The largest operator in the Barnett shale play, Devon Energy Corp., Oklahoma City, in the past year launched a horizontal drilling program in both its Barnett core and non-core areas with encouraging results.
Brad Foster, vice-president and general manager, central division, and Jeff Hall, exploration and exploitation manager for Devon, provided the following update to OGJ on Devon's success in the Barnett shale.
Devon now operates about 1,500 wells in the Barnett core area that encompasses Denton, Wise, and a portion of Tarrant counties in the Fort Worth basin of Texas. This represents about 60-70% of the producing wells in the total Barnett play, which now produces about 800 MMcfd.
Devon holds about 120,000 acres in the core area and 430,000 acres outside. The company began experimenting with horizontal drilling in the core area because residential and other construction limited its access to some surface locations in the Newark East field. Horizontal drilling also has helped the company overcome problems with underlying frac barriers. This field is developed on 40-acre surface spacing, although reservoir evaluation indicates most wells drain only about a 27-acre elliptical pattern.
Outside the core area, Devon's experiments with horizontal wells hope to overcome the more complex geology found in this region.
In 2003, Devon will drill 315-330 total wells of which 65-70 were horizontal. Of these horizontal wells, it has hooked-up for production 38 wells in the core area and 16 wells outside of the core, as of mid-December 2003.
It estimates that horizontal wells drilled on 160-acre spacing in the core area will recover about 2.5-3.5 bcf/well, while outside the core area the recovery will be 1.5-2.5 bcf/well.
Initial production from a horizontal well, after being hydraulically fractured, in the core area averages about 2.5 MMscfd, while outside the core area the average is 1.5 MMscfd.
The horizontal well production typically shows a hyperbolic decline with an initial steep 30% decline in the first year.
Devon typically drills 2,500-3,500 ft horizontal laterals that usually have 51/2-in. or 7-in. casing in the lateral. It perforates the laterals and stimulates the extremely tight shale typically with 2-4 million gal waterfracs containing a small amount of sand.
Its typical vertical well in the core area costs $680,000-800,000 compared with the $1.6 million required for drilling and completing a horizontal well. But it expects a horizontal well to have 2-2.5 times greater production rates and total gas recovery than a vertical well.
In 2004, Devon plans to drill about 150 wells, of which about 95 will be horizontal.
Foster said that in 2004 Devon is drilling fewer wells in the Barnett because the company will be "transitioning to the non-core areas." He emphasizes that outside the core area Devon will continue to experiment with drilling and completion techniques.
Once Devon gains a better understanding of the geology involved, Foster expects to increase drilling activity again.
