Extended Reach Pipeline Blockage Remediation

Abstract

Development of the ability to do extended reach pipeline blockage remediation. Results of full scale testing in a pipeline designed to have the degree of difficulty of a 5 mile subsea pipeline are included. Also, a discussion of the extended reach impact of viscous friction drag on coiled tubing is included. Vendors who have succeeded in passing the DeepStar test requirements are indicated along with possible extensions of this technology to longer distances than 5 miles. 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. DeepStar 3202: A committee formed to further the technology of pipeline blockage remediation. 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 on 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. 2) Skate: A non-powered wheeled means which is attached to a coiled tubing string to assist in extended reach remediation. 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 testing of 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 1½ miles. The primary means to achieve the goals of the DeepStar CTR 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. Steps in the Program In order to identify and move the state of the art forward in extended reach pipeline blockage remediation, several steps were undertaken in this program.