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Light well intervention provides the potential for increased safety and recovery

The use of light well intervention in subsea wells on the Norwegian shelf may provide substantial safety gains and contribute to reduced operating costs, extended lifetime and increased recovery totaling tens of billions of kroner. The Petroleum Safety Authority Norway (PSA) encourages the industry to further develop technology that leads to increased use of light well intervention.

Illustration: Courtesy of FMC EnergySystems
Statoil has qualified a new and pioneering
technology for light well intervention in subsea
wells. (Illustration: FMC Energy Systems)

Light well intervention entails that a number of operations on subsea wells can be conducted without a riser to the surface.

The technology is based on cable-based well maintenance, where the cable is routed via a subsea lock system into the subsea well.

Typical activities are the use of "electrical" or "smooth" cable operations for logging, setting plugs, perforating, pulling equipment and minor repairs.

The use of light well intervention may provide substantial safety gains, inter alia because one avoids hydrocarbons (gas, condensate and/or oil) being transported/ conduited to the installation on the sea surface. At the same time, well interventions are challenging operations in terms of safety, and require special expertise and control in all phases of the preparations and implementation.

Substantial potential for increased value creation
This year the approximately 400 subsea wells on the Norwegian shelf will account for nearly half of the oil and gas produced. Statoil operates about 60 percent of these wells, while Norsk Hydro's share is about 25 percent.

The recovery rate from platform wells is generally higher than for subsea wells. Even though there are differing opinions on how high the recovery rate will be through increased use of light well intervention in subsea wells, tests, experience from other countries' shelves and the industry's own forecasts show that the potential is substantial.

Storting (Norwegian Parliament) White Paper No. 39 (1999-2000) - Oil and gas activities - also emphasized that having such tools available is important with regard to resource management, and may be crucial to whether we manage to exploit the recovery potential of subsea developments.

Faster, cheaper, better
The subsea wells contribute to a steadily increasing maintenance demand that has so far been carried out through well intervention from full size mobile drilling units. Due to the limited availability of purpose built light intervention ships, the more expensive approaches have been employed.

Light well intervention is included as one of the projects of the technology commitment Demo 2000, which was initiated in the fall of 2000 to increase profitability on the Norwegian shelf. It is assumed here that it will be possible to halve the costs associated with well interventions, because it is easier and cheaper to retrieve valuable well information and make simple interventions if necessary with the new technology.

Light well intervention enables the use of smaller ship solutions instead of chartering large mobile installations to carry out relatively simple operations in subsea wells. The technology also makes it possible to exploit the effect of consecutive well programs for longer periods of time. This is unique and provides substantial efficiency gains.

In the British sector there has already been extensive use of light well intervention, with good results.

Important technology for the Norwegian shelf
The Petroleum Safety Authority Norway takes a positive view of activities that improve the technology and the light well intervention services offered on the Norwegian shelf. In this connection we would emphasize the close and good cooperation with central operators/contractors/suppliers within the light well intervention segment.

Under the direction of Demo 2000, Statoil developed new technology in cooperation with Prosafe and FMC Kongsberg Subsea, and in the fall of 2003 a successful three-well campaign was conducted for qualification of the technology using the installation "Regalia".

Thorough technical qualification work was here followed up with good execution in terms of safety and operations. This demonstrated that subsea cable operations are feasible with the relevant technology, which seems to have contributed to increased demand from the oil companies in Norway.

Statoil has inter alia established a 150-day program for light well intervention on the Norwegian shelf with planned start-up in the summer of 2004. In order to implement this program the Petroleum Safety Authority Norway has received an application for consent for use of the well intervention installation Seawell, which is operated by the company WellOps (UK) Ltd.

This application is being processed by the authorities. The PSA's general view is that it is useful and important for the Norwegian shelf to gain further experience in light well intervention, and thus contribute to laying a foundation for more long-term solutions. The objective must be to obtain a better light well intervention services for subea wells.

In this connection the PSA has also implemented its own expertise project in light well intervention. The goal is to contribute to a better understanding of the technology and, if necessary, contribute to stipulating the conditions for new technology so that both the safety level and value creation from the petroleum activities on the Norwegian shelf increase.

Contacts in the PSA Norway: