RESEARCH ON CO₂ MICROBUBBLE DISSOLUTION KINETICS AND ENHANCED OIL RECOVERY MECHANISMS

CO₂ microbubble is a promising enhanced oil recovery and carbon sequestration method. In this paper, based on microbubbles porous media generation method, a self-designed microbubble generator featuring the porous ceramic membrane was developed. The morphology and dissolution characteristics of CO₂ microbubbles at different initial CO₂ concentrations were experimentally investigated. The results showed that the CO₂ microbubbles prepared at 10 MPa were distributed in the range of 10 ~ 70 μm with an average bubble diameter of 34.43 μm. At 15 MPa, CO₂ microbubbles with smaller diameter were generated, with an average bubble radius of 25.03 μm. However, under high salinity condition, microbubbles with average diameter of 277.17 μm were produced. The brine salinity decreased microbubbles stability, which leading to bigger bubble. In a word, the microbubbles diameter was highly affected by the pressure in microbubbles porous medium generation method. Then, the static and dynamic dissolution kinetics of microbubbles in the porous media were investigated by microfluidics. The results of dissolution experiments showed that microbubbles had excellent dissolution efficiency. When contacting with formation water, microbubbles would rapidly dissolve and the undissolved microbubbles were still migrating the porous media in the form of bubbles. CO₂ microbubbles could form a migration mode with carbonated water in the front and microbubbles in the rear, after microbubble were injected into the reservoir. For the first time, the enhanced oil recovery mechanisms of CO₂ microbubbles were studied under high-temperature high-pressure conditions, which mainly include: ①Microbubbles carry residual oil on the pore wall during migration; ②Microbubbles carry residual oil droplets out of the pores with dead ends through dissolution and oil swelling; ③Break the capillary force balance of residual oil droplets and promote the flow of oil droplets; ④Block the high permeability channel to improve the sweep efficiency. This paper provides valuable guidance for CO₂ microbubble to enhanced oil recovery and carbon sequestration.