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 produced water has also been driven by both environmental and economic benefits. Currently, most friction reducers on the market are anionic friction reducers, which are fully compatible with most produced water with low to medium level of total dissolved solids (TDS) but show a significant drop at high TDS conditions in terms of their friction reduction performance in most cases. On the contrary, cationic friction reducers are believed to have better TDS tolerance and friction reduction performance under high TDS conditions. However, concerns remain 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 anionic and cationic HVFRs in high TDS and reservoir temperature environments. An anionic HVFR and a cationic HVFR, both at 4 gallons per thousand gallons (GPT), were selected and analyzed. The rheology measurements of these anionic and cationic HVFRs were conducted in deionized (DI) water and high TDS water conditions. Static and dynamic proppant settling tests were conducted at various TDS conditions at reservoir temperature. Wall retardation and particle hindering on the performance of both anionic and cationic HVFRs were also observed and investigated using the particle image velocimetry (PIV) method. The results showed that the anionic HVFR had higher viscosity than the cationic HVFR due to larger molecular weight and had much higher elasticity. Increase in TDS concentration would decrease the viscous and elastic profiles of both anionic and cationic HVFRs. In particular, the elastic profile became negligible for both HVFRs. Besides, the “critical salinity” phenomenon was observed. Above this salinity, the viscosity of HVFRs was no longer affected by increasing TDS level. The “critical salinity” for both of the 4-GPT anionic and cationic HVFRs was in the range of 30 000 to 200 000 mg/L. Moreover, the cationic HVFR had lower “critical salinity” than the anionic HVFR. Finally, the correlation between rheology and proppant transport capabilities of HVFRs is discussed in this paper, and a simplified decision-making process of selecting fracturing fluids is proposed.

You can access this article if you purchase or spend a download.