G. Alan Petzet
Exploration Editor
A Houston independent has staked a rare, remote wildcat in nonproducing Hays County, central Texas, in the frontal portion of the buried Ouachita Thrust Belt.
Portsmouth Resources Inc. plans to drill 1 Bittick et al. to 9,500 ft or Cambro-Ordovician Ellenburger 2 miles south-southwest of Dripping Springs and 27 miles west of Austin. Location is in Stiles J. Fowler survey #31, A-174.
The vertical wildcat, in Texas Railroad Commission Dist. 1, is 200 miles east of Cambro-Ordovician Ellenburger production in JM field, Crockett County, and 300 miles southwest of Arbuckle production in Wilburton field, Latimer County, Okla.
It is the first well permitted in Hays County in more than 7 years.
An exhaustive reference work on the Ouachita Thrust Belt published 30 years ago concluded, among other things, that Ouachita frontal zone structures in the Fort Worth, Kerr, and Val Verde basins and in the Sheffield channel, a late Permian successor to the Val Verde basin, seem relatively promising places for further exploratory drilling.
Ellenburger and multipay potential is thought to exist southwest of the Portsmouth wildcat in the Kerr basin (OGJ, Aug. 6, 1990, p. 82).
AREA'S GEOLOGY COMPLEX
The wildcat, drilling below surface pipe in mid-March, is expected to penetrate Ouachita facies, said Kes Gaizutis, Portsmouth geologist.
The nearby area contains complex geology and a thick sedimentary section, according to The Ouachita System, published in 1961 by the University of Texas Bureau of Economic Geology.
"East and south of the Llano uplift in parts of Bell, Travis, Blanco, Hays, and Kendall counties, wells and seismic studies indicate a narrow, arcuate, very thick body of Paleozoic rocks between rocks of the Llano uplift and the Ouachita facies rocks in the Ouachita structural belt.
"The intervening rocks appear to be foreland facies rocks deformed when the Ouachita prism was crushed against the Llano buttress. The trough in which they lie apparently connects the Fort Worth and Kerr basins around the southeast bulge of the Llano uplift.
"Seismic interpretations indicate that the sedimentary rocks are more than 12,000 ft thick in western Hays and Travis counties so that the Precambrian basement rocks exposed in the Llano uplift drop off sharply to the southeast."
The publication noted that most wells along the southeastern edge of the Llano uplift, the area of Portsmouth's well site, penetrate a typical shelf sequence of Atoka, Marble Falls, Barnett, and Ellenburger. Cretaceous rocks rest directly on Ellenburger in some wells.
"Along the southeastern margin of the shelf, however, the Atoka sandstones are of orogenic facies and contain abundant chert and phyllite fragments and a higher percentage of feldspar (10-15% more) than normally. The shales are brecciated and deformed, and there is an indication of incipient metamorphism in both shales and sandstones.
"These rocks reflect active tectonism in their source areas and apparently took part in subsequent orogenic movements."
The volume refers to the Shell Oil Co. 1 Purcell, 18 miles northwest of Georgetown in Williamson County, a dry hole drilled to 9,485 ft in 1954. The Shell well, about 45 miles north of Portsmouth's location, penetrated more than 6,000 ft of Atoka beneath which are Marble Falls-Barnett, Ellenburger, Cambrian, and Precambrian granite gneiss of Town Mountain type.
HAYS COUNTY DRILLING
Last drilling in Hays County was a 1,507 ft test completed in late 1983 about 4 miles south of Portsmouth's site.
According to Petroleum Information records, 19 wildcats 540-2,028 ft deep and one 14,020 ft test have been drilled and abandoned in the county. Six other locations were staked, then abandoned without being drilled.
The nearest previous production is one well Schubert field, 23 miles southeast of the Portsmouth well site.
That well flowed 2 b/d of 25 gravity oil from Austin chalk open hole at 741-765 ft in March 1955 but never produced a commercial volume of hydrocarbons.
Copyright 1991 Oil & Gas Journal. All Rights Reserved.