Perpustakaan Digital ITB

This study presents a comprehensive rheological characterization of Carboxymethyl Hydroxypropyl Guar (CMHPG)-based fracturing fluid and its flow behavior in porous media, aimed at evaluating its suitability for hydraulic fracturing operations in low-quality reservoirs. Two fluid systems were investigated: CMHPG dissolved in deionized water and CMHPG dissolved in Field X brine. Rheological measurements were performed using a rheometer at temperatures of 25°C, 45°C, 60°C, and 70°C across polymer concentrations of 1000, 2000, and 3000 ppm, while pore-scale flow behavior was further evaluated using a microfluidics system (Micronit micromodel) at 45°C and 70°C. Results show that apparent viscosity increases with polymer concentration and decreases with rising temperature in both fluid systems, consistent with a transition from a non-entangled to an entangled polymer network and the thermally induced weakening of intermolecular interactions. The deionized water system consistently exhibited higher viscosity than the brine system, with differences of approximately 57–64% at 1000–2000 ppm, narrowing to 20–30% at 3000 ppm, attributed to charge screening of the anionic CMHPG chains by dissolved ions. Microfluidics testing revealed that viscosity reduction after flowing through the porous media was smaller in the brine system (approximately 6–23%) than in the deionized water system (approximately 11–24%), owing to the more compact polymer coil conformation in brine, which is less susceptible to shear-induced chain scission. Permeability measurements showed significant formation damage in both systems after soaking, with reductions of 48–81% in the deionized water system and 64–83% in the brine system, attributed primarily to mechanical entrapment of polymer aggregates at pore throats, and further intensified in the brine system by ionic bridging through divalent ions. These findings indicate that although the brine system exhibits more favorable (lower) viscosity loss during flow through porous media, it poses a greater risk of formation damage than the deionized water system, underscoring the need for careful concentration optimization and ion-control strategies in field applications.