Riser and Vessel Motion Data From Deepwater Drilling Operation

This paper discusses the use of a real-time monitoring system to track wave driven fatigue damage at critical locations in a subsea well during a 290-day drilling operation in the Mediterranean Sea. Real-time monitoring was employed due to up-front finite element (FE) analysis predicting fatigue damage rates of sufficient magnitude that the required safety factor would not be met. LMRP/BOP motions were recorded using two subsea monitoring units (each containing accelerometers and angular rate sensors). These were installed on the LMRP and above the lower flex joint. The accelerometer signals were used to deduce the static inclination of the well and the angular rate signals the dynamic inclination due to vessel motion and wave loading on the riser. Data was transmitted in real-time to a central processing unit on board the vessel. This converted the motion data into fatigue damage accumulation using non-linear transfer functions derived from the FE model. The damage was displayed in a simplified format for use in decision-making. The recorded data revealed the motions of the LMRP/BOP and hence the damage rates in the well to be considerably less than predicted by the FE analysis. The damage rates derived from the monitoring system therefore served as a continuously updating demonstration that an acceptable margin of safety against suffering a fatigue failure was being maintained thus permitting drilling to proceed safely. A subsequent benchmarking study which additionally involved processing of recorded vessel motion data, current data and seastate data was undertaken to identify possible reasons for the differences between the predicted and measured LMRP/BOP motions. This showed that conservative assumptions made on the soil stiffness (due to limited availability of data), differences between the predicted and measured riser natural periods and differences between the predicted and measured vessel motions all contributed to the LMRP/BOP motions and hence the damage rates predicted by the up-front FE analysis being larger than measured in the field. The systematic identification of the factors which contributed to the differences between the predicted and measured response is described in this paper. Areas where further work would be of value to help improve the reliability of up-front, analytically predicted fatigue damage rates are also discussed.

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Analytical modelling of temperature profiles during deepwater drilling operation

Journal of Petroleum Science and Engineering ◽

10.1016/j.petrol.2019.106582 ◽

2020 ◽

Vol 184 ◽

pp. 106582 ◽

Cited By ~ 5

Author(s):

Boyue Xu ◽

Hewei Tang ◽

David Fyfe ◽

A. Rashid Hasan

Keyword(s):

Analytical Modelling ◽

Temperature Profiles ◽

Deepwater Drilling ◽

Drilling Operation

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Studi On Person Over Board dalam Pendidikan dan Pelatihan Maritim di Polimarin Semarang

Jurnal Maritim Polimarin ◽

10.52492/jmp.v6i2.4 ◽

2020 ◽

Vol 6 (2) ◽

pp. 32-41

Author(s):

P. Tony Kusumartono ◽

Hero Budi Santoso ◽

Noviarianto Noviarianto

Keyword(s):

Negative Impact ◽

Time Factor ◽

Crew Member ◽

Student Responses ◽

Motion Data ◽

Ship Maneuverability ◽

Time Distance ◽

Vessel Motion

Person Over Board (POB) is one of the emergencies that still occurs on board, a passenger or crew member falls into the sea. This situation is very dangerous if it occurs in the middle of the ocean or in cold waters because of hypothermia which can cause unconsciousness and death within minutes. This research focuses on investigating the improvement of the response of polytechnic students during emergencies, namely Person over board (POB) with the support of manouver onboard training in Bridge Simulator as well as making decisions on safe maneuvering and precise ship response manouvre in POB rescue actions. This study uses descriptive methods to assess ship manouvre training especially when person over board (POB) among Indonesian maritime polytechnic students, which are designed for students and researchers to gather information about the conditions needed in the field of nautical studies. The rescue attempts of the Anderson, Williamson and Scharnow model of rescue turn are carried out in radar and arpa simulators, student responses with the support of manual maneuvers on board and vessel motion data which include time, distance, speed and direction of the ship or angle of target bearing. The accuracy of student responses made during a POB emergency does not always comply with the instructions in the Manouvre on Board manual. Errors occur at the beginning of the maneuver which could mean a negative impact that endangers POB safety. Safe and precise ship maneuverability in the POB situation is influenced by the time factor of the incident and when the POB is known.

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