posted on 2021-02-15, 18:03authored byFelipe
J. Cardoso-Saldaña, David T. Allen
The
methane emission intensity (methane emitted/gas produced or
methane emitted/methane produced) of individual unconventional oil
and gas production sites in the United States has a characteristic
temporal behavior, exhibiting a brief period of decrease followed
by a steady increase, with intensities after 10 years of production
reaching levels that are 2–10 times the 10 year production-weighted
average. Temporal patterns for methane emission intensity for entire
production regions are more complex. Historical production data and
facility data were used with a detailed basin-wide methane emission
model to simulate the collective behavior of tens of thousands of
wells and associated midstream facilities. For production regions
with few to no new wells being brought to production, and existing
wells having reached a mature stage, as in the Barnett Shale production
region in north central Texas, the methane emission intensity gradually
increases, as natural gas production decreases faster than emissions
decrease, following the general pattern exhibited by individual wells.
In production regions that are rapidly evolving, either with large
numbers of new wells being put into production or with the introduction
of source-specific regulations, the behavior is more complex. In the
Eagle Ford Shale, which has had both a large number of new wells and
the introduction of source-specific regulations, the methane emission
intensity stays within relatively narrow bounds but the distribution
of sources varies. As source distributions vary, basin-wide propane-to-methane
and ethane-to-methane emission ratios vary, impacting methods used
in source attribution.