Gathering pipeline methane emissions in Fayetteville shale pipelines and scoping guidelines for future pipeline measurement campaigns

Abstract

Zimmerle, DJ, et al. 2017 Gathering pipeline methane emissions in Fayetteville shale pipelines and scoping guidelines for future pipeline measurement campaigns. Elem Sci Anth, 5: 70. DOI: https://doi.org/10.1525/elementa.258 Introduction U.S. dry natural gas production increased from 18 to 27 trillion ft 3 between 2005 (EIA, 2016b. Use of natural gas offers potential climate benefits compared to coal or oil (EIA, 2016a), but those benefits depend upon the emissions of methane, the primary component of natural gas and a potent greenhouse gas. This study is part of a larger study designed to compare, and possibly reconcile, estimates of methane emissions developed from aircraft "top-down" measurements (Schwietzke et al., 2017) and inventory-based "bottom up" estimates, including the results presented here and studies of production facilities , gathering compressor stations , and measurements made by downwind techniques (Robertson et al., 2017;Yacovitch et al., 2017) at a variety of facilities.Gathering pipelines refer to the pipelines that connect wells to gathering compressor stations or processing plants, and connect those facilities to transmission pipelines or distribution systems. Inlet pressures of gathering systems range from 30 to 7,720 kPa (Mitchell et al., 2015), but most gathering pipelines operate at the low end of that pressure range. Gathering pipeline systems consist of pipelines and auxiliary components for operation of the pipelines including pig launchers and receivers, blocking valves, and a variety of other, less common, components (e.g. "knock out bottles" used to remove liquids from pipelines on older systems). Pig launchers/receivers are used to insert/remove cleaning plugs, called "pigs", into gathering lines to remove water and debris from the pipeline. Block valves are used to isolate sections of pipeline, or reroute the flow of natural gas (SM-S1).Gathering pipeline network methane emissions originate from three sources: RESEARCH ARTICLEGathering pipeline methane emissions in Fayetteville shale pipelines and scoping guidelines for future pipeline measurement campaigns Gathering pipelines, which transport gas from well pads to downstream processing, are a sector of the natural gas supply chain for which little measured methane emissions data are available. This study performed leak detection and measurement on 96 km of gathering pipeline and the associated 56 pigging facilities and 39 block valves. The study found one underground leak accounting for 83% (4.0 kg CH 4 /hr) of total measured emissions. Methane emissions for the 4684 km of gathering pipeline in the study area were estimated at 402 kg CH 4 /hr [95 to 1065 kg CH 4 /hr, 95% CI], or 1% [0.2% to 2.6%] of all methane emissions measured during a prior aircraft study of the same area. Emissions estimated by this study fall within the uncertainty range of emissions estimated using emission factors from EPA's 2015 Greenhouse Inventory and study activity estimates. While EPA's current inventory is based upon emission factors from distr...

Temporal variability largely explains top-down/bottom-up difference in methane emission estimates from a natural gas production region

“…The mix of emission sources and their temporal behavior will likely vary substantially among basins, due to differences in facility age, gas composition, production volume, infrastructure, operator practices, and other factors. However, the methods presented here [and in the many supporting papers from this overall study ( 12 , 23 – 28 )] are broadly applicable and, when used together, can lead to improved understanding of emission sources from a production region. Understanding the relative contribution of specific sources, and their time dependency, forms a sound basis for prioritizing emission reduction at the regional level.…”

“…In a significant advance over prior TD–BU comparison studies, measurement and activity data for key sources within the study area were combined with literature data to develop a spatially and temporally resolved BU Monte Carlo ( 29 ) model. The BU model developed herein combines and extends those employed in Bell et al ( 28 ), Vaughn et al ( 26 ), and Zimmerle et al ( 27 ). The BU model also allows a direct comparison with TD AMB estimates of Schwietzke et al ( 12 ) during TD measurement windows on both days of the study period.…”

“…This study addressed the issue of spatiotemporal misalignment, which is present in all prior TD–BU comparisons in O&G basins. Six measurement teams ( 12 , 23 – 28 ) made a combination of coordinated basin-, facility-, and component-level measurements of key sources within the “study area” during a 4-wk field campaign in September–October 2015. The study area spans ∼150 km east–west and ∼65 km north–south and covers the eastern portion of the Fayetteville Shale play in Arkansas, as shown in SI Appendix , Fig.…”

Comparing facility-level methane emission rate estimates at natural gas gathering and boosting stations

“…S1 provides an equipment overview of a typical Fayetteville gathering station measured in this study. Emissions from gathering pipelines outside of the gathering station boundary are not considered in this study, but are addressed in a companion study performed during the same field campaign by Zimmerle et al (2017).…”

Methane source attribution in a U.S. dry gas basin using spatial patterns of ground and airborne ethane and methane measurements

“…The work presented here is part of a larger coordinated intensive study conducted in the Fayetteville Shale dry gas play in north-central Arkansas in September and October 2015 to compare state of the science bottom-up and topdown regional NG CH 4 emission estimates. Emissions quantification at the facility or equipment level is presented by , Conley et al (2017), Robertson et al (2017), Vaughn et al (2017), Yacovitch et al (2017), and Zimmerle et al (2017). An aircraft mass balance estimate of spatially resolved CH 4 emissions from the study area on two consecutive days is described in Schwietzke et al (2017), and a reconciliation between this top-down estimate and a bottom-up CH 4 emissions estimates is provided by Vaughn et al (2018).…”