3D Subsurface Modeling of Gumuskoy Geothermal Area, Aydin, Turkey

Abstract

Most of the geothermal systems in Turkey are in Western Anatolia. Geothermal energy power plant (GEPP) capacity in this area is 87 MW, with a further 200 MW of capacity under construction. The Gümü?köy geothermal project is at the westernmost boundary of Büyük Menderes graben (BMG) with an initial capacity of 25 MW. BM Engineering and Construction Inc. started exploration studies for Gümü?köy in 2005. Studies completed so far include: geology, geochemistry, geophysics, and numerous shallow and deep wells. The geothermal system of Gümü?köy can be defined as a hot-water-dominated convective hydrothermal resource with deep circulation of water along fractures in the BMG. Previous studies were carried out with the limited scope of a 2D approach, but they did not provide a better understanding of the study area. A 3D earth model of the Gümü?köy geothermal area was generated to visualize and analyze the subsurface geology and geothermal system using existing information. For this purpose, petrel software was used to prepare lithology, structural geology, geophysics, and thermal models in 3D within the study area. The 3D modeling methodology comprised four stages: data input, structural modeling, property modeling, and uncertainty analysis. In structural modeling, a 3D fault model was generated and a 3D grid system was created. Three-dimensional subsurface geology, magnetotelluric (MT) resistivity, and temperature models were generated using both deterministic and stochastic approaches. Additionally, uncertainty analysis was conducted by applying probabilistic methods. All relevant data was combined to build a fit-for-purpose model, which has been validated by a new well drilled in the area. The 3D subsurface model helped in visualizing and understanding the structural framework, geology, and interactions with the geothermal system. This model will be used as the basis of a 3D numerical dynamic flow model of the existing reservoir.