Offshore water injection

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Courtesy of atg UV Technology

Client: PPCoN  
Location: North Sea
Description: UV disinfection of seawater for offshore reservoir injection

The process of disinfecting water with UV light is a proven technology for drinking and process water in many industries. It has now been applied with great success to the disinfection of seawater for use well injection water. atg UV Technology understanding of UV disinfection combined with the knowledge and experience to apply the technology and the development of monitoring systems has created many successful and reliable systems.

Pilot Evaluation to Full Scale Plant - West Omikron Project.

During the evaluation of the West Omikron Project, Phillips' (PPCoN) engineers approached atg and our agents Tech Trade to discuss the possibility of utilising Ultraviolet as an alternative to biocides on the water injection. During discussions, Phillips realised that comparison between UV plants of varying geometry's was difficult, as the comparable dose rates might have widely different effects depending on both the calculation method employed and the geometry of the system. Accordingly, it was decided that equipment should be type tested under offshore operating conditions rather than relying on either laboratory work or manufacturer's stated doses.

atg and our agents Tech Trade A/S undertook a full-scale pilot trial on 2/4 Kilo platform. The objective of the exercise was:-

  • To verify the performance of a single lamp system on SRB's (Sulphate Reducing Bacteria).
  • To establish the energy levels required to achieve the desired kill at the end of lamp life.
  • To establish the effectiveness of the system in varied conditions.

In order to verify our equipment, under the full range of water quality parameters experienced by a typical offshore plant during the worst spring operating conditions, our UV disinfection unit was installed downstream of the final filter offshore and operated during the SRB blooming period.

The pilot plant unit was identical in configuration to any systems that were subsequently offered to PPCoN for use in water injection and accurately measuring the side-stream flow meant that the unit could be precisely rated to the actual flow. This would allow PPCoN to rate the unit for the flow that achieved the total disinfection that they required.

As a result, and in consultation with Phillips' process engineers, the pilot plant was rated at 32,000 bwpd (barrels of water per day) for 2 micron-filtered seawater.

As a consequence of the pilot plant trial, atg and Tech Trade were commissioned to provide a full-scale UV plant for operation on West Omikron. The plant was rated for a peak design flow rate of 320,000 bwpd.

The final package proposed utilised 12-off type tested model TL-132 arranged in pairs to achieve the optimal flow conditions for both the UV process and for the material selection, considering the possible corrosion effects of the seawater.

The system was fully automatic, PLC controlled with standby facility and a cleaning system.

The full system has now been in operation for many years and has proved highly reliable, despite operating continuously on or above its peak flow. The system was fully tested to 25 bar ensuring the highest integrity system under all conditions. atg and Tech Trade have spent many years proving and developing the system for the exacting process, engineering and design requirements of the offshore industry. The close monitoring of the West Omikron plant has been utilised to improve our system still further to increase reliability, reduce maintenance and provide the most effective and safe system possible.

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