Efficient Produced Water Management at Norwegian Platform through online Oil in Water monitoring

Nov 18 2009

At StatoilHydro’s Snorre B platform in the North Sea, an Argus^® in-line Oil in Water (OiW) monitor from the Norwegian company ProAnalysis AS (Norway) has been in operation since early 2006, contributing to a 40% reduction in OiW 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. Water is processed through hydrocyclones downstream the inlet and test separators, followed by a degassing drum. In February 2006, following offshore testing of different OiW monitors, an Argus Environment OiW monitor was installed at outlet to sea downstream the degassing drum, at temperature 65°C and pressure 1 bar g. Snorre B has actively used the Argus instrument for monitoring and management of the produced water treatment process. The following cases describe typical situations where the operator has taken advantage of the online OiW monitor. A sudden significant increase in produced water oil concentration was observed with the Argus OiW monitor. Spot samples were taken to confirm, showing 24-27 mg/l OiW at a sample point where the concentrations were close to 5 mg/l some days earlier. Different solutions were tested without any effect, as verified by Argus as well as spot samples. Eventually, the injection of flocculants showed results and the most effective concentration was found to be 4 ppm. The Argus OiW monitor was actively used during testing to verify effects on the process. Due to one new oil-rich production well recently on stream, increased water in oil concentrations were observed. Emulsion breaker was used, but experience showed that overdosing (>1 ppm) could give pronounced separation problems. Hence, emphasis was put on identifying the optimal concentration of the emulsion breaker – both to improve separation (water and oil quality) and to minimize deterioration of water quality (environmental impact). The challenge was met by active use of the Argus OiW monitor, and optimisation of the separation system was completed within a few days resulting in excellent water quality. Accumulated data and experience from 20 months of operation clearly document the online OiW monitor as an efficient tool in produced water management at Snorre B, as exemplified by these cases. At Snorre B, the daily use of Argus has contributed to a 40% reduction in oil in water concentrations over the last 12 months (6.3 vs. 10.5 mg/l).