Novel Approach to Co-Produce Geothermal Energy from Oil and Gas Wells

Abstract

Co-production of thermal energy from producing oil and gas wells has been receiving interest and attention in recent times. For instance, existing assets at moderately high temperatures (~120°C to 150°C) can be worked over to enable extraction of some of the thermal energy in the produced fluids. The extracted thermal energy can be used either directly or to produce electricity, serving to reduce the carbon footprint of existing assets. This work presents some novel ideas for recovery of thermal energy from producing oil and gas assets. A novel Annular Circulation Co-production (ACC) approach to thermal energy extraction, first published by the authors in 2011 (Suryanarayana, et al.), is revisited. In this method, a separate circulation loop within the production tubing by production casing annulus is used to circulate a working fluid. The working fluid extracts heat from the produced fluid in a way analogous to a flow heat exchanger. In this work, we describe a thermos-hydraulic model developed to calculate ACC system performance, and several performance metrics are defined to characterize system performance. The model is used to evaluate the effect of various sensitivity parameters, including circulation direction, divider string insulation, circulation depth, and working fluid flow rate. Finally, a high-level procedure to implement the workover is describe, facilitating modification of some existing oil and gas wells to produce attractive levels of thermal energy, either for direct use or for electricity generation.