Study on Rheological Properties of Fiber Fracturing Fluid and Mixing Morphology of Fiber-Proppant

To optimize the sand-carrying capacity and construction effect of fracturing fluid in channel fracturing technology, this paper systematically studies the influence of fibers on the rheological properties of hydroxypropyl guar gum (HPG) fracturing fluid base fluid and gel, as well as the mixing morphology characteristics of fibers and proppants. Through rheological tests, crosslinking-breaking experiments, viscoelasticity analysis, visual experiments on proppant cluster settlement, and scanning electron microscopy (SEM) observations, the mechanism of action of factors such as fiber concentration, length, thickener concentration, and temperature is revealed. The results show that: Fibers can significantly improve the apparent viscosity of the base fluid; 0.2% fiber increases the base fluid viscosity by two orders of magnitude at low shear rates. The power-law model (R2 > 0.9) can accurately describe its rheological properties, and the increase in thickener concentration will weaken the viscosity-increasing effect of fibers, while temperature (20–70 °C) does not change this law. Fibers have no significant effect on the crosslinking (the viscosity initiation time is 20–22 s, and the complete crosslinking time is 60–65 s) and gel breaking (the gel breaks to 3–4 mPa·s within 4 h at 90 °C) of the gel, and have little effect on the apparent viscosity of the gel (viscosity ratio of 0.7–1.2). However, they can significantly increase the elastic modulus of the gel (0.4% fiber increases the elastic modulus by 97% at 1 Hz), and the longer the fiber length and the higher the concentration, the more significant the viscoelasticity enhancement effect. Fibers can effectively inhibit the dispersion of proppant clusters, and the stability is optimal when fibers are only added to the proppant clusters. Moreover, fiber concentration (0.0%–0.3%) and length (3–9 mm) are negatively correlated with the settlement velocity of proppant clusters. Fibers with a length of 9 mm and a concentration of 0.3% can reduce the settlement velocity from 0.100 cm/min to 0.040 cm/min. This study provides a theoretical basis and experimental support for the formula optimization and field application of fiber fracturing fluid for channel fracturing, and is complementary to existing low-viscosity fiber fracturing fluid technology and efficient proppant placement technology.