O. T. GUDMESTAD, J.E. VINDSTAD, H. GREIFF JOHNSEN, A. B. ZOLOTUKHIN

Statoil, Stavanger, Norway
Statoil, R&D Centre, Trondheim, Norway
Stavanger University College, Stavanger, Norway
Gubkin University of Oil and Gas, Moscow, Russia

Abstract

Statoil has during the last decade earned out a specific research project aimed at developing technologies for offshore areas with cold climate and ice.

Highlights from the project will be presented in this paper. Furthermore, there are several technologies that have been developed within the company that are needed for efficient field developments in the Arctic offshore. Statoil1 s high focus on safety and a clean environment must also be emphasised due to the remoteness of possible Arctic offshore developments and the Arctic's high vulnerability to pollution, hi order to ensure high quality offshore structures in the Arctic, we strongly support the ongoing ISO initiative to prepare an international Arctic Offshore Structural standard.

For the purpose of the 2005 budget, we have introduced the following activity split:

Arctic environmental issues
Arctic drilling
Ice occurrence and ice loading
Arctic field development
Flow assurance in pipelines
Transport in ice infested areas
Project execution and logistics

Supporting technologies

For economic development of offshore hydrocarbon fields it is most important that the number of platform locations be minimized to reduce the capital costs of the development. This is achieved through use of long reach wells and sub sea tie back of wells to fixed platform locations. For mature North Sea fields there is an ongoing effort to drain all reservoirs in vicinity of existing platform units. The general goal is to reach out 10 km from any platform location with long reach wells and horizontal wells, while any hydrocarbon accumulation up to 80 km from an existing platform is aimed at being produced to the platform through use of sub sea wells and pipelines that are insulated if necessary to avoid hydrate formation.

Statoil has over 20 years spent a considerable amount of the company's research budget on two-phase and multi-phase flow in pipelines. The use of the two-phase flow technology, where the well-stream is consisting of water and gas, can be extended to much longer reach as is demonstrated in the Snohvit field development project where full well-stream of relatively dry gas is sent 140 km to the onshore facilities without any treatment offshore.

One should, however, recognize that a considerable amount of mono-ethylene glycol (MEG) injection at the wellhead is necessary to avoid hydrate formation. For the multi- phase transport of gas. oil and water, the limitations with regards to length of transport of untreated well steam depend more on the properties of the oil and that vax formation in the pipeline can become a serious problem. Research is ongoing to extend the distance of pipeline well-stream transport. Statoil considers this technology to be crucial for arctic development projects and has established a close link between the flow assurance project and the more specific Arctic engineering project.

Statoil is also playing a leading role in developing clean and efficient exploration drilling technology. The on-going exploration drilling campaign in the Norwegian Barents Sea will serve as a full-scale test of new equipment for storage, handling, and transfer of drill cuttings from rig to vessel (e.g. stand-by boat). Statoil is also financing a Ph.D. study aiming at developing a multi-criteria assessment tool for total fluid management during drilling operations.

For successful development in the Arctic the technology for optimum production from a reservoir is crucial. Through reservoir monitoring, successful application of gas and water injection, and deviation drilling to reach smaller pockets of oil and gas, Statoil has been in a position to produce up to 65% of the reservoir accumulation in the Statfjord oil field. At present the company's research programme involves a project to produce 70% of the hydrocarbons in the reservoir from platform-completed wells and 55% from sub sea completed wells. A conference on Enhanced Oil Recovery was held at the Gubkin Russian State University of Oil and Gas in 2003: https://www.force.org/PDW-Seminars/Progi'am-En 26.03.031.doc. A follow up to this conference is planned in Stavanger in 2005. The Ministries of Russia and Norway, Statoil and the participating Universities support the conferences.
Technologies to ensure safe and environmentally friendly development of hydrocarbon fields in the Arctic.

Statoil's corporate HSE strategy is founded on the zero harm principle, and Statoil has through the corporate and business HSE strategies identified risk assessment as the key approach to meet these requirements. Risk assessment as a HSE management tool has gradually found more acceptance within national and international regulating authorities over the past years. Traditionally, the industry has strongly encouraged this development, since this approach provides higher flexibility and possibility for cost-beneficial HSE management.

For the development of any Arctic hydrocarbon field, the clean environment is a key consideration. Technologies that will be used for the Arctic are at present being implemented at the North Sea platforms. These technologies include cleaning and injection of produced water and reduced emissions from operations of the platforms. For the Snohvit development, LNG is produced at Melkoya close to Hammerfest and the CO2 that is produced at Melkoya is injected into the reservoir to reduce climate gas emissions.

From the viewpoint of structural engineering- contributions related to design of safe structures and handling of ballast water are important contributions to safety and clean environment (Gudmestad, 2003).

Even if the considerations should be on development of safe and environmental friendly technology and on safe operations, it will be of vital importance that one can handle any hydrocarbon releases into the environment. Statoil has therefore focused much on developing environmental risk assessment tools, contingency plans and oil spill response methods for containing any releases. Participation in, and contribution to. international joint industry technology development projects are seen as the best way to ensure that all operations in the Arctic are associated with an acceptable risk to personnel, environment and assets.

Some specific results from Statoil's Arctic Offshore Engineering research project

During the last decade a research project to develop generic technologies for development of fields in the Arctic has been ongoing in Statoil. The project has emphasised on the key technologies needed for successful development of facilities for the Arctic (Gudmestad and Loset, 2004). These technologies are relevant for the development of the ice-free part of the Norwegian Barents Sea, and for development of areas with considerable ice aggregations. The research supports Statoil's Barents Sea drilling programme and the business development attempts Statoil has ongoing in relation to involvement in other areas of the Arctic. The project focuses on transport technology as the different physical environmental parameters vaiy from location to location in the Arctic while generic problems related to transportation are common for all areas of consideration.

A key aspect of the Arctic Offshore Engineering research project is the cooperation with Norwegian and Russian universities to educate the generation of engineers and researchers that will be involved in the development of the Arctic. Cooperating institutions are The Norwegian University of Science and Technology in Trondheim, Gubkin Russian State University of Oil and Gas in Moscow. St. Petersburg State Technical University in St. Petersburg and Stavanger University College in Stavanger. Professors from these universities have prepared a text-book (Zolotukhin et aL, 2000) that identifies characteristics of the Arctic conditions, summarizes several of the concerns that are associated with Arctic developments, and points to technical solutions that are viable for the sustainable development of hydrocarbon fields in the Arctic.

The text-book is being used for teaching the course Arctic Offshore Engineering, that is given annually at UNIS, the University Studies at Svalbard see https://www.unis.no/ as well as being used at courses held at the participating universities. An exchange programme between NTNU and St. Petersburg State Technical University, where students have been invited to spend up to one year at UNIS has been supported by Statoil. The programme has given a considerable group of Russian and Norwegian students an opportunity to get in contact for future cooperation between engineers from the two countries. Students from the Gubkin University have, furthermore, been invited to Stavanger. A paper on "Uncertainty and Associated Risk in the Development Planning of an Offshore Field'4 has recently been published (Kochnev et al., 2004).

The strong support of students is being materialized through financial and technical support of thesis and doctoral studies. An important part of the research is earned out in the Van Mijenfjord at Svalbard. The ice aggregation in this fjord is typical for the Arctic, however, the fjord is nearly closed at the outlet by an island, creating very stable ice conditions where full scale controlled experiments can be earned out. There is furthermore, a fully developed infrastructure at Svea, a mining settlement at the bottom of the fjord.

At this location, experiments of dragging artificially created ridges into the sea-bottom to investigate ridge to sea-bottom interaction has taken place to investigate effects of ridges interacting with shallow water seabed pipelines (Liferov et al., 2004, Liferov and Hoyland. 2004, Hoyland and Liferov, 2004). The objective of the research is to obtain improved background for the determination of trenching depth of sub-sea pipelines in the shallow water zone.
Another experiment has been carried out at this location to investigate the interaction between sea ice and a vertical pile (Moslet et al, 2004 and Moslet and Hoyland, 2004). This problem is one of the classical problems in ice engineering and the Van Mijenfjord location has allowed for full scale testing under well-controlled conditions.

The work is ongoing with emphasis on understanding the properties of ice ridges (Shafrova, 2004) and plans are made to expand the research into further studies of ice-ridge structure interaction.

We have, furthermore, considered the transfer of fluid from an offshore storage to a tanker in the Arctic to be a key aspect for safe and environmental friendly operations in the Arctic. Amor Jensen (2002) demonstrated the efficiency of using the Submerged Turret Loading Technology for Arctic conditions. The STL technology is a technology originally developed by Statoil, http ://www. apl.no/products/prod stl. asp, hi order to document that the riser connecting the tanker to the storage is safe under adverse loading conditions, Loset and Bonnemaire (Bonnemaire, 2004) have developed an armoured riser specifically aimed at resisting the loads from ice floes from floating ridges.

Development of an ISO (International standardization Organization) standard for design of offshore Arctic structures
An ongoing international effort is being undertaken to develop an international standard for design of Arctic Offshore Structures. Statoil supports this work by participating in the Workgroup developing the standard, in Panels preparing the text of specific paragraphs and by giving financial support to persons involved in the work in several of the panels. We are in particular aware that the safety inherent in Norwegian standards is being implemented in the ISO code. Although it takes time to develop an international standard, it is expected that a working draft of the standard will be available in 2006 for reference in developing Arctic offshore fields.

References
B. Bonnemaire:. "Response of an armoured riser for Arctic Offshore Loading", paper presented at the 17th hit. //Symposium on ice, IAHR. St. Petersburg, June 2004.
О. Т. Gudmestad: "Contributions from the structural engineering discipline of the oil industry to a clean environment", //paper presented at POAC conference, Trondheim 2003.
О. Т. Gudmestad and S. Loser. "Key considerations in the design of offshore production facilities for Arctic Offshore Conditions", paper presented at the 17th Int. //Symposium on ice, IAHR, St. Petersburg- June 2004.
K. V. Hoyland and P. Liferov: "Ice ridge scouring experiments. Part II: Consolidation and Physico-mechanical properties", //paper submitted to: Cold Regions Science and Technology, 2004.
Jensen: "Evaluation of Concepts for Loading of Hydrocarbons in Ice-infested Waters", Dr Ing. //Thesis, NTNU, Trondheim, 2002.
E.A. Kochnev, A.B. Zolotukhin, LT. Mishchenko, D. Michel evichius, V.L. Petrakov, ОТ. Gudmestad: "Uncertainty and Associated Risk in the Development Planning of an Offshore Field". //Journal "Oil, Gas and Business", No. 1, 2004, pp.13-19.
"P. Liferov and K. V. Heyland: "In-situ ice ridge scour tests, Part I: Experimental set up and basic results", //paper submitted to: Cold Regions Science and Technology, 2004
P. Liferov, P.O. Moslet, R. Nilsen, K. Heyland and S. Loser. "In-situ ice ridge scour test", paper presented at the 17th hit. //Symposium on ice, IAHR. St. Petersburg- June 2004.
P.O. Moslet, P. Liferov, R. Nilsen, K.V. Heyland, M. Bjerkas, B. Bonnemaire, J. Dybdahl and S. Loser. "Sea - Ice Vertical Pile Interaction Experiment- Part I: Test Set-up and Ice Properties, paper presented at the 17th hit. //Symposium on ice, IAHR, St. Petersburg, June 2004.
P.O. Moslet and K.V. Hoyland: "Sea - Ice Vertical Pile Interaction Experiment. Part II: Test Results 2003". paper presented at the 17 1 Int. //Symposium on ice. IAHR. St. Petersburg, June 2004.
S. Shafrova, P. Liferov and K. Shkhinek. Modelling Ice Rubble with Pseudo-discrete continuum model", paper presented at the 17th hit. //Symposium on ice, IAHR. St. Petersburg, June 2004.
A.B. Zolotukhin, ОТ. Gudmestad, A.I. Ermakov, R.A. Jakobsen. I.T. Michtchenko. V.A. Vovk, S. Loset and K.N. Shkhinek: "Fundamentals of offshore petroleum engineering and development of Arctic marine facilities". //Printed by Oil and Gas Publishing House. Gubkin University, Moscow, ISBN 5-7246-0117-6. December 2000. 770 pp. (This is the Russian version, an English version was issued in 1999).

ARCTIC SHELF OIL AND GAS CONFERENCE 2004