AWMA 2016 Critical Review: Emissions from oil and gas operations in - PowerPoint PPT Presentation

AWMA 2016 Critical Review: Emissions from oil and gas operations in the United States and their air quality implications David Allen Department of Chemical Engineering, and Center for Energy and Environmental Resources University of Texas at Austin

What have we learned from 15 years of VOC, NOx and GHG emission studies along the oil and gas supply chains?

Multiple approaches for measurement (bottom ‐ up and top ‐ down) • Direct measurements of sources • Fixed ground measurement network • Mobile ground monitoring • Aircraft monitoring • Satellite measurements • Different approaches provide complementary information

What do the measurements tell us? • Spatial variability in emissions • Temporal variability in emissions • Super ‐ emitting sub ‐ populations

Spatial variability in emission magnitudes by equipment or operation type Spatial variability in emissions Spatial variability in emissions per pneumatic controller due to liquid unloadings

Spatial variability in emission compositions within production basins Barnett Shale (Texas) ethane and Oklahoma % VOCs in produced propane to methane ratios gas

Spatial variability in the nature of emissions between regions and on scales as small as a few kilometers

Temporal variability of emissions on multiple time scales, from minutes to years • Changes in equipment on site and in reservoir characteristics as wells age • Shorter term emission variability associated with planned episodic emissions – Start ‐ ups – Shutdowns – Blowdowns, separator dumps – Pneumatic controllers – Liquid unloadings • Unplanned emission events

What do the measurements tell us? • Recent reviews by Miller, et al (2013) and Brandt, et al. (2014) conclude that top ‐ down data indicate methane emissions are higher than current bottom ‐ up estimates (a 50% increase over current bottom ‐ up anthropogenic emissions from all sources) • Geographical variability

Synthesis • Emissions have significant spatial and temporal variability • Magnitudes of activity and emissions are changing • Some bottom ‐ up and top down approaches lead to different assessments of emission magnitudes

Super ‐ emitters A general finding emerging from many studies of the emissions from oil and gas supply chains

What is a super ‐ emitter?

What is a super ‐ emitter? • 10% of the passenger vehicle fleet on the road generates approximately 50% of total passenger vehicle emissions • Super ‐ emitters caused by age, modifications, and equipment malfunction

Super ‐ emitters in the oil and natural gas supply chains: Methane emissions • New findings that sub ‐ populations of sources methane emissions along the natural gas supply chain (super ‐ emitters) dominate emissions in many source categories

Super ‐ emitters in the oil and natural gas supply chains • 2% of sites in the Barnett shale lead to >50% of the emissions • 19% of pneumatic controllers lead to 95% of emissions • 3 ‐ 5% of wells with 1% of annual natural gas supply liquid unloadings chain emissions from one large leak account for more than at a storage facility near Los Angeles (equivalent to >10,000 wells in half of emissions…….. routine operation)

Case study of a super ‐ emitting sub ‐ population: Liquid unloadings (wells without plunger lifts) Wells without Plunger Lift (32 total) Sampled Emissions Sampled Wells 70% 60% Percent of Sample 50% 40% 30% 20% 10% 0% <1 1 to 10 10 to 100 100 to 1,000 1,000 to 5,000 to > 10,000 5,000 10,000 Annual Methane Emissions Range (MSCF/yr) Numbers of devices in various emission bins are well distributed about a mean value, but distribution of emissions is dominated by high emitting sub ‐ population

Super ‐ emitters in the oil and natural gas supply chains • Super ‐ emitters and emission events known to occur (batch or episodic processing, upsets, periodic maintenance, blowdowns, process start ‐ ups, process shut ‐ downs) but have been poorly quantified • First detailed analyses of super ‐ emitters in the oil and gas supply chain done for downstream processing in Houston

Texas Air Quality Study (TEXAQS ‐ 2000) Provide scientific basis for air quality management strategies in southeast Texas (www.utexas.edu/research/ceer/texaqs/) (www.utexas.edu/research/ceer/texaqsarchive)

Emission events (episodic super ‐ emitters) in Houston cause transient ozone events Houston Dallas ‐ Fort Worth

Evolution of Houston ozone spike Ozone plume Industrial source region Wind

TexAQS addresses key areas of uncertainty • Chemical and physical processes in the atmosphere, particularly those leading to rapid and efficient ozone formation (a.k.a. ozone “spikes”)

TexAQS data played a crucial role in understanding these events

TexAQS addresses key areas of uncertainty • Chemical and physical processes dominated by highly reactive volatile organic compounds (light olefins) that were being emitted in much greater quantities than expected • This led to a search for missing emissions

The missing emissions • Findings from TexAQS began the search for missing emissions • They were found in barges, tanks, loading and off ‐ loading, flares, emission events,……. • New technologies were demonstrated that made finding the emissions possible

Super ‐ emitters: Continuous or episodic emissions?

Self reporting of process emissions • Based on findings on emission variability, new emission event reporting required beginning in 2003

Harris, Galveston, Chambers, and Brazoria Counties Event Emissions VOC Event Emissions 2001 Annual Avg as Reported Jan 31 - Dec 31, 2003 50,000 64,860 53,983 86,557 64,539 45,000 lbs/hr lbs/hr lbs/hr lbs/hr 40,000 VOCs 35,000 Emissions (lbs/hr) 4,000,000 lb 30,000 25,000 20,000 15,000 10,359 lbs/hr 10,000 5,000 0 0 730 1460 2190 2920 3650 4380 5110 5840 6570 7300 8030 8760 Jan 1 Dec 31 Yearly Hour Total Event Emissions = 4,035,322 lbs • Total mass of over 4 million pounds (2000 tons) contributes 4% to the 45,000 tons of VOC emitted over a single year from point sources in the four counties. • 14 times (18 hours) during the eleven ‐ month period, event emissions exceed the annual average for all facilities in the region.

What are the characteristics of the events in terms of time, space, and composition? Unscheduled All HRVOC Events Frequency of HRVOC events by HRVOC mass as Reported Jan 31 - Dec 31, 2003 Scheduled As Reported Jan 31 - Dec 31, 2003 600 500 500 375 400 Number of Reported Events Less than 24 hours Daily Number of Events 400 300 300 2-3 times per 200 160 142 200 week 100 100 33 1 0 0 0-100 100-1000 1,000-10,000 10,000-100,000 >100,000 0-24 24-48 48-72 72-96 96-120 120-144 144-168 >168 Mass of HRVOC per Event (lbs) Event Duration (Hours) Most events last less than a day, many last less than an hour Largest number of events is from events of 100-1000 lb, but most of the mass is associated with events greater than 1000 lb, which occur, on average, several times per week

Conceptual issue In most of US, industrial emissions are relatively constant or are small enough that meteorology is cause of “worst conditions” In Houston, both meteorology and emissions are cause of “worst conditions”

An album of emission snapshots

An emission snapshot for a sub ‐ region

How do we reduce emissions? Case study of flares • Flares have narrow operating windows to achieve both high combustion and low soot • Full scale field studies to define those operating windows and then train operators

Mitigating the impact of super ‐ emitters: Improvements 2000 ‐ 2006 Data from NOAA

Applying these approaches to the Eagle Ford

Quantify the emissions from the Eagle Ford • While emissions of volatile organic 350 350 Exploration Exploration compounds are the Pad Construction Pad Construction Eagle Ford Base Case Emissions Inventory (tpd) Drilling Drilling 300 300 Hydraulic Fracturing Hydraulic Fracturing largest in quantity, Well Completion Well Completion Routine Production Routine Production Midstream Midstream they are relatively 250 250 unreactive, and in the 200 200 Eagle Ford occur in a 150 150 region with high emissions of biogenics 100 100 • Ozone formation in the 50 50 Eagle Ford is due 0 0 almost exclusively to NOx VOC CO NOx

Where the emissions occur also matters NOx emissions that impact San Antonio NOx emissions that impact Austin

What is the magnitude of the impact? • Magnitude of impact approximately 1 ppb in Austin and San Antonio, depending on day and location; effects are likely to be stochastic

Summary (Findings) • How we address emissions along oil and gas supply chains is one of the most significant issues at the intersection of energy and air quality for the nation and the world • Air emissions in the oil and gas supply chain are changing and have complex spatial and temporal variability • Addressing super-emitters is a significant part of this challenge • Experience over the past decade provides information about what will and will not work

Recommendations • Quantifying super ‐ emitters