OTC: Compact well designs will lead the trend for deepwater

May 7, 2002
The economics of deepwater development will demand compact well demand compact well designs. Technology advances will make more-slender and smaller wells possible, reducing wellbore volume by as much as 40%. That was the message delivered by ABB Vetco Gray Vice-Pres. Norman Brammer at Monday's Offshore Technology Conference topical luncheon on "Deepwater Drilling Systems: Evolution and Integration with Production Systems."

Mike Sumrow
Drilling Editor

HOUSTON, May 7 -- The economics of deepwater development will demand compact well designs. Technology advances will make more-slender and smaller wells possible, reducing wellbore volume by as much as 40%.
That was the message delivered by ABB Vetco Gray Vice-Pres. Norman Brammer at Monday's Offshore Technology Conference topical luncheon on "Deepwater Drilling Systems: Evolution and Integration with Production Systems."

Brammer, responsible for ABB Vetco Gray's engineering policies, procedures, standards and specifications, material engineering, and product development, said, "The 18¾-in., 10,000 psi blowout preventer (BOP) with 21-in. drilling riser has become the dominant riser system; however, I predict that is going to change."
He added that, even though deepwater wells require high structural capabilities, the economics of deepwater development would drive operators to use compact wells.

Brammer noted that the industry has applied slimhole-drilling techniques to land-based operations for a long time and that Brazil's state oil company Petroleo Brasileiro SA (Petrobras) had pioneered the used of slender wells offshore.
He defined a compact well as effectively having 40% lower wellbore volume. Drilling operations would generate 40% fewer drill solids, and the well would require 40% less steel, mud, and cement to construct.
In addition to lower direct well construction costs, the secondary benefits of compact wells would improve the capacity and capability of smaller and older rigs to drill and complete wells at greater water depths. Compact well designs will also keep the costs down for newbuild rigs.

Brammer said, "If you go from a 21-in. riser to a 16-in. riser, you're going to save 40% of the mud volume in 5,000-ft water depth or whatever water depth you're drilling in." He added that the 16-in. risers and related equipment are available and that more of the smaller risers are under construction.
He noted that Petrobras has drilled about 50 wells patterned to a slender well design using 16 3/8-in. BOP stacks and conventional wellheads.

Technology
Looking forward, Brammer said the offshore oil and gas industry must learn and is learning to do more with less. Reviewing technologies that will make his envisioned compact wells viable, Brammer highlighted expandable tubulars and slimhole-drilling technologies such as coiled tubing drilling.

Concerning dual-density mud systems, however, Brammer said that the complexity of the equipment involved, establishing its reliability, and the high capital investment are question marks for the technology's further use in the industry.
"I wish the [subsea mudlift] technology every success, but I cannot see it becoming the routine solution," he said.

Brammer said that the offshore drilling industry has come a long way in 40 years since it installed the first subsea wellhead in 51 ft of waterin 1961 and highlighted some current industry records:
-- Unocal Corp. and Transocean Sedco Forex Inc. hold the record for the well drilled in deepest water with the Trident II discovery in 9,727 ft of water.
-- BP PLC's Thunderhorse project holds the record for the deepest well drilled in the deepwater environment at 29,060 ft TD and in 6,300 ft water depth.
Other records Brammer noted included the well completed in deepest water at 7,209 ft of water, the well drilled in deepest water from a deep draft caisson vessel or spar at 4,800 ft of water , and the record well drilled from a floating vessel with surface BOP was 6,730 ft of water.

Brammer said, "It has really been [since] the late 1990s that we've seriously started drilling in deep water, with 4% of all wells drilled last year in water depth greater than 5,000 ft." He added that the trend ahead looks steady, with 6% of all wells drilled by 2004 in deep water.
For well completions, 20% of all wells completed for production in 2001 were in water depths greater than 3,000 ft, indicating that the motivation for drilling deepwater wells more efficiently should be clear.


Contact Mike Sumrow at [email protected]