Remotely Controlled Pipeline Isolation Plugs
Authors: Garpestad Harald , Tveit E. , Aleksandersen J. 
Published: October 2008

Often subsea pipelines require planned shutdown/intervention due to repair, rerouting, addition of valves, etc. The negative economic impact can be dramatically reduced if the product in the line can be retained and if dewatering of the line can be prevented This paper will discuss the past applications of HydroPlug pipeline isolation plugs manufactured by Oil States HydroTech Systems, Inc, marketed and serviced by IsoTech International AS. Past plugs have been built in sizes to 32" and test pressures to 250 bar Numerous special 72" plugs have been built to operate at '50 bar and 720 Fahrenheit for a government sponsored project All past isolation plugs were controlled and powered through umbilicals The umbilicals, which passed through special lubricators in the launchers, restricted the distance in the pipeline at which the isolation plug could be used. This paper will discuss new technology which IsoTech will apply to remotely control isolation plugs through the wall of the pipe using Extremely Low Frequency magnetics This eliminates umbilicals and facilitates the use f isolation plugs at any location in a pipeline. The development and application of 34" and 36" isolation plugs using this remote control technology will be addressed.

Introduction

Phillips Petroleum Company Norway, as operator of the Ekofisk field in the Norwegian part of the North Sea, is currently performing a major redevelopment of the Ekofisk Complex. Part of the redevelopment includes installation of a new drilling and a new process platfonn and replacing parts of the pipeline systems within the Ekofisk subsidence zone. One of the pipelines affected is the 34" Teesside oil pipeline, which is the main oil export pipeline from Ekofisk. A pipeline section from the old export platform is going to be replaced by a new seven kilometer section from the new process platform when changing over to the new platforms in August 1998 Tn order to maintain production from several third party fields during the tie-in operation, which fields are connected to the pipeline downstream from the tie-in point, it was decided to utilize a remotely operated isolation plug to isolate the pipeline approximately seven and a half kilometers downstream from the launch platform However, there existed no remotely operated isolation plugs capable of isolating a differential pressure of 70 barg. A contract was awarded HydroTech Systems Inc. to develop the new remotely operated isolation tool based on their existing HydroPlug. Control Data Inc was engaged to develop the control and communication technology The major functional requirements called for a remotely operated isolation plug with a double block isolation capable of holding 70 barg differential pressure. It must be bidirectional and able to run for 354 kilometers in the pipeline, through mechanical connectors and a wye piece, and must be safe over the entire differential pressure range from zero to seventy barg Last, it must be remotely controlled and monitored from a surface vessel by external communication through the pipe wall. Safety aspects are of paramount importance as divers will be working behind the plug in a welding habitat.