A unit of Shell Oil Co. has claimed an oil industry first in a novel use of 3 1/2 in. coiled tubing in California's Huntington Beach oil field.
The project involved installing 3 1/2 in. coiled tubing liner and two telephone cable bundles in an existing 8 in. gas production pipeline that connects Shell's Platform Emmy in 45 ft of water off Huntington Beach to the onshore receiving area at the company's Huntington Beach production unit.
Sam Mabry, project coordinator for Shell, termed the operation a complete success.
Other operators have had good results as the use of coiled tubing spreads throughout the industry (OGJ, Oct. 3, p. 18).
PROJECT PARAMETERS
Shell's 8 in. gas line, about 7,500 ft long, had been installed in 1962 by a previous operator.
Although the line needed to be replaced, Mabry noted, the permitting time required for another pipeline was estimated at 4 years, and the economics of that project appeared marginal.
At stake was production of about 4 MMcfd of dry gas from two wells. Emmy wells also produce about 1,500 b/d of crude oil.
While 3 1/2 in. coiled tubing has been used before in oil drilling, Shell said that as far as anyone knew, it had not been used for such an application as the company suggested.
"We put together a plan and executed it," Mabry said. "By slipping the coiled tubing into existing line, we didn't damage the environment, minimizing the permitting process."
The three major players in the project were Shell's Huntington Beach unit, headquartered in Bakersfield, Calif., which handled management and coordination; Dowell Schlumberger's Bakersfield based California district, which helped with initial planning and provided the coiled tubing unit; and Precision Coil Tubing (PCT), Houston, which supplied coiled tubing and associated equipment.
"It took only 8 working days from the time we closed down the existing line until the 3 1/2 in. coiled tubing had been run, hydrotested, and the line returned to service," Mabry said.
Running the 3 1/2 in. coiled tubing through the existing line was accomplished in 2 days, with work limited to daylight hours.
PROJECT DETAILS
Carl Benge, vice-president of technical operations for PCT, said the job was accomplished with only three welds in the full length of the pipeline.
The three spools used in the project, each with about 3,500 ft capacity, were trucked from the mill to Huntington Beach.
The push/pull operation involved the onshore coiled tubing injector unit and a pulling cable that extended from the platform to shore. The cable served the dual purpose of keeping the tubing from buckling and pulling the tubing around the 90 riser bend at the platform.
Dowell installed the coiled tubing injector head in a trench that provided access to the existing 8 in. pipeline. Communications cables were fed through 150 ft of 1 1/2 in. coiled tubing to provide protection through the riser. They were attached to the pulling head and banded to the 3 1/2 in. coiled tubing. Pulling contractor was United Pipeline, Durango, Colo.
To facilitate installation in the pipeline, the injector head was placed horizontally on a purpose built stand and chained down to deadman hooks driven into the ground. Tubing was spooled off the bottom of the reel, instead of the usual off the top, through the tubing straightener, which was placed in the position the gooseneck normally would occupy.
After the push began, initial rates of 10-15 ft/min were established. That increased until consistent rates of 50-55 ft/min were attained.
Weights of 1,000-2,000 lb were registered at the beginning of the push with 4,000-5,000 lb needed to travel around the bend in the riser pipe at Platform Emmy.
A continuity check of telephone cables showed that of 24 pairs, 22 made the push successfully.
Payout for the entire project was only 1 month.
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