Objective: In this study, changes in capillary entry pressure of shale upon interaction with CO 2 under different temperatures have been investigated. The combined impact of temperature and petrophysical properties of shale (water content, water activity, permeability, and porosity) on capillary entry pressure was addressed.Methods: Pressure breakthrough measurements were used to evaluate the minimum entry pressure of CO 2 through shale. A heavy-duty oven was used to vary the temperature to investigate the impact of temperature on CO 2 capillary entry pressure through shale.
Results:The obtained findings revealed that the shale's capillary entry pressure upon interaction with CO 2 was highly affected by temperature. Higher temperatures decreased the capillary entry pressure of shale. We believe that pore dilation, where pore throat size expands due to the high temperature, may have caused this decrease in capillary entry pressure. However, in some cases, higher temperature activated clay swelling that may have caused an apparent decrease in pore throat radii of shale, which translated into higher capillary entry pressure. Furthermore, no distinct relationship between shale's petrophysical properties and measured capillary entry pressure was detected upon interaction with CO 2 at different temperatures.
Conclusion:Heat could alter pore throat radii and cause pore dilation, which could change capillary entry pressure. Interfacial tension decreases with increasing temperature, which can be attributed to the weakening of intermolecular forces at the two immiscible fluids interface. The swelling of clay could be related to the temperature-induced transition from passive to active clay.