Safety of DP Operations on MODUs on the NCS
Project Background
A joint industry research project - safety of dynamic positioning (DP) operations on mobile offshore drilling units (MODUs)
on the Norwegian Continental Shelf (NCS) was carried out from August 2003 to December 2005.
The project was initiated by the operations committee of offshore drilling companies in Norwegian Shipowners Association (DUBE),
and the Centre for Ships and Ocean Structures at NTNU (CESOS).
The project is sponsored by the former two organizations, Statoil, Hydro, Smedvig Offshore and Scandpower Risk Management AS.
The main objective of the project is to improve safety of DP operation on MODUs on the NCS.
The research activities and results are subjected to reviews from a reference group which includes representatives from: Statoil, Hydro,
Centre for Ships and Ocean Structures at NTNU, drilling rig workgroup at DUBE, Smedvig Offshore, Stena Drilling, Saipem,
Fred Olsen Energy, Prosafe Offshore, PSA, HSE (UK), NMD, DNV, Kongsberg Maritime and Ship Manoeuvring Simulator Centre in Trondheim.
DP Drilling Basics
There are two safety concerns within the scope of this project:
- Loss of position. This failure is generic to DP vessels. There are two basic failure modes defined in this project, namely drift-off and drive-off.
- Failure of disconnect. Given a critical loss of position, MODU must shut in the well and disconnect the riser in time.
Fail to do so may result in damage of riser, wellhead or BOP, and in worst case an uncontrolled subsea blowout.
DP Incidents on MODUs on the NCS
DP incidents occurred during DP drilling on the NCS are collected. The data collection work is performed based on the definitions developed in this project.
Detailed analyses of each loss of position incidents are performed. One loss of position scenario was found critical on the NCS.
It is a drive-off initiated by DP controller due to erroneous position data from DGPS.
Safety Modelling in the Light of Barrier Philosophy
Based on the knowledge gained through DP incident data collection and analyses, safety modelling of DP drilling operation is further developed in the light of
the barrier philosophy. The following three main barrier functions (Figure 2) are identified:
- Barrier function 1: to prevent loss of position
- Barrier function 2: to prevent critical loss of position, given a loss of position
- Barrier function 3: to prevent loss of well integrity, given a critical loss of position
It is believed that by strengthening these three main barrier functions (via systematic identification and analysis of technical, human and organizational barrier elements involved),
the safety of DP drilling operation on the NCS could be diagnosed and effectively improved.
We analyzed each barrier function by using the identified critical scenario on the NCS. The barrier elements associated with each barrier functions are identified,
their current deficiencies are revealed, and recommendations to strengthen Barrier Function 1, 2 and 3 are proposed.
Detailed analyses could be found from Report No.2, 3 and 4 respectively.
Project deliverables
The project deliverables are presented in the following documents:
- Summary report
- Report No.1: DP incident Data Collection and Analysis
- Report No.2: Barriers to Prevent Loss of Position
- Report No.3: Barriers to Prevent Critical Loss of Position
- Report No.4: Barriers to Prevent Loss of Well Integrity
In order to let the DP drilling industry on the NCS benefit from this study, it was agreed by the sponsors and reference group members that the methodology,
main findings and recommendations in this project should be made accessible to the offshore industry.
Consequently, the summary report, together with report No.2, 3 and 4 will be made available to the offshore industry from January 2006.
Price: NOK 1.000.- / €125 / $175 per report. Postal cost is not included.
Please follow this link to order the reports.
Please contact Dr. Haibo Chen or Mr. Jan K. Lund for further questions or comments