Rheological Characteristics and Engineering Predictive Modeling of Liquid CO₂/Guar Foam Fracturing Fluids

Abstract

Although CO₂ foam fracturing fluids are partially heated by the formation during injection, the majority of the CO₂ phase remains in a liquid state along the wellbore. Therefore, investigating the rheological behavior of liquid CO₂ foam fracturing fluids is essential for accurate friction prediction and hydraulic parameter optimization. In this study, a high-precision rotational rheometer was employed to characterize the rheological properties of liquid CO₂/guar-based foam fracturing fluids under controlled temperature and pressure conditions. Compared with conventional large-scale pipe rheometers, the present method provides improved measurement accuracy, repeatability, lower experimental cost, and better variable control. Experimental results indicate that under high shear rate conditions (>30 s⁻¹), the power-law model adequately describes the flow behavior of the liquid CO₂/guar foam system, with a coefficient of determination (R²) greater than 0.996. The effects of CO₂ volume fraction, temperature, and pressure on the flow behavior index (n) and consistency coefficient (K) were systematically analyzed. An exponential temperature-dependent correlation model for rheological parameters was established, yielding an average prediction error of only 0.658%. The obtained constitutive relationship provides a reliable theoretical basis for generalized Reynolds number calculation and wellbore friction prediction, offering significant engineering guidance for CO₂ foam fracturing design.