Oryx Energy Co., Dallas, last week disclosed reserve additions of a net 42 million bbl of oil equivalent (BOE) from its Cretaceous Austin chalk drilling program in South Texas.
Oryx booked a net 28 million BOE this year, supplementing the 14 million BOE recorded in 1989. The company has drilled a total of 46 horizontal wells in the Austin chalk trend.
The company also gauged a 1,700 b/d discovery, the latest Austin chalk success in its exploratory drilling program in the Pearsall field area.
CURRENT ACTIVITY
Oryx has seven rigs at work in the Austin chalk trend. The company had expected to drill 85 horizontal wells by yearend, based on an average of one well with a lateral displacement of 2,500 ft being drilled every 30 days.
However, experience has enabled Oryx to drill longer reach wells.
The average drilling time is now 40 days, so the company has cut its yearend target to 75 wells.
"With the longer horizontal displacements, wells can drain reservoirs more efficiently," said James E. McCormick, president and chief operating officer. "Lateral displacement was less than 1,000 ft when the program began. Our newer wells can stretch out more than 4,000 ft."
McCormick said the reserve additions are based on well performance and reservoir simulation studies. The studies postulated hyperbolic decline curves for horizontal wells instead of straight line declines previously supposed.
"Horizontal wells have higher initial production volumes," McCormick said. "The hyperbolic curves show that, on a percentage basis, the production rate declines more slowly with each passing year."
Oryx owns or holds an option on about 240,000 acres in the Pearsall area. More than 200 well locations have been identified on its acreage, and the company plans to drill them over the next several years.
"The outlook for this program is much brighter than when we began," McCormick said. "The Austin chalk horizontal play is larger and longer lived than we had thought. We're looking for ways to extend it."
As a result of associated gas production from the Austin chalk, yearend output from the recently reopened Big Wells gas processing plant is expected to double to 2,000 b/d of processed liquids from 20 MMcfd of wet gas.
NEW STRIKE
Oryx's latest Pearsall area discovery, 1 Lloyd W. Booth, flowed 1,697 b/d of oil and 744 Mcfd of gas through a 20/64 in. choke with 490 psi flowing tubing pressure. The well has a horizontal displacement of 4,204 ft and produces from open hole intervals between 6,165 and 10,126 ft, total measured depth.
The 1 Booth is about 5 miles north of Big Wells on the Zavala-Dimmit county line.
Copyright 1990 Oil & Gas Journal. All Rights Reserved.