Application of Multirate Tests to Scale Management: Part 1—Interpretation of Produced-Water Analyses

Abstract

Summary 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.

Application of Multirate Well Tests to Scale Management: Part 2—Interpretation of MRTs With Known Produced-Water Origin

“…Determine water allocation: On the basis of interpretation of the water analyses, determine the fraction of PW being derived from each pressure zone at each test rate. See accompanying paper (McCartney et al 2012).…”

“…The rate-dependent variations in water composition can be used to determine the fraction of the total PW flow derived from each pressure zone at each choke setting (McCartney et al 2012). From these results and the measured total PW rates at each setting, the water rates for each zone can be calculated.…”

“…Another parameter that is included in the regression model is the water allocation. Hence, the model is simultaneously optimized so that the fraction of total water flow produced from each zone is the same as that estimated from interpretation of the PW analyses (McCartney et al 2012).…”

“…Interpretation of the PW analyses from the MRT also allowed the compositions of the water being produced from the IDS and Oseberg zones to be estimated (McCartney et al 2012). Accounting for these results, the preceding information can be interpreted further:…”

“…Interpretation of the MRT water-sample analyses, in conjunction with PW and formation-water analyses from the field and simulated PW compositions obtained from a 1D reactive transport model of SW injection into the reservoir, has been performed and is discussed in detail in an accompanying paper (McCartney et al 2012). …”