Comparing the performance of supercritical CO_2 fracking with high energy gas fracking in unconventional shale

Fracturing plays, a vital role to achieve the optimal recovery from the unconventional shale gas reservoirs and fracturing fluid is considered as “blood” in the entire operation. There are various fracking technology to frack the shale viz., traditional hydraulic fracturing, nitrogen based fracturing, high-energy gas fracturing (HEGF), supercritical carbon di oxide fracturing (SC-CO_2), plasma fracturing, etc. However, SC-CO_2 fracking requires less water and is able to generate three-dimensional fractures with its low viscosity. It is also considered as a good option for using as a fracking fluid in unconventional shale or tight gas reservoirs because of its properties of liquid like density, low viscosity, without any capillary force, good miscible characteristics with hydrocarbons. The low viscosity of SC-CO_2 can create complex, multi-orthogonal fracture networks in unconventional shale reservoir resulting into high flow rates. Similarly, HEGF is also characterised by less water consumption, it uses propellant to burn the formation around wellbore area and make tailored pressure–time behaviour. This burning is fully controllable from surface and is able to produce multiple fractures in all radial directions at short distance. The present review paper discusses the recent scientific studies on supercritical CO_2 fracking and high energy gas fracking in unconventional shale and examine its experimental results, field results, its advantages and disadvantages. Graphical abstract As the world is moving towards low carbon emission sources and low water consumption techniques in meeting today’s energy requirement, there is an urgent need to increase natural gas production especially from unconventional gas reservoirs. Due to scarcity in water resources, the fracking techniques with low water usage are in demand like Supercritical CO_2 and high energy gas fracking (HEGF) techniques.