With the increase in sustainable energy demand across the globe, there has also been an increase in interest in geothermal energy sources. Industries are increasingly seeking an interest in the exploration of potential geothermal sites for geothermal reserves. However, the geothermal development process itself can be challenging and may involve financial risk.
Precise analysis of the subsurface and surface exploration data helps in minimizing the associated uncertainties regarding geothermal potential. In addition, it also helps in the development phase by facilitating the site selection for geothermal power plants and well locations.
Types of Geothermal Power Plants
Geothermal power plants are set up for exploiting high-temperature geothermal resources (300° F to 700° F) to power the turbines and generate electricity. The same resource can be used in multiple different ways for power generation. The understanding of the type of geothermal power plant is essential in determining the parameters for its site selection. Depending upon the operation type, the geothermal power plants can be:
- Dry steam power plant: A dry steam power plant directly uses the hydrothermal fluid or steam from the geothermal reservoir to operate a generator turbine. This produces electricity without the need to burn any fossil fuels.
- Flash steam or double flash cycle power plant: A flash steam geothermal plant pumps the hydrothermal fluid from the reservoir into a tank under high pressure. During the process, the fluids that rapidly vaporize drives the generator turbine. This is the most common type of geothermal power plant.
- Binary cycle power plant: The binary power plant uses an indirect method of generating energy without allowing reservoir steam to directly operate the turbine. A moderately heated secondary or binary fluid with a lower boiling point than water passes along with the geothermal fluid through a heat exchanger. The binary fluid flash vaporizes due to the heat from the geothermal fluid and operates the generator turbine.
The understanding of power plants operation type allows engineers to locate the site based on location on geoscientific parameters.
Parameters for Geothermal Site Selection
There are many variables involved in the site selection of a geothermal power plant. The geothermal exploration method seeks to reduce this variability with the capture of a wide range of geoscientific data at a local and regional level. Information can be obtained through the analysis of well log data, temperature logs, magnetotelluric data, and gravity or ground deformation studies. This analysis facilitates the characterization of the subsurface environment which can help in determining the physical data such as rock formation, presence of faults and fractures, and rock layer thickness. As fluid mostly flows through fractures, the presence of faults and fractures is a strong indicator for a potential power plant site.
The characterization of surface and subsurface at the local level allows engineers to make a decision on the exact location for well planning and site development. Further, a detailed 3D model developed through the integration of relevant geoscientific data allows well planners and designers to easily locate and design the well path. Depending upon the decision on well location and path, the site should be located nearby for facilitating proper transport of geothermal fluids.
Topographic surface of a geothermal site with surface deformation draped on the surface. Well and gravity station locations also posted on the surface. Data courtesy USDOE Geothermal Data Repository.
CoViz 4D: Visualizing Geographical Data for Geothermal Power Plant Site Selection
CoViz 4D allows integration and visualization of a wide range of geospatial data. The integrated exploration and existing data can be used to develop a 3D geological model that characterizes the surface and reservoir conditions. The model allows engineers to analyze the geophysical properties for determining the optimal well path. The ability to visualize the location of faults and fractures and the geographical slope will allow engineers and geoscientists to make an accurate decision regarding the site selection for geothermal power plants.