Screening and Guided Measurement Protocol...Annex 1: Screening and Guided Measurement Protocol 7 | P a g e be included. The route will be selected to include all gathering facilities

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Annex 1: Screening and Guided Measurement Protocol

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Screening and Guided Measurement Protocol

Authors: Dan Zimmerle, Tim Vaughn, Clay Bell, Colorado State University

Laurie Williams, Fort Lewis College

STATUS: Final

Special Note

The attached document is the protocol utilized for the study, and was developed prior to field campaign.

With the exception of grammatical corrections, the protocol is included intact as it was utilized for the

field study, with two exceptions:

1) Notes have been added where significant deviations from the field plan occurred during

operations. These are discussed in more details in the main body of the report.

2) Some information has been redacted to protect confidential data of the industry study partners.

1.0 Overview

This document provides an overview of the facility screening plan to guide facility level measurements at

natural gas production and gathering facilities in the RPSEA target basin. The overall goal of the RPSEA

project is to reconcile aircraft mass balance and facility-based emissions estimates at the facility and sub-

basin level. Separate measurement protocols will be utilized for each O&G sector included in the study –

transmission compressor facilities (downwind measurements only); Gathering facilities (onsite and

downwind measurements); distribution facilities (onsite measurements); distribution and gathering

pipelines (onsite measurements); and production (onsite and downwind measurements). The Production

Module: Measurement Protocol provides an overview of the methane emission measurement collection

and conduct of field teams. The specific objective of the facility screening is to:

Guide subsequent measurements in order to characterize both the “body” and “long tail”

emission distributions.

We shall achieve the project objective by making measurements of methane emissions on a number of

partner facilities using source level measurement techniques and downwind methods. A fundamental aspect

of the project is to pair the two measurement techniques at multiple sites, allowing a comparison of the

measurement techniques and, potentially, a better estimate of measurement uncertainty. To the greatest

extent possible, measurements will also be conducted contemporaneously with aircraft overflights to assess

the impact of the spatial and temporal alignment between facility-based ground-level measurements and

aircraft measurement and mass balance methods, including some aerial sampling at a facility level, if

possible. Each team in the group will operate, measure and consolidate results independently for each

facility measured, maintaining the independence of the paired measurements.

Measurement of production and gathering facilities will follow the Production Module: Measurement

Protocol and Booster and Gathering Module: Measurement Protocol respectively. Site selection will be

guided by facility level screening performed following this protocol. Screening is intended to quickly

provide an approximation of the rate of methane emissions from a production well pad or gathering facility

(compressor station) using the inversion plume method. Bottom-up measurement teams will then be

directed by the screening results during subsequent days, allowing an increased number of sites with higher

emissions rates to be measured in order to better characterize the “long tail” (or “fat tail”) of the distribution.

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An approximately equal number of measurements will be taken from the upper third and lower two thirds

of screened facilities allowing the “body” of the distribution to also be well characterized. The resulting

measurements will be weighted in the analysis to avoid over-representing the large sources and potential

bias in the results.

Note: During the field campaign, pre-screening proved unsuccessful due to the weather and road access

issues, and the screening process was discontinued after the first week. See main report.

2.0 Clustered Sampling and Site Identification

To facilitate screening, a clustered sampling method is adopted. Clustered sampling allows the teams to

focus in a smaller geographic area reducing driving time between sites in order to increase the total number

of samples. The clustered sampling approach will also improve the coordination between onsite and

downwind teams during contemporaneous measurement.

A unique RPSEA Pad ID and RPSEA Station ID have been assigned to each known production site and

gathering station in the study region in advance of the field campaign. The unique IDs will be used for

communication and coordination between teams. Two clusters are assigned to each week of the campaign

as shown in Table 2-1. Figure 2-1 shows the outline of the clusters overlaid on the study area. Facility

locations in the clusters assigned to each week are shown in Figure 2-2, Figure 2-3 and Figure 2-4.

Table 2-1: Selected production clusters

Week Cluster IDs

A B

1 1 3

2 10 11

3 14 17

Figure 2-1: Selected clusters for measurement campaign

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Figure 2-2: Cluster 1 (blue polygon) & 3 (red polygon) assigned to week one of campaign. Marker

style represents facility type: star paddles for gathering stations, push pins for production wells.

Marker color represents operator: red is non-partner, white and blue are partner facilities.

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Figure 2-3: Clusters 10 (blue polygon) & 11 (red polygon) assigned to week two of campaign.

Marker style represents facility type: star paddles for gathering stations, push pins for production

wells. Marker color represents operator: red is non-partner, white and blue are partner facilities.

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Figure 2-4: Clusters 14 (blue polygon) & 17 (red polygon) assigned to week two of campaign.

Marker style represents facility type: star paddles for gathering stations, push pins for production

wells. Marker color represents operator: red is non-partner, white and blue are partner facilities.

3.0 Weekly Schedule

Screening will be performed Monday each week and used to guide the measurements during subsequent

days as illustrated in .

Non-partner facilities which are encountered on the screening route may be screened. These facilities may

be included in guided sampling to be measured from public road access using the OTM33A downwind

method, however non-partner facilities will not be measured by on-site teams.

Table 3-1. Screening may be performed Tuesday if weather prohibits screening Monday. Three mobile

emissions laboratories will perform screening; one operated by the University of Wyoming and two

operated by Aerodyne Research, Inc. One team will screen <redacted, company ID> production and

gathering facilities within cluster A while a separate team screens <redacted, company ID> facilities in

cluster B. The third team will screen <redacted, company ID> facilities in both clusters A & B. A company

escort will accompany each screening team enabling site access during screening. Additional screening

may be performed from public roads on Saturday and/or Sunday, however site access will not be possible

as company escorts will not be available.

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While downwind teams are screening, onsite teams will perform unguided measurement of production and

gathering facilities within the clusters assigned that week. Site selection during unguided measurement is

described further in section 7.0.

After screening, onsite and downwind teams will perform guided measurement of production and gathering

facilities for the remainder of the week. Site selection during guided measurement is described further in

section 8.1. <Weekly schedule by company redacted to protect company confidentiality. Screening is

allocated to partner companies in proportion to the size of their operations in the basin>. An escort will

accompany each measurement team to provide site access. Measurements may be taken on Saturday if

weather prohibits measurement during one or more weekdays and an escort is available. Teams will

coordinate to maximize the number of facilities at which contemporaneous onsite and downwind

measurements are made during the guided sampling period. Contemporaneous measurements and

coordination are described further in section 8.2.

Non-partner facilities which are encountered on the screening route may be screened. These facilities may

be included in guided sampling to be measured from public road access using the OTM33A downwind

method, however non-partner facilities will not be measured by on-site teams.

Table 3-1: Screening and measurement schedule. Identification of companies engaged on each

day has been redacted.

Team Protocol Sun Mon Tues Wed Thu Fri Sat

Aerodyne

Research

Inc. 1

Screen/

Tracer -

Screen

Cluster A

Scheduled assignments for study teams based on

proportion of size of partner company operations

-

Aerodyne

Research

Inc. 2

Screen/

Tracer -

Screen

Clusters A&

B

-

University

of Wyoming

Screen/

OTM33A -

Screen

Cluster B -

AECOM 1 Onsite - Onsite

facility

Measurement

-

AECOM 2 Onsite - -

SWN

LDAR Onsite - -

4.0 Site Accessibility Grades and Screening Route Determination

In advance of the field campaign sites within a cluster will be graded based on the downwind accessibility.

Grades will be assessed for each site for different wind directions. A route will be selected during the

evening preceding screening. The specific route will be chosen based on the anticipated wind conditions.

The list of sites within the cluster will be ordered by the grade for the predicted wind conditions to determine

a screening route which takes advantage of sites with high accessibility grades. As the wind conditions

change throughout the day, the site list may be re-ordered and the route adjusted. Sites with the highest

grades for the wind conditions will be the primary screening targets, however if wind conditions allow the

plume to be seen at sites with lower grades encountered in-route between primary targets these sites may

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be included. The route will be selected to include all gathering facilities within the cluster with downwind

access.

5.0 Screening Method

Screening will use the “inversion plume” method (Yacovitch, et. al.) to determine an estimate of the rate of

methane emissions from production and gathering sites on the screening route. 95% upper and lower

confidence bounds will be provided in addition to the estimate for each site. The screening team is permitted

to perform multiple passes by a single facility to improve uncertainties, or if wind conditions change to

allow an improved estimate to be made. As production sites are screened, the screening team will generate

a list of screened facilities within a cluster including the RPSEA Cluster ID, RPSEA Pad ID, number of

wells, latitude and longitude, estimated emissions rate, and 95 % upper and lower confidence bounds as

illustrated in Table 5-1. Sites which are attempted and determined as a “zero” or “unscreened” facility will

be documented in the table as described in section 6.0. A separate list will be developed for gathering

sites during the screening process as illustrated in Table 5-2.

When possible, screening will be performed from public roads. If obstructions exist between sites and

public roads which prohibit measurement, screening may be performed on the well pad or from private

access roads provided the vehicle is located far enough from potential leak locations for dispersion to be

considered Gaussian.

Table 5-1: Example table of screened production pads

RP

SE

A C

luster ID

RP

SE

A P

ad ID

No

. of W

ells

Latitu

de

Lo

ng

itud

e

Estim

ated E

missio

ns

(SC

FM

)

95

% U

pp

er Bo

un

d

(SC

FM

)

95

% L

ow

er Bo

und

(SC

FM

)

Su

ccessfully

Screen

ed

Attem

pted

“Zero

”

Attem

pted

“Un

screened

”

IR V

erification

(Plu

me/ N

oP

lum

e)

1 Pad 1 X XX.XX XX.XX XX.XX XX.XX XX.XX Y X - No Plume

1 Pad 2 X XX.XX XX.XX XX.XX XX.XX XX.XX Y - - -

1 Pad 3 X XX.XX XX.XX XX.XX XX.XX XX.XX N - X Plume

…

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Table 5-2: Example table of screened gathering facilities

RP

SE

A C

luster ID

RP

SE

A S

tation

ID

No

. of C

om

presso

rs

Latitu

de

Lo

ng

itud

e

Estim

ated E

missio

ns

(SC

FM

)

95

% U

pp

er Bo

un

d

(SC

FM

)

95

% L

ow

er Bo

und

(SC

FM

)

Su

ccessfully

Screen

ed

Attem

pted

“Zero

”

Attem

pted

“Un

screened

”

IR V

erification

(Plu

me/ N

oP

lum

e)

1 Station 1 X XX.XX XX.XX XX.XX XX.XX XX.XX X X - No Plume

1 Station 2 X XX.XX XX.XX XX.XX XX.XX XX.XX - - X Plume

1 Station 3 X XX.XX XX.XX XX.XX XX.XX XX.XX X - - -

…

6.0 Facilities with Near Background Concentration

Distinguishing facilities with near zero emissions from missed plumes presents a challenge and could

potentially bias the sample. The sample could be biased high if sites are truly “zero” emitters but omitted

from the list of screened facilities because the plume is not encountered during screening. The site would

not be considered in the subsequent random sample collected by measurement teams. Conversely the

sample could be biased low if a “non-zero” site is included as a “zero” in the list of screened facilities when

the plume was not actually encountered. However, this site could be selected during the subsequent random

sample reducing the opportunity for bias. To minimize the opportunity for bias, sites will be distinguished

as “zero” or “unscreened” using the following rules.

A site is considered “unscreened” and will not be included in the list of screened facilities if an attempt is

made to screen the facility however the methane concentration is near background levels and the screening

team is uncertain if the plume would be encountered at their location due to wind conditions, distance, or

obstructions between the site and screening vehicle.

A site may be considered screened successfully and included in the list of screened facilities as “zero” if

the concentration is near background, the screening vehicle is located directly downwind of the site, and

the space between the site and screening vehicle is free of obstructions. In this case only an upper limit

will be reported.

Additionally it is possible for the screening team to be located too close to a facility for the dispersion to be

considered Gaussian, in which case the inversion plume method would result in an estimate biased high.

In this case the facility will be considered “unscreened” if the screening team cannot repeat the measurement

further downwind.

In all cases the screening team will note that the site was visited and whether it was considered “unscreened”

or “zero”. When possible, the screening team will verify whether or not the plume is missed using an

optical gas imaging camera to ensure zero sites are not being mislabeled as “unscreened” potentially

resulting in a biased sample.

7.0 Coordination with Measurement Teams during Screening

Screening teams may not be able to start early in the morning before winds have developed. As a result,

onsite teams may be dispatched first as illustrated in Table 7-1. Onsite teams will be vectored to sites which

have a high probability of being screened as determined by the study coordination team using predicted

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wind directions and the routes proposed by the screening teams (Sites Gath A, Prod A-D in Table 7-1 are

selected this way). If screening had been performed from public roads on the Sunday prior, successfully

screened sites will be selected. In the afternoon onsite teams are vectored to <redacted, company ID> sites

which have been screened by ARI or UWyo. (Sites Gath B, Prod E-H in Table 7-1 are selected this way).

During screening no paired measurements are made.

Table 7-1: Coordination with measurement teams during screening

Time of Day 7 8 9 10 11 12 1 2 3 4 5

ARI 1 - - Screening

ARI 2 - - Screening

UWyo - - Screening

AECOM 1 Gath Site A - Gath Site B -

AECOM 2 - Prod Site A Prod Site C - Prod Site E Prod Site G -

SWN LDAR - Prod Site B Prod Site D - Prod Site F Prod Site H -

8.0 Analysis of Screening Results and Guided Measurement

Following the screening an evening “all hands” meeting will be held. The purpose of the meeting will be

to review screening results, perform site selection for subsequent measurements within the clusters, and

coordinate contemporaneous measurement of facilities. The meeting will be led by the CSU Coordination

Team. Prior to the meeting screening teams will provide the list of screened facilities in the form of Table

5-1and Table 5-2 to the Coordination Team. The onsite teams will provide a list of facilities measured

during un-guided measurement. Site selection will be made for the remaining samples within the clusters

as described in section 8.1.

8.1 Site Selection for Guided Measurement

The lists generated during screening will be combined to include screened facilities operated by both partner

companies, SWN and XTO Energy. One list will be generated for production and one list for gathering for

each cluster. Each cluster will then be sorted by the magnitude of the emissions estimate from screening.

The upper one third and lower two thirds of the list will be identified. Routes will then be selected for each

measurement team for each remaining sampling day. Daily routes may consider sites in both clusters

assigned to the week, provided the expected number of sites covered in each cluster is approximately equal

at the end of the week. The priority for selecting routes is:

1. Contain approximately equal number of sites from the upper third and lower two thirds of

screened sites;

2. Overlap downwind and onsite teams to maximize contemporaneous measurements.

3. Contain alternate sites in case wind conditions, access issues, or safety prevent

measurement of facilities earlier on the list.

4. Consider geography to reduce transit time between sites;

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At the discretion of the CSU Coordination Team measurement teams may be re-routed in order to obtain

improved coverage within each cluster, balance the number of samples from the upper third and the lower

two-thirds of screened facilities, or improve the coordination of contemporaneous measurements.

Each evening the study team will host a similar meeting at which the route and sampling targets for the

next day will be reviewed and updated.

8.2 Contemporaneous Measurements

Onsite and downwind measurements taken at a facility on the same day will be considered

contemporaneous provided no significant changes in equipment states occur between. The company escort

will assist the measurement team (onsite or downwind) to record the equipment states during their

measurement. Equipment states during onsite and downwind measurement of each facility will be

compared to determine if the operational configuration is the same and the measurements may be

considered contemporaneous.

Coordination between the onsite and downwind teams at production facilities is illustrated in Table 8-1 and

at gathering facilities in Table 8-2 and Table 8-3. In order to maximize contemporaneous measurements

the sites in the route developed in section 8.1 may be visited out of order by one or more teams. The CSU

observer will act as the liaison between teams and coordinate contemporaneous measurements. This will

require the teams be operating nearby and some flexibility in the daily schedule.

Table 8-1: Coordination of onsite and downwind teams for contemporaneous measurement of

production facilities

Time of Day 7 8 9 10 11 12 1 2 3 4 5

UWyo (OTM33A) - - Site 2 Site 1 - Site 5 - Site 6 -

AECOM (Onsite) - Site 1 Site 2 - Site 3

SWN (LDAR) - Site 4 - Site 5 - Site 6 - -


large gathering facilities

Time of Day 7 8 9 10 11 12 1 2 3 4 5

ARI (Dual Tracer) - - - Site 1 Site 2 -

AECOM (Onsite) - Site 1 -


small gathering facilities

Time of Day 7 8 9 10 11 12 1 2 3 4 5

ARI (Dual Tracer) - - - Site 1 Site 2 Site 3 -

AECOM (Onsite) - Site 1 - Site 2 -

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9.0 References

Mobile Laboratory Observations of Methane Emissions in the Barnett Shale Region Tara I. Yacovitch,

Scott C. Herndon, Gabrielle Pétron, Jonathan Kofler, David Lyon, Mark S. Zahniser, and Charles E.

Kolb Environmental Science & Technology 2015 49 (13), 7889-7895 DOI: 10.1021/es506352j

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Screening and Guided Measurement Protocol...Annex 1: Screening and Guided Measurement Protocol 7 | P a g e be included. The route will be selected to include all gathering facilities