Gary S. Swindell, P.E. Back to home page
Estimated Ultimate Recovery (EUR) Study of 7,300 Marcellus Shale Wells in Pennsylvania. February 2021 Update (pdf)
Gary S. Swindell, P.E., Consulting Petroleum Engineer, Dallas, Texas
Copyright 2021, Gary S. Swindell, P.E.Summary
This study summarizes the results of an updated and expanded evaluation of the estimated ultimate recovery (EUR) for all horizontal Marcellus Shale completions from 2008 through 2018 in Pennsylvania. Individual well rate vs. time plots using publically available production data through September 2020 were used to forecast the EUR of 7,336 wells. Not included were the 516 wells with first production in 2019 and 392 wells with first production in 2020 (through September) as the decline behavior is not believed to be sufficiently established for reliable projections. The primary study objective was to determine the distribution and trends in EUR.
A considerable number of wells are exhibiting a change in the nature of the decline, generally about 2,500 MCF per day and about 3 years into the production. This may represent a different flow regime in the reservoir than that present in the early months of production.
For 7,336 horizontal wells first produced in 2008-2018 with enough history to forecast a decline profile, the estimated ultimate recovery across the whole state averages 7.7 billion cubic feet equivalent (Bcfe) per well with a median of 6.5 Bcfe. Note that the distribution covers all the wells during a 10 year period - there are further changes over time. The results vary considerably by region - in six counties in the Northeast part of Pennsylvania, the average is 8.6 Bcfe per well and in Wyoming County the mean EUR is 13 Bcfe. In that Northeast region there are a number of wells exceeding 20 Bcfe EUR.
Lease liquids (oil and condensate) were converted to an equivalent gas volume using a price ratio of 20 thousand cubic feet (Mcf) per barrel). Much of the reported lease liquids production is from wells in Washington and a few other southwestern counties, however only Range Resources and a few other operators are reporting those liquids. The economic limit was estimated assuming final operating costs of $3,000/month per well, $2.50/MCF and 20% royalty burdens.
The data shows that apparent operational changes across the area, probably due to compression and added take-away capacity along with higher hyperbolic behavior in the rate vs. time plots, have improved EUR estimates by about 6% for those wells which were included in the 2018 study.
It should be noted that the estimates are done under the Proved Developed Producing reserve classification and by deterministic methods (rate vs. time). While deterministic estimates may have broadly inferred confidence levels, they do not have the defined confidence levels of Probabilistic estimating methods, which for PDP is a 90% confidence that the reserves are less than the amounts stated. Furthermore, operational improvements such as well recompletions, re-fracs and additional compression cannot usually be considered in a Proved Producing reserve classification, with the result that the Proved reserves tend to grow over time as other reserve classes are moved into the Proved category.
A regional breakdown, dividing the state into six areas, Northeast, Northwest, West Central, Mountain, Green-Fayette, and Washington, was made to analyze well performance in a more local way. Fig. 3 in the appendix shows the location of many of the wells in the study and the regional divisions.
Charts and tables in the following pages summarize the results.
Summary of Projected EUR by County
Fig. 3 - The region divisions used in the study.
NORTHEAST REGION - Bradford, Lycoming, Sullivan, Susquehanna, Tioga, Wyoming counties
NORTHWEST REGION - Cameron, Elk, Forest, McKean and Potter counties
WEST CENTRAL REGION - Allegheny, Armstrong, Beaver, Butler, Clarion, Indiana, Jefferson, Westmoreland
MOUNTAIN REGION - Blair, Centre, Clearfield, Clinton, Somerset counties
GREEN-FAYETTE REGION - Greene and Fayette counties
Copyright 2018, Gary S. Swindell, PEBack to home page