Testing And Evaluation Of Coiled Tubing Methods To Remove Blockages From Long Offset Subsea Pipelines
Authors: Baugh Benton F. , McStravick David M. , Warren Wayne , Clark Jim 
Published: October 2008

A presentation of the analysis, testing, and development of the ability to do extended reach pipeline blockage remediation. Results of scale model testing, full scale testing, technical surveys, and computer analysis of coiled tubing performance as an extended reach transportation means is included. A discussion of an invitation and requirements for DeepStar funding in a pipeline test loop is included.

DEFINITIONS

DeepStar: An industry wide cooperative effort to develop economically viable, low risk methods to produce hydrocarbons from deepwater tracts in the Gulf of Mexico.

Differential Pig: a tool in the bore of the pipeline which has a pressure differential across it for the purpose of generating an axial force of an internal work string (coiled tubing)

Degree of Difficulty: A term used within the paper to try to compare different styles of pipeline construction on an objective basis.

Extended reach: For the purpose of this program, a nominal 5 mile distance into a pipeline.

Nominal 5 mile pipeline: An idealized pipeline which generally reflects the averaged degree of difficulty of typical Gulf of Mexico pipelines of 5 mile length.

Vendor: a company that volunteered to take part in this project by offering "long offset blockage removal tooling" for testing in the simulated 5 mile test loop.

Simulated 5 Mile Test Loop: A short test loop fabricated to be as difficult to traverse as a typical 5 mile subsea pipeline. (See fig. 10)

OVERVIEW

Of major concern, to an Oil Operator embarking on a long offset subsea production development, is the possibility of encountering a subsea pipeline blockage, due to wax or hydrates problems. Very often, such blockages are inaccessible to either chemical or mechanical removal and therefore necessitate removal of section of pipeline, or indeed, pipeline abandonment.

DeepStar has provided for the testing coiled tubing technologies and extended reach concepts with the objective of extending the reach of coiled tubing blockage removal techniques from approximately 1 mile to 5 miles. Current technology limits the extended reach to the range of 1 to 1 ½ miles.

The primary means to achieve the goals of the DeepStar 3202 program is to build a 900' long 6 5/8" pipeline which can be reasonably said to simulate a 5 mile nominal subsea pipeline in degree of difficulty; and then do comparative testing in that pipeline. When a Vendor can navigate the standardized test pipeline and remove a standardized wax blockage under standardized test conditions, the Vendor will be reported to the oil companies supporting DeepStar as having extended reach remediation capability.

This program is being conducted in several steps:Define what 5 miles meansDefine the characteristics of a test pipeline to simulate a 5 mile subsea pipeline.Define a standardized waxDefine a standardized blockageDefine a standardized test program considering the reality of a 5 mile subsea pipeline and the specific characteristics of the test loop.Do loop testing to develop systems and to demonstrate systems capabilities.Participate in actual field testing to confirm the results.