Joule Heating of Brine Saturated Berea Sandstone: Observations from DC Electric Current

ABSTRACT High-voltage electrical current can be utilized to increase rock permeability and can be a sustainable alternative to decrease water consumption associated with hydraulic fracturing. During previous applications of this technique, ion carriers, mainly brine water, evaporated as temperature increased during electrical resistive (joule) heating of the reservoir, limiting effectiveness of the technique. Understanding how electrical conductivity evolves as a function of applied electrical current is fundamental for developing methods to overcome previous limitations of the technique. In this study, we developed a first-of-its kind triaxial cell that allows one to apply electrical current, with temperature and pore pressure data collected during the joule heating process of a Berea Sandstone rock specimen. We investigated the relationships between pore fluid composition, pore pressure, and electrical conductivity evolution. The relationships between pore fluid composition, and joule heating evolution under variable electrical energy inputs are important to understand for analyzing the long-term effectiveness of electrical rock fracturing. INTRODUCTION Waterless permeability enhancement techniques including mechanical, gaseous, and electrical based methods have been previously investigated to address the environmental concerns associated with hydraulic fracturing (e.g., Gandossi 2013, Kumar et. al, 2017, Wang et. al, 2016). However, widespread adoption of these techniques has stalled due to limitations in stimulated reservoir volume, and environmental safety concerns associated with the exposure of hazardous gases as a fracturing fluid. Alternatively, electrical resistive heating has proven effective at stimulating petroleum reservoirs to increase production (e.g., Elder et. al, 1957, Rehman and Meribout, 2012). Waterless permeability enhancement techniques including mechanical, gaseous, and electrical based methods have been previously investigated to address the environmental concerns associated with hydraulic fracturing (e.g., Gandossi 2013, Kumar et. al, 2017, Wang et. al, 2016). However, widespread adoption of these techniques has stalled due to limitations in stimulated reservoir volume, and environmental safety concerns associated with the exposure of hazardous gases as a fracturing fluid. Alternatively, electrical resistive heating has proven effective at stimulating petroleum reservoirs to increase production (e.g., Elder et. al, 1957, Rehman and Meribout, 2012).