"Production decline curves and payout thresholds of horizontal Woodford wells in the Arkoma Basin, Oklahoma"

Richard Andrews1

¹Oklahoma Geological Survey

Through August 2008, the Woodford Shale in SE Oklahoma produced >180 billion cubic ft gas from >630 horizontal wells. Average production per well is ~700,000 cubic ft gas per day (cfgpd) with initial rates as high as 5–10 million cfgpd. Typically, wells are drilled with a 4,000 ft horizontal lateral close to the center of the formation and fractured treated in 3–9 stages utilizing ~200,000 pounds proppant per stage. The degree of induced fracturing liberates gas from microfractures in higher volumes for longer periods than compared to vertical wells.

Monthly production from several high-volume Woodford wells is tabulated in MS Excel and 20-year decline curves are extrapolated. Predicted well performance is realistic since hard data defines the most significant period of decline for each well history. Initial annual declines are 50–75% but gradually fall to ~4%.

Payout thresholds occur when net revenue (80% of gross) equals well cost. Depending on depth, lateral length, and the number of frac stages, drilling and completion costs are estimated at $4–$6 million.

Results of this study show that above-average wells will pay out in a few years with wellhead gas prices =$8/mcf. At $5/mcf, payout for most wells is =5 years whereas below-average wells will never pay out. Due to gas price indexing, discounted spot prices of only $2/mcf make most horizontal Woodford wells in this play area uneconomical.

AAPG Search and Discover Article #90097 © 2009 Tulsa Geological Society, Tulsa, Oklahoma