The U.S. Department of Energy's National Energy Technology Laboratory (NETL) announced that the composite drill pipe has been successfully tested in a horizontal gas well in Oklahoma. The pipe, developed by Advanced Composite Products and Technology of Huntington Beach, Calif., proved convincingly that it could withstand the stresses encountered in commercial drilling operations.
The flexible pipe is manufactured by winding graphite fibers and epoxy resin around a spindle. The composite tube is cured, and the supporting spindle is removed. The pipe is machined, and then coated to resist abrasion.
Developed under a $2.82 million, five-year contract with the Energy Department's Office of Fossil Energy, the drill pipe could be the next major technical achievement emerging from the joint government-industry natural gas research program.
"It could revolutionize the drilling industry because of its versatility and strength," said Gary Covatch of NETL's Gas Technology Management Division.
"The composite pipe is more flexible than steel drill pipe. This flexibility is an especially important advantage in permitting producers to re-enter old wells and drill horizontally to reach untapped natural gas formations. It could provide an important new tool for the industry to recover more gas, keep recovery costs low, and extend the life of many of the nation's gas wells," said Covatch.
The most recent field test was conducted this summer in Le Flore County, Okla., at a depth of 1,385 feet in a formation that was hard and extremely abrasive. Unlike field tests last November and January which used rotary drilling tools to re-enter existing wells, the latest test was conducted in a new well using air-hammer drilling to propel the 2.5-inch diameter pipe.
The air hammer severely challenged the pipe's fatigue life, mechanical strength, and ability to deal with stress. After a week of drilling, the pipe was extracted and examined. It showed little or no signs of wear.
Steel drill pipe, by contrast, can suffer fracturing and rapid wear when continually bent in a horizontal drilling operation. While the price of the composite pipe is currently about three times the cost of steel drill pipe, researchers are working to reduce this cost. They also plan additional tests in the coming months to ensure industry confidence.
The carbon fiber make-up of the new pipe could also be a major step toward developing future "smart" drilling systems. Future work will include embedding wire in larger, 7-inch composite drill pipe to carry the data from the bottom of the hole to the surface while drilling is ongoing. With digital communications capability, "smart" drilling systems can give operators real-time data to monitor drilling progress, avoid undue stresses on the drill pipe, and make virtually instantaneous decisions to better target the drilling operation.
Such systems will help reduce the risks and costs of drilling deeper gas wells, an important factor for a domestic industry that is probing increasingly deeper and into more challenging formations to meet the Nation's growing demand for clean-burning natural gas.
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