Model Tests for Floatover Installation of Spar Topsides

There are several substantial advantages to installing an integrated deck on a Spar using floatover installation, particularly for large topsides which exceed the single lift capacity of the available heavy lift derrick barge fleet. These advantages include schedule and cost savings for the integration and commissioning of modules on land rather than at sea. Uncoupling the deck fabrication schedules from the availability of heavy lift vessels is another advantage. The purpose of the model tests described in this paper was to generate data on motions and loads for the operational sea states in the Gulf of Mexico, and to define and validate different approaches of transferring the topsides to the Spar, using a catamaran configuration. The data are intended to (1) demonstrate the feasibility of the installation method for the GOM, and (2) validate Technip’s analysis tools. The model tests were performed at OTRC (Texas A&M) with a model set-up corresponding to a 1:60 model scale. The simulated topsides was about 18,000Te, and Jones Act compliant barges were modeled for the catamaran configuration. The paper will describe the catamaran and spar models, and the instrumentation to measure motions and loads for transportation and installation. It will also describe the shock cell configuration used for the mating operation, and several alternative methods for performing the mating. The environmental conditions tested included several random sea states, harmonic waves, and three headings (beam, head, and quartering seas). Selected data will be shown to demonstrate the range of motions and loads associated with the floatover installation in the GOM. Estimates of limiting sea states for the GOM will be discussed. The validation of the analysis tools is the subject of another paper in Ref [1].