During the recent years DHI has experienced an intensive interest for offshore model testing within the transport and energy sectors. Several major test programmes have been carried out successfully over the past few years including oil and LNG platforms, FPSO’s, LNG carriers, and offshore mooring systems. The tests provide valuable information for the design and installation phase – often in combination with numerical models.
Examples of extreme wave tests with significant wave height at 14.6m. Video courtesy Sigma Offshore Ltd., UK and Fetl Ltd, UK One of the recent offshore tests undertaken by DHI included an extensive wave tank model test programme for an offshore FPSO mooring system named SMART. This innovative system has been developed and patented be SIGMA Offshore Ltd, Aberdeen, UK. The SMART mooring system consists of a mooring canister attached to a cantilever structure mounted on the deck of an FPSO. Three or six mooring chains extended from the mooring canister down to the sea bed. Furthermore four risers in a steep S-configuration were included likewise extending from the bottom of the mooring canister down to the seabed.
The main purpose of the project was to test the SMART mooring system under different environmental conditions in order to enable a better understanding and prediction of the response of the SMART system and the moored FPSO.
Two systems were tested: a disconnectable mooring canister which allows the FPSO to be disconnected from the mooring system and a non-disconnectable mooring canister where the FPSO is permanently fixed to the mooring. Furthermore the disconnectable mooring canister was tested alone without the FPSO moored to the system.
Examples of extreme wave tests with significant wave height at 14.6m. Video courtesy Sigma Offshore Ltd., UK and Fetl Ltd, UK
Two overall wave conditions were included, Hs=7m and Hs=14.6m. A number of test combinations were set up including different orientations of the mooring system, different draughts of the FPSO, both with and without wind and current. The results of the model tests were used to assess and calibrate the results of computer simulations performed by SIGMA Offshore Ltd. The data obtained from the model tests are now being used in further development, certification, and design of the SMART mooring system by SIGMA Offshore Ltd.
"The model tests were managed, completed and reported on time and within budget by DHI's professional team - the comprehensive data set obtained will help us to optimise our new innovative SMART mooring system (SMS)." Robin Colquhoun, Sigma Offshore Ltd, UK
DHI offshore test facility
DHI has carried out offshore model tests during the last three decades. The facility consists of an offshore wave tank with a size at 20mx30m and an overall depth at 3m. At the central test area of the tank the water depth can be increased down to 12m. With the 60 segmented 3D wave makers a wide range of wave conditions can be generated including regular and directional irregular waves. Both wind and current can be included in the facility providing the capability to reproduce a very realistic and harsh offshore environment.
DHI’s offshore test facility is ideal for testing innovative concepts and technology advancements in the offshore oil & gas industry and the booming marine renewable industry. This is owing to flexibility and efficiency of the facility and of our experienced engineers which allows us to react to clients’ often very tight time lines.