Pull-through composites may give new life to damaged offshore pipelines
William Furlow
Senior Editor
With an eye to operators' desire to reduce costs, Fiberspar has devel-oped a composite line pipe that could simplify not only pipeline reme- diation projects, but the installation and operation of infield flowlines in deepwater.
Fiberspar's first oilfield venture came when Halliburton tapped the company to provide SmartPipetrademark for the Anaconda system. This is a composite coiled tubing with imbedded copper wires. The wires allow for communication downhole during coiled tubing drilling operations. The company has also developed spoolable composite line pipe for flowline remediation and installation of new flowlines in various onshore and shallow-water applications. This includes a pull-through remediation technique made possible by LinePipe, CEO Peter Quigley said.
Pipeline leaks
Canadian regulations are very strict concerning pipeline leaks. Quigley said a line, that reports three separate incidents of leakage due to corrosion must be shut down. If a line develops a leak less than six months after it is activated, Quigley said, this line also would be shut down. These regulations are exacerbated by the fact that the product passing through these lines can be very corrosive. As a result, Quigley said operators were looking for a means to replace damaged or leaking lines without going through the time and cost of digging up the lines and replacing them conventionally.
Composite solution
Fiberspar LinePipe, made of glass fibers and epoxy resin, reinforcing a thermoplastic pressure barrier, can be pulled through the existing pipeline with a minimal reduction in the internal diameter (ID). The composites offer a number of advantages, according to Quigley. The material is light enough to pull through miles of pipeline. The composite material is resistant to corrosion, and its polyethylene liner actually has better flow characteristics than the steel it replaces.
This means, even though the repaired pipeline has a slightly reduced ID, in many cases it is still able to flow the same volume of product with little or no pressure drop. In addition to the superior flow characteristics of polyethylene, it also reduces the risk of blockage from paraffin or hydrates developing on the pipeline wall. LinePipe has the same pressure ratings as the steel line. Once the LinePipe is installed, the existing steel line merely serves as a conduit. It does not have to contain pressure. Installation in long continuous sections reduces the number of connections required. Thomas Ayars, Vice-President of Sales and Marketing at Fiberspar, said the LinePipe has been used to remediate numerous lines in both the US and Canada. To date, the company has installed more than a million ft of the product, in continuous sections up to 10,000 ft long.
Installation
The pull-through installation procedure is relatively straightforward. A soft pig is run into the damaged pipeline to clean the old line and pull through a wireline. The wireline is then used to pull the composite line pipe through the existing line at rates up to 100 ft per minute. A simple, full-strength connection joins the sections. Making up the connection takes about 30 minutes.
LinePipe is transported on a spool. The largest spool that can readily be transported on trucks to onshore sites is 16-ft in diameter. The larger the outside diameter (OD) of the pipe, the larger the core required on the spool, which also determines the amount of pipe that can be transported. The company is capable of manufacturing sizes up to 12-in. OD, but due to the shipping limitations the largest OD the company manufactures is 5-in., 2,000 ft of which can be rolled onto a spool.
Manufacturing
The pull-through composite pipe starts out with an inner polyethylene pressure barrier. This barrier is pressurized to give it enough strength to maintain roundness during the manufacturing process. The liner is run through an automated weaving station that covers it with a mesh of glass fibers. The liner is then soaked in an epoxy resin before a second weave is applied. In this fashion any number of layers can be added. The number of layers needed depends on the pressure requirements of the pipe.
The pipe is then wrapped in compaction tape and run through ovens that are 250 ft long. This cures the epoxy resin. Coming out of the oven the pipe is tested for roundness, run through a cooling tank then spooled up. All of the pipe is pressure tested to full rating before shipping. The epoxy used is not rapid set, Quigley said, so the line may be shut down without fear of an incomplete job being spoiled.
Offshore applications
For offshore applications requiring larger diameter pipe, Quigley said larger spools could be used since they can be transported by ship from a near shore facility. Fiberspar has already done some shallow-water remediations using standard 16-ft reels offshore Louisiana. The first of these was performed in the Black Bay area, where more than 100,000 ft of 23/4-in., 750-psi LinePipe was used to refurbish older flowlines. In addition to the lower costs, pulling this product through the existing line does not damage the seabed environment.
Quigley said the key to moving offshore with this technology was to find an operator who will sponsor it before the MMS. Fiberspar has an operator who would like to apply the technology in 210 ft water depth in federal waters. Ayars said early meetings with the MMS were encouraging.