Prelay Mooring Campaign offshore Indonesia

30th May 2016

Engineered Mooring Design for Operational Effectiveness in Indonesia.

Location: Makassar Strait, East Kalimantan - Offshore Indonesia

The project:

In 2014 Viking SeaTech Indonesia was awarded a contract to provide prelay mooring systems along with associated engineering, marine and positioning services for a large Drilling and Completion Campaign in the Makassar Strait in East Kalimantan Indonesia. The Campaign consisted of multiple wells to be drilled and completed over a two year period. The drilling rig was a fifth generation semi-submersible Drilling Rig (MODU) operating at water depths of 200m-550m. Subsea Infrastructures are present at the field and were installed at various stages of the campaign resulting in continuous re-engineering and optimisation throughout the project.

The challenges:

This was the first time Viking SeaTech had undertaken a project in Indonesia, so naturally it was imperative that there was no room for error. The high gradient seabed across mooring patterns necessitated distinct attention to anchor positions and buoy-off locations in the design phase to ease the operation which was achieved by close collaboration between the Engineering and Survey Departments.

The solution:

In addition to Viking SeaTech equipment, the rig’s own anchors and ground chain were utilised in such that two sets of prelay mooring system were present during the campaign to allow the MODU to be leap frogged between two drilling locations. The prelay mooring system was designed to 100-yr RP metocean conditions at anchor range 1500 - 1650m, where water depth at anchor positions varied from 200m to 550m. Each mooring line comprised of 76mm studlink ground chain, 90mm wire rope and chaser stopper assembly connected to rig wire.

The survey provision:

Viking SeaTech provided High Accuracy Dual DGNSS Positioning systems for the MODU and 2 AHVs. This system was integrated to the main survey navigation PC. All vessels were inter-linked via Wi-Fi telemetry. This system allowed for all vessels to see where they are in relation to each other and also known subsea assets. All vessel movements were logged and by utilising an interface to the vessel winches, tensions and payouts were monitored and recorded accordingly.

The outcomes:

We ensured our client benefited from Viking SeaTech’s full in-house services; Engineering, Marine Operations, Survey and Positioning and Equipment Supply. To minimise potential for multiple interfaces, we ensured there was a simple line of communication with a single point of contact for all services provided, whilst also establishing a local base of operations in Balikpapan, Indonesia.

By utilising the Prelay Mooring System, Viking SeaTech were able to assist the client to significantly reduce the average Rig Move duration compared to Conventional Mooring Deployment Methods; thus closing out the project ahead of schedule and budget.