model up to date with the most current information.
When only one conceptual model is developed, there is sometimes a tendency to interpret data to fit that model. Therefore, it is important to develop multiple possible conceptual models that are consistent with all data, so that, as additional data are collected, the model(s) can be adjusted based on the new information. The exploration plan may still target the elements of the most likely model, but probabilities should be estimated for all models to consider the risks being taken for each.
- Gudni Axelsson. 2013. Conceptual Models of Geothermal Systems – Introduction. In: Short Course V on Conceptual Modelling of Geothermal Systems. United Nations University Geothermal Training Programme; 2013/02/24; Santa Tecla, El Salvador. Reykjavik, Iceland: United Nations University; p. N/A
- William Cumming. 2009. Geothermal Resource Conceptual Models Using Surface Exploration Data. In: Thirty-Fourth Workshop on Geothermal Reservoir Engineering; 2009/02/09; Stanford, California. Stanford, California: Thirty-Fourth Workshop on Geothermal Reservoir Engineering; p. N/A
- Gudmundur S. Bodvarsson,Karsten Pruess. 1983. A Summary of Modeling Studies of the Krafla Geothermal Field, Iceland. Geothermal Resources Council Transactions. 7:391-396.
- Mortensen A.K.,Gudmundsson Á.,Steingrímsson B.,Sigmundsson F.,Axelsson G.,Ármannsson H.,Björnsson H.,Ágústsson K.,Saemundsson K.,Ólafsson M.,Karlsdóttir R.,Halldórsdóttir S.,Hauksson T. (Iceland GeoSurvey). 2009. The Krafla Geothermal System. A Review of Geothermal Research and Revision of the Conceptual Model. Reykjavik, Iceland: Iceland GeoSurvey. Report No.: ISOR-2009/057.
- William Cumming. 2009. Geothermal resource conceptual models using surface exploration data. In: Thirty-Fourth Workshop on Geothermal Reservoir Engineering; 2009/02/09; Stanford University. Stanford University: Stanford University; p. 6
- Blue Mountain Geothermal Area
- Coso Geothermal Area
- Dixie Valley Geothermal Area
- Fenton Hill HDR Geothermal Area
- Long Valley Caldera Geothermal Area
- North Brawley Geothermal Area
- Raft River Geothermal Area
- Salt Wells Geothermal Area
- Salton Sea Geothermal Area
- Valles Caldera - Redondo Geothermal Area
- Valles Caldera - Sulphur Springs Geothermal Area