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A geospatial method to assess site suitability for static vehicle-based measurements of methane plumes
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  • Mozhou Gao,
  • Chris Hugenholtz,
  • Thomas Fox,
  • Thomas Barchyn
Mozhou Gao
University of Calgary

Corresponding Author:mozhou.gao@ucalgary.ca

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Chris Hugenholtz
University of Calgary
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Thomas Fox
University of Calgary
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Thomas Barchyn
University of Calgary
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Abstract

Vehicle-based methane-sensing systems are gaining popularity as tools for monitoring site-level methane emissions from oil and gas (O&G) sites. To measure emissions, vehicles equipped with methane sensors intersect plumes along roads downwind of target sites and acquire measurements in static (parked) or mobile modes. The downwind distance between the emissions source and the measurement location is one of several factors that must be considered in planning these types of surveys. Here we present a method to estimate the suitability of O&G facilities for vehicle-based measurements using downwind distances recommended in OTM 33A and the tracer technique. We present two types of analyses: (1) a historical analysis using weather reanalysis data and (2) an operational analysis using forecast data. The method uses modeled wind direction and geospatial data to identify O&G facilities that have roads between 20 and 200 m downwind for OTM 33A and between 500 m and 3000 m downwind for the tracer technique. We apply the method to O&G facilities in Alberta that will soon require annual or triannual LDAR surveys. For the historical analysis we use ERA-Interim wind data and calculate the vectorial average (resultant) of modeled winds for the period 2009-2018. Of the 35047 O&G facilities examined, we find that 7% are, on average, suitable for OTM 33A and 69% are, on average, suitable for the tracer technique, based solely on downwind distance. We surmise that other factors like landcover, weather conditions (e.g., stability), and topography would likely reduce the candidate pool from these estimates. We demonstrate the operational utility of the method by examining a subset of 100 O&G facilities in southern Alberta and using forecast wind direction from the Canadian High Resolution Deterministic Prediction System (HRDPS), which has a 2.5 km grid spacing. We propose that the method can be used as a screening tool to estimate site suitability for static vehicle-based surveys and that it will likely translate to mobile surveys once the effect of downwind distance is clarified. Other factors can be incorporated in the method once test results are available.