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Field Testing of ElectrofracTM Process Elements at ExxonMobil's Colony Mine Colorado School of Mines Colorado Energy Research Institute; 29th Oil Shale Symposium October 19-23, 2009 W. A. Symington, J. S. Burns, A. M. El-Rabaa, G. A. Otten, N. Pokutylowicz, P. M. Spiecker, R. W. Williamson, J. D. Yeakel ExxonMobil Upstream Research Company, Houston, Texas, USA This paper was prepared for presentation at the 29th Oil Shale Symposium, held at the Colorado School of Mines in Golden, Colorado, October 19-23, 2009. ABSTRACT: ExxonMobil's Electrofrac' process is an energy-efficient method for converting oil shale to producible oil and gas. The method heats oil shale in situ by hydraulically fracturing the oil shale and filling the fracture with an electrically conductive material, forming a resistive heating element. The generated shale oil and gas are produced by conventional methods. Because Electrofrac relies on heat conduction from a large planar heat source, it has the potential to provide cost-effective recovery in deep, thick oil shales with less surface disturbance than other proposed methods. Electrofrac laboratory research has included small-scale experiments, numerical modeling, and resource description work addressing critical technical issues. The results of this research have been encouraging. As a result, field tests are currently underway at ExxonMobil's Colony Oil Shale Mine. These tests are aimed at testing Electrofrac process elements at a larger scale. They address Electrofrac construction and low-temperature operation. This paper describes these field tests and their results. 1. INTRODUCTION Electrofrac is an energy efficient method for converting oil shale to producible oil and gas. The concept was first described by Symington, et. al. [1] at the 26th oil Shale Symposium at the Colorado School of Mines. As illustrated in Figure 1, the method heats oil shale in situ by hydraulically fracturing the oil shale and filling the fracture with an electrically conductive material, forming a heating element. The converted shale oil and gas are then produced by conventional methods. Initial laboratory research on Electrofrac focused on critical technical issues for the process. These included: • Identification of a suitable Electrofrac conductant, • Ascertaining whether electrical continuity through a fracture could be maintained while the rock is heated, • Assessing whether oil and gas would be expelled from oil shale heated under in situ stress, and, • Designing a completion strategy for creating fractures that can deliver heat effectively. Laboratory research results on these critical issues were encouraging. They indicated that Electrofrac should deliver heat far more effectively than processes relying on radial wellbore conduction, which was estimated to require twenty times as many wells to accomplish the same heating. Based on these encouraging laboratory results, ExxonMobil has conducted field research to determine the feasibility of constructing an Electrofrac in the field. This field testing has been undertaken at ExxonMobil's Colony Oil Shale Mine in northwest Colorado. The current field program has established unequivocally, that it is possible to pump an electrically continuous hydraulic fracture, to build power connections to such a fracture, and. to operate it as a heating element, at least at low temperature, for a period of several months. The remainder of this paper provides details concerning ExxonMobil's Electrofrac field research that allows us to make these statements. 29th Oil Shale Symposium Page 1 of 13 October 19-23, 2009