(589e) Sensitivity Study of Fracture Propagation By Foamed Fluids and Slickwater in Unconventional Reservoirs

In-situ stresses and heterogeneity of the formation rock are the dominant factors that influence hydraulic fracturing process. The rheology of frac fluid also significantly affects hydraulic fracturing treatment regarding fracture propagation, proppant transport, formation property alteration, and flow back process. Recently, non-Newtonian CO₂ foams stabilized by nanoparticles has been studied as a promising frac fluid, which is advanced in less water contents, proppant placement, fast clean and maintaining conductive channels. It’s critical to study hydraulic fracturing in heterogeneous formation with a complicated fluid. The current effort investigates the fracture propagation and proppant transport using CO₂ foams. The objective of this study is to analyze sensitivity of fracture propagation by CO_2 foams and slickwater in unconventional reservoirs.

This study simulated hydraulic fracturing and proppant transport by viscous gas foams in a horizontal well perforated in Eagle Ford Shale formation of Zavala County, Texas. A 3D numerical model was setup with heterogeneous reservoir properties using a commercial fracturing simulator. To represent formation heterogeneity, the rock mechanical properties were derived from well logs including Gamma Ray, Resistivity, Neutron Porosity, and Density Porosity logs, characterized by Young’s modulus (3×106 ~ 6× 106 psi), Biot constant (0.6 ~ 0.8), and Poisson's ratio (0.2 ~ 0.4). The flow behavior of CO₂ foam stabilized by nanoparticles was characterized by Carreau rheological model based on the experimental data. Fluid leakoff during the fracturing process was investigated by pressure dependent leakoff method for different CO_2 foam qualities.

During the pumping schedule for multistage fracturing process, the effects of variable injection rate (20 ~ 40 BPM), CO₂ foam quality (50 ~ 80 %), incremental proppant distribution (0 ~ 5 PPA), and fluid leakoff were investigated. Current study acquired a laterally un-even shape of fracture propagation profile during multi-stage CO₂ fracturing which represents the reservoir heterogeneity with varying in-situ stress and poroelastic properties. The results showed that the rheology of fracture fluid significantly influences the fractures propagation. Along with foam quality increased from 50% to 80%, the fracture width increased from 0.29 inches to 0.35 inches and fracture half-length decreased from 780 ft to 660 ft. The fluid leakoff rates decreased from 13 to 9 ml/cm² at 10 √min along with the CO₂ foam quality increased from 50% to 80%. Fracture propagation using CO₂ foams with varied injection rates compared to slick water fracturing and results showed that CO₂fracturing develop less fracture length compare to slick water fracturing but superior fracture width and height growth than slick water ranging from 15% to 20%.

This study provides a revolutionary insight and improved fracture treatments design by non-Newtonian frac fluids - CO₂ foams application with increased fracture conductivity and efficiency compare to slickwater which is vital for fossil fuel exploitation from unconventional reservoirs with reduced environmental impacts.