Evaluation Of Geothermal Potential Research Articles

Evaluation of geothermal potential in some parts of Bida Basin of Nigeria using Curie point depths and heat flow from spectral analysis of aeromagnetic data.

The Centroid method of Spectral Depth analysis was used to evaluate the Curie point depth (CPD), Geothermal Gradient and Heat Flow in some parts of the Bida Basin of Nigeria with a view to determining the energy potential of the area. The reduced-to-pole aeromagnetic data was divided into 16 overlapping ensembles and Fast Fourier Transformed to decompose the anomalies into their energy and wavenumber components using Oasis montaj software. The radial power spectrum was calculated for each of the grid points with the locations of the centres of the ensembles and a plot of Energy spectrum versus frequency was carried out to generate two different gradients: s<sub>1</sub> and s<sub>2</sub> representing different depth source models. These gradients were used to evaluate the average depth to the top of the deepest crustal block, Z<sub>t</sub>, depth to the centroid of the deepest crustal block, Z<sub>0</sub>, CPD, Geothermal Gradient and Heat flow. From the results obtained, the CPD varied from 2.59 to 8.23 Km while the thermal gradient and heat flow in the area revealed values ranging from 70.45 to 224.15 <sup>o</sup>CKm<sup>-1</sup> and 176.13 to 560.37mWm<sup>-2 </sup>respectively. The results of the contouring in conjunction with the CPD, geothermal gradient and the heat flow values have shown that the area has a greater energy potential in the south-eastern block of Katonkarfi, with shallow CPD and high geothermal gradient and heat flow. These results could be incorporated in the GIS and available geological, geophysical and geochemical information of the area to facilitate selection of the optimum site for energy exploration.

Thermo-Physical and Mechanical Properties of Al Hashimiyya Basaltic Rocks, Jordan

Geothermal exploration in northern Jordan is in juvenile phase. North eastern basaltic desert is expected to host, with other rock formations, a shallow geothermal field. For efficient geothermal potential evaluation, a complete understanding of thermo-physical properties of deep reservoir rocks is of utmost importance. Due to the complex technical thermo-physical evaluations of basalts in depth, surficial basalts extending to the west were evaluated. Accordingly, six basaltic sub-flows from Al Hashimiyya were examined into their thermo-physical and mechanical properties. The flows represent the western extinction of large olivine basalt eruption. Different properties were evaluated for oven dried samples: thermal conductivity, permeability, porosity, density and specific heat capacity. In addition, basalts mechanical properties were examined: compressional wave velocity, unconfined compressive strength, indirect tensile strength and point load tests. The results were correlated in proportional patterns. They indicated that thermal conductivity of the studied basalts is dependent on porosity and permeability in parallel with mineral composition. It’s found that mechanical properties are controlled by porosity and permeability, too. The studied basalt properties exhibit slight deviation from the continental basalts thermo-physical and mechanical properties reported in the region. Thermal conductivity ranges between 1.89 and 1.32 W·m-1·K-1, whereas the porosity and permeability averages at 10.64% and 9.75899E-15 m2, respectively. Additionally, unconfined compressive strength averages at 104.9 Mpa and it’s almost 20 times higher than indirect tensile strength which ranges from 8.73 to 2.21 Mpa. As the samples were tested under laboratory conditions, in situ conditions will not be reflected by such values. At greater depth, temperature, pressure and hydrothermal activities will certainly affect rock properties. Micro fractures, whether it will be filled or not, will affect basalts properties, too. The results of this work will be used to develop a comprehensive thermo-physico-mechanical model, and improve the ability to predict rock properties at greater depths of Jordanian basalts.

Geothermal potential evaluation and development prioritization based on geochemistry of geothermal waters from Kangding area, western Sichuan, China

Kangding geothermal area is located in the western Sichuan, belonging to southeastern margin of Tibetan Plateau. Similar to world-renowned south Tibetan and western Yunnan geothermal belt, western Sichuan has intensive surface thermal manifestations including boiling and hot springs. The emerging temperature of thermal waters ranges from 47 to 79 °C with total dissolved solids lying between 899 and 2550 mg/L. δ2H–δ18O isotopes indicate a meteoric source for the thermal waters and a significant positive oxygen-18 shift in the southern region. It is suggested that southern thermal waters experienced stronger water–rock interaction and are closer to thermodynamic equilibrium, which is also proved by the water type classification. The reservoir temperature calculated by empirical and theoretical chemical thermometry is 180–225 °C for the north and 225–310 °C for the south. Evidences of hydrogeochemistry, stable isotopes, geothermometry and radiocarbon dating indicate that southern region of Kangding area shows greater geothermal potential than the northern region. In addition, based on the hydrogeochemical modeling of mineral saturation, underlying problem of scaling is likely to occur in the study area. According to the results of reservoir temperature, south Kangding sub-district has greater potential in geothermal power generation and development than northern Kangding. Therefore, further exploration and drilling work should give priority to the south Kangding area.

Contour map of the top of the regional geothermal reservoir of Sicily (Italy)

An integrated review of existing geological and geophysical data – partly acquired during oil and gas exploration – combined with new data provided by deep geothermal studies of selected key areas, was used for the 3D modeling and mapping of the top of the geothermal reservoir developed at a regional scale in Sicily (Central Mediterranean). The resulting 1:500,000 scale map covers the area of the whole Sicily (about 25,700 km2) and is devoted to represent the main input for both the thermal modeling and the evaluation of geothermal potential at a regional scale. As the map indicates the distribution at depth of a likely target for geothermal drilling, it can be also used as a rough indicator of expected drilling cost for geothermal projects. Such a map can be seen as a useful planning tool for any geothermal project, and related exploration to be carried out in the Sicily region in the future.

Development of a regional geothermal resource atlas

Increased interest in geothermal energy has led to the need for more sophisticated analyses of available geothermal resources for heating and power production. The evaluation methods have traditionally used 1D models, but progress in computing power allows us now to perform joint interpretations that include large-scale effects of geological, topographical and hydrogeological structures. This paper describes the steps taken in such an integrated assessment. The evaluation of geothermal potential is actually finalized for one of the most populated areas of Switzerland. The methodology accounts for individual utilization scenarios and is based on various temperature data that have been systematically collected over many years. The state-of-the-art compilation involves comprehensive 3D regional geological and thermal models. An excellent data fit with >20 boreholes in northern Switzerland is achieved using the calculation scheme presented here. Zones of significant convective flow are identified and the flow velocity is quantified. In contrast to the results obtained from earlier geothermal resource assessments, the existing geological, hydrogeological and petrophysical data are included in the full 3D numerical evaluation. The results obtained for a regional scale of a well-documented subsurface area in northern Switzerland are displayed in terms of geothermal productivity and energy. The calculations identify the topmost crystalline basement as a most promising structure for geothermal exploitation with predicted maximum doublet productivities of >100 MWt. The annually extractable energy of 13 PJ km−3 easily covers a broad range of Swiss energy needs. The atlas can be further expanded to cover utilization schemes not treated here, such as ground-coupled heat pump systems.

Evaluation of Geothermal Potential, Albuquerque Area, New Mexico: ABSTRACT

The first comprehensive evaluation of the geothermal potential of the Albuquerque, New Mexico, area, recently completed, included gravity and magnetic surveys, electrical resistivity measurements, temperature logging of water wells and of shallow (25 m) temperature-gradient boreholes, and geochemical analysis of local waters. Local seismic history and temperature records from municipal water wells were also analyzed. Geothermal anomalies of the Albuquerque area were delineated if temperature gradients in excess of 35°C/km were detected, as this figure is the average temperature gradient for the Rio Grande rift. Temperature logging of city water wells resulted in the identification of two well fields having anomalously warm water at shallow depth. The Walker well field, on Albuquerque's north side, has 32°C water at a depth of 320 m, representing a gradient of 53°C/km. At the West Mesa well field, on Albuquerque's west side, recent pumping prevented the obtaining of an accurate temperature gradient. However, repeat measurements at selected depths suggest a gradient of approximately 65°C/km. A third site, about 8 km west of Albuquerque, was found to have shallow temperature gradients in excess of 120°C/km. Near this site, magnetic surveys indicated that several igneous bodies are buried beneath 300 m of alluvial sediments. Because no water wells exist at this remote location, shallow boreholes were drilled for temperature logging. The resulting values of temperature gradient show a distinct high of greater than 120°C/km superposed on a background of 60°C/km. End_of_Article - Last_Page 566------------