Green Smart Open-hole Continuous Casing System (Green SOCCS)

WHY

Energie Beheer Nederland estimated in 2024 that by 2050, approximately 100,000 km of underground medium- and high-voltage cables and 4,500 km of cables will be needed to connect offshore and onshore substations. Expanding this infrastructure using traditional cable-laying-by-trenching methods will be challenging if not impossible. The alternative, conventional horizontal directional drilling, alsohas limitations, as the length is constrained by soil friction. The work is weather-dependent and requires digging trenches or large laydown areas at places with limited to no space, possibly crossing existing pipelines and passing through nature sensitive areas. In addition, the cables may become a target for sabotage. The cable laying activities can also harm flora and fauna and significantly impact daily life in densely populated areas.

Moreover, cable construction projects are often delayed by lengthy permitting procedures. These are usually caused by complex discussions with landowners and other parties involved. A recent example is the offshore wind project "Ten Noorden van de Wadden", which has been delayed because none of the proposed cable routes in the PAWOZ-Eemshaven plan are considered suitable. A 27 km long tunnel beneath the Wadden Sea has been considered as a solution.

Callidus, Ampelmann and Delft Offshore Turbine (DOT) have joined forces to re-introduce the Smart Open-hole Continuous Casing System (SOCCS) to accelerate offshore wind development by speeding up the permitting process of infrastructural projects. SOCCS is a trenchless cable installation solution based on the inside out steel pipe inversion principle. The technology combines the commonly used Horizontal Directional Drilling (HDD) technique with a continuously formed casing to allow drilling over long distances.

WHAT

The essence of the Green SOCCS technology is to lay an in-situ formed steel casing pipe without trenching over distances exceeding 8 km. The ultimate goal is to achieve an end-to-end solution (i.e. including cable installation) for distances exceeding 30 kilometers from a single onshore drilling site. Power cables can then be installed in the casing pipe. The core idea is to place the drilling unit and steel casing pipe production side by side, as shown in the figure on the right. After drilling, a pipe tractor pushes the casing into the hole using force. This tractor provides enough power to overcome friction, invert the pipe, and continuously pushes it into the hole. Before this, the pipe is made on site by rolling strip sheet metal into a tube and welding the seam. As this process takes place, a drill pipe is fed into the tube through a horizontal guide, using a conventional electric horizontal drilling rig.

This project focuses first on defining project requirements and technology design details. It includes specifying the cable or pipe network, which helps to determine the size of the test machine. In this phase, the drilling distance is also determined in more detail – for now, we are thinking of 8 km through the Wadden Sea – to plan the required resources. Given the size of 3 to 5.5 inches high voltage cables, a 14-inch (350 mm) Green SOCCS pipe is large enough to accommodate them. The final dimensions are based on the current cable needs and will determine the design of the equipment. We will test the pipe reversal concept, supporting the feasibility study and the scale-up to 14 inches.

In the next step, we determine the design and engineering of the key components for the Green SOCCS machine. We make a final list of all required components. This design phase ensures that the machine meets all technical requirements and functions effectively in the field. This step lays the foundation for testing, production and implementation.

Subsequently, we integrate the standard Horizontal Direct Drilling (HDD) technology with our custom-designed pipe former and pusher. This phase includes the procurement, construction, assembly and initial testing of the integrated Green SOCCS machine. The main result is a fully assembled machine ready for operational testing.

In the testing phase, the different components will be assembled and tested at a test location. Groningen Seaports has already identified several potential locations near the Eemshaven. Another option is close to the Rotterdam harbour. The operational data and further test drilling results will be presented in a detailed test campaign report. The test is essential to prove that the technology works under real conditions. The results will allow us to refine the system and ensure it meets the technical and environmental standards. After a successful test, we will follow with a semi-commercial project (installation of 3-5 km of pipeline) on a "no cure, no pay" basis, and it will be outside this project's scope. Opportunities will be identified during the duration of this project.

EXPECTED RESULTS

By the end of the project, we will have designed and built a large version of the Green SOCCS machine, based on standard electric horizontal drilling equipment. The machine will have been tested by drilling and installing a 14-inch pipe over a relatively short distance. The system will also have been thoroughly checked to confirm that it performs well under real-world conditions. We will also have completed a desktop study, analysing potential other applications for the Green SOCCS technology, such as transporting hydrogen, CO₂ and water.

Our long-term goal is a Green SOCCS cable in pipe installation technology for distances of more than 30 km from a single onshore drilling location. The first step will therefore be a semi-commercial project to install a 3-5 km long casing pipe.