Observation on Overtrawlable Structure and Christmas Tree Deployment

EV Offshore Ltd supply Sacrificial Cameras and Monitors and camera technician to operate and maintain EVOLeye® CS Subsea Inspection System for overtrawlable structure and Christmas Tree deployment on British Gas Apollo Field.

February/March 2003, Labrador 1 Jack-Up Rig, North Sea, Blocks 42/28 and 47/2 and 3.

EV Offshore sacrificial cameras and top side monitors, CCTV System and EVOLeye® CS were used extensively as to assist in deployment of subsea overtrawlable structure and christmas tree on the Apollo A1 well in the North Sea.

Project overview

The operation involved the deployment of an overtrawlable structure onto the seabed wellhead, followed by the mounting on the structure of the christmas tree.

Preliminary Operation – Pick-up of structure from supply vessel.

Equipment used Portable CCTV System

The overtrawlable structure was to be lifted from the supply vessel using a tool attached to a drill string. The lift for the driller was blind, so the 2 CCTV cameras were mounted in positions that allowed telephoto and wide views of the supply vessel during the pick-up and lift to the Texas deck. The zoom function allowed a clear view of the deck of the supply vessel, a wide view was ideal for giving the driller the wider picture.

Secondary Operation – Deployment of Structure to Seabed.

Equipment used Sacrificial Camera System, 2 cameras operational

External Halogen Lights

EVOLeye® CS Camera System

Two sacrificial cameras with halogen lights were mounted to the underside of the structure on custom brackets that had been pre-fitted. The cameras were mounted at 90B to each other, one focused on the lead-in funnel of the structure, the other angled slightly downwards to view first sight of the approaching wellhead. Painted on the funnel was a datum line that aligned with a keyway and a similar line painted on the wellhead. A switching break-out box was mounted onto the structure with a weak-link to the umbilical.

The picture shows the 2 sacrificial cameras test fitted onshore viewing the funnel prior to deployment offshore.

The EVOLeye® CS pan & tilt camera was mounted on the tool of the BHA that was J-fitted to the structure. The camera was positioned to view the hydraulic locking latch indicator and also the view of the J-slot.

As the structure was lowered and approached the wellhead, the sacrificial cameras were used to guide the driller to position the structure in exactly the right orientation to line up with the wellhead such that the key and keyway lined up. By switching between the sacrificial cameras, an accurate 2-axis position of the structure could be achieved, thus allowing a smooth positioning on the wellhead.

A hydraulic locking latch was operated from topside, which locked the structure to the wellhead. The latch was continually observed by EVOLeye® CS to confirm the latch had travelled full distance. An over-pull by the drawworks confirmed the latch. The pan & tilt camera module on EVOLeye® CS was repositioned to assist the driller in removing the BHA from the J-s-slot.

The picture clearly shows EVOLeye® CS’s camera that allows views of the latch indicator (painted black and orange) in the ’retracted’ and ‘locked’ positions.

The entire BHA was pulled out of hole to surface, leaving the sacrificial cameras on the structure, their job completed successfully.

Tertiary Operation – Deployment of Christmas Tree to Structure.

Equipment used Sacrificial Camera System, 3 cameras operational

External Halogen Lights

Three sacrificial cameras were mounted on the christmas tree to perform a similar function to those on the structure. One camera was mounted on the underside viewing the lead-in funnel; one was mounted on the side with a full view of the manifold block and hydraulic flow line; the third camera was mounted on the hydraulic locking latch. A 3-way camera break-out box was also mounted on the tree with the umbilical weak-link.

On deployment, the lead-in funnel and flowline observation cameras were continually monitored to aid landing the tree, and also ensuring that the hydraulic flowline adequately cleared the side members of the overtrawlable structure.

When the tree was landed, the third camera was used as verification that the hydraulic latch had travelled its full seating distance. A drawworks over-pull confirmed the tree was locked in position on the structure.

The umbilical weak-link was severed on pulling out of hole, and once again the sacrificial cameras remained on the seabed after their successful deployment.

More information on this application and other camera system and instrumentation can be obtained from EV Offshore, please follow this link <contacts>