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Calculations Based on Outdated Standards US Regulators use the USEPA AP-42 Standards that assume worst possible emissions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

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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?

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