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Figure 4-13. Safety-related issues assessed by the operator in the early phase. (Source: Acona) 4.2.6 Risk understanding and worker participation
The project devoted great attention from the start to critical elements of the concept:
• risers – materials and failure mechanisms
• mooring – materials and installation
• condensate storage – safety
• offshore loading – Goliat experience
• climate conditions – Multiconsult study
• weight control.
Equinor has several major projects under way in parallel at all times. Over the years, it has established a best practice on how to involve the safety service, unions and not least the operations team in the various project phases. This reduces the risk of later changes and contributes to production-friendly technical and operational solutions.
Risks were systematically identified as early as the feasibility studies and followed up
systematically in all parts of the project in terms of establishing actions, implementing these and checking that they had the desired effect.
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• mooring, including the use of polyester mooring lines
• SCRs, including solution for pull-in/hanging off
• system for well workovers.
Solutions were established by the Feed studies for both hull and topsides which provided the basis for realistic weight and cost estimates. Figure 4-14 presents developments in topsides weight from Feed to completion. Because experience indicates that some increase must be expected, a more conservative weight estimate was adopted at DG3. This was 22 593 tonnes, or 23 743 after risk adjustments. A final figure of 24 358 tonnes means the weight gain after DG3 was only 2.6 per cent. Increases for the hull were even smaller.
Figure 4-14. Topsides weight development and overview. (Source: Acona)
Topsides dry weight provides the basis for cost calculations and is an important figure for weight reporting and control. Normal practice is to divide it between equipment weights, bulk weights per discipline and construction steel. Weight composition varies from platform to platform, but a marked deviation from the average should be investigated in more detail.
Figure 4-15. Analysis of discipline weights. (Source: Acona)
Figure 4-15a presents discipline weights in relation to equipment weights. Weights for Aasta Hansteen’s topsides are compared with average values for 16 different platforms
(references). Figure 4-15b presents discipline weights as a percentage of total dry weight for Aasta Hansteen and the reference projects.
The figure shows that Aasta Hansteen’s weights deviate little from the average for the reference projects, except for the fact that the share of construction steel is high.
After DG2, a systematic investigation was conducted to improve and simplify the process plant. This led to some measures, but no major changes.
However, it became clear that the decision to incorporate condensate storage in the hull had bigger consequences than expected. HC inside the hull’s main structure, combined with the
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need for safe access by lifts and stairs very much increased complexity. In addition, a more complicated and active ballast system was needed to be able to control the platform’s draught when the condensate store was filled to different levels.
4.3.2 The government’s assessments and conditions – Proposition 97 (2012-13) to the Storting
Main conclusion: the MPE approves the PDO of Aasta Hansteen field in accordance with the plans submitted by the operator and the comments presented in this Proposition.
In connection with their consideration of the PDO, the PSA and the NPD had the following comments:
The PSA has certain comments which are specified in the Proposition text, but sees no need to set special conditions and recommends that the plans be approved. The ASD has no additional observations.
Various development solutions for Aasta Hansteen have been assessed by the licensees in an early phase. The main alternative to today’s development solutions were various subsea development variants with landing to Nordland, other fields in the Norwegian Sea or directly to Nyhamna. The chosen solution came across as advantageous, based on higher present value, less need to mature technology and increased opportunities for resource utilisation in Aasta Hansteen and the surrounding area. On that basis, the NPD has no objections to the operator’s choice of concept. Nor has the NPD had objections to the choice of the Spar concept at the expense of alternatives, particularly FPSOs and a semi- sub/TLP.
The NPD notes that the licensees have implemented extensive technology qualification up to the submission of the PDO. Although the technology qualification has been implemented, the NPD would observe that the development solutions involve a number of elements which are new and untested for the operator and/or the NCS. The project therefore contains elements of risk which call for very good project and contract management by the operator. The NPD also wants to call attention to the fact that the development will take place in a period when a very high level of activity prevails in the petroleum sector, which could pose challenges in relation to the availability of materials and costs. The NPD notes that new information from suppliers on delivery times has resulted in a postponement of the expected start to production from the fourth quarter of 2016 to the third quarter of 2017.
Calculations of power from shore by the operator show high supplementary costs, and the NPD therefore supports the operator’s assessment that Aasta Hansteen be developed with gas turbines. The NPD notes the gas turbine for export compression has heat recovery (for the process and the living quarters), and can thereby achieve a higher level of efficiency.
The NPD had no comments on the impact assessment.
The NPD takes the view that the operator, with the present development plans, makes good provision for new and existing discoveries in the area, both within and beyond the Aasta Hansteen licence.
4.3.3 Contract strategies. Prequalification, tender documents and format
Technip was commissioned in July 2012 to design, procure and deliver the Spar platform hull ready for mating with the platform topsides in Norway. The supplier was also to design and prepare specifications for SCRs and for a complete mooring system.
As hull supplier, Technip had to establish cooperation with a yard. Virtually all earlier Spar platforms have been built at a Finnish yard which has specialised in such structures over more than 20 years. Because this yard was fully engaged on another project, Technip now decided to enter into a collaboration with HHI, which in turn contracted with Kværner for mating and completion of hull and topsides at Stord.
The fact that the topsides contract was also awarded to HHI with CB&I responsible for engineering was an unrelated matter.
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Figure 4-16. Placing of the most important contracts. (Source: Equinor)