Energy Intensity and Greenhouse Gas Emissions from Crude Oil Production in the Eagle Ford Region: Input Data and Analysis Methods

Abstract

An exponential increase in horizontal drilling and hydraulic fracturing in shale and “tight” formations in the U.S. since 2007–2008 has resulted in record increases in oil and natural gas (NG) production from seven of the most significant tight oil and shale formations, including the Bakken, Eagle Ford, Haynesville, Marcellus, Niobrara, Permian, and Utica plays. Crude oil and gas production in Eagle Ford has steadily increased since 2010. By the summer of 2015, oil and gas production reached 1.59 million barrels (bbl) per day and 7.14 billion cubic feet, respectively. This study summarizes liquids and gas production in the Eagle Ford Shale in South Texas from 2010 through 2013 and calculates energy consumption and greenhouse gas (GHG) emissions associated with the crude oil and NG extraction using the Oil Production Greenhouse Gas Emissions Estimator (OPGEE) model. OPGEE is an engineering-based life cycle assessment tool for estimating GHG emissions from the production, processing, and transport of crude petroleum. The system boundary of OPGEE extends from initial exploration to the refinery entrance gate. The operational energy consumption and flaring/fugitive emission intensities that are modeled by OPGEE provide the key inputs for the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model developed at Argonne National Laboratory for modeling the life-cycle GHG emissions of crude oil and NG production in the Eagle Ford shale. The Eagle Ford can be characterized by four distinct production zones—the black oil (BO), volatile oil (VO), condensate (C), and gas (Gas) zones—with average monthly gas-to-liquid ratios (million cubic feet /bbl/month/well) that vary from 0.91 in the BO zone to 13.9 in the Gas zone. We found that the recovery energy efficiency, process fuel consumption, flaring and fugitive intensities, and water use showed little variation over time between 2010 and 2013. Wide variations in energy use and production among the thousands of wells were observed. In the BO zone, on an energy basis, about 20% of the NG produced is either flared (12%), emitted (1.5%), or used for self-consumption (5.7%), and 81% is sent to the market as pipeline NG and natural gas liquids (NGL). In comparison, only about 2% of the NG produced in the Gas zone is either flared (0.1%), emitted (0.01%), or used for self-consumption (2.4%), and 98% is sent to the market as pipeline NG and NGL. The proportion of NG sent to the market is about 45–49% as NG and 51–55% as NGL (on an energy basis). Process fuel consumption rate, flaring and fugitive intensities, and water use rate are in general higher in the Gas and C zones than in the BO and VO zones. The total MMBtu of energy (including diesel, NG, and electricity) used for production, extraction, and surface processing per MMBtu energy produced (including liquids, net NG sale, and net NGL sale) ranges from 0.012 MMBtu/MMBtu in the BO zone to 0.024 MMBtu/MMBtu in the Gas zone, with an average of 0.015 MMBtu/MMBtu across all wells. The well-to-wheels GHG emissions of gasoline, diesel and jet fuel derived from crude oil produced in the BO and VO zones in the Eagle Ford play are 89.2, 87.8, and 82.5 gCO2e/MJ, respectively.