Theoretical Calculation of High-Pressure CO2 Jet under Composite Rock-Breaking Based on Span-Wagner Equation of State

Although some theoretical calculation methods for high-pressure jet have been proposed, there is currently no theoretical model for high-pressure CO2 jet based on high-precision equation of state (EOS). Aim to investigate the flow field of high-pressure CO2 jet under composite rock-breaking of high-pressure CO2 Jet & PDC cutter, a semi-analytical approach of high-pressure CO2 jet was established based on the Span-Wagner EOS and CO2 jet theory. Semi-analytical calculations and physical properties calculations with the high-pressure CO2 jet were conducted considering the factors of jet pressure, jet distance, nozzle diameter and jet angle. The results indicate that the physical properties distribution calculated by the semi-analytical approaches is similar to that of experimental monitoring and numerical simulation, which indicates that the calculation method of high-pressure CO2 jet presented in the study is effective and reliable. The properties of CO2 jet calculated by theoretical calculation shows obvious difference between the initial region and the jet impact region. At the temperature of 300K, the increase in initial pressure can effectively increase the impact force and the cooling ability of the jet. The proportion of the jet core lengths in the jet on the axis rise with increasing ratio of nozzle diameter to jet length, leading to enhancement of the impact force of the jet. The increasing of the jet angle can efficiently rise the impacting force of the jet, but habit the fluid diffusion. The study combines the theoretical calculation of jet with the physical properties’ calculation of high-pressure CO2 firstly, comprehensively understanding the CO2 jet field in the composite rock-breaking of high-pressure CO2 jet & PDC cutter. This theoretical calculation of CO2 jet based on the high-precision EOS maybe a great option for the convenient calculation of CO2 drilling in practical engineering.