214. reuse of abandoned oil and gas wells for geothermal energy production

Department: Structural Engineering
Faculty Advisor(s): Ingrid Tomac

Primary Student
Name: Robert Alexander Caulk
Email: rcaulk@ucsd.edu
Phone: 720-935-9388
Grad Year: 2020

An investigation was performed on the suitability of abandoned wells in California for Enhanced Geothermal Systems (EGS) and low-temperature deep Borehole Heat Exchanger (BHE) applications. The study identified three counties characterized by high numbers of abandoned wells, medium to high crustal heat flows (75-100 mW/m^2), and suitable sedimentary geology: Santa Clara, Monterey, and Santa Barbara. Temperature gradients ranging between 4 and 7.3 degC/100 m access bottom hole temperatures between 40-73 degC for an average 1,000 m deep well. These rock temperatures are sufficient for low-temperature direct use EGS such as district heating, greenhouse heating, and aquaculture. The mitigation of drilling costs and the documented lithology both reduce the risk associated with EGS. However, hydraulic fracturing of loosely to moderately consolidated sedimentary rock in transitional stress regimes remains one limitation to the EGS conversion of these abandoned wells. The feasibility of deep BHE applications within abandoned oil and gas wells was also demonstrated by a mathematical model. Predictions show that outlet fluid temperatures >40 degC can be achieved for 1,000 m deep wells in regions with temperature gradients >7 degC/100 m.

Industry Application Area(s)
Civil/Structural Engineering | Energy/Clean technology

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