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Offshore oil and gas development in Russian Arctic zones



B.A. Nikitin1, D.A. Mirzoyev2 and E.V. Bogatyreva3

1 Gazprom
2 VNIIGAZ
3 Gubkin Oil & Gas University

Progressively growing global energy demand - most importantly, automotive fuels and petrochemicals feedstock - under the generally maturing onshore oil and gas fields and subsequent production declines, calls for special emphasis on offshore development. This appears to involve a major challenge as it would require a basically new oil and gas sector to be set up, with all related infrastructure and its unique features such as innovative surface and subsea technologies as well as installations suitable for the harsh Arctic environment.

Enormously high costs in volved in offshore oil and gas production raise responsibility of shelf operations, for which reason the price of mistakes becomes extremely high - whether it is related to the choice of offshore oil and gas fields, or to determining the structure of facilities required for field development - thereby underlining the urgency of in-depth research into this area.

To our opinion, all known types of offshore oil and gas fields should be covered by such analysis, complemented by their advantages and shortcomings as well as by hydrometeorological conditions in the Arctic shelf, after which related methodology guidelines could be made available. This effort is supposed to place special emphasis on appropriate choice of underlying technology and economically sound ways of field development.


Figure1. Coast-based directional well drilling


Figure 2. Sea bed filling


Figure 3. Sea bed drainage in the oil and gas area
 



Figure 4. Subsea production outline:

1 - Protective structure; 2 - Manifold; 3 - Wellhead; 4 - Pipeline; 5 - Sea
bottom basement; 6 - Control/monitoring flexible cable; 7 - Control and
monitoring system

The oil and gas industry has accumulated vast experience with offshore development in moderate climate conditions, but it still fails to demonstrate feasible technology and necessary tools which would be adequate to organise full-scale drilling and production operations in the Arctic seas. For this reason, today, when formulating a range of technical concepts relating to northern continental shelf development, it should be emphasised that they remain largely built around our present knowledge of underlying ideas and proposals that are still far from being well established and justified by the real-world experience.

A more detailed environmental data input (hydrometeorological, geology engineering, seismic, environmental, geographic, mining and geological) is believed essential for designing sustainable and economically viable technical solutions. Obtaining the majority of these characteristics is associated with significant scope of field observations to provide statistical integrity of the source data set.

It should be noted that ice conditions are central for the case, and are decisive for appropriate choice of target offshore oil and gas fields in the Arctic seas. This predetermines special importance involved in examination of actual ice conditions and loads on offshore facilities. Presently available ice-related data are largely attributable to various ice environment studies focused on forthcoming polar stations, landing grounds, various crossings, and vessel navigation through ice-dominated areas.

This ice research programme targeted on the offshore oil and gas activity can be sub-divided into the two main parts:

  • examination of ice hydrometeorological conditions, and its physical and mechanical properties
  • research into interaction of ice with supporting engineering structures of oil and gas production facilities.

The first part of this programme has to be undertaken in particular water areas, in the natural environment, while the results of its second part are assumed to be largely applicable to any ice-prone area, and such research should be conducted in both field and laboratory conditions.

Analytical results of ice hydrometeorological conditions in the Arctic shelf obtained to date reveal that hydrocarbon resources can be equally found both in shallow and deepwater portions of Russia’s northern seas which are known to have harsh ice environment. The ice-free period varies between 2.5 and 5-to-6 months, which would be insufficient for drilling offshore production wells. Such conditions calls for building dedicated drilling rigs including ice-resistant designs.

All types of Arctic oil and gas production schemes (onshore, offshore, subsea, underground, and combined) can be potentially employed for development of hydrocarbon resources in the Barents Sea including Pechora shelf, and the Kara Sea with its Ob and Tazov bays.

Offshore field development can be accomplished in several stages and built around onshore-based projects (see Figures 1, 2, and 3):

  • drilling out subsea oil and gas deposits and production operations using inclined and horizontal wells running from the coast
  • producing artificial lands by filling soil in the oil and gas acreage and installation of production facilities in this area
  • drainage of the sea bottom in the oil and gas acreage achievable by dike construction with subsequent water removal.

When building offshore production facilities, development of oil and gas fields also assumes several construction stages:

  • sea dikes and dike area earth islands
  • offshore loading piers with associated sites
  • tension leg platforms (TLP), or SPAR-type and other semi-submersible or floating drilling and production platforms
  • integrated projects using facilities mentioned above.

When developing offshore oil and gas fields by means of sub-sea production facilities (see Figure 4), production wells are commonly drilled from floating rigs. All wells are normally drilled in a subsea wellhead configuration. Production, gathering, treatment and transportation facilities should be placed at sea bed level. Process control of wells and subsea production facilities is carried out remotely, from coast or an intermediate floating engineering unit.

Underground production facilities assume construction of a tunnel/mine or a tunnel/chamber grid to accommodate drilling complexes, well clusters with production system, pipelines, ventilation conduits, along with connecting chambers for vehicles passing and communications arrangement from the tunnel to drilling clusters.

In this case the integrated oil and gas production facilities imply a combination of sub-sea and surface offshore development schemes. For example, some wells undergo underwater completion and others have surface wellheads, and basic field development assets and subsea production/flow control facilities could be installed either on drilling or on processing/service platforms.

Advantages and shortcomings of these field facility arrangements have been analysed by S.A. Orudzhev, I.P. Kuliev, A.I. Gritsenko, Ya.S. Mkrtchyan, and by the authors of this report. At present, several projects have been launched, they are focused on Arctic shelf oil and gas facility construction and field development start-ups, with special emphasis being made on natural and climatic conditions in this challenging offshore zone.

Such offshore production facilities are believed applicable to deep-sea conditions with brief ice-free periods. It is also essential to consider adequate spacing between the field and coast facilities, thereby facilitating direct transportation of field production to avoid its upstream treatment.

Integrated oil and gas facilities are believed to be increasingly popular as they help avoid individual shortcomings of sub-sea and surface installations. It is noteworthy that the predominant use of any individual approach to production has been reported successful only in few offshore oil and gas developments since the integrated techniques appear to be most preferable for the majority of offshore development projects.

In a conceptual development project for Varandey-More field, the authors have proposed the new integrated method whereby the offshore portion of the field is to be developed using inclined wells drilled from the coast and its other part - by wells drilled from ice-resistant platforms.

In shallow water with heavy ice conditions the use of wells with subsea completion systems requires special structures such as reinforced-concrete or metal caissons, to accommodate the subsea wellheads and protect them against mechanical damage by pack ice.

However, it should be noted that such combined production facilities have one major disadvantage - significant capital investments involved in field facility construction making them unjustifiable for marginal reserves. Moreover, such facilities appear to be also inexpedient in deep-water zones with heavy ice conditions (such as in the Kara Sea).

Therefore, in order to choose the most economically sound option of oil and gas development, in-depth analysis of geo-technical, hydrometeorological, and nature/climatic conditions in a particular field is believed critical. The analysis of advantages and shortcomings of the discussed field development methods shows that the onshore-based, subsea, above-water production facilities, and combinations thereof, appear to be most preferable for Arctic shelf conditions.

The above-water production facilities have proved effective in Pechora Sea conditions, in water depths ranging 30 - 40 m. In greater depths, subsea wellheads become more feasible, i.e. the integrated production facilities appear to be the best choice. The combined approach involving elements of both the onshore and above-water facilities is likely to be most useful in shallow water applications.

Subsea production facilities can be predominantly used in the Kara Sea environment (such as Rusanovskoye and Leningradskoye fields).

Application of the above mentioned offshore production facilities calls for development of special tools, installations and technologies targeted on field types highlighted by authors in this report.



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