The AAPG/Datapages Combined Publications Database
AAPG Bulletin
Figure
AAPG Bulletin;
Year: 2024;
Issue: January
DOI: 10.1306/10242221078
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Figure 6.
Illustration of the approach to obtain historical well prototype for each well cohort. As an example, we pick cohort-7, which samples all of the horizontal gas wells in the southwest core area of the Marcellus Shale, completed between 2015 and 2016. We split cohort-7 into the subcohorts 7-j that contain all of the wells with at least j years on production. In this case, 
yr. For each subcohort, we fit a generalized extreme value (GEV) distribution and obtain the 
(upper bound), P50 (mean), and 
(lower bound) of the annual gas rate (billion standard cubic feet [BSCF]/yr/well). We then connect the 
, P50, and 
points from the five subcohorts, and use cumulative production as the stable historical well prototype for cohort-7. 
= location parameter of GEV PDF; 
= scale parameter of GEV PDF; CDF = cumulative distribution function; CI = confidence interval; PDF = probability density function.