Location: UK Oil and Gas Sector
During installation, a wellhead was impacted by a Blow-out Preventer (BOP), resulting in inward bending of the inner tree hub, deformation of the top and outer BOP mating surfaces of the outer hub, and wedging of the gasket between the inner and outer hubs. The client required the geometry of the wellhead to facilitate removal and replacement of the damaged gasket.
Figure 1: Wellhead and Tree Cap Prior to Gasket Removal
Figure 2: Wellhead and Tree Cap Prior to Gasket Removal
Welaptega constructed two 3D models to provide the geometry of the wellhead prior to, and following the removal of the gasket. A marker and two magnets were placed on the wellhead during photography to provide scaling references.
The 3D modeling system was deployed to a depth of approximately 140m to capture images of the wellhead from the camera stations shown in the following figure. Camera stations are represented in purple, and the model point cloud is shown in yellow.
Figure 3: Camera Stations Used for Image Capture
A total of 164 images were processed to generate the model shown in the following figures.
Figure 4: Wellhead Model I (2D)
Figure 5: Wellhead 3D Model I (2D with photo-overlay)
The wellhead I model was exported as a *.stp file and provided to the client to facilitate tooling design.
Divers were then deployed to remove the damaged gasket, grind the outer hub surface to be flush with the rest of the wellhead, and cut or bend the internal tree cap to prevent obstruction of tooling to be deployed at a later date.
The following figures show the wellhead following the removal of the gasket.
Figure 6: Wellhead Post-Gasket Removal
Figure 7: Wellhead Post-Gasket Removal
The second 3D model, Wellhead model II, is shown in the figure below. It represents the geometry of the wellhead following the gasket removal.
Figure 8: Wellhead II 3D Model (2D)
Figure 9: Wellhead II 3D Model (2D with Photo-overlay)
Both 3D models were provided to the client as *.stp files.
The first model (wellhead I ) was opened in a 3D CAD drawing package to design the diamond rope cutter used to remove the gasket.
The second model (wellhead II) was also opened in a 3D CAD drawing package to assess the condition of the sealing surface for the replacement gasket.
