CO_(2)微气泡溶解动力学及提高采收率机理研究

RESEARCH ON CO_(2) MICROBUBBLE DISSOLUTION KINETICS AND ENHANCED OIL RECOVERY MECHANISMS

CO_(2)微气泡是一种具有潜力的提高采收率与碳埋存方法,本文在自主设计的CO_(2)微气泡发泡装置的基础上,表征了高温高压条件下微气泡形态,进一步研究了微气泡的溶解特征,研究结果表明:10 MPa下制备出的微气泡直径10~70μm,平均直径34.43μm;15 MPa下制备的微气泡直径更小,平均直径25.03μm;地层水高矿化度条件下,平均气泡直径277.17μm,且气泡稳定性降低.微气泡的溶解实验结果表明CO_(2)微气泡的溶解速率较高,但是未溶解的CO_(2)仍以气泡的形式在地层中运移,微气泡注入地层后将形成“碳化水+微气泡”的运移模式.采用可视化微流控平台,首次研究了高温高压条件下无化学剂辅助CO_(2)微气泡的提高采收率机理:(1)提高微观洗油效率;(2)通过体积膨胀、溶解携带作用将油滴带出盲端,采出盲端中的剩余油;(3)打破油滴的毛管压力平衡状态,采出柱状残余油;(4)在流动中产生“贾敏效应”,封堵大孔隙、提高波及效率.本文研究可为CO_(2)微气泡提高油藏采收率与碳封存提供指导.

CO_(2) 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 CO_(2) microbubbles at different initial CO_(2) concentrations were experimentally investigated.The results showed that the CO_(2) microbubbles prepared at 10 MPa were distributed in the range of 10~70μm with an average bubble diameter of 34.43μm.At 15 MPa,CO_(2) microbubbles with smaller diameter were generated,with an average bubble radius of 25.03μm.However,under high salinity condition,microbubbles with average diameter of 277.17μm 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.CO_(2) 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 CO_(2) microbubbles were studied under hightemperature 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 CO_(2)microbubble to enhanced oil recovery and carbon sequestration.