G. Alan Petzet
Exploration Editor
Exploration and development programs are maintaining their brisk pace in the Arkoma basin of Arkansas and Oklahoma.
The basin is playing host to a round of drilling that involves the deepest holes and heaviest rigs ever concentrated there.
OXY USA Inc. late last month was preparing to spud a projected 21,000 ft, $12 million wildcat near Danville, Ark., to Cambro-Ordovician Arbuckle, a formation that does not produce commercially in Arkansas.
An OXY led group has put 14 months of engineering into the drilling to avoid problems that plagued a nearby well. Environmental considerations also are paramount at the OXY test. It's in the Ouachita National Forest.
Several other wildcats to Arbuckle and other zones are being drilled or planned in Arkansas.
Drilling activity is intense south and southeast of Wilburton field on the Oklahoma side of the basin. pushing south beyond the Choctaw fault into the Pine Mountain and Ti Valley fault blocks.
Meantime, Amoco Production Co. expects flow to increase through a gas gathering system south of Haileyville and Hartshorne, Okla., and an Exxon Co., U.S.A. unit is acquiring right-of-way for another system east of Amoco's in the busy drilling area south of Wilburton.
Farther south, ARCO Oil & Gas Co. plugged a wildcat projected to Arbuckle that might have become the basin's deepest penetration in Oklahoma.
OXY WILDCAT
OXY's Oklahoma City drilling department has been planning the 1-A Danville USA wildcat in 33-5n-22w for 14 months.
The well is in nonproducing Yell County south of the Arkoma basin producing trend. It is to be the first well in Arkansas to penetrate Arbuckle at great depth.
OXY holds about 11,000 net acres in the prospect, about 4 miles east of Danville.
The company was elected operator for a 3 sq mile area of mutual interest for a seven company group that also involves Murphy Oil Corp., Anadarko Petroleum Corp., Amoco, Pennzoil Exploration & Production Co., Santa Fe Energy Co., and Arkla Exploration Co.
A Mobil Oil Corp. unit is contributing support in the project associated with its adjacent leases.
Nearest deep Arbuckle production is about 110 miles west in Wilburton field, Latimer County, Okla., where at least 500-600 bcf of reserves have been established in the zone at about 14,500 ft.
Arkansas' deepest well went to 17,349 ft in Hempstead County in 1979.
DRILLING, CASING PROGRAM
OXY projects 470 drilling days to 21,000 ft through hard, abrasive, faulted, and fractured sands and shales that dip at angles of as much as 80 from horizontal.
Murco Drilling Corp., Shreveport, will tackle the job with its Rig No. 58, whose rated hookload capacity is 2.5 million lb.
A unique 30 in. flat bottom bit and air hammer will be used to drill to 1,700 ft, allowing room for five casing strings from surface to total depth.
Such a large hole has never been air drilled below 200 ft, OXY said.
OXY plans to use 22 in. air hammers from about 1,700 ft to 6,000 ft or deeper, a record depth for 22 in. hole.
OXY figures the large diameter air bits and hammers could save more than 100 drilling days and about $1.5 million.
The company will run hydrogen sulfide resistant, 146 lb/ft, 16 in. casing as deep as 1 0,000 ft.
If run to that depth, the string will weigh nearly 1.5 million lb.
About 9,000 sacks of cement with additives for temperature and thickening time modification will isolate the 16 in. casing annulus from the surface and from possible high pressures below.
More than 750 Mcf of nitrogen will be injected into the cementing mixture to lighten the hydrostatic load imposed on the formation by the cement column, making this one of the largest foamed cementing operations ever performed.
CIRCULATING SYSTEM
OXY engineers used a computer model tested and refined on air drilling projects in the Appalachian basin and several shallower Arkansas wells to predict compressed air volume and pressure requirements for the Danville well.
OXY and Ingersoll Rand Corp. engineers worked out methods for using air drilling as deep as possible.
Water based drilling fluids will be used in the surface part of the hole after air drilling is no longer possible.
Below 1,700 ft, when air drilling is no longer feasible, oil based fluid will be used to minimize damage to highly reactive shales expected as deep as 16,000 ft.
The OXY group is betting the improved technology will help it surmount drilling problems ARCO and Santa Fe Minerals Corp. encountered in 1985 at 1-32 Peeler Gap. That well, projected to Arbuckle at 20,000 ft, was abandoned at 13,919 ft after 329 days because of drilling problems.
ENVIRONMENTAL EFFORTS
The OXY group's wildcat location falls under U.S. Forest Service jurisdiction on a lease acquired from the Bureau of Land Management.
The partners funded archaeological studies and an environmental assessment and obtained Arkansas Oil and Gas Commission and Department of Pollution Control and Ecology permits.
The 8 acre drillsite was designed so that no contaminating fluids will touch the ground.
A closed loop drilling fluid system is installed at the rig. Concrete pads and ditches that run to concrete sump tanks have been built throughout the location to contain diesel oil, soap, wash water, and other fluids.
As secondary containment, the location is equipped with berms that direct drainage through a valved French drain system, allowing total control of fluids, OXY said.
MORE ARKANSAS DRILLING
Arbuckle is the objective at several other wildcats and deeper pool tests in Arkansas.
Coastal Oil & Gas Corp., Houston, staked a 14,800 ft wildcat to Cambrian Reagan, presumably to test Arbuckle. Its 1 Thompson, 2-5n-31w, is in Witcherville field, Sebastian County.
Pennzoil is drilling near projected depth of 13,500 ft at 30-33 Mitchell, an Arbuckle wildcat in Pope County, Ark., about 6 miles south of Oak Grove field.
Arkla is under way at 1-19 Gronwald, 19-7n-26w, a planned 13,500 ft Arbuckle deeper pool wildcat in Pine Ridge field, Logan County.
And Seeco Inc., Fayetteville, Ark., plans a 5,500 ft Arbuckle test at 1-33 Federal, 33-12n-24w, in Batson field of Johnson County.
Later this year or early in 1991 a Mobil Oil Corp. unit is expected to drill a 20,000 ft test in Perry County, Ark.
OKLAHOMA DRILLING
In Oklahoma, ARCO plugged 1 Ulysses, 35-4n-18e, at 17,480 ft due to unspecified drilling problems. The well was to have gone to 20,250 ft to test the Arbuckle.
ARCO staked a west offset for 15,520 ft or Pennsylvanian Wapanucka, and BTA Oil Producers, Midland, Tex., completed a Pennsylvanian Spiro discovery just 2 miles north of ARCO's deep dry hole.
BTA's 1 Amason, drilled to 14,090 ft in 24-4n-18e, flowed 5.111 MMcfd of gas through a 26/64 in. choke with 1,500 psi flowing tubing pressure from perforations at 13,649-696 ft. BTA in August completed 1 Mabry, 11-4n18e. The discovery, which opened South Wilburton field, flowed 2.522 MMcfd from Pennsylvanian Atoka perforations at 8,580-8,604 ft.
Exxon plugged the basin's deepest hole, 1 Retherford, 5-3n-18e, at 19,046 ft in 1985. Several other wildcats projected to as deep as 22,500 ft are being drilled or evaluated in Latimer and LeFlore counties (see map, OGJ, June 4, p. 60).
Meanwhile, Helmerich & Payne Inc. and Oneok Resources Co., Tulsa, started the first well under a 2 year joint exploration program that covers prospects in Pittsburgh, Haskell, Latimer, and LeFlore counties, Okla., and other Arkoma basin counties.
H&P is operator, and Oneok has a 30% interest.
Amoco expects its 1991 Arkoma drilling program to be about the same size as in 1990, a $20-30 million effort that entailed 10-12 company operated wells and participation in several outside operated wells.
Most of the drilling will be development in both years. The company is still targeting mostly imbricately thrusted Pennsylvanian Spiro sandstones.
Copyright 1990 Oil & Gas Journal. All Rights Reserved.
