Acoustic Emission Monitoring And Characteristic Analysis Of Supercritical CO₂ Phase Transition Cracking In Dense Rock

In recent years,supercritical carbon dioxide?SC-CO₂?fracturing has been widely concerned due to its wide application prospects in the development of tight rock reservoirs.Considering the unique physical properties of SC-CO₂,the existence of phase change induced fracture in SC-CO₂ fracturing is demonstrated and verified by experiments.In this paper,acoustic emission?AE?model of fracture propagation in SC-CO₂ fracturing was firstly established based on AE monitoring of dynamic fracture propagation.Then,AE parameter characteristics were extracted through dynamic and static fracturing test and SC-CO₂ fracturing phase change test which applied in SC-CO₂ fracturing simulation experiments to verify SC-CO₂ phase change.Through the analysis of AE characteristic parameters and AE source location,the phase transition of SC-CO₂ fracturing was explained in term of experiments.Results&Findings:?1?The analysis of RA value and B value are given to reflect the fracture initiation,opening and closing.?2?The energy transformation characteristics of SC-CO₂ phase transition are included in parameters such as amplitude,energy,ringing count and hit.?3?The analysis of the spatial distribution of acoustic emission source with energy as the characteristic parameter proves the microfracture caused by SC-CO₂ phase transition.