Master of Science (MS), Ohio University, 2021, Geological Sciences (Arts and Sciences)

Past geological, geochemical and geophysical studies by LaGeo have shown the presence of a 12 km2 geothermal reservoir at San Vicente Geothermal Field (SVGF) . This reservoir has an estimated thickness of 600 to 1200 m underneath a 600 to 800 m thick capping rock. All this located under the northern flank of San Vicente volcano. Potential drilling targets for geothermal exploitation are determined through visual geographical correlation of geological, geochemical and geophysical variables. However there are statistical methods such as geographical weighted regression and cluster analysis that allow us to establish statistical correlation between the geochemical and geophysical variables that are related to fluid storage and flow. Carbon dioxide (CO2) diffuse degassing and other gases, and geophysical variables such as resistivity and gravity, are related to high permeability areas, such as faults, and underground fluid movement within a geothermal field. In order to establish more accurate drilling targets for geothermal exploitation, a better and more objective data interpretation can be achieved by establishing the statistical correlation of CO2 diffuse degassing to other geochemical or geophysical variables. We have used Geographically Weighted Regression (GWR) models via computer program GWR4 to determine the statistical correlation between the space dependent geophysical and geochemical variables. Data from San Vicente Geothermal Field in El Salvador was used to determine the spatial correlations between CO2 soil concentration and the concentrations of He, 222Rn, 220Rn, Hg, resistivity and gravity measurements. Bivariate GWR showed statistically significant correlations between CO2 diffuse degassing, He concentration, Hg concentration, 222Rn concentration, 220Rn concentration and Magneto-telluric measurements. He concentration had the greatest statistical weight (푅푝 2 = 0.55, F = 7.21, p < 0.001). Stepwise multivariate GWR was applied and the most stati (open full item for complete abstract)

Committee: Dina Lopez Dr (Advisor); Katherine Fornash Dr (Committee Member); Schenk Xizhen Dr (Committee Member) Subjects: Earth; Energy; Environmental Geology; Geochemistry; Geographic Information Science; Geology; Natural Resource Management; Statistics

Master of Science, The Ohio State University, 2014, Geological Sciences

The overarching objective of this study is to document the water-rock interaction at the Coso geothermal area where the U.S. Department of Energy Enhanced Geothermal Systems (EGS) experiments are conducted to better understand the thermal evolution of this system. This effort quantifies the relationship between mineralogy and the pore/fracture network in order to track the evolution of water-rock interaction as a function of space and time. The relationship among the size, shape and distribution of pores relevant to mineralogy and mineral abundance are used as indicators of how fluids migrate through and react within the micropore environment. This paper summarizes petrologic and geochemical characterizations on well cuttings from three East Flank wells, and one West Flank well, with the focus on one of the East Flank wells, Navy II well 42A-16, to better understand the geologic process of hydrothermal alteration, its evolution, and how changes in mineralogy impacted porosity and permeability. Several alteration types in these well cuttings are observed with the two most important being: NaAlSi3O8 • CaAl2Si2O8 + H4SiO4 + Na + = 2NaAlSi3O8 + Al+3 + Ca+2 + 4OH- (1) (xNa, yCa)AlSi3O8 + K+ + Na+ + Fe+3 + Mg+2 + H2O -> (2) (K, Na)2(Al, Fe, Mg)4Si6O20(OH)4 + (x+mNaAlSi3O8, y-mCaAlSi2O8) +2mCa+2 where albitization of calcic-plagioclase is represented by (1), and sericitization after plagioclase is represented by reaction (2). Collectively these reactions are two of the most significantly occurring over the range of depths in Navy II well 42A-16. This albite-sericite alteration tends to be associated with the potassic alteration, and often occur together especially in quartz diorite and granodiorite host rocks. Secondary albite and sericite formed at the mid-stage of mineral paragenesis in this system. The earliest minerals to form were epidote, titanite, rutile/anatase, and chlorite (perhaps of earlier metamorphic origin); whereas the most recently formed mine (open full item for complete abstract)

Committee: David Cole Prof. (Advisor); Michael Barton Prof. (Committee Member); Ann Cook Prof. (Committee Member) Subjects: Geochemistry

Master of Science (MS), Ohio University, 2008, Geological Sciences (Arts and Sciences)

The Berlin hydrothermal field in El Salvador, Central America is located in the San Simon River Basin on the northwest slope of the Berlin-Tecapa volcanic complex, in the eastern portion of the country. This hydrothermal field is a liquid-dominated system governed by fault structures allowing infiltration and transport of meteoric fluids. Exploitation involves the removal of hot fluids from the geothermal reservoir and re-injection of lower temperature fluids. This study analyzes the surficial hydrology and groundwater storage change (since exploitation) in the hydrothermal reservoir to produce a water budget. Field monitoring of springs, fumarole activity, domestic wells, tributaries to the San Simon River, and meteorologic data provide constraints on the hydrology. A correlation between the composition of the fumarolic gases and the diffuse flux of soil CO2 was performed to complete the balance. An analysis of the increase in chloride concentration with time in the deep aquifer and the net mass withdrawn from this aquifer allow an estimation of the decrease in storage in the hydrothermal aquifer. This water balance will assist future operations in optimization and sustainability of the geothermal reservoir and could be used to evaluate extraction and re-injection procedures.

Committee: Dina L. Lopez Ph.D. (Advisor); Gierlowski-Kordesch Elizabeth (Other); Gregory Nadon (Other) Subjects: Geology