Hydraulically centralized 15-slot subsea drilling template
The Volve template has enabled Maersk to employ the Inspirer jackup in a role for which it was not originally designed. It has also defined a new option for field developers; Claxton has received expressions of interest in the technology from at least one other operator. In conclusion, it could be said that Volve has itself provided a valuable template for further applications of this nature.
Central to the development
The Volve template was designed and built by Acteon company UWG, which is now incorporated into Claxton. It has 15 slots in three banks of five; the central slot was used to run the template as well as for drilling. The template was approved by DNV, whose representatives witnessed all the pre-delivery tests. Weighing in at 50 t, the structure was built in five parts in Great Yarmouth, UK. It was then transported to Haugesund in Norway for assembly before being sea-fastened to the Maersk Inspirer for the journey to the field.
A key feature of the template is the mechanism used to centralize the conductors within the slots during the primary cementing operations. It was a condition of the design that point loading on the production risers through the template during well construction and throughout the life of the field should be eliminated. There was to be no contact between the conductors and the template after the conductors had been cemented in place. This meant having centralizers that could be withdrawn from the slots once they had performed their important role.
Claxton’s solution to this problem was to build three retractable hydraulic cylinders into each slot. Activated by the ROV, these were extended to hold the 30-in. conductors in place during cementing, and were later retracted. The cylinders, each rated at 2100 psi, were grouped in five banks of nine and were powered from the ROV using the same environmentally acceptable hydraulic fluid used to control the ROV’s other mechanical functions. It is believed that this is the first time such a conductor centralizing system has been used.
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