Comparing the Alberta Taciuk Processor and the Shell In Situ Conversion Process - Energy Inputs and Greenhouse Gas Emissions

Abstract

This paper compares the Shell in situ conversion process (ICP) to the Alberta Taciuk Proc- essor (ATP) using metrics of energy efficiency and carbon dioxide emissions. The ICP is an experimental method of retorting oil shale without removing it from the earth. The ICP utilizes electricity to heat the underground shale slowly over a period of 2 years. The generated hydrocarbons are then produced using conventional oil production techniques, leaving the shale oil coke within the formation. This study modeled the energy inputs and outputs, and the greenhouse gas (GHG) emissions from two possible implementations of the ICP, as applied to oil shale of the Green River formation of western Colorado. The Alberta Taciuk Processor (ATP) is an above-ground oil shale retort. The ATP retort re- quires less external fuel input than other above-ground retort designs, because it combusts the coke or "char" deposited on the shale during retorting to provide heat to the retorting process. However, this requires combustion of the spent shale, potentially increasing tem- peratures high enough to induce carbonate decomposition, thus liberating additional CO2 from minerals in the shale. This paper reports modeling of two cases of ATP deployment. Results suggest that primary energy inputs per unit of energy output range from 0.46 to 0.73 megajoules (MJ) per MJ of final fuel delivered for the ICP process and from 0.36 to 0.59 MJ/MJ for the ATP process. For the ICP, upstream greenhouse gas emissions range from 7.7 to 16.6 grams of carbon equivalent per MJ final fuel delivered, whereas emissions from the ATP range from 34 to 42 gCeq/MJ FFD, depending on the ATP operation. These emissions are roughly 10% to 70% higher than those from conventionally produced petro- leum-based fuels on a full fuel cycle basis.