*4.1.5 CO2-based fracturing fluid*

Consideration of the use of CO2 as a fracturing fluid was mooted due to problems encountered with water-based fracturing fluids in terms of permeability damage. Liquid CO2 is considered an alternative to water-based fracturing fluids because it causes minimal formation damage plus clean-up is easily achieved. Lower viscosity, miscibility of CO2 with hydrocarbons, ease of displacing methane from organic matter and the ease of recovery of CO2 enables it to

create extensive and complex fractures at lower breakdown pressures [63, 64]. However, high pumping rates needed to enhance proppant carrying capacity of CO2 makes CO2-based fracturing fluids relatively expensive. Additionally CO2 is not readily available at all sites. The future applications may change if CO2 can be sequestered.
