Lessons Learned from 20 Years of Production in the Barnett Shale

Abstract:

We analyze a 22 years of shale gas production, from more than 18,000 wells, in the Barnett formation to better characterize and understand shale gas production. The Barnett Shale formation has a relatively long history of exploration and shale gas production using both hydraulic fracturing and horizontal wells. The original Barnett well, a vertical well that used a nitrogen foam working fluid, dates back to 1981, and the first horizontal wells were drilled in 1991. However, the first “successful” production wells were not drilled until around 1997-1998.

Gas production data for the Barnett is publicly available dating back to 1993. Here, we analyze gas production from ~18,000 individual wells (data collected in July 2014) in order to understand and quantify how shale gas has been produced in the Barnett. This includes understanding how and when shale gas production techniques have improved resulting in enhanced gas production. Several key trends and hypotheses emerge from this analysis. For example, the data shows a distinct and strong pattern of “learning by doing”, whereby per-well gas production rates have notably increased over time. For example, a typical well drilled in 2011 takes three years to produce 1,000 MMcf, whereas a typical 2007 well takes seven years to produce the same quantity. The data can also be differentiated by parameters such as depth and well type (principally vertical vs. horizontal); we show a clear link between drilling techniques and production. The analysis also reveals unexpected outcomes. For instance, wells drilled in the period 1994-1999 have greater cumulative production than wells drilled in the period 2000-2006. We hypothesize that the older wells often performed poorly when first drilled and were thus subsequently re-fractured one or more times, whereas the later wells were re-fractured much less frequently.

Finally, we compare shale gas production from the Barnett formation with more recent production from the Hayneville-Bossier and Eagle Ford formations. We believe that lessons learned from historic shale gas production can help us better understand shale production, including quantifying “rates of learning”, as well as providing the foundation of understanding the benefits and challenges of alternative working fluids such as CO₂.