Measurements of methane emissions from natural gas gathering facilities and processing plants: measurement methods

J R Roscioli,R Subramanian,D Zimmerle,S C Herndon,T I Yacovitch,A L Robinson,D M Martinez,T L Vaughn,D S Tkacik,A L Mitchell,L Williams,C Floerchinger,A J Marchese

doi:10.5194/amt-8-2017-2015

Abstract

Abstract. Increased natural gas production in recent years has spurred intense interest in methane (CH4) emissions associated with its production, gathering, processing, transmission, and distribution. Gathering and processing facilities (G&amp;P facilities) are unique in that the wide range of gas sources (shale, coal-bed, tight gas, conventional, etc.) results in a wide range of gas compositions, which in turn requires an array of technologies to prepare the gas for pipeline transmission and distribution. We present an overview and detailed description of the measurement method and analysis approach used during a 20-week field campaign studying CH4 emissions from the natural gas G&amp;P facilities between October 2013 and April 2014. Dual-tracer flux measurements and on-site observations were used to address the magnitude and origins of CH4 emissions from these facilities. The use of a second tracer as an internal standard revealed plume-specific uncertainties in the measured emission rates of 20–47%, depending upon plume classification. Combining downwind methane, ethane (C2H6), carbon monoxide (CO), carbon dioxide (CO2), and tracer gas measurements with on-site tracer gas release allows for quantification of facility emissions and in some cases a more detailed picture of source locations.

Highlights

The natural gas industry has undergone a transformation in recent years, largely due to technological advancements such as hydraulic fracturing and horizontal drilling
These facilities typically include equipment such as inlet separators to remove liquid phase water and condensate (C5+), when present, and systems for pipeline maintenance activities (e.g., “pigging”). Compression at these facilities is accomplished by a series of 1 to 20 individual compressors powered by electric motors, reciprocating engines, or gas turbines with total engine powers ranging from 500 to 25 000 HP depending on the inlet gas pressure and total gas throughput (Mitchell et al, 2015)
In the case of wet compressor seals, it should be noted that the primary emission route is due to absorption of methane into the seal fluid at high pressure, followed by exposure of the fluid to ambient pressure, where the methane is routed through a vent to atmosphere (EPA, 2006)

Summary

Introduction

The natural gas industry has undergone a transformation in recent years, largely due to technological advancements such as hydraulic fracturing and horizontal drilling. Presented here is a discussion of the methods used during one such investigation in which tracer release techniques were used to study emissions from gathering and processing (G&P) facilities (Mitchell et al, 2015; Marchese et al, 2015).

Objectives

Results

Conclusion