Chemicals-CO2 mechanisms of inhibiting steam heat transfer and enhancing oil film strip: Steam flow through the wall-adhering oil film surface in porous medium

The CO2 and Sodium Dodecyl Sulfate (SDS) assisted steam flooding technology was an effective approach addressed the persistent issues that have hindered the stable development of high-viscosity cold oil through steam injection. However, in the process of steam flow through porous media, the synergistic influence of the oil film adsorbed in near wellbore porous media, and the CO2-SDS on steam heat transfer has not been investigated. Steam heat transfer is the key factors affecting heavy oil recovery. The primary objective of this study was to research the effect of CO2-SDS on steam heat transfer and oil film stripping by designing experiments. The study results demonstrated that in the initial stage of displacement, the heat transfer resistance between the steam and the porous medium was increased by the oil film adsorbed in near wellbore area. In additional, the condensation mode of the steam was altered from bead condensing to film condensing by the composite thermal fluid flooding, preventing the steam heat dissipation near wellbore area and transferring more thermal to the long-distance area. At the later stage of displacement, the interfacial tension between oil-water and oil-gas was reduced by CO2-SDS, improving the fluidity of oil and providing the seepage channel for steam, and increasing the steam thermal sweep range. Compared to the sandpack experiment of steam flooding, the temperature at the output end of the sandpack model increased from 69.8 degrees C to 88.7 degrees C, indicating an expansion of the steam heat sweep range and successful long-distance heat transfer during composite thermal fluid flooding. In the process of composite thermal fluid flooding, the maximum displacement pressure difference increased from 2.28 MPa to 3.07 MPa, and the maximum oil recovery rate increased from 2.48 g/mL to 2.81 g/mL. The peak of the high production period was raised, resulting in a 40.97% to 51.86% increase in recovery rates.