Date of Award

May 2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Energy Engineering

First Advisor

William D. Gosnold

Abstract

Geothermal energy is a reliable renewable energy source capable of delivering consistent baseload electricity while emitting very low concentrations of greenhouse gases. In very low permeable geothermal reservoir, the geothermal system’s efficiency and economic feasibility are heavily dependent on reservoir productivity, which includes the fluid circulation and heat extraction efficiency. This research assesses the geothermal inlet temperature dynamics, fluid production and techno-economic viability of two reservoir productivity enhancement approaches: Hydraulic Fracturing (Base Case model) and Fishbones stimulation (Proposed Case model) under various operational conditions. The research aims to evaluate the influence of these two approaches on the geothermal inlet temperature, sCO2 and water production rates (mass or volume), and overall project economics. The CMG-STARS numerical approach was utilized to simulate the Red River geothermal reservoir response under original and modified permeability and various injection scenarios. The stimulation models examined changes in the produced fluid temperatures, carbon dioxide and water production rate. The GHEOPHIRES model evaluated essential project economic performance metrics, such as Levelized Cost of Electricity (LCOE) and Net Present Value (NPV), and their influence on project profitability. The results indicate that the Proposed Case method yielded consistent geothermal inlet temperatures within the range of 139–141 °C, indicating numerical stability. Consequently, the Base Case model displayed greater temperature variability at lower injection rates. Carbon dioxide (produced gas rate) production remained predominantly influenced by injection rate under the original permeability conditions, while under very low reservoir permeability, without natural fracture permeability, the Base Case yielded higher gas production, attributed to higher fractured reservoir volume and fracture connectivity. Under the original reservoir conditions, the water production rate of the Proposed Case surpassed that of the Base Case, which was attributed to fluid viscosity, density, high stimulated lateral density, shorter laterals and shorter transit time. The economic evaluation indicated that the project's viability depends heavily on the mass flow rate, with the break-even point estimated at 26 kg/s, above which the project becomes profitable. Higher mass flow rates resulted in lower LCOE and increased NPV.

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