Hydraulic fracturing is the most common stimulation treatment in unconventional resources. One of the most important challenges in fracturing operations is the large volumes of water consumption and waste water disposal. Environmental and economical attributes of flowback fluids in the oil industry make water treatment an inevitable decision. Applications of produced water in hydraulic fracturing jobs result in low quality fracturing fluid. This is especially true for flowback fluids, which contain high polymer loading. Currently, no practical operating range for produced water content is available, and applied methods are individually developed for specific jobs.
This paper focuses on the analysis of the dissolved solid contents of produced water, which affects the application of flowback fluids and the capability of prepared fluids in proppant transport and handling. A series of laboratory experiments were conducted on a high-pH borate crosslinked guar-based polymer to determine the effects of salt species on the prepared polymer, ranges of acceptable salts contents, and ability to transport proppant. For this purpose, analyses of 36 flowback fluid samples from the West Texas region have been collected, and the maximum and minimum values of all of the contents have been determined to investigate the impact factor of each component. Dynamic rheology tests, traditional changing shear rates, the steady-shear viscosity, and small-amplitude oscillation rheology, were the methods used to evaluate prepared samples.
The prepared polymer shows high sensitivity to the change of some ions such as calcium and magnesium, and the maximum acceptable values were lower than 90% of reported ones in field analysis. Some others such as sodium and potassium were tolerable at higher concentrations, and more than 70% of samples do not need to be treated for these ion contents. On the other hand, there are other ions in different samples, which have ranges of concentrations that were very similar at low concentrations. Although no significant variation in fracturing fluid properties were detected when the different concentrations of them were applied in experiments, their presence can affect post-treatment jobs. The fluids prepared with the determined ranges of dissolved solids showed reasonable rheological stability and proppant handling characteristics.