Vicksburg, Frio successes lift Galveston Bay area prospects

G. Alan Petzet
Exploration Editor

Tertiary plays are yielding gas and condensate reserves in Galveston and Trinity bays and adjacent Galveston and Chambers counties along the Upper Texas Gulf Coast.

The area south and southeast of Houston has long been productive of gas mainly from Upper Frio sands. Operators armed with modern geophysical techniques are now targeting reserves in deeper Frio and Vicksburg horizons.

Interpretation of 3D seismic data is being used on some projects, and 2D data and AVO analysis have also been helpful, companies said.

TransTexas Gas Corp., Houston, believes it has encountered large potential reserves of high pressure gas in Vicksburg in Galveston Bay just north of Texas City. Several operators are drilling exploratory wells within 5-10 miles west of TransTexas' indicated discovery.

And Enserch Exploration Inc., Dallas, and Vintage Petroleum Corp., Tulsa, are successfully exploring Trinity Bay and northeastern Galveston Bay in Chambers County southwest of Anahuac.

Elsewhere in Chambers County, Columbus Energy Corp., Denver, completed a Frio F-16 deeper pool gas/condensate discovery beneath giant Anahuac oil field. And several operators are reporting success at gas/condensate tests across the county.

Galveston Bay work

TransTexas planned to drill four prospects in mid-1997 in the bay and nearby land areas.

The company said the four prospects could exceed the proved and future reserves contained in its recent sale of South Texas Lobo trend properties to First Intercontinental Leasing Trust for more than $1 billion. Conoco Inc. purchased part of those properties for $900 million.

TransTexas' sale to First Intercontinental included 550 bcf of reserves.

TransTexas is drilling an apparent large volume gas/ condensate discovery about a mile off San Leon in the Galveston County portion of Galveston Bay. The drill site is about 5 miles southwest of Red Fish Reef field.

The 1 State Tract 331, permitted to 18,000 ft on a 1,150 acre structure, encountered 9,600 psi surface pressure on May 6 while drilling at 15,400 ft in Vicksburg. The well kicked gas and 47° gravity condensate, and the pressure collapsed the drill pipe. Mud at 19.3 lb/gal was required to control the well, which blew out briefly.

TransTexas said it believed it encountered Vicksburg 400 ft high to the original well prognosis. It said company geologists calculated that the gross Vicksburg interval might be as thick as 2,000 ft and contain larger gas and condensate pay intervals.

The well also cut significant hydrocarbon shows in shallower Frio sands.

TransTexas in June spudded the second prospect, the 1 State Tract 88A. It is being drilled from land about 5 miles south of Texas City and 10 miles due south of the 1 State Tract 331 well and is permitted to 19,000 ft. TransTexas plans to start drilling the other two wells soon.

TransTexas said the four wells are tests of seismic prospects along trend from Chocolate Bayou and Treasure Isle fields in Brazoria and southwestern Galveston counties, respectively. The State Tract 331 well is about 20 miles east-northeast of Chocolate Bayou field.

Cumulative production is more than 2 tcf of gas and 30 million bbl of oil at Chocolate Bayou field and 300 bcf of gas at Treasure Isle field.

Enserch/Vintage work

Farther northeast in the Chambers County portion of the bay, Enserch Exploration Inc., Dallas, and Vintage Petroleum Inc., Tulsa, are successfully exploring between Red Fish Reef and Trinity Bay fields.

Vintage controls about 30,000 acres in Galveston and Trinity bays. About half that is acreage held by production from Trinity Bay, Fishers Reef, and Red Fish Reef fields, which Vintage purchased from Exxon Co., U.S.A., in 1991.

The 30,000 acres includes adjacent Tracts 64, 65, and 84 acquired in an April 1997 Texas lease sale. The companies have identified several leads on those three parcels.

Either company will operate wells under a 50-50 Enserch/Vintage joint venture. They are using data from a 180 sq mile 3D survey acquired in 1995 by Western Geophysical.

Another smaller 3D survey was run the past few weeks south of Red Fish Reef field.

The 3D data show the area to be much more structurally complex than is apparent on an older loose 2D grid. The operators have had success using inversion to image the deeper sands, said S. Craig George, Vintage president and chief operating officer.

Wells in the bay are drilled to 12,000-13,000 ft in 10-25 ft of water. Vintage puts costs at $2.2 million for a dry hole to 12,500 ft and $4.2 million for a completion, including single-well jacket and pipeline tie-in.

Finds and extensions

Enserch and Vintage plan to start production in early September at the State Tract 77-1, in the White Heron area of Trinity Bay.

It cut more than 90 ft of net pay in two productive zones of Textularia II sands. Based on the initial production test, the well is estimated to produce a gross 8 MMcfd of gas.

The White Heron area is just east of the Umbrella Point East area, where Enserch and Vintage completed a late 1996 discovery well and mid-1997 delineation well.

Those two wells, State Tract 75-1 and State Tract 75N-2, were producing a combined 29.5 MMcfd of gas and 570 b/d of condensate at end July, George said.

The 75-1 well went to TD 12,332 ft and encountered 16 ft of pay in Text II and an interval of Oligocene Anomalina sands. The 75N-2 well, TD 10,250 ft, cut more than 100 ft of Anomalina pay.

The companies planned two more Galveston Bay wells this year. One, a new field wildcat 1 mile west of Umbrella Point field, was drilling below 9,300 ft at end July enroute to 12,500 ft. The other is to be at White Heron North.

The companies declined to reveal reserves, but the play commands a sizable chunk of Vintage's U.S. exploration spending of $25 million this year, up from $18 million in 1996. George said Vintage is a likely bidder at an October 1997 lease sale.

Other bay programs

Several other companies plan to drill on bay tracts acquired at recent Texas school land lease sales.

The Meridian Resource Corp., Houston, formerly Texas Meridian Resources Corp., acquired 100% working interest in three tracts totaling 960 acres in Galveston Bay at the April 1997 sale. These parcels cover an extension of the Frio sand trend northeastward from the company's Chocolate Bayou field.

Meridian Resource also acquired rights to a 150 sq mile 3D seismic survey under a joint venture agreement with Southwestern Energy Production Co., Fayetteville, Ark. Under that pact, Meridian Resource will be operator of and own a 50% interest in 18 more tracts in the bay.

Meridian Resource has a permit for an 11,500 ft TVD wildcat, 1 State Tract 179A, in the eastern reaches of East Bay, Galveston County. It is northwest of the Gilchrist/ Caplen area on the Bolivar Peninsula.

CNG Producing Co., New Orleans, acquired 17 tracts in the Apr. 1 sale, comprising four prospects in the East Bay, Galveston Bay, and offshore Matagorda Island areas.

Phillips Petroleum Co. holds about 8,000 acres in the Smith Point and Cedar Point areas of the bay acquired at the October 1995 lease sale. Cedar Point is off the southeast tip of Baytown.

Galveston land drilling

Numerous wells were drilling in late July west of the bay in Galveston County.

Enserch is drilling a projected 13,650 ft deeper pool test in Nassau Bay field, Harris County, west of Seabrook and just east of the NASA Space Center facility.

Enserch's early 1996 Nassau Bay field discovery well, bottomed beneath Clear Lake, flowed 3 MMcfd of gas with 90 b/d of condensate from Frio at 11,427-467 ft. Enserch said it logged 60 ft of net pay and has the potential to recover 30-70 bcf of gas. Global Natural Resources Corp., Houston, since merged into Seagull Energy Corp., holds an interest.

Just south of Bacliff townsite, Enron Oil & Gas Co. is drilling a 13,500 ft test on the grounds of an HL&P generating station in San Leon field.

The former Pend Oreille Oil & Gas Co. opened the field in 1982 with a Frio gas/condensate completion at 12,046-64 ft, and Valero Producing Co. added a new pool in 1984 flowing gas and condensate from below 11,600 ft.

Burlington Resources Oil & Gas Co., formerly Meridian Oil Inc., completed as a dry hole a planned 14,300 ft wildcat, 1 Clements et al., near Hitchcock South gas field. It tested noncommercial oil in Middle Frio Upper Houston Farms sand.

Treasure Isle area

Privately held Tepco Inc., Houston, is exploring the area around Treasure Isle field south of the city of Hitchcock, where it holds about 5,400 acres.

It is drilling 1 Morris, projected to 14,000 ft TVD, just south of Hitchcock high school and 3-4 miles north of Treasure Isle field. Objectives are deeper Frio sands than those producing in Treasure Isle field.

Tepco discovered Treasure Isle field in 1993 and is drilling continuously there now. Largely underlying Greens Lake, it produces through directional wells drilled from a central pad. The company in early August was completing its sixth Big Gas Sand (Upper Frio) well, said Bill Farrar, production and reservoir engineer.

The five existing wells went on production in September 1993, February, July, and October 1995, and March 1996. Flow was a combined 15 MMcfd of gas and 110 b/d of condensate in late July. Three shallow Miocene wells make a combined 150 b/d of oil.

All of the wells produce from Big Gas Sand and Alibel sand and have Grubbs and Alibel pay behind pipe. They are on two fault blocks, and the sixth well, 6 Halls Bayou Ranch, is testing a third fault block. It was to be tested in early August. Tepco has mapped a further six fault blocks within the field complex.

The Frio gas was sold into a 3 in. gas line until Tepco laid an 8 mile, 6 in. gas line in mid-1996 to Amoco's Hitchcock gas processing plant.

Tepco acquired some of its leases and 3D seismic data from Mobil Producing Texas & New Mexico Inc.

Mobil had drilled three deep wells, one of which flowed gas and condensate from Frio at 19,572-20,208 ft in 1989. This is thought to be one of the deepest indications of production along the Texas Gulf Coast, although the well was plugged.

Tepco plans to drill a 21,000 ft test in the area, probably from a barge rig, in late 1997-early 1998.

Tepco has also shot two additional 3D surveys in the immediate area.

Anahuac discovery

East of Trinity Bay, Grimes Energy Co., Houston, developed and drilled a prospect at giant Anahuac oil field based on 2D seismic and AVO analysis.

Columbus Energy then assumed operations of and completed the 1 Syphrett Heirs, on a 480 acre unit on the northeast side of Anahuac field.

It flowed 4.6 MMcfd of gas and 88 b/d of condensate on a 14/64 in. choke with 4,950 psi FTP from Frio 16 sand perforations at 8,974-90 ft.

CAOF is 147 MMcfd. Gross Frio 16 sand thickness is 45 ft. Reserves are an estimated 10-15 bcf of gas and 160,000-240,000 bbl of condensate.

Participants are Columbus 35%, Etoco Inc., Houston, T-R Oil & Gas Inc., Victoria, Tex., Cobia Oil & Gas Inc., Beaumont, Tex., and Grimes.

The well was perforated and placed on production on July 3 after installation of all surface equipment and pipeline hookup. Experience has shown that Frio wells can be lost if shut-in after being perforated, said Mike Grimes, president.

The group owns 600 additional acres southeast of the discovery on a separate fault block, where they intend to drill another exploratory well later this year.

Anahuac field, discovered in 1932, has produced more than 300 million bbl of oil, mostly from Upper Frio sand at about 7,000 ft through 500 or more wells.

More Chambers action

Ballard Exploration Co., Houston, spudded a deeper pool wildcat in mid July in Turtle Bay East field of Chambers County. The 1 Wilcox Estate is permitted to 10,500 ft.

HS Resources Corp., Denver, and Aspect Resources LLC, Denver, spudded an 11,000 ft Vicksburg test in Devillier field last month. HS attributed about 1.5 million bbl of oil equivalent in Vicksburg Lox B at 11,000 ft to its 2 Cooper gas/condensate well completed in April at Devillier. The companies said that 3D seismic data indicated 5-10 more locations in the immediate area.

TransTexas is well along at the 1 Barrow Ranch, permitted to 18,000 ft, on the southwest side of Willow Slough field in Chambers County.

TransTexas is also amid a five well program to develop North Seabreeze Frio gas/condensate field in eastern Chambers County. Three wells were on production by early April, one that sustained 22.5 MMcfd of gas and 334 b/d of condensate from 92 ft of net pay in a gross interval at 8,700-10,550 ft.

Oryx Energy Co., Dallas, plans two more wells this year in Seabreeze field and has identified more well locations for drilling in 1998.

Oryx established production on two new fault blocks at Seabreeze as the result of 3D seismic interpretation.

The two wells flowed a combined 33 MMcfd of gas and 1,160 b/d of oil. Oryx holds 100% of the working interest.