BUDA STRIKES MAY BOOST SOUTH TEXAS ACTION

G. Alan Petzet
Senior Staff Writer

Cretaceous Buda limestone oil production has been established in an area of South Texas that could give further impetus to the already hot Austin chalk horizontal drilling play.

Two wells almost 1 1/2 miles apart in Frio County, Tex., along the Atascosa County line have begun producing oil at high rates from Buda.

The wells appear to be zone discoveries in the same fault block in Pruitt (upper Cretaceous Navarro) field, about 15 miles east of Pearsall, Tex.

FIRST WELL

Fossil Bay Petroleum Inc., Irving, Tex., drilled 1 Tschirhart in March and April vertically into Buda. The company intended to drill through Austin chalk and Buda into Del Rio shale and then run logs.

The well began flowing oil during drilling at 6,577 ft, 70 ft into Buda, and 6 days were spent attempting to kill the well with brine. To kill the well, a 150 cp viscosity plug was pumped down and a new mud system built on top of the plug.

Completed, the well flowed 5,317 bbl of oil in its first 7 days. Official Texas Railroad Commission initial potential test rate was 842 b/d of oil and 360 Mcfd of gas from Buda.

Through the first week in May the well had produced more than 8,000 bbl of oil.

SECOND WELL

Fossil Bay drilled 1 Williams, about 7,000 ft west-southwest of 1 Tschirhart, in early May, expecting a different fault block.

The well cut a fault. Buda and Austin chalk were logged. Horizontal tools were picked up and began to build angle, and the fault was encountered again at about 70.

Evaluation shows a 160 ft displacement, which puts the Buda formation in the same fault block as 1 Tschirhart. The company plugged back and kicked off again into Buda on the upthrown side of the fault.

The 1 Williams began flowing at the same true vertical depth as 1 Tschirhart. The 1 Williams was flowing at the rate of about 36 bbl/hr of oil. The operator is rigged up to handle twice that much produced fluid during drilling.

Fossil Bay plans to drill the entire Buda section, about 110 ft thick vertically, at 45-70, penetrate slightly into underlying Del Rio shale, and run several conventional logs.

The company believes at least six more locations are prospective, possibly more depending on the extent of the field. Next well will be 1 Rankin, a northwest offset to 1 Tschirhart, to spud in late May.