Several multirate separator tests (MRTs) have been undertaken on wells in the Veslefrikk field that are on commingled production from the Brent Group and Intra Dunlin Sand. During these tests, produced-water samples were also collected. Integrated analysis of the results of interpretion of the produced-water analyses and the MRT results have provided a range of information for each production zone including the nature and composition of the produced water, seawater fraction of these produced waters, fraction of total water flow being produced, pressure, productivity index, oil and water rates, and water cut. This information can reduce the need for deploying production-logging tools (PLTs), allows the scaling potential between the deeper and the shallower zones to be evaluated, aids squeeze-treatment design, is beneficial for predicting formation damage from crossflow, and aids water-shutoff decisions.

In this paper, the methods of interpreting the produced-water analyses are presented through the use of a field example. To aid interpretation, interpretation of other produced-water analyses from the field and reactive-transport modeling have been undertaken to better understand reactions occurring in the reservoir as a result of seawater injection and the effects of these reactions on produced-water compositions. In an accompanying paper (Tjomsland et al. 2011), the integrated MRT-analysis techniques are described and the results and applications of additional field examples are presented.

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