Case study: Snorre B

At StatoilHydro"s Snorre B platform, an Argus in-line online Oil in Water monitor has been in operation since early 2006, contributing to a 40% reduction in oil in water concentrations in 2007.

The oil producing Snorre B platform, located in the Tampen area of the Norwegian North Sea, had an average water production of 26.600 m3 per day in 2006. In February 2006, following offshore testing of different oil in water monitors, an Argus Environment in-line online oil in water monitor from ProAnalysis was installed at outlet to sea downstream the degassing drum (process temperature 65°C and pressure 1 bar g).

Process management

Snorre B has actively used the Argus for monitoring and management of the produced water treatment process. Typical situations where the operator has benefited from use of the online oil in water monitor include:

• Identification of the most effective and optimum dosage of production chemicals (flocculants) in the water treatment process, dealing with sudden increase in oil in water concentrations.
• Optimising the use (dosage) of production chemicals (emulsion breaker) in order to improve separation (water and oil quality) and to minimise deterioration of water quality (environmental impact) while new oil-rich production wells are put on stream.

Accumulated data and experience since start-up clearly document the online oil in water monitor as an efficient tool in produced water management at Snorre B. The daily use of Argus has contributed to a 40% reduction in oil in water concentrations (6.3 vs. 10.5 mg/l) over the last 12 months (December 2007).

Discharge monitoring

As for most other production facilities, discharging produced water to sea, manual sampling and laboratory analysis have been resource-demanding activities at Snorre B. Manual samples are collected 4 times every 24 hours, mixed and analysed by a laboratory technician in the platform laboratory. The result of this process is one single (averaged) oil in water concentration value per day.

Following the introduction of Argus at Snorre B, a programme has been initiated to qualify the oil in water monitor for reporting of oil in water concentrations to the Norwegian Pollution Control Authority, replacing manual sampling for this purpose. The need for manual sampling with laboratory analysis will be reduced to the minimum accepted level of 5 times per month, resulting in significant cost reductions.