Reconciliation Research. Daniel Zimmerle, Colorado State University

Transcription

1 Reconciliation Research Daniel Zimmerle, Colorado State University

2 Topics Intro to current basin-level project Observations from facility-level work Impact of activity data 2

3 Reconciling Basin-Scale Top-Down and Bottom-Up Methane Emission Measurements for Onshore Oil and Gas Development (RPSEA ) Sponsors 3

4 Project Goals Develop and reconcile independent topdown and bottom-up methane emission measurements At facility and basin levels for a US shale gas play Using multiple state-of-the-science measurement methods at the same time Scaling bottom-up estimates using spatiallyand temporally-resolved activity data 4

5 Location What Has Been Compared in Past Studies Component Emission Studies Episodic Event Count Study Window Airborne Basin and Facility Measurements The Study Basin Component Inventory Facility-Level Emission Measurements Time Facility measurements not statistically representative Episodic data from annualized counts aggregated at basin level (at best) Vague component inventory values Component measurements from distant times & places 5

6 3 Levels Basin Regional Mass Balance Facility Facility Spiral Flight Tracer Flux OTM33A Device Onsite 6

7 Location What is Unique: Aligned Measurements Airborne Basin and Facility Measurements Component Emission Studies Facility-Level Emission Measurements from Random Sample of Sites Industrysupplied Episodic Event Count Study Window The Study Basin Detailed Site Inventory (inc. key component counts) Time Statistically representative facility measurements Episodic data resolved at fine detail during measurement window Specific, high-resolution facility inventory and key component counts for >75% of facilities (we have 98%) Multiple measurement approaches utilized and compared for facilities Component measurements from distant times & places couldn t fix this one 7

8 SELECTED RECONCILIATION RESULTS 8

9 Reconciliation / Comparison Process Facility Spiral Flight Onsite X Emission source count and timing Tracer Flux OTM33A 9

10 Compressor Facility Comparisons T&S Study * : Engine Emissions from AP42 Basin Study / Gathering Stations Engine Emissions from Recent Tests + Most variance due to uncertainty in exhaust emissions Better exhaust data less uncertainty Normal operations show good agreement between onsite and downwind Strongly dependent on engine exhaust modeling Operational data critical to compare small populations * Subramanian, R. et al. Methane Emissions from Natural Gas Compressor Stations in the Transmission and Storage Sector: Measurements and Comparisons with the EPA Greenhouse Gas Reporting Program Protocol. Environ. Sci. Technol. 49, (2015). + Vaughn, T. L., et. al., Reconciling Facility-Level Methane Emission Rate Estimates Using Onsite and Downwind Methods at Natural Gas Gathering and Boosting Stations, in preparation 10

11 Facility-Level Reconciliation: Normal / Abnormal Operations 40% of observed emissions due to abnormal operations seen by downwind but not measurable onsite * Subramanian, R. et al. Methane Emissions from Natural Gas Compressor Stations in the Transmission and Storage Sector: Measurements and Comparisons with the EPA Greenhouse Gas Reporting Program Protocol. Environ. Sci. Technol. 49, (2015). Good agreement for facilities measurable by both methods Downwind detects emissions identified but not measurable onsite Often poorly modeled in bottom-up models 11

12 Example of Emission Factor Uncertainty for Small Populations Data: Single region data from Allen et. al. 7.2:1 range of average emission rates Instantaneous rate not steady over duration Comparisons Comparison complicated by range of data 1 site: [35% - 260%] 100 sites: [86% - 114%] Complicates comparisons for small populations 12

13 Method Comparison Two well-recognized methods Near-contemporaneous, independent measurements Experienced teams Bell, C. et al. Reconciliation of methane emission estimates from multiple measurement techniques at natural gas production pads, preparing for submission

14 Same Data: Linear Plot Methods my be internally consistent, but may vary substantially from true emissions 14

15 Facility Level Under controlled conditions, good method agreement Measured or good models for both methods Good understanding of activity data Downwind (aggregate) methods see emissions not measurable on-site even if identified Agreement does not extend to all pairs Wide variations with some methods Wide emission factor variations can 15

16 Impact of Activity Data Example From Transmission & Storage Good agreement with GHGI but significant shifts in why Zimmerle, D. J. et al. Methane Emissions from the Natural Gas Transmission and Storage System in the United States. Environ. Sci. Technol. 49, (2015). Emissions, Facility Count, Comp. Diff. Offsetting Usage + Emissions Factors (esp transmission) Usage Difference (esp transmission) More Data Available (transmission GHGRP) 16

17 CH 4 Estimate for Gathering and Processing New emissions data + substantial update to activity estimates Marchese, A.J., Zimmerle, D.J, Vaughn, T. L. et al (2015). Methane emissions from United States natural gas gathering and processing. Environ. Sci. Technol /acs.est.5b02275.

18 Basin Study Results Upwind Downwind Both top-down (aircraft) and bottom-up models show significant structure Structure is strongly related to activity data (known & unknown) 18

19 Basin Study Results Reasonable agreement between TD & BU estimates Relies on very complete activity data No special modeling of BU emissions required Basin Results from One Day Top Down Bottom Up 8-10 papers in progress First publications in early-mid summer Basin reconciliation results published by early fall 19

20 Basin/National Reconciliation Observations Focus has been on emission rates but activity has similarly large impact on total emissions Basin: O&G operations vary significantly over short periods Atmospheric methods (mass balance or downwind) are sampled in narrow time / activity windows Comparisons to annualized activity miss short term variations National: Activity mix can substantially change emission drivers can impact policy choices 20

21 Dan Zimmerle