Geothermal Gradient Variations in the Buyuk Menderes Graben: Implications for Geothermal Potential of the Graben

Abstract

The Büyük Menderes Graben (BMG) is an E-W oriented active extensional basin within the Menderes Massif, a metamorphic core complex, in Western Anatolia, Turkey. The BMG is a geothermal basin. In total, 1500 (megawatts-energy) MWe of installed geothermal capacity for power production exist as of December 2019 in Western Anatolia, most of which is generated in the BMG (Yamanlar et al., 2020).While the BMG is a vastly producing geothermal resource, Yamanlar et al. (2020) predict that it has higher production potential. Yamanlar et al. (2020) used stochastic modeling to predict geothermal power potential in the BMG. However, the study does not include field-scale geothermal power potential, nor does it include any geothermal gradient maps.This study aims to first quantitatively test the horizontal and vertical geothermal gradients in the Aydın-İncirliova-Osmanbükü 2015/4 Geothermal Field (IGF), then map the information. This study also aims to compare the study area with other geothermal fields in the BMG.To complete this study, information from 13 geothermal wells is utilized. Stratigraphic columns, bottom hole temperatures, and continuous temperature logs from the wells are all used with the software Leapfrog Geothermal to create 3D models of the geology and subsurface temperature distribution. This information is then used to create isothermal contour maps of the field.The geologic modeling suggests that synextensional deposition has occurred within the graben. The temperature modeling suggests that thermal breakthrough may have occurred in the geothermal field. The temperature modeling also suggests that the IGF has a higher geothermal gradient than the Germencik Geothermal Field, a similar field in the BMG.This work may be combined with future work that tests other geothermal fields in the BMG to create a large-scale analysis of the heat flow and temperature distribution throughout the BMG. Therefore, through iterative quantitative modeling of geothermal fields in the BMG, graben-scale heat flow and geothermal gradient maps may be created, and an overall power production potential may be estimated and compared with existing literature.