Predictive Simulations Matched By As-Laid Parameters Of Sicily Channel Sealine Project
Authors: Bianchi Stefano , Oliveri Vincenzo 
Published: October 2008

The unprecedented nature of the TRANSMED project (three 20" O.D. lines across the Sicily Channel for a total 480 km in extreme water depth - 608 mt max - and along almost prohibitive seabed profiles (see fig. I) has suggested a special approach to the job. With this aim, a series of studies and simulations have been performed and partly inserted into the contract documents to assess main pipelaying parameters.

Using the same logic and the same calibrated computer programmes which govern Castoro Sei operations it is hardly surprising to note that the predictive theoretical analysis have matched the actual operational parameters.

A detailed description of the area covered by such simulations, the quality of the relevant systems on board is given with specific reference to general optimization of job planning, pipe stress analysis and subsequent control during operations, automatic navigation and control.

Introduction

At an early stage of preparation to the project, utmost care has been devoted to pipe stress analysis due to the unprecedented overall difficuIties of the TRANSMED, also to assist final optimization of detailed engineering on specific problem areas and to cover main operational implications.

Furthermore, facing a very huge and complex job implying continuous operations expected to last 16 months, through two winter seasons, an adequate job planning, using non _ tradi tional tools, has appeared essential. With the computer facilities of the Castoro Sei a series of programmes have been developed to perform a simulation study to optimize:Castoro Sei production cycleLogistics and pipe handlingAncqor planning program. In a logical order these latter problems are treated first, followed by pipe stress analysis (with special reference to seabed profil!9 influence on pipelaying, laying procedures and pipe stress monitoring and control) and by automatic navigation (station keeping and moving up).

Job Planning Optimization Programs

Castoro Sei production cycle

A P.E.R.T. package, implemented on the computers facili ties of Castoro Sei has allowed the analysis of all phases of the production cycle on board from pipe stocking areas to the field joint station. The entire cycle is splitted into elementary operations whose statistical durations (minimum, average, maximum time) are assumed on the basis of previous experience. This program aims at minimizing time gaps and at improving overall reliability. Standard deviation along the critical path is analyzed to assessthe confidence on the results, mainly:accurate estimate of production rate and ensuing implications forwelding teams, weld passes for each station,interrelations between double joint production andfiring line and storage capacity for double joints,interference of various mechanical breackdowns on the production rate and means of keeping it as regular as possible. These analysis have proved extremely useful in production planning and during operations as detailed specific answers have been readily available to cope practically with all contingencies. Conclusions of these analysis have been used also as input to the following programmes.