Tandem offloading
General information
With its relatively short distance between the bow and stern of two vessels, tandem offloading always has been considered as an complex operation. Taking into account that in collinear wind, waves and current ‘fish-tailing’ can occur and that in non-collinear environments the mean heading of the two vessels can be different due to their difference in draft, this operation needs careful consideration. Nowadays, tandem offloading is performed with a passive bow hawser mooring from trading tankers and with dedicated DP shuttle tankers. In mild environments, tandem offloading is also applied for the offloading from spread moored FPSOs. Especially in this situation it is very important to take into account the possibility of sudden changes in the environment, such as wind squalls and tide-rips (changes of current direction).

Services & Activities
The Offshore Department has a lot of experience in the testing and numerical modelling of tandem offloading operations, it is almost standard for each FPSO project. Recently, as part of the ‘Offloading Operability’ JIP, the SHUTTLE program has been developed, which can simulate tandem offloading operations, including the wind, wave and current interaction effects between the two vessels. This dedicated tool can be applied for our clients.

The Trials and Monitoring Department can be involved in full-scale measurement of tandem offloading operations.

Facilities & Tools
Tandem offloading model tests are carried out in the following MARIN facilities :

The following tools are used to study tandem offloading :

Software Sales
Some software tools are available for commercial use outside MARIN. A complete overview of these software tools for sale can be found under Software Sales.

Experience
The list below gives a review of tandem offloading projects carried out at MARIN:

  • Shell LNG FPSO development: tandem offloading tests (Shell, 2002)
  • Azure LNG FPSO development (BV, 2000)
  • Chevron tandem offloading / fishtailing mitigation study (Chevron, 2000)
  • Shell Soroosh tandem offloading tests (London Marine Consultants, 2000)
  • JIP ‘Offshore LNG offloading System’ (FMC, 1998)
  • Girassol tandem tests (ELF, 1998)
  • Spread moored Bonga FPSO tandem simulations (Shell, 1998)
  • Campeche model tests (PEMEX, 1998)
  • Marlim field FPSO (Petrobras, 1997)
  • Shell Maui Bay FPSO (Sofec, 1995)
  • Escravos FPSO (Chevron, 1995)
  • Fife field FPSO (Bluewater, 1994)
  • BHP Liverpool Bay model tests for shuttle size optimisation (BHP, 1994)
  • Griffin, Jabiru, Challis and Skua tandem tests (BHP, to 1993)
The following Joint Industry Projects (JIPs) were focussed on tandem offloading:

  • Offloading Operability (development of SHUTTLE)
Most recent tandem offloading papers presented by MARIN
(complete overview of papers can be found under Publications)

Past, Present and Future of Hydrodynamic Research for DP Applications
Hans Cozijn and Eelco Frickel, MTS DP Conference, 2015

Wind Shielding Estimation of a Tandem Vessel Using Disturbed Velocity Field from CFD
Arjen Koop, Bruno Rossin, Wei Xu and Arjan Voogt, SNAME 20th Offshore Symposium, Houston, Texas, 2015

Integrating hydrodynamic and nautical studies for offshore LNG operations
Arjan Voogt, Jaap de Wilde and Johan Dekker, OTC, 2014

aNySIM, a versatile hydrodynamics engineering tool
Joris van den Berg, MARIN Report, 2014

Logistical scenario analysis for hydrodynamic applications
Jorrit-Jan Serraris, MARIN Report, 2014

Most recent tandem offloading articles written for MARIN Report
(complete overview of articles can be found under Publications)

Past, Present and Future of Hydrodynamic Research for DP Applications
MARIN has been involved in model testing for DP vessels for almost 4 decades. In 1976 a first project was carried out in which the main propeller of an offloading tanker was controlled based on the measured bow hawser tension....

Wind Shielding Estimation of a Tandem Vessel Using Disturbed Velocity Field from CFD
The wind forces experienced by a receiving transport vessel in a tandem configuration will be influenced by so-called shielding effects, caused by the distorted wind flow field in the wake of an FPSO (Floating Production...

Integrating hydrodynamic and nautical studies for offshore LNG operations
For offshore LNG production, the ability to safely offload LNG to shuttle carriers is an important driver in the design. Hydrodynamic studies and nautical studies can be used to select an offloading concept, optimize the...

aNySIM, a versatile hydrodynamics engineering tool
During the past 10 years, MARIN has successfully developed and used the time domain simulation program aNySIM.

Logistical scenario analysis for hydrodynamic applications
To calculate the operability of the whole logistics chain, rather than only individual operations, MARIN has developed the hydrodynamic scenario analysis program ScenSim.

Contact
For more information on how MARIN can help your organisation with the issue of tandem offloading, please contact:
For model test and simulation activities: Offshore Department
For nautical training: MSCN
For full-scale measurements: the Trials and Monitoring Department

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