Erosion Behavior of Sandstone Treated by CO2 Soaking under Pulsed Abrasive Supercritical CO2 Jet Impact

The technique of refracturing horizontal wells with carbon dioxide (CO₂) is viewed as a propitious alternative in advancing the extraction of unconventional oil and gas reserves and older well reserves. When the reservoir rock is refractured by CO₂, the physical properties of the reservoir rock have changed greatly. Therefore, when the pulsed abrasive supercritical CO₂ jet is used to perforate the rock again, the erosion behavior of the jet will also be influenced by these changes in the rock properties. In order to better match the perforation process parameters, sandstone was used as the target material in an experimental study on the erosion behavior of sandstone treated by CO₂ soaking under PASJ impact. The pit’s erosion area and macroscopic erosion depth were both thoroughly discussed. By optical profilometry and scanning electron microscopy (SEM), the micromorphology of the erosion pits’ surfaces was meticulously investigated. The failure mode and damage mechanism of the sandstone impacted by PASJ were disclosed. It was discovered that the erosive capacity of PASJ for soaked rock samples was greater than that of the untreated rock samples under the same nozzle pressure differential. With the increase in soaking pressure and soaking temperature, the resistance of sandstone to abrasive jet erosion diminishes and the size of the erosion pit enlarges. As the nozzle pressure rises, the erosion pit becomes larger and loses its distinct cone shape, which is mainly attributed to an increase in the kinetic energy of the jet impact. The optical profile instrument and SEM inspections indicate that the complexity of the micropore structure and porosity increase on the surface of the soaked sandstone. The mineral solutes inside the sandstone soaked by carbon dioxide are extracted, and the coarse aggregate is exposed, which offers convenience for subsequent direct crushing by the abrasive particles.