Abstract
Shale gas plays have taken precedence over shale oil plays since 2009. With the price of oil falling, gas may take a more predominant role in 2015. In 2010, in a paper presented at the SPE Technical Conference and Exhibition (SPE-135555-MS), authors of this paper analyzed the production decline trends from public data in five major US shale gas basins—Barnett, Fayetteville, Woodford, Haynesville, and Eagle Ford. Much has changed over this time, and rig counts have fallen in gas-rich areas all over the US from their 2010 numbers. Over that same period, gas production from these five plays has increased from 9.2 Bscf/D to 16.7 Bscf/D. Shale gas decline trends continue to be a point of contention in the industry from some consultants and investment firms. This manuscript builds upon the previously published work to include new production from the last five years. Updates to the estimated ultimate recovery (EUR) analyses and the overall economic feasibility of horizontal shale gas wells were made taking into consideration of how new wells have performed.
In this new study, we updated the production of existing wells (used in our previous study) and included production from new wells. We used the same geologic areas as before, with a refinement made for the Haynesville and Eagle Ford plays. We compared the original Arps decline curve estimation predicted in the previous publication and the new estimation performed with five years' additional data. Changes in EUR by play and vintage were also studied as was the impact of available production history on Arps's decline parameters for each basin. From these analyses, we developed recommendations for a minimum production period to properly assess EURs when using Arps method.
The production type curves by play were updated with wells drilled in the studied geographic areas from 2010 onwards. These newer vintage wells were compared with older wells to determine which plays are still realizing improved well performance and which plays have seen some plateauing or decrease in production. The drilling and completion factors were analyzed in plays where average well production continues to improve, and we investigated possible contributing factors impairing production of new wells in plateauing shale plays.
An economic analysis was performed to determine the break-even cost for each shale gas basins studied. The decline curves and EURs were incorporated along with well costs. This study helps to explain if wells are still improving in each basin, what the improvement drivers are, and what impact infill drilling has had on these plays.
