UK-based Independent Oil and Gas (IOG) has completed the first run on the Thames Pipeline intelligent pigging program with one more to come in the following weeks.
IOG said on Tuesday that the intelligent pigging program (IPP) was being conducted in cooperation with Subsea 7 as a diving support vessel provider, Rosen as a pig supplier, operational management from ODE, and engineering support from EnerMech.
The company added that three 12-meter sections of the Thames pipeline were cut 60 kilometers offshore on May 3, just beyond the point where the Southwark gas field will tie into the recommissioned 24-inch Thames export pipeline.
“These were transported onshore and visual inspection showed them to be in extremely good condition, with very little evidence of corrosion or wall thickness degradation. This was a significant first step in verifying the integrity of this gas pipeline, which was decommissioned in 2015,” the company said.
A temporary subsea pig receiver was then installed at this 60km tie-in point and a successful pipeline pressure test was undertaken from the Bacton gas terminal to this receiver.
Next, a cleaning and roundness gauging pigging run was successfully conducted from Bacton to the offshore tie-in point, where an offshore pig launcher was then installed. This enabled the 60km intelligent pigging run from offshore to Bacton to be completed on May 26.
Intelligent pigs are devices run through pipelines to assess pipeline wall thickness and to evaluate any evidence of corrosion.
“While the steps mentioned above give IOG’s management very strong confidence in the pipeline’s condition, in order to recommission this pipeline the company nonetheless firmly requires a complete data set from an intelligent pigging inspection, so that all stakeholders including contractors and funders are fully satisfied as to its reuse. IOG is, therefore, planning a second intelligent pigging run to complete data acquisition at the earliest opportunity, which is expected to be within weeks,” IOG added.
Following the intelligent pig run, the pipeline was successfully hydrotested with inhibited sea water for 24 hours to confirm integrity and has now been suspended in a safe condition.
Hydrotesting involves elevating the water pressure in the pipeline for a sustained period and is another key step in pipeline validation. According to the company, the success of this test provides evidence that the pipeline is fit for purpose for IOG’s needs.
IOG also said that the need for a second intelligent pig run would inevitably have some impact on the project schedule. The company advised the Oil and Gas Authority (OGA) of this requirement and will request a short extension on the FDP approval target date, which is currently the end of August 2018.
Subject to final pigging results, the pipeline will be ready for recommissioning to export IOG’s Southern North Sea gas portfolio, which contains 303 BCF of 2P gas reserves across five proven fields, plus further development and appraisal assets.
Over January to May 2018, the Fugro MV Galaxy vessel completed the various offshore surveys needed to support the development of the Blythe and Vulcan Satellites Hubs. The work program comprised geophysical surveys, shallow seismic of the four platform and five drill sites, general inspection surveys of the Thames pipeline, environmental surveys, and geotechnical surveys.
Post survey work will entail data processing, analysis, interpretation and reporting, geotechnical laboratory testing and analysis of cores, environmental laboratory testing and analysis of samples and the integration of geophysical, geotechnical and environmental data and final reporting. All of this acquired data is required for field development plan approvals.
Andrew Hockey, CEO of IOG, said: “The Intelligent Pigging Programme has so far provided extensive and valuable new information to the IOG team to support our plans to recommission the fully-owned Thames Pipeline and produce our Proven and Probable reserves of over 300 BCF safely into the Bacton gas terminal and the UK market.”
He also added: “While this gives us even greater assurance on the pipeline’s fitness for purpose, we do still require the intelligent pigging data acquisition to be fully and properly completed. We are now fast-tracking plans to have this done as soon as possible, while our other project development workstreams continue in parallel to maintain our good momentum towards FDP approvals for this substantial UK gas project.
“The successful completion of our four-month offshore survey program, which has provided a wealth of required data, is also a key step in that regard.”