ANALYSIS OF THE INFLUENCE OF TEMPERATURE AND PRESSURE ON THE FIRST INTERFACE OF LIQUID CARBON DIOXIDE FRACTURING WELLBORE

摘要

Liquid CO2 is injected into the wellbore, which could be affected by the change of temperature and pressure, influencing the quality of interface bonding. In order to study this phenomenon, we took the Sulige dense sandstone gas reservoir wellbore in Changqing Oilfield as an example to study the change of liquid CO2 temperature metastasis and injection pressure through indoor physics simulation experiments. The results showed that the strength of the first interface bonding was reduced by 44.79% and 43.41%, respectively. The numerical simulation showed that the loading and unloading of pressure in the casing could cause an irreversible plastic deformation of the cement ring, resulting in an irreversible deformation of the cement ring-casing or cement ring-layer interface, the disengaged interface and finally forming the microloop gap. The micro-ring gap change of casing and cement ring bond surface caused by the liquid CO2 temperature is greater than the micro-ring gap between the cement ring and formation. As the temperature difference decreases from the liquid CO2 injection, the micro-ring gap between the cement ring and the formation decreases, the changing trend of the micro-ring gap between the casing and cement ring bond surface is not obvious. Therefore, in the process of liquid CO2 fracturing, the reasonable improvement of casing and cement stone performance is necessary to ensure the integrity of wellbore.