Utilization of abandoned oil well logs and seismic data for modeling and assessing deep geothermal energy resources: A case study

Abstract

Hammam Faraun (HF) geothermal site in Egypt shows potential for addressing energy demand and fossil fuel shortages. This study utilizes abandoned oil well logs, seismic data, and surface geology to assess HF geothermal energy resources. Seismic interpretation identified a significant clysmic fault parallel to Hammam Faraun fault (HFF), named CLB fault. The two faults together create a renewable geothermal cycle through circulation of mixed formation-sea waters. Petrophysics revealed two main geothermal reservoirs: the Nubian sandstone reservoir and the Eocene Thebes carbonate reservoir with water saturation values approaching 100 %. Corrected borehole temperatures indicated reservoir temperatures around 120 °C and 140 °C for the Thebes and Nubian reservoirs, respectively. Fracture analysis and stress state provided insights into subsurface fractures. A geomechanical model demonstrated the impact of different stresses and pore pressure on geothermal fluid flow. NE-SW oriented fractures showed a higher dilation tendency due to aquathermal expansion. The integrated conceptual geothermal model suggested a magma chamber beneath HF as the heat source, related to Oligo-Miocene volcanic activity. The breached relay ramp and fault-related open fracture system serve as pathways for geothermal fluids. Evaluation of the geothermal potential utilized volumetric calculations and Monte Carlo simulation. The estimated hot water volumes were 1.72 km3, 4.242 km3, and 5.332 km3 for the Nubian reservoir in the onshore part, Thebes reservoir in the offshore part, and Nubian reservoir in the offshore part, respectively. The results indicate a medium enthalpy resource suitable for electricity generation using a Kalina geothermal power plant. The predicted geothermal power output is promising, with an average power output of 9.64 MWe, 21.38 MWe, and 43.76 MWe for the Nubian reservoir in the onshore part, Thebes reservoir in the offshore part, and Nubian reservoir in the offshore part, respectively. These outputs can potentially supply electricity to approximately 12,000, 29,000 and 53,000 households, respectively.