CO₂ Foamed Fracturing Fluids for High Temperature Hydraulic Fracturing

CO₂-foamed fracturing fluids injection can assist water conservation during hydraulic fracturing. Moreover, foamed fracturing fluids offer a desirable alternative over conventional fracturing fluids, particularly in stimulating water-sensitive formations, the need for shortened flowback time, and energizing created fracture geometry. The thermal stability of foam at high temperatures is one of the main challenges. In this paper, CO₂-foamed acrylamide-based terpolymer based fracturing fluid was developed for high temperature application. The foam viscosity development depends on the gas, foam quality, the viscosity of the external phase, foaming agent and foam stabilizers. Rheological properties of N₂ and CO₂ foams containing acrylamide-based terpolymer were measured at high temperatures i.e. 300 to 350°F and shear rate from 100 to 500 1/s. A circulating flow loop foam rheometer was used to measure the rheological behavior of foamed fluid prepared using linear gel. Foam stability improvement using nanoparticles was also demonstrated. The viscous character of the external phase of the foam plays a considerable role in the viscosity of foam. In this paper, water and linear gel prepared using 35 ppt acrylamide-based terpolymer has been studied at 75% foam quality and two different temperatures. A 75% quality foam viscosity having water as the external phase gave 70 cp with N₂and 31 cp with CO₂ at 100 1/s, whereas viscus linear gel gave 146 cp with N₂ and 64 cp with CO₂ at 100 1/s studied at 300°F. After increasing the test temperature to 350°F, there was a significant drop in viscosity noticed. The thermal stability of foam can be enhanced by the synergetic effect of surfactant and nanoparticles. The foam half-life was delayed from 5.5 min to 9.1 min after the addition of silica nanoparticles using water as base fluid. Viscous properties of the fracturing fluids influence the fracture geometry and capability of transporting proppant into the fracture. Based on available literature reports, the rheological properties of foamed fracturing fluids limit to 300°F. This paper reveals the rheological properties of CO₂-foamed fracturing fluids in a temperature range of 300 to 350°F and therefore helps to design fracturing treatment to stimulate reservoirs with high temperatures.