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.
