G. Alan Petzet
Exploration Editor
Onshore exploration in the Lower 48 east of California is busy in frontier as well as mature areas.
And the action isn't confined to high-visibility horizontal and coalbed methane drilling, important as they have become to activity levels and reserves additions. Here are some highlights:
- The first regional seismic line, complete with geological interpretation, of the planned 16,000 line mile Megaregional Project designed to cover the entire contiguous U.S. and adjacent offshore areas has been made available for licensing to the industry at large.
- South Louisiana's deep sandstone reservoirs, with multiple pay zones, large reserves, and high flow rates, are hosting a large number of exploratory wells even at gas prices well below $2/Mcf at the wellhead.
- A Pennsylvanian gas play is rambling eastward south of the Choctaw thrust fault in the frontal Ouachita/Arkoma basin area of eastern Oklahoma.
Amoco Production Co. said gas fields being developed by several operators along the Choctaw thrust south and east of Wilburton, Okla., could portend recoveries as large as South Hartshorne field, the largest discovery so far in terms of reserves in the thrust play.
- A deep test on the Overthrust Belt in Montana, drilling since June 1990 in remote Jefferson County, heads a list of deep tests under way in several key Rocky Mountain areas.
- Overthrust evidence is mounting in Nevada, where exploratory drilling is under way in several valleys outside the two primary producing areas.
- In the Four Corners area, a joint venture has completed a large seismic program on the Navajo Indian Reservation in the Four Corners area and plans to drill 30-40 more Pennsylvanian Desert Creek algal reef mounds there this year.
SEISMIC PROJECT
The first of a nationwide series of regional seismic lines extends from Franklin County, Ark., in the eastern Arkoma basin across the Ouachita Thrust Belt and Gulf Coastal Plain into Red River Parish, La.
The information has been proprietary to consortium members for several months and is now available to anyone at $150/mile. The line eventually will stretch 500 miles, ending in the Gulf of Mexico East Cameron area about 100 miles off Louisiana.
The pre-Jurassic section in the northern Gulf Coastal Plain appears quite different in the regional seismic data than was generally accepted, says Allen J. Bertagne, senior staff geologist, CGG American Services Inc., Houston.
CGG and a consortium of more than 20 oil companies are compiling the regional lines from three sources: CGG's nonexclusive library, contributions from consortium members, and Cornell University's Cocorp project seismic data.
The project staff compiled 250 line miles of data in its first year, 1990, and plans to boost output to about 1,000 miles/year.
Focus of the project is on the land area. Eventually three lines would traverse the Lower 48 east-west and five north-south.
The next priorities with consortium members are two lines that extend across the Gulf Coast basin and into the gulf from the Black Warrior and Permian basins, Bertagne said.
GULF COAST DEEP PLAYS
Several papers presented last fall at the Gulf Coast Association of Geological Societies meeting described the size and geologic setting of several of the area's deep fields.
The Lake Arthur complex encompasses six producing fields, mainly in Jefferson Davis and Vermilion parishes, that produce from multiple sands from middle Oligocene through lower Miocene.
Among the more significant producing intervals are the sand packages in middle Oligocene Camerina A-Miogypsinoides A sediments, according to a paper by Norman E. Smith of Lafayette Exploration & Development Co., Lafayette.
Ultimately the complex may produce more than 5 tcf of gas, about 75% of it from Camerina A-Miogyp A.
One of the six fields, South Lake Arthur, was discovered in November 1979 and at 31 wells is nearing the end of primary development, wrote Michael A. Barnes, vice-president-exploitation, Sandefer Oil & Gas Inc., Houston.
Various independents drilled 31 wells costing $6-10 million/well in and near the field's productive area in Jefferson Davis and Vermilion parishes. Three Miogyp reservoirs produce from 16,600-17,500 ft.
Before this discovery Miogyp trend reserves averaged 100-200 bcf/field, Barnes wrote.
"Prior to 1985 (with seven wells drilled) South Lake Arthur field was not expected to be five to 10 times greater than the trend norm" until two key wells drilled 8 months apart had a combined 386 ft of productive sand and dip logs that recorded southwest dip.
Two basic well designs have resulted in sustained deliverabilities of 12-20 MMcfd of gas, Barnes wrote.
The field produced 214.4 bcf and 563,000 bbl of condensate through Jan. 1, 1990. Average daily production rate peaked in January 1989 at 256 MMcf, and maximum daily production was not believed to have been reached.
"We must understand and clearly demonstrate why and how these subtle giant fields can exist within productive trends thought to have realized upper reserve potential limits in order to encourage wildcat drilling," Barnes wrote.
In Cameron Parish, Exxon Co., U.S.A. expects productive capacity to reach 300 MMcfd of gas from Miogyp sands in Chalkley Deep field (OGJ, Mar. 11, Newsletter).
About 20 new field and deeper zone wildcats projected to 17,500-21,000 ft are in various stages of operations in Cameron, Iberia, Jefferson Davis, Pointe Coupee, St. Mary, and Vermilion parishes of southwestern Louisiana.
Plains Resources Inc., Houston, is preparing to spud 1 Miami Fee, in 2-14s-14w, Cameron Parish, a 16,500 ft wildcat 3 miles northeast of Deep Bayou field.
The wildcat, with an expected dry hole cost of about $3 million plus $1 million for road and location, is to evaluate a very large Eocene structure and multiple Oligocene objectives visible on seismic sections.
Plains' 28,900 acre Miami fee acreage is a nearly undrilled spread between Sabine and Calcasieu lakes.
ARKOMA BUSY
The Arkoma basin is yielding an increasingly rich harvest of gas from Pennsylvanian zones as Cambro-Ordovician Arbuckle, which kicked off the 3 year old play, has been disappointing since the initial discovery.
Amoco claims a string of nine significant discoveries along the Ouachita Thrust Belt in Latimer and Pittsburg counties, Okla., the past 2 years.
Its most recent completion is 1 Bobcat Ridge Unit, in 30-5n-20e, about 5 miles southeast of Wilburton in Latimer County.
The well flowed 4 MMcfd of gas through a 48/64 in. choke with 270 psi flowing tubing pressure from perforations at 6,244-6,300 ft and 5.8 MMcfd through a 24/64 in. choke with 1,650 psi flowing tubing pressure from perforations at 14,642-666 ft. Both zones are in Pennsylvanian Spiro sandstone and Wapanucka limestone.
Two or more structurally repeated sections of Pennsylvanian Spiro and Wapanucka are typical of wells along the 25 miles from Amoco's 1 Zipperer in eastern Pittsburg County to its 1 Raymond Smith Unit 8 miles east of Wilburton in Latimer County.
The widely separated producing intervals in the well have similar formation characteristics.
As the play has developed from west to east, various wells have exhibited considerably different production rates, generally 2-30 MMcfd/well.
This is believed related to the degree of porosity development.
Wells completed naturally are interspersed with those that are treated.
However, how burial depth affects production performance is not well understood. Amoco said its 160 MMcfd of net production from the area will grow as more wells are connected to its Choctaw gathering system.
Meanwhile, the drilling pace remains strong. About 50 wells projected to 13,000-22,000 ft are between permitting and completion/reporting stages in Latimer and LeFlore counties, Okla.
At least one operator expects the industry to maintain current levels of drilling in the basin for 2-3 years.
ARBUCKLE STILL PRIZED
Arbuckle remains the primary objective at numerous wildcats along a 250 mile arc from Atoka County, Okla., to Conway County, Ark.
Of four ultradeep tests spudded during 1990 or in late 1989, two have been abandoned, and two are drilling.
Amoco topped Arbuckle at 19,055 ft at 1 Devil's Backbone, in 31-5n-24e, LeFlore County, Okla. It abandoned the wildcat, projected to 22,500 ft or Cambrian Reagan, in Arbuckle at 21,019 ft.
ARCO Oil & Gas Co. abandoned 1 Ulysses, in 35-4n-18e, Latimer County, Okla., a planned 20,250 ft Arbuckle wildcat. ARCO drilled to 17,480 ft and lost the hole, plugged back to 12,570 ft, and drilled a sidetrack to 15,910 ft before terminating operations.
Mobil Oil Corp. spudded Mar. 28, 1990, at 1 Green Bay Packaging Inc., in 8-4n-23e, LeFlore County, and is drilling below original projected total depth of 19,600 ft. New objective is 22,500 ft or Arbuckle. Well site is 9 1/2 miles southeast of Red Oak-Norris gas field.
And in Yell County, Ark., Oxy U.S.A. Inc. spudded last September at 1 -A Danville, in 33-5n-22w, a projected 21,000 ft Arbuckle wildcat 15 miles south of Mount Nebo field.
Elsewhere in Arkansas, Coastal Oil & Gas Corp. drilled 1 X Thompson, in 2-5n-31w, Sebastian County, to 13,400 ft in Reagan, but plugged back for a modest Pennsylvanian Basham sand gas completion at about 5,200 ft in Witcherville field.
The company junked its first attempt in the section at 9,400 ft, skidded 32 ft east, and drilled 1X Thompson.
In Pope County, Ark., Pennzoil Exploration & Production Co. drilled 30-33 Mitchell, a 13,500 ft Arbuckle wildcat, to 13,250 ft but set casing at 9,450 ft. Well site is in 30-7n-18w, 6 miles south of Oak Grove field.
Near the basin's eastermost producible well, Yates Petroleum Co., Artesia, N.M., staked 1 Landrum-Quitman, in 12-9n-12w, Cleburne County, Ark., 2 miles north of Quitman. It is a planned 8,500 ft Arbuckle wildcat.
ROCKIES DEEP EXPLORATION
Deep exploration was under way in several Rocky Mountain states.
Norcen Explorer Inc., Calgary, was drilling near permitted depth in mid-March in a sidetracked hole at 1-11 Kimpton Ranch, in 11-4n-2w, Jefferson County, Mont. The Overthrust Belt wildcat, 31 miles south-southeast of Helena, is permitted to 15,000 ft.
Objectives are Paleozoic sediments beneath an elongated, compressed surface anticline of Precambrian metamorphics, Petroleum Information reports.
The well is on a farmout from Balcron Oil Co., Billings, Mont., 150 miles south-southeast of Blackleaf Canyon gas field.
In Garfield County, Colo., Mobil is drilling F11X-34P O'Donnell, in 34-7s-92w, 6 miles northwest of Divide Creek gas field.
Projected depth is 19,500 ft or Mississippian Leadville. Well site is on the Grand Hogback monocline about 11 miles southeast of Rifle.
Four Wyoming deep tests are active. They are:
- W.A. Moncrief Jr., Fort Worth, 1 Badwater Creek, in Natrona County, 8-10 miles east of Madden Deep Unit, projected to 24,500 ft or Mississippian Madison.
- Amoco 4 Frewen Deep, on the Wamsutter arch in Sweetwater County, a planned 18,662 ft Cretaceous Frontier replacement well for Amoco's Cretaceous Lakota gas discovery of Frewen field completed in 1989.
- Exxon and Celsius Energy Co. 34 Canyon Creek Dome Unit, an 18,000 ft Madison test in the Vermilion Creek basin, Sweetwater County.
- Chevron U.S.A. Inc. 1 Chevron-UPRC, on the Overthrust Belt 1 1/4 miles southeast of the shut-in discovery well for Glasscock Hollow Jurassic Nugget gas-condensate field in Uinta County.
COLORADO DEVELOPMENT
Development drilling has been brisk in eastern and western Colorado.
Several new Pennsylvanian fields were opened during 1990 on the Las Animas arch, but most of the activity consisted of development drilling in Cheyenne County, on which an active Morrow sand oil play has been centered for about 4 years.
Arapahoe field contains 96 wells producing a combined average of more than 6,800 b/d of oil and 5.7 MMcfd of gas from Morrow, Petroleum Information reported. Cumulative production through September 1990 was about 1.8 million bbl of oil and 1.4 bcf of gas.
Harker Ranch field, discovered in 1989, had produced more than 146,000 bbl of oil and 145 MMcf of gas through last September. The field had 14 wells producing a combined 784 b/d of oil and 680 Mcfd of gas.
Both fields are still growing.
In the Piceance basin, Barrett Energy Corp., Denver, produced 8.6 bcf of gas during January-September 1990 from 211 gas wells, most of them in Parachute and Grand Valley fields of Garfield County.
Parachute field produced 16 MMcfd of gas from 65 wells, and Grand Valley field produced 14.5 MMcfd of gas from 53 wells.
Barrett completed more than 40 wells in Parachute, Grand Valley, and Rulison fields during 1990 from Eocene Wasatch and Cretaceous Mesaverde sands, including Cameo coal intervals.
PARADOX BASIN PROGRAM
A program of exploring mainly Desert Creek algal reef mounds near giant Aneth field in southeastern Utah has gone well for a group of companies led by Chuska Energy Co., San Antonio.
Chuska has established gross production of 3,761 b/d of oil and 8.184 MMcfd of gas from 19 wells on the Navajo reservation in about 2 years.
Five of the wells are on acreage covered by a 1983 operating agreement with the Navajo Tribe, and 14 are on 1987 operating agreement acreage.
Chuska's gross proceeds interest in the production averages about 37%.
All of the joint venture's exploratory successes have been algal mounds except the Tower well, which is a Pennsylvanian Ismay completion.
Chuska places its success rate for algal mound targets on 1987 agreement lands at 78%-seven discoveries in nine holes drilled in San Juan County, Utah-excluding completions in progress at 33I1 Navajo Canyon and 12L1 Beaver.
Chuska in 1989 reworked three gas wells in Black Rock gas field, Apache County, Ariz., and six oil wells in Rattlesnake field, San Juan County, N.M. The company completed two more Black Rock field wells last year.
It also reentered and established commercial gas producing capability at the Beclabito well in San Juan County, N.M., but the well is not currently producing.
The joint venture has completed six wells as dry holes, including one at South Verde in New Mexico's fractured Mancos shale oil play; two algal mounds in Utah, 9M1 Summit and 2011 North Village; and three non-algal mound tests, Big Bend, Rabbit Ears, and Ranger.
NEVADA ACTION
A considerable volume of activity is centered on the established Railroad and Pine Valley producing areas, but exploratory drilling is taking place in earnest outside those areas in Long, White River, Steptoe, and Antelope valleys.
Interest is growing in the concept of overthrusting in Nevada.
Work in the Timpahute Range, between Yucca Mountain and prolific Grant Canyon field, confirms the thrust belt concept, said Alan K. Chamberlain, Cedar Strat Corp., Denver.
The work also sheds light on source and reservoir rock quality and thrust belt geometry, Chamberlain says in an abstract of a poster session to be presented at the American Association of Petroleum Geologists annual meeting Apr. 7-10 in Dallas.
Chamberlain believes the Central Nevada thrust belt could contain billion barrel oil fields.
The belt coincides with a high organic richness fairway and a maturation fairway of Mississippian source rocks that have already produced more than 25 million bbl of oil, he wrote.
He cited a strong possibility that subthrust source rocks may have generated large quantities of hydrocarbons that may be trapped in large thrust features beneath Yucca Mountain, which has been proposed as a high level nuclear waste repository.
During 1990, operators opened Three Bar field, Eureka County, in Pine Valley near Blackburn field, and a not yet named Nye County field in Railroad Valley 11 miles south-southwest of Currant.
Nevada's cumulative crude oil production exceeded 30 million bbl during November 1990, state figures showed. Production in recent months has averaged more than 11,000 b/d.
Grant Canyon field of Nye County accounts for about 60% of the state's daily production and about 46% of cumulative production.
Two Apache Corp. operated wells there are capable of producing about 2,400 b/d and 4,400 b/d of oil, respectively, but these volumes sometimes overtax local processing capability.
Cumulative production for the state's main fields, with discovery year, through late 1990 are: Grant Canyon (1983) 13.8 million bbl, Trap Spring (1976) 9.1 million bbl, Eagle Springs (1954) 3.9 million bbl, and Blackburn (1982) 2.1 million bbl.
Copyright 1991 Oil & Gas Journal. All Rights Reserved.