Energy Return on Energy Invested for Tight Gas Wells in the Appalachian Basin, United States of America

Abstract

Abstract:The energy cost of drilling a natural gas well has never been publicly addressed in terms of the actual fuels and energy required to generate the physical materials consumed in construction. Part of the reason for this is that drilling practices are typically regarded as proprietary; hence the required information is difficult to obtain. We propose that conventional tight gas wells that have marginal production characteristics provide a baseline for energy return on energy invested (EROI) analyses. To develop an understanding of baseline energy requirements for natural gas extraction, we examined production from a mature shallow gas field composed of vertical wells in Pennsylvania and materials used in the drilling and completion of individual wells. The data were derived from state maintained databases and reports, personal experience as a production geologist, personal interviews with industry representatives, and literature sources. We examined only the "upstream" energy cost of providing gas and provide a minimal estimate of energy cost because of uncertainty about some inputs. Of the materials examined, steel and diesel fuel accounted for more than two-thirds of the energy cost for well construction. Average energy cost per foot for a tight gas well in Indiana County is 0.59 GJ per foot. Available production data for this natural gas play was used to calculate energy return on energy invested ratios (EROI) between 67:1 and 120:1, which depends mostly on the amount of materials consumed, drilling time, and highly variable production. Accounting for such OPEN ACCESSSustainability 2011, 3 1987 inputs as chemicals used in well treatment, materials used to construct drill bits and drill pipe, post-gathering pipeline construction, and well completion maintenance would decrease EROI by an unknown amount. This study provides energy constraints at the single-well scale for the energy requirements for drilling in geologically simple systems. The energy and monetary costs of wells from Indiana County, Pennsylvania are useful for constructing an EROI model of United States natural gas production, which suggests a peak in the EROI of gas production, has already occurred twice in the past century.

A Preliminary Energy Return on Investment Analysis of Natural Gas from the Marcellus Shale

“…Conversely, the NEER is a more useful measure of the contribution of an energy source to the energy supply of society because it counts only the inputs that must be produced and delivered externally through the existing energy supply system. The NEER form used herein is consistent with a recent study by Sell and colleagues (). These authors provide the relationship, as shown in equation , where P is production, s is shrinkage, and the (S + C + p + D) denominator represents steel, cement, proppant, and diesel fuel, which, they say, represent the chief energy inputs of the extraction effort.…”

“…However, some gas plays have a higher EROI; vertical tight gas wells in the Appalachian basin in Pennsylvania, which are typically hydraulically fractured, have been found to have an EROI in the range of 67:1 to 120:1 (Sell et al ). (A “play” is a known or postulated gas or oil accumulation sharing similar geologic, geographic, and temporal properties.)…”

Analysis of Point-of-Use Energy Return on Investment and Net Energy Yields from China’s Conventional Fossil Fuels

“…It has obviously made a tremendous contribution to China's oil industry and has maintained a long-term stable yield. Compare EROI POU of China's conventional fossil fuels with EROI of unconventional fossil fuels [34][35][36][37][38][39][40][41] from another country, it can be seen that the EROI for China's conventional fossil fuels is lower than the EROI of unconventional fossil fuels based on current literature. Figure 6 also shows the EROI of U.S. shale oil & gas and China's conventional oil & gas.…”

Coal-based synthetic natural gas vs. imported natural gas in China: a net energy perspective

“…Almost all these analyses have shown that the EROI for oil and gas is high but is decreasing. Other papers have focused on other energy resources, such as coal (Cleveland et al, 1984;Hu et al, 2013), shale gas (Aucott and Melillo, 2013;Yaritani and Matsushima, 2014), tight gas (Sell et al, 2011), oil shale (Brandt, 2008(Brandt, , 2009Cleveland and O'Connor, 2011), hydropower (Weißbach et al, 2013;Atlason and Unnthorsson, 2014b), wind (Brown and Ulgiati, 2002;Wagner and Pick, 2004), bio-fuels (Atlason and Unnthorsson, 2014b;Weißbach et al, 2013), wind (Brown and Ulgiati, 2002;Wagner and Pick, 2004), bio-fuels (Agostinho and Ortega, 2013;Aitken et al, 2014), and solar (Dale and Benson, 2013;Kubiszewski et al, 2009;Raugei et al, 2012). However, the peer-reviewed literature has paid only minimal attention to the EROIs of SNG (EROI SNG ) and ING (EROI ING ).…”