Aerial Surveys of Elevated Hydrocarbon Emissions from Oil and Gas Production Sites

Abstract

Oil and gas (O&G) well pads with high hydrocarbon emission rates may disproportionally contribute to total methane and volatile organic compound (VOC) emissions from the production sector. In turn, these emissions may be missing from most bottom-up emission inventories. We performed helicopter-based infrared camera surveys of more than 8000 O&G well pads in seven U.S. basins to assess the prevalence and distribution of high-emitting hydrocarbon sources (detection threshold ∼ 1-3 g s(-1)). The proportion of sites with such high-emitting sources was 4% nationally but ranged from 1% in the Powder River (Wyoming) to 14% in the Bakken (North Dakota). Emissions were observed three times more frequently at sites in the oil-producing Bakken and oil-producing regions of mixed basins (p < 0.0001, χ(2) test). However, statistical models using basin and well pad characteristics explained 14% or less of the variance in observed emission patterns, indicating that stochastic processes dominate the occurrence of high emissions at individual sites. Over 90% of almost 500 detected sources were from tank vents and hatches. Although tank emissions may be partially attributable to flash gas, observed frequencies in most basins exceed those expected if emissions were effectively captured and controlled, demonstrating that tank emission control systems commonly underperform. Tanks represent a key mitigation opportunity for reducing methane and VOC emissions.

Life cycle greenhouse gas emissions and freshwater consumption associated with Bakken tight oil

“…One recent study has, however, revealed specific equipment sources of fugitive emissions via helicopter-based infrared camera surveys of Bakken pads (35). That study reported 13.8% of Bakken pads yield fugitive emissions and that 93% of those emissions were associated with tank vapors.…”

“…Recently published work has called attention to fugitive emissions in the Bakken shale play (33)(34)(35). Some of these studies used satellite or airplane flux measurements, i.e., top-down approaches.…”

The recent increase of atmospheric methane from 10 years of ground-based NDACC FTIR observations since 2005

“…On the other hand, it has been shown that the current emissions inventories, including EDGAR v4.2, underestimate the emissions of methane associated with the gas and oil use and exploitation, as well as livestock emissions (Franco et al, 2015Turner et al, 2015Turner et al, , 2016. Furthermore, Lyon et al (2016) pointed out that emissions from oil and gas well pads may be missing from most bottom-up emission inventories. The problem of the source identification clearly resides in the need for a better characterization of anthropogenic emissions and especially in emissions of methane from the oil and gas and livestock sectors.…”

Quantifying alkane emissions in the Eagle Ford Shale using boundary layer enhancement

“…The composition of these gases are dominated by the most volatile hydrocarbons, i.e., methane and ethane. In comparison, emissions from storage tanks, used to store liquids from wells prior to transportation and further processing, have been shown to contribute largely to hydrocarbon emissions in UOG shale plays (Lyon et al, , 2016). Since gas produced at the well is separated from liquids prior to storage, the headspace in storage tanks is primarily composed of hydrocarbons heavier than ethane, notably short-chain alkanes such as propane, butanes, and pentanes, although methane and ethane may still be present.…”