Trace Gas Emissions from Oil and Gas Operations Considerations for - - PowerPoint PPT Presentation

NASA AQAST Meeting June 17, 2014 Cambridge, MA

Trace Gas Emissions from Oil and Gas Operations

Considerations for Atmospheric Researchers

• Numerous studies of emissions from oil and

gas production, gathering systems, and gas

• processing. Some address criteria pollutants
• r HAPs, but majority focused on methane

emissions.

• Some of these studies, coupled with agency

programs such as EPA’s GHG Reporting Rule, have increased understanding of sector

• emissions. Many other studies have just

raised more questions.

• Challenge for researchers measuring

atmospheric concentrations and estimating mass fluxes is accounting for the unique

• perating characteristics of the oil and gas

sector.

2

Industry Characteristic: Variability of Gas Composition

• Composition of hydrocarbons in the reservoir is a key factor in VOC and

GHG emissions

– Widely variable – spans entire range of hydrocarbons (think pure methane to tar). There is no “mean composition”. – Also drives what equipment and processing are necessary

• Hydrocarbon composition of a “gas well” typically has 2 phases: gas and

condensate (liquids)

– Species partitioning between gas and liquids depends on the initial composition, and the T and P at which gas and liquids are separated. Emissions speciation also depends on the T and P of the process – Different speciation profiles on a single well-pad (e.g., tank flashing, dehydrator overhead, raw gas) – A single surface well can access multiple subsurface reservoirs with different compositions

3

Gas, Produced Water, and Condensate Separator Combustor

• r Flare

Dehydrator Skid Condensate Dry Gas to Sales Wet Gas Produced Water Tank vapors may be recovered or combusted Wellheads Produced Water Condensate

Example Well Pad*

Produced gas

• r “raw gas”

Sales gas Dehydrator vent gas Flash gas

*Simplified diagram for illustrative purposes – one of many possible well configurations 4

5

Example Speciation Profile Produced Gas v. Flash Gas

Mole Percent

Produced Gas Flash Gas

Methane 84.98% 34.40% Ethane 6.81% 13.74% Propane 3.17% 18.28% i-Butane 0.64% 6.79% n-Butane 0.71% 9.12% i-Pentane 0.24% 4.27% n-Pentane 0.20% 3.71% Benzene 0.01% 0.30% Toluene 0.02% 0.38% CO2 2.73% 2.86%

Em Emission

• ns com
• mpos
• sition
• n v

varies a acros

• ss t

the well pad

% Ethane % CO2

Formation Type Region

Ave Low High Ave Ave High Permeability Gas North East 83 70 98 10 0.07 878 Gulf Coast 86 54 98 5 1.20 727 Rocky 93 90 94 3 2.72 3848 Shale Gas North East 85 69 98 9 0.12 2584 Gulf Coast 92 75 98 3 3.20 414 North East 87 74 98 8 0.08 862 Gulf Coast 87 59 96 5 0.92 808 Rocky 86 82 89 7 2.01 1129 Oil North East 77 70 83 15 0.10 129 Gulf Coast 80 66 92 9 1.08 2028 Coal Seam Rocky 88 NA NA 2 8.26 30 Gulf Coast 89 77 94 4 0.21 14

• No. of Data

Points

Other Tight Reservoir Rock % Methane

Example Sales Gas Compositions* Comp mpositions are n not c consistent by f forma mation type

*Compositions are taken from random industry data and do not represent overall formation averages

6

7

Mole %

Methane Ethane Propane Butanes Pentanes Hexanes CO2 Dataset 1 68.75 19.28 8.44 2.35 0.53 0.22 0.09 Dataset 2 69.36 19.31 7.69 1.97 0.44 0.18 0.06 Dataset 3 73.76 15.83 6.58 1.92 0.53 0.25 0.08 Dataset 4 73.80 16.69 6.23 1.83 0.48 0.22 0.08 Dataset 5 74.15 14.95 6.59 1.98 0.54 0.29 0.09 Dataset 6 75.90 13.49 6.22 1.74 0.43 0.22 0.07 Dataset 7 76.59 14.33 5.47 1.87 0.55 0.31 0.10 Dataset 8 76.61 13.20 6.11 1.48 0.30 0.11 0.07 Dataset 9 76.85 12.65 5.70 1.69 0.46 0.29 0.19 Dataset 10 77.89 13.55 5.37 1.61 0.44 0.21 0.10 Dataset 11 78.06 10.65 5.32 1.77 0.51 0.24 0.05 Dataset 12 78.40 13.54 4.63 1.58 0.50 0.29 0.11 Dataset 13 78.69 12.03 4.87 1.35 0.34 0.17 0.05 Dataset 14 87.09 8.97 2.36 0.70 0.20 0.11 0.07 Dataset 15 90.54 4.92 1.91 1.06 0.39 0.22 0.01

Comp mpositions are n not c consistent within a a single ba basin in

Example Sales Gas Compositions Appalachia Basin – Shale Gas

Example VOC Emissions Breakdown for Two Basins1

1 from October 21, 2013 presentation by Tom Moore, WRAP/Westar, Air Quality and Oil & Gas Development in the Rocky

Mountain Region, Boulder, CO. Data are for 2008 WRAP inventory.

VOC emissions sources vary significantly from basin to basin – tank flashing, dehydration and pneumatic devices are consistently large source categories in most basins, but for coal bed methane (CBM) dominant basins other categories are significant

8

Composit itio ions drive ive equip quipment a and p processin ing

Compressor Engines 2% Drill rigs 1% Pneumatic devices 17% Pneumatic pumps 6% Fugitives 24% Dehydrator 10% Condensate tank 33% Oil Tank 2% Venting - initial completions 1% Venting - recompletions 0.5% Other Categories 3% Compressor engines 27% Drill rigs 2% Venting - initial completions 5% Venting - recompletions 7% Fugitives 14% Miscellaneous engines 3% Artificial Lift 2% Dehydrator 6% Oil Well Truck Loading 6% Pneumatic Devices 20% Other Categories 8%

Southwest Wyoming Basin Powder River Basin

Industry Characteristic: Temporal Variability

Episodic Emissions

• Engine emissions during drilling, completion,

and workovers

• Maintenance blowdowns

Continuous Emissions

• Glycol dehydrators
• Equipment fugitives
• Compressor engines/turbines
• Continuous fired heaters/boilers
• Continuous bleed pneumatic controllers
• Tank working/breathing (non-flash) losses

9

Some examples. Along with frequency, the magnitude of these emissions will also vary with production, load, etc.

Periodic or Intermittent Emissions

• Well venting for liquids unloading (wide frequency

range: 1/day to less frequent than 1/year or never)

• Truck loading
• Tank flashing (depends on separator dump frequency

to storage tanks)

• Pneumatic pumps and intermittent vent controllers
• Intermittent fired heaters/boilers

Another consideration: Some emissions typically

• ccur during daylight

hours, such as truck loading emissions

Industry Characteristic: Production Decline

• 500

1,000 1,500 2,000 2,500 3,000 0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00 MSCF/Day Days From Initial Prod.

• 500

1,000 1,500 2,000 2,500 3,000 0.00 20.00 40.00 60.00 80.00 100.00 MSCF/Day Days From Initial Prod

10

Example for Western US – Tight Sands Gas Well

Accounting for Background and Non- Oil and Gas Sources

From EPA 2012 National GHG Inventory

Methane from natural geologic seeps can be significant. Geological sources have been estimated to account for 7-14%1 of global methane emissions, with some researchers suggesting that the contribution could be as much as 30%2.

11 141 102.8 88.6 73 55.8 52.9 15.3 12.8 7.4 5.7 12

2012 CH4 Emissions, MMT CO2e Enteric Fermentation Landfills Other Oil and Gas Oil and Gas Production Coal Mining Manure Management

Forest Land Remaining Forest Land

Wastewater Treatment Rice Cultivation Stationary Combustion Other

• Non-oil and gas

sources, which may be co-located in production areas, are a significant portion of US methane emissions.

• Is it reasonable for

studies to attribute any “gap” between study estimated methane flux and bottom-up inventory estimates solely to the oil and gas sector?

1Etiope, G., 2012. Methane Uncovered. Nature Geoscience 5, 373-374; 2 http://newsinfo.iu.edu/news-archive/24236.html

From EPA 2012 National GHG Inventory

Considerations for Experimental Design

 Many emission sources from oil and gas production are not at steady-state, and there is a tremendous amount of variability depending

• n hydrocarbon composition, site-specific

geology, and operational practices  Uncertainty in flux calculations coupled with variability in emissions lead to non-trivial uncertainties – experiments must be carefully designed  Background and non-oil and gas emission sources should be considered  Close collaboration with industry could help to design experiments to capture a full range of emissions, which will allow more quantitative comparisons with inventories

12

 Workshop focused on major methane-producing industries (oil and gas, agriculture, landfills, etc.) and exploration of how to fill research gaps  Guidance Manual on Methane Emissions Sources

• Encompass production, gathering and

collection, and processing sectors

• Address minimization and control of methane

emissions

13

API Efforts Under Consideration – Methane Emissions