Experimental investigation on flow field and induced strain response during SC-CO2 jet fracturing

Abstract

Even though some numerical simulations and experiments of high-pressure CO2 jetting have conducted, the concerns of the flowing field and induced strain response during SC-CO2 jet fracturing are still unclear. Thus, this study is aimed to investigate the SC-CO2 jetting flow field and strain response in the rock via directly High-Speed Photography (HSP) and strain analysis. The development of SC-CO2 jet in high ambient pressure and limited perforation was analyzed. And the effect of jet pressure, ambient pressure and jet distance on the flow field and strain variation on organic glass was comprehensively studied. According to the results of the flow field of, it is found that the length of the jet core grows with the jet velocity gradually increasing in the time of (0.5–8)x104μs level when SC-CO2 jet starts to penetrate into the perforation and the wall-attached jet appears in the ambient vessel. when the jet pressure varied from 15 MPa to 55 Ma, the penetration depth sharply grows and the maximum strain increases approximately 9.4 times. When the ambient pressure is 8.5 MPa, the optimal jet distance is 6 mm because of the largest penetration depth and maximum strain value. Reducing the ambient pressure to 5.5 MPa, the optimal jet distance rise up to 10 mm. It is concluded that there is optimal jet distance under low ambient pressure, and reducing jet distance is better for the jet fracturing under high ambient pressure. Finally, the relationship between the flow field and strain variation is investigated and discussed by combining the HSP images and strain curves. The above research would be helpful for understanding the flow characteristic and its influence on strain variation around perforation under the ambient environment, which is meaningful for improve the operation procedure of CO2 fracturing.