Date of Award

January 2025

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geological Engineering

First Advisor

Dongmei Wang

Abstract

This study investigates the potential to enhance geothermal sweep efficiency in the fractured, low-permeability Deadwood Formation using a cellulose-based biopolymer and gel treatment. A geological model was developed using well log and structural data from four wells in the Williston Basin and subsequently upscaled into a numerical reservoir simulation in CMG/STARS. Laboratory core-flooding experiments on Deadwood samples were used to calibrate gel behavior under high-temperature (160 °C) and high-salinity (17% TDS) reservoir conditions.Simulation results indicate that a short-duration gel treatment—equivalent to 0.03 pore volumes over one year—can significantly reduce channeling through high-conductivity fractures. The reduction in channeling improves thermal conformance and extends the heat retention capacity of the reservoir. Unlike water injection alone, gel-treated scenarios increased heat recovery by approximately 20%, with lower thermal breakthroughs and improved temperature stability, particularly at 2–5 GPM injection rates. Two horizontal well patterns were evaluated, both yielding favorable economics. The best pattern achieved a Net Present Value (NPV) of over $190 million and a Levelized Cost of Electricity (LCOE) below $16/MWh, indicating strong commercial viability. This work presents one of the first demonstrations of conformance control using biopolymer gels in unconventional geothermal systems. The results support targeted gel treatments as an effective strategy for improving sweep efficiency and economic returns in fractured geothermal reservoirs, particularly those transitioning from hydrocarbon production to renewable heat extraction.

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