Texaco Exploration & Production Inc. has completed the first dual lateral horizontal well in East Texas and claimed a horizontal oil well record in the Gulf of Mexico.
The East Texas well, 1 Texaco Fee Brookeland, is the company's first dual lateral well. Site is in Newton County.
The Brookeland well was drilled vertically to the top of Cretaceous Austin chalk at 9,138 ft. Texaco set casing, then drilled horizontally 3,242 ft to the southeast and 3,000 ft to the northwest for a total horizontal displacement of 6,242 ft.
William F. Wallace, vice-president of Texaco E&P's eastern region, said Texaco set an industry record offshore with its B19-ST well on its Teal prospect in Eugene Island Block 338, its first horizontal oil well in the gulf, by drilling a horizontal section of 1,414 ft. Measured depth (MD) is 7,500 ft and true vertical depth (TVD) 4,662 ft.
Site is in 268 ft of water. Drilling horizontally through the Pleistocene prograding sand complex allowed Texaco to penetrate 50% more of the reservoir than would have been possible with a conventional well, Wallace said.
Before B19-ST, Texaco drilled five horizontal gas wells in the Gulf of Mexico: A-12 on the Bass prospect in Ship Shoal Block 343, D-10 in South Marsh Island Block 239, and B-11, B12, and B-14 in East Cameron Block 265 field.
In another industry first, Texaco isolated the Teal reservoir gas cap by setting intermediate casing 50 ft below the oil-gas contact with the 90 angle already established because of concern that the reservoir had an expanded gas cap.
"Isolating the gas cap by setting casing significantly beneath the oil-gas contact reduced or eliminated the effect of gas coning," Texaco said.
Wallace said Texaco achieved considerable cost savings by using horizontal well technology on its Brookeland and Teal acreage.
The dual lateral Brookeland well cost $500,000-700,000 less than two vertical wells capable of comparable production rates and recovery. Texaco expects the full cost of the well, production facilities, and gathering system to pay out in about 4 months.
Texaco estimates the B19-ST well cost about 10% more than a Teal vertical well.
A cross discipline team of Texaco geologists, geophysicists, engineers, and field technicians contributed to the success of both projects, Wallace said.
STEADY PRODUCTION
On a 24 hr test soon after completion, the Brookeland well flowed 1,192 b/d of oil and 5 MMcfd of gas through a 24/64 in. choke with 2,900 psi flowing tubing pressure. The well produced 11,400 bbl of oil and 40 MMcf of gas in its first 11 days of production.
Following completion May 5, B19-ST flowed 1,219 b/d of oil and 697 Mcfd of gas through a 37/64 in. choke with 420 psi flowing tubing pressure. That rate is about 2.6 times more than the next best Teal well.
Production from both new wells has held near those early test rates.
In a 24 hr period ended June 10, 1 Texaco Fee Brookeland flowed 1,027 b/d of oil, 4.669 MMcfd of gas, and 234 b/d of water through a 24/64 in. choke with 2,800 psi flowing tubing pressure. B19-ST production has averaged 1,222 b/d of oil, 1 Mcfd of gas, and 306 b/d of water through a 45/64 in. choke with 340 psi flowing tubing pressure.
The Brookeland and Teal wells have encouraged the company to try other horizontal projects. The company is drilling an undisclosed number of U.S. horizontal wells onshore and offshore.
Two dual lateral horizontal wells are in progress on the same Texaco Mineral Fee lease where 1 Texaco Fee Brookeland was drilled. Texaco geologists said the next well to be spudded on the Teal prospect will be a horizontal well in the same reservoir.
From the 1 Texaco Fee Brookeland well, Texaco concluded a sand reservoir does not have to be thick or clean for horizontal technology to work well.
"The well also showed that reservoirs with high permeability gas caps and low permeability laminated oil zones can be drilled and produced with low GORs," Texaco said. "Conventionally drilled wells in the same reservoirs produce with a high GOR, even though the wells are perforated in the oil zone."
BROOKELAND WELL
Texaco owns a 100% interest in the 28,000 acre Texaco Mineral Fee lease but has partners in active drillsites adjacent to the acreage.
Austin chalk thickness at 1 Texaco Fee Brookeland's location is 545 ft. Texaco had a 25 ft target window within an 85 ft chalk zone.
Texaco's Brookeland wildcat drillstring design used a vertical hole pendulum assembly with fifteen 8 in. drill collars and 4 1/2 in. S-135 drill pipe and jars.
Texaco drilled an 8 1/2 in. hole to the first wing build section. The bit assembly included a downhole motor (DHM) with a 4 1/2 in. measurement while drilling (MWD) tool.
Build rates in the horizontal laterals ranged from 12/100 ft to 17/100 ft.
Texaco used 16 joints of heavyweight drill pipe in the build section in the first horizontal lateral. The first wing's angle hold bottom hole assembly included a 4 1/2 in. DHM, MWD tool, and jars. The angle hold line consisted of 15 joints of 4 1/2 in. S-135 heavyweight drill pipe.
For the second lateral, Texaco drilled a 6 1/2 in. hole with a DHM and MWD using 3 1/2 in. S-135 drill pipe.
Texaco's casing program on the Brookeland well included 20 in. drive pipe to 40 ft, 13 3/8 in. surface casing to 1,720 ft, and 9 5/8 protection casing to the top of the Austin chalk at 9,347 ft.
Drilling fluid used near surface on Brookeland's vertical section was 8.5 ppg fresh water and gel drilling fluid. For the intermediate section of the vertical hole, Texaco used 8.5-10.4 ppg polymer mud with additives to control water loss and inhibit shale. For the lateral sections, the company used 9.3-10 ppg brine mud with slugs of 11.6 ppg calcium chloride for trips.
Texaco completed the laterals open hole.
Prior to spudding the well, Texaco laid a 3 mile, 6 in. high pressure fiberglass pipeline to transport Brookeland gas production to the Maersk gathering system, which delivers gas into the Tennessee Gas Pipeline system. Fiberglass pipe was used to avoid corrosion.
Texaco trucks oil from the well. Carbon dioxide is separated with a membrane unit and vented at a central production facility equipped with electronic gas measurement instrumentation with telecommunication capacity.
TEAL PROSPECT
Texaco's Teal prospect covers 10,000 acres on Eugene Island Blocks 338 and 339, about 160 miles southwest of New Orleans. Operator Texaco and Chevron U.S.A. Inc. are 50-50 partners on the acreage.
Since Teal production began in 1974, the field has produced 28.9 million bbl of oil and 87.8 bcf of gas. But Teal production records show that much of the reservoir's oil and gas has not been produced.
Texaco spudded B19-ST Apr. 11.
The well is producing on gas lift from fine grained Pleistocene sand at 4,500 ft deposited during the Yarmouth interglacial and laminated with very shaley, slightly silty lamina. The 4,500 ft sand was chosen because it is a shallow reservoir with underproduced oil reserves.
B19-ST's vertical target window was 10 ft. Texaco encountered the pay interval throughout the well's entire horizontal section from 5,536 to 7,500 ft MD.
Texaco drilled B19-ST with an inverted drillstring with a weight on bit of 10,000-20,000 lb. The BHM was a steerable system, and the build rate of the horizontal section was 5.75/100 ft MD.
For B19-ST's casing program, Texaco set 20 in. drive pipe at 607 ft MD/TVD, 13 3/8 in. at 2,870 ft MD/TVD, and 9 5/8 in. at 6,086 ft MD (4,680 ft TVD). Texaco waived conductor casing on the well.
B19-ST's production tubing is 3 1/2 in., 9.3 lb/ft CS Hydril tubing. The production string includes a 7 in. uncemented liner run to 7,452 ft MD (4,663 ft TVD) and slotted from 6,215 to 7,441 ft MD.
During completion, Texaco displaced the well with 10.5 ppg CaC12 through 2 7/8 in. wash pipe. Texaco then set a Baker hydraulic liner packer at 5,846 ft MD, ran a Baker sand control 5 in. by 3.5 in. prepacked gravel pack screen from 7,432 to 6,620 ft MD, set a Baker SC-1 packer at 5,725 ft MD, and ran production tubing.
B19-ST's mud program included fresh water Bentonite drilling fluid to 9 5/8 in. casing point. For the horizontal section Texaco used 10.5 ppg mixed metal hydroxide with calcium chloride for weight.
A cross discipline team of Texaco geoscientists is completing an in depth field study of the Teal prospect using production history, sequence stratigraphy models, 3-D seismic interpretation, and horizontal well technology.
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