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A Better Way to Estimate Emissions from Oil and Gas Operations. Dr. Susan Stuver Research Scientist 10 /10/2013. Energy, Air & Water A Comprehensive Study of the Issues of Today. UNIVERSITIES. HEALTH SCIENCES. AGENCIES. Who We Are. Research Objectives. Problem Statement. Solution. - PowerPoint PPT Presentation
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A Better Way to Estimate Emissions from Oil and Gas Operations
Dr. Susan StuverResearch Scientist
10/10/2013
Energy, Air & WaterA Comprehensive Study of the Issues of Today
Who We Are
UNIVERSITIES AGENCIESHEALTH SCIENCES
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Policy without DataConservative data assumptions leads to over estimation – assume 100% engine load and 24/7 operation times
Measure Equipment Emissions Engine load data and activity times would make estimates more realistic
Calculations Based on Outdated Standards US Regulators use the USEPA AP-42 Standards that assume worst possible emissions
Problem Statement Solution
Use Engine Emission FactorsUse EPA certified tiered engine emission factor data from engine manufacturers
OUTDAT
ED
Research Objectives
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Max Regional 8-hr Ozone Impact derived from worst case estimates
Wind Direction from Eagle Ford into San Antonio Texas
Bad Science leads to Bad Policy
Hey – who messed up the math?
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CALCULATION – the old fashioned way…
2,250 hp Pump truck deck engine and 12 pump trucks engines are used for the hydraulic fracturing process2,250 hp/pump truck engines x 12 pump truck engines = 27,000 hp ENOx = EF x HP x LF Where, ENOx = NOx Emissions (lb/hr)EFNOx = NOx Emission Factor (lb NOx/hp-hr)-No Emission Controls are assumedHP = Total power output (hp)LF = Load factor-100% assumed
So, ENOx = 2.4 x 10-02 lb NOx/hp-hr x 27,000 hp x 1 = 648 lb NOx/hr
How Emission Estimations Are Done-Site Unseen-
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Vehicles Make/Model Fuel Rating NumberMobile Command Center SMT 503 Mobile Monitoring Unit Diesel 210 hp 1Crane (large) - Operating Engine ATC3200 Diesel 517 hp 1Pickup Trucks GMC 2500 HD Gasoline 360 hp 2
Equipment Make/Model Fuel Rating NumberLight Tower (mobile) RL4000 Diesel 13.6 hp 6Bulldozer TR95 w/Engine Diesel 99 hp 1Backhoe 420D Diesel 88 hp 1Generator - Cooling Room Model QAS25 Diesel 29.6 hp 1
New MethodStart with Collecting Data
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EMISSION GROUP RANKING SYSTEM
RANK 1 Largest Sources- EX: Pump Trucks (Fracturing/Perfing)
RANK 2 Medium Sources- EX: Fracturing Water Pumps
RANK 3 Small Sources- EX: Light Carts
New MethodPrioritize the Sources
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There are 7 of them - Using worst case can cause huge variation
New MethodFind the Correct Emission Factors
Worst Case
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New MethodCalculating Engine Load
GPSA Engineering Data Book (2004)6 and Carl Branan’s Process Engineer’s Pocket Handbook (1984)7 provides the equation
BHp = Q x ∆P/1714(e)
Where,
BHp = Required brake horsepower Q = Fracturing fluid flowrate (gal/min)∆P = Pump discharge – Pump suction (inlet pressure) (psi)1714 = Conversion factor (convert to BHp)(e) = Pump efficiency = 90% (see Note)
Note 1 – Inlet pressure was not recorded so it is conservatively assumed to be zero (psi)
Note 2 - The combination of mechanical and volumetric efficiency is normally 90% or higher for non-compressible fluids (GPSA Engineering Data Book, 2004)8
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New MethodCalculating Engine Load
BHp = Q x ∆P/1714(e)
BHp = ((65 bbl/min x 42 gal/bbl x (6000 psi – 0 psi))/1714)/(0.90)=10,618 Bhp
LF= BHp and divide it by full horsepower. Full horsepower is obtained by the engine HP times the number of engines.
LF = 10,618 Bhp/(2250 hp x 12 engines = 27,000 hp) = 39.2% while the engine was under load.
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2,250 hp Pump truck deck engine and 12 trucks Epoll = EF x P x N x LFA
Where, Epoll = Emissions for pollutantEF = Emission factor in lb/hp-hrP = Brake horsepower in hpN = Number of unitsLFA = Load factor Average (39% for 7.5hr and 15% for 4.5hr)So, ENOx = (1.34 x 10-02lb/hp-hr x 2250hp/eng x 12 eng) x 39% x 7.5 hr/day + 15% x 4.5 hr/day
12 hr/day
Nox = 108.5 lb Nox/hr
AP-42 factors with 100% estimated load = 648 lb Nox/hr that’s 539 pounds per hour difference.
539 lb/hr x 12 hour day = 6,468 pounds (3.2 tons) per day for 1 frac job
New MethodPutting it Together
Lets compare the results• Nox AP42 100% LF = 648 lb/hr• Nox Tier Eng LF Avg = 108.5 lb/hr
• VOC AP42 100% LF = 19 lb/hr• VOC Tier Eng LF Avg = 5.7 lb/hr
• CO AP42 100% LF = 149 lb/hr• CO Tier Eng LF Avg = 20 lb/hr
• PM/PM10 100% LF = 19 lb/hr• PM/PM10 LF Avg = 1.6 lb/hr 12
• 539 lb/hr • 12 hour day = 6,468
pounds (3.2 tons) per day for 1 frac job
• 2000 frac jobs = 6,400 tons of emissions that are not really there.
ResultsComparing the 2 Methods
Tier IV engines would be much lower Are actually measured in grams (not pounds) per hour
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Results – Graphic
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No Wonder the Maps Look so Bad
6,400 Tons of Over Estimation
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Moving on to Rigs
Using engine load is not realistic
Too much variance – need an entirely new way to estimate
ENOx = EF x HP x LF
Conceivable to use
• total fuel consumption, • brake specific fuel consumption • diesel density• tier rated emissions
to estimate emissions from a job
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Example CalculationAssume a drilling operation uses 5,000 gallons of diesel per day for 5 daysAnd Assume we know the BSFC is 0.35 lb/bhp-hrAnd Assume we know that diesel density is 7 lb/gallonAnd Assume we know the engines are Tier 1 – 6.9 g/hp-hr for NoxAnd we want to estimate NOx Emissions
Calculating Hp-hr/job = (fuel for job, gallons) X 7 lb/gal = 500,000 Hp-hr/job0.35 lb/bhp-hr
Tons = Hp-hr/job x tier rated emissions g/hp-hr x 1/454 g/lb x 1/2000 lb/ton
Nox Tons = 500,000 hp-hr/job x 6.9 g/hp-hr x 1/454 g/lb x 1/2000 lb/ton = 3.8 tons
This will be compared to the traditional method:ENOx = EF from AP42 x total HP x 100% LF X 100% activity
And backed up with measurements to validate
Note: numbers
aren't actual
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NG, Bi-fuel and Dual FuelNo engine certification for emission factors
Emission Reduction Potential Not Recognized
engines are currently being loaded into the regional air shed model as diesel
Measurement of emission reduction is needed. We are securing study sites to quantify the emissions reduced by switching to bi-
fuels, dual fuels and /or NG
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Advances in MeasurementRemote Monitoring with Low Cost Sensors
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Advances in MeasurementWireless Data Networking
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Advances in MeasurementAdvanced Analytics for Fugitive Sampling
There's no protocol for the use of relatively new
technology in oil and gas operations
Fugitive Emissions Produced Water TrmtWater Screening Kits Soil Impacts
Managing Misinformation
Temporary Roads Adv. Analytics Livestock Impacts Wireless Data Loggers
Stray GasInvasive Species Education and Outreach
Utilizing the EFD Network
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Questions?
Aggie Pigeon