Structural support of fracking operations

Maintaining full production throughout structural works

In July 2014, Shell/NAM commenced a well clean out and fracking project on the L02-FA-1 gas platform, located within the Dutch sector of the Southern North Sea (SNS). The plan was to carry out a process of Coiled Tubing (CT) clean out followed by a Perforating Run and then Fracking.

To execute these works a self-propelled jack-up barge was used to install a 20m high, 30 tonnes, CT tower onto the gas platform over the well bay, from which the well intervention work would be carried out. Frack hoses were also connected between the platform and a dedicated project support fracking vessel.

The Project Challenges

The well that was to be fracked was located very close to the platform edge and adjacent to live production instrumentation equipment.

The main deck structure over the well bay was relatively weak and unable to support the weight of the tower without spreading the load across multiple beams.

The platform was to remain in full production throughout the structural works.

The challenge was therefore to provide a safe and functional working environment with structural support of the fracking operations, and to install this without any offshore category 1 hot works (e.g. welding) and without drilling any of the primary platform structure.

The Design

Pinnacle designed and detailed a new bottom section of CT tower to allow the upper tower sections to cantilever over the top of the instrumentation.

The cantilever tower was then supported off temporary skid beams, which were designed to achieve a balanced flexural stiffness and calculated to spread loads into adjoining platform deck beams by the required magnitude. This ensured that none of the existing platform beams were overloaded.

Guy wires were arranged to restrain the tower laterally and coordinated with the proposed locations of interface gangway and utility bridge all within a relatively small and congested area of the platform.

As part of our design package the three dimensional position of guy-wires, pad-eyes, interface gangway locations, skid beams and tower set up, were all fully coordinated and detailed by Pinnacle ensuring no clashes on site.

Avoiding Delays

Before commencing the live project, a full tower set up was installed in the fracking contractor’s yard in order to test that all the connections between lower and upper tower sections fitted correctly and that erection on site would be as planned.

The structural works to install the skid beams, pad-eyes and lower tower were installed on the gas platform pre-works, ensuring that when the jack-up barge arrived with the coil tubing and fracking equipment there were no delays with the structural preparation.

At the end of the project all of the temporary structures were removed and the platform reinstated to its existing structural condition.

In July 2014, Shell/NAM commenced a well clean out and fracking project on the L02-FA-1 gas platform