But the estimates vary greatly among regions within the play and even well to well, especially wells of different ages. The median EUR across all 32 Eagle Ford counties over the study period was 103,000 bbl/well.
The Eagle Ford analysis, by Dana Van Wagener, appears as part of EIA’s Annual Energy Outlook 2014 in a report illustrating assumptions for shale and tight oil plays in forecasts of total US production of crude oil.
For each tight or shale well with initial production in 2008 or later and for which at least 4 months of production data are available, the analysis fits monthly production to a decline curve that begins hyperbolic but shifts to exponential after the decline rate reaches 10%/year. The EUR for each well is the sum of past production plus an estimate of future production based on the fitted production decline curve for a 30-year well life.
Van Wagener noted that EURs generally stabilize after 3 years of production because for many wells in tight formations half the EUR is produced in that period. Per-well EURs based on 3 years of data differ from EURs based on 4 years of data by an average of 6,000 bbl and range from 65,000 bbl higher to 98,000 bbl lower.
Eagle Ford results
Van Wagener calculated the Eagle Ford per-well average EUR from 5,384 wells. That group came from a database of 6,594 wells, from which the analyst excluded 927 with less than 4 months of production data and 283 for which monthly production wasn’t successfully fitted to a hyperbolic decline curve.
Seven counties in the Eagle Ford play had more than 400 oil and natural gas wells at the time of the analysis. Among those, DeWitt County had the highest mean EUR per well, 334,000 bbl among 453 wells, followed by Karnes County with 226,000 bbl among 975 wells. Other mean per-well EURs and well totals were Gonazales County, 198,000 bbl, 486 wells; LaSalle County, 153,000 bbl, 755 wells; Dimmit County, 137,000 bbl, 820 wells; McMullen County, 127,000 bbl, 455 wells; and Webb County, 80,000 bbl, 593 wells.
For counties with little or no drilling, the analysis assumed EURs to be the average of mean estimates from adjacent counties. Average EURs fell below 25,000 bbl/well in Burleson and Maverick counties.
“There is still a great deal of uncertainty underlying the recovery of tight oil in known plays as well as the potential for production from additional plays or other layers within a currently productive formation that has not been tested,” the report cautions. “The application of refinements to current technologies, as well as new technology advances, can also have significant but uncertain impacts on the recoverability of tight and shale crude oil.”