Surfactant is a significant component within fracturing fluid additives used for enhancing oil and gas production following stimulation of unconventional reservoirs. To help ensure optimum applications of surfactants, operating and service companies have been searching for tools for tracking surfactant residuals in flowback and produced waters, which can be possibly correlated with well productivity. Conventional wisdom suggests using a dye-based approach (i.e., methylene blue (MB) typically combined with anionic surfactants). The concentration of the combined complex can then be determined using spectroscopic methods. This approach, however, can cause erroneous results because of the presence of anionic friction reducers, scale inhibitor, or gelled fluids. This paper discusses the residual surfactant concentration measured in produced water from example Barnett shale formation wells using a dynamic surface tension technique, which yields much more accurate measurements. A comparison of dynamic surface tension includes comparing the diffusion coefficient to the reaction kinetics of adsorption of a known molecule(s) in produced water. Short time kinetics of adsorption of different molecules vary based on chemical nature and molecular size. UV-Vis spectroscopy is used to confirm the results. An estimate of residual concentrations from UV-Vis appears to be coherent with dynamic surface tension measurement values.

Such measurements can be useful to determine the surfactant concentration during pumping and surfactant performance during and after hydraulic fracturing operations. Additionally, these measurements serve a vital role in tailoring the surfactant additive to specific reservoir conditions to achieve higher oil recovery. Real-time production results from these different wells are analyzed and appear dependent on the corresponding residual surfactant concentrations from produced waters. This unique technique is new to the authors’ knowledge and used to study and analyze produced water for surfactant additive concentration.

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