| dc.description.abstract | The past decade has shown a fast growing subsea production market tending to complete factories on the seabed involving even more complicated infrastructure, increasing size and weight of components to be installed. Deep water fields are expected to deliver a growing share of offshore oil and gas in the years to come. This new subsea market triggers a need for an increased deep water lowering capacity to enable safe and efficient installation of this infrastructure. Present Capital Expenditures (CAPEX) of the marine operations for a subsea production system in 300-3,000 [m] water depth is for some cases in the range 30-40 [%] of the total capital invested.
The self-weight of the steel wire makes installation operations using conventional steel based deployment systems inefficient and impractical in deep water. Synthetic fiber ropes provide a potential solution to the self-weight problems, as some ropes are neutrally buoyant. The intension of this thesis is to evaluate the potential of a crane based Fiber Rope Deployment System (FRDS) for subsea installation operations.
A numerical simulation model including installation vessel, object to be installed and a crane based FRDS is established in SIMO. The object to be installed is Statoil ASA's newly developed Dual CAP-X module, mainly consisting of two suction anchors and a frame with a trawl protection cover. Relevant numerical simulations of the subsea installation operation are conducted to determine design parameters that may determine the design operation limits. The sensitivity of the design responses for relevant parameters are investigated through sensitivity studies. Based on the simulation results, the operability of a specific subsea installation operation is assessed.
An overall conclusion from this study is that FRDSs provide a potential solution to the self-weight problems of conventional installation methods. It is observed through a sensitivity study that the static component of the total hoist line tension for the steel based system correspond to approx. 250 [%] of the static force component for the fiber based system at a depth of 3,000 [m], when a 180 [mT] payload is installed. But, the FRDSs clearly face several challenges, such as fatigue of the synthetic ropes and reduction of mechanical properties of the ropes due to heat generation.
As a supplier of high capacity lifting systems, the largest FRDS delivered by Rolls-Royce today has a lifting capacity of 300 and 150 [mT] to a depth of 3,200 and 6,500 [m] in two-fall and single-fall configuration, respectively. | en |
