Laboratory investigation of enhancing the electrical conductivity of brine for water-flooding front tracking

Liu, Lei, M.S. in Engineering
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Prevention of early water breakthrough requires accurate tracking of fluid-front location in reservoirs. Various methods have been explored to provide time-space images of fluid movement. Among these methods, cross-well resistivity and in situ permanent monitoring are used to map the spatial distribution of electrical conductivity, which helps to monitor fluid location between wells during production at the reservoir scale. However, both approaches have limitations in their detectability and sensitivity of fluid fronts. To improve the accuracy and sensitivity of resistivity monitoring systems, a viable option is to increase the contrast in resistivity between in situ formation and injected fluids by enhancing the electrical conductivity of the injected fluid. This report presents laboratory experimental work carried out to explore options to enhance the electrical conductivity of the injected water-based fluid with respect to that of a sodium chloride (NaCl) solution. A series of case studies with nanofluids, conductive hydrogels, and highly conductive electrolytes, were conducted to quantify how temperature, additive types, and concentration affect the conductivity of NaCl solutions. An experimental system was built for conductivity measurements of fluids via the conductometric method. The electrical conductivity tests performed using conductometric and conductivity meter methods indicate that the conductivity of brine can be increased substantially by adding sodium hydroxide (NaOH) or ammonium chloride (NH₄Cl). Results confirm that the conductivity of NaCl-NaOH solutions can reach 10.6 S/m for 2 wt.% NaOH and 1 wt.% NaCl, as compared to 1.7 S/m for 1 wt.% NaCl solution without NaOH. Measurements performed with the conductometric method agree with those performed with the conductivity meter method when the concentration is less than 10 wt.%