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Spraberry Trend resource estimate up sharply

By OGJ editors
HOUSTON, Apr. 10 -- Pioneer Natural Resources Co., Dallas, estimated that its properties in the Spraberry Trend in West Texas contain 1 billion boe of net resource potential in addition to the 481 million boe of proved reserves the company had booked at the end of 2007.

Pioneer, which plans to accelerate drilling in the giant field in 2009, estimated it has a drilling inventory of 19,000 locations. It is the field's largest driller and producer with 869,000 acres more than 75% held by production, 5,300 active wells, and 16 rigs running.

The 1 billion boe of further net resource potential includes 200 million boe of resource potential, beyond the 248 million boe of proved undeveloped reserves already booked, related to Spraberry formation development on 40-acre spacing with deeper Wolfcamp drilling where applicable; 500 million boe related to 9,500 highgraded 20-acre infill locations; and 300 million boe related to waterflooding selected areas.

Production history suggests that 20-acre infill wells can be expected to recover 75-80% of the reserves being recovered by 40-acre wells, Pioneer said. The company drilled four successful 20-acre infill wells in the 2008 first quarter and plans 20-25 more this year.

Ten waterfloods have recovered 82 million bbl of oil, and their histories suggest that "secondary waterfloods" where appropriate can be expected to recover a further 50% of the reserves recovered under primary recovery, the company said.

Pioneer estimated that 40% of its Spraberry acreage has waterflood potential and plans to begin a large-scale waterflood program in 2009. It also sees substantial upside from completion technology advances and plans to frac five previously drilled horizontal wells with isolation packers.

Pioneer expects to add 250 million boe of proved reserves in the next 5 years and average 15% compounded annual production growth from the field through 2011. It foresees before-tax internal return rates for 40-acre and 20-acre wells of 50% and 40%, respectively, at $95/bbl.

The company information is derived from a comprehensive 2007 study by Pioneer's Permian Basin asset team that found the field to have contained more than 30 billion boe of original oil in place with estimated ultimate recovery of 3.5 billion boe (OGJ, Apr. 27, 2006, p. 30).

The study indicated that primary recovery is 12-13% on 40-acre spacing with the potential to increase 6 percentage points with 20-acre infill drilling and 9 percentage points more with waterflooding.


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