SiO₂ synergistic modification of siloxane thickener to improve the viscosity of supercritical CO₂ fracturing fluid

ABSTRACT

Supercritical carbon dioxide (SC-CO₂) fracturing technology has the advantages of CO₂ storage and waterless fracturing and has great application potential in the development of unconventional oil and gas resources. However, the low viscosity of SC-CO₂ limits the development of this technology. This paper investigates the synergistic effect of nanomaterials on a developed thickener (HBD-2, high branched D4H). The research results show that among the five micro/nanomaterials Cu-BTC, SiO₂, MCC, MWCNTs, and TiO₂, only SiO₂ has a good synergistic effect on the HBD-2/SC-CO₂ system, and significantly improves its thickening, temperature resistance, temperature resistance and shear resistance. At 60s⁻¹, 305.15 K and 10 MPa, 5 wt.% HBD-2 + 1 wt.% SiO₂ increased the apparent viscosity of SC-CO₂ to 5.82 mPa·s(The viscosity of 5 wt.% HBD-2 under the same conditions is 4.48 mPa·s). The apparent viscosity of SC-CO₂ is positively correlated with pressure and SiO₂ dosage and negatively correlated with temperature and shear rate. The SiO₂/HBD-2 system can effectively avoid clay swelling and can change the water wetness on the core surface to neutral wettability. In addition, we also studied the mechanism of SiO₂ in HBD-2/SC-CO₂ thickening system by RDF(radial distribution function). The results show that the introduction to SiO₂ shifts the peak position of the system to the left and enhances the peak intensity. The macroscopic manifestation is the enhancement of the apparent viscosity of HBD-2/SC-CO₂.This paper proves the feasibility of nanomaterials to synergize SC-CO₂, and provides a new thread for the research and development of SC-CO₂ thickeners in the future.

KEYWORDS:

• Nanomaterials
• supercritical carbon dioxide
• thickening
• rheology
• synergy

Acknowledgments

The authors acknowledgment the support of the National Natural Science Foundation of China (U1762212).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [U1762212].