High viscosity friction reducers (HVFRs) have been recently gaining more attention and increasing in use, not only as friction-reducing agents but also as proppant carriers. Reusing of produced water has also been driven by both environmental and economic benefits. Currently, most of friction reducers on the market are anionic friction reducers, which are fully compatible with most of produced water with low to medium level of Total Dissolved Solids (TDS) but show significant decreasing at high TDS conditions in term of their friction reduction performance for most cases. On the contrary, cationic friction reducers are believed to have better TDS tolerant and performance under high TDS conditions. However, concerns are remained about performance of using anionic and cationic HVFRs with produced water to transport proppant. The ultimate objective of this experimental study is to comparably analyze the proppant transport capabilities of HVFRs in high TDS environments. The effects of TDS, temperature, wall retardation, and particle hindering on the performance of both anionic and cationic HVFRs are investigated.
During the last few years, the industry has been accelerating the adoption of HVFRs to replace traditional fracturing fluids, such as slickwater and guar, in hydraulic fracturing (Hu et al. 2018; Johnson et al. 2018). This is mainly due to several operational and economic advantages of HVFRs including significantly cutting operational cost with less process and equipment required, exhibiting a higher retained conductivity in the fractured formation, and yielding ideal production improvements in fields (Johnson et al. 2018; Ba Geri et al. 2019; Biheri and Imqam 2020, 2021). Besides these benefits listed above, the most critical consideration behind using HVFRs in place of traditional fracturing fluids is their proppant-carrying and transporting capability. For traditional fracturing fluids treatment, because the viscosity is too low to suspend the proppant for a sufficient time, the dominant proppant transporting mechanism occurs at a high injection rate. However, even with a significantly high pumping rate, only small and light proppant (40/70 sand, resin coated sand [RCS], and 40/80 lightweight ceramic [LWC] are the most popular) are pumped with slickwater in the early stages (Palisch et al. 2008). Then, larger and heavier proppant is typically pumped with linear or crosslinked gels, which can better carry and transport this proppant deep into the fractured formation.