Experimental Study On Optimization Of Supercritical Co2 Viscosity In Unconventional Shale Reservoir Fracturing

Unconventional shale reservoirs have the characteristics of low permeability, low porosity and high clay content. The elastic production process has a low production capacity. Conventional hydraulic fracturing could cause severe water absorption and clay expansion, resulting in poor fracturing efficiency. Supercritical CO2 fracturing fluid can effectively avoid the phenomenon of clay swelling and water absorption, and the fracture distribution after fracturing is complex. In this paper, six sets of supercritical CO2 fracturing shale experimental studies were conducted. The low sand-carrying capacity caused by the low density of supercritical CO2 were improved. The rupture pressure and initiation time of supercritical CO2 fracturing fluid with different viscosity were recorded, and the final fracturing effect was evaluated by the synergistic coefficient. The experimental results show that increasing the viscosity of supercritical CO2 fracturing fluid will increase the rupture pressure and reduce the initiation pressure time. The fracture shape is maintained well after fracturing. The optimal efficiency coefficient is 233. The research in this paper shows that increasing the viscosity of supercritical CO2 fracturing fluid can effectively reduce the initiation pressure time, and can obtain a better fracturing development effect in unconventional shale reservoirs.