Ice-resistant drilling platform for the Tazov bay |
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MOROZOV A.N., POTAPOV V.M., BLAGOVIDOV L.B. In 1999, OJSC “CDB “Corall” (Sevastopol) developed conceptual design of ice-resistant drilling platform (IRDP) for the Tazov Bay, and specifically for the Ader-Payutinskoye gas field, as ordered by the OJSC “Gazprom”. Previously worked-out technical solutions were modified and refined in this Project. Severe arctic conditions, with prolonged winter and shortened cool summer periods, are peculiarities of the local climate.In winter period, all the surface of the Bay is covered with ice field 140-170 cm thick to increase up to as high as 250 cm in coldest years. Ice loads are considerable in winter and ice floating periods, while available data on upper seabed layers at the site suggest lower strength of those layers. That provided reason enough to select pile-supported platform as early as at basic design stage. Considering peculiarities of local climate (specifically, the shorter ice-free summer period), the ice-resistant platform is designed as a combined structure consisted of two parts as follows:• floating submerged platform itself, Such a configuration makes it possible to preinstall substructure and secure it with piles during a shorter summer period. The submerged platform is mounted on during the consecutive summer period. The ice-resistant platform is intended for installation in the area of the Tazov Bay or other areas characterized with similar water depths and hydrometocean conditions, to ensure the following: Type of the platform is ice-resistant, floating, submerged, with pre-installed piled substructure. Endurance (days) is as follows: Weight/overall dimensions of the platform and substructure are listed below: platform substructure length, m 48.0 56.4 width, m 24.0 32.4 Principal parameters of process equipment are: maximal length of inclined well up to 5,000 quantity of production wells, pcs 10 quantity of injection wells, pcs 2 type of production flowing reservoir pressure, MPa 8.7 distance to integrated gas treatment unit, km 200 (approximately) Production facilities provide the following: • gathering of products derived from gas wells, To save costs for the platform as much as possible, accepted production equipment includes just the equipment for primary treatment and transmission of gas field products. Where integrated gas treatment is a must, the corresponding equipment is more feasible to install onshore. • 317.5 t cargo hoisting capacity (maximal), Both the substructure and the production platform are floating. Their transportation to the site is intended by means of standard towing. First, the substructure is delivered, submerged and piled to the seabed. Then the production platform is inserted inside the piled substructure. This design approach has the following advantages: Conclusion In the process of development of the Project, a wide range of issues was considered and examined to deal with ranking and optimizing results of calculation of ice load affecting the IRFP, soil engineering analysis, design approaches related to the IRFP providing its reliable all-the-year-round operation in the Tazov Bay. The conclusion which can be drawn based on results of calculation performed is that the IRFP structural components strength and buckling stability are ensured for the case of acting combined design loads for the entire period of IRFP operation. Study of the structure and equipment to be applied has shown that the IRFP can be constructed in shorter terms, i.e. for 44 months if constructed at Tyumen Region shipyards, or for 21 months if constructed at Tyumen Region shipyards. Developed as part of the conceptual design, the process facilities incorporating only the minimal required equipment package provide Ader-Payutinskoye field development at minimal possible production expenditures, as well as reliable operation and distinguished by not high price. The basic design stage shall include a more detailed study of material and heat balance of the process to be performed onboard the IRFP and parameter of two-phase well product transmission. Based on the scope of work performed and results gained it can be said with confidence that the IRFP can actually be constructed and reliably operated at the Ader-Payutinskoye gas field of the Tazov Bay. Oil and gas of Arctic shelf 2008
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