Abstract
<jats:p>Foam-based fracturing fluids have emerged as a viable alternative to conventional water-based systems for hydraulic fracturing in high-pressure, high-temperature (HPHT) reservoirs, where fluid efficiency, formation protection, and environmental considerations are critical. The performance of these fluids is governed by a strong coupling between foam stability, rheological behavior, and proppant transport capacity under elevated temperature and pressure conditions. This chapter presents a comprehensive analysis of foam-based fracturing fluids for HPHT applications, integrating experimental observations and modeling insights to link laboratory-scale characterization with fracture-scale performance. Key aspects examined include foam quality, surfactant chemistry, nanoparticle stabilization, salinity effects, and their combined influence on apparent viscosity, shear-thinning behavior, viscoelastic response, and drainage characteristics. Results from high-temperature rheometry, stability testing, and proppant transport studies demonstrate that enhanced foam stability leads to improved rheological resilience and more effective proppant suspension under HPHT conditions. Simulation studies further illustrate how these rheological properties translate into fracture propagation and proppant placement outcomes. The findings provide practical guidance for the design and selection of foam-based fracturing fluids in deep and thermally challenging reservoirs, supporting safer, more efficient, and lower water-intensity stimulation strategies.</jats:p>