层内生成CO2缓释体系优选与性能评价

OPTIMIZATION AND PERFORMANCE EVALUATION OF IN-SITU CO 2 GENERATION SUSTAINED-RELEASE SYSTEM

针对常规层内生成CO2体系反应速度快、作用半径小的问题,优选出以NH 4Cl和乙酸复配为释气剂、碳酸钠为生气剂的缓释体系,并对缓释体系的耐温抗盐性能、封堵能力和调驱效果进行了评价。实验结果表明,该缓释体系反应时间长、生气效率高、耐温抗盐、安全可靠,有效克服了现有技术的缺点。NH4Cl与乙酸的质量比为4∶1时体系缓释效果最好,反应时间可延长至50 min,最终生气效率高达91.5%;体系反应时间会随着温度增加逐渐缩短,适用温度范围为低于100℃;体系生气效率随着矿化度增加略有下降,矿化度为20000 ppm时,生气效率仍能维持85%。缓释体系的封堵效果和调驱效果明显优于常规体系,相同条件下,缓释体系封堵率较常规体系高20.83%~23.08%;与常规体系相比,缓释体系对低渗岩心的采收率能够提升4.48%,总体采收率也能进一步提升2.25%。

Aiming at problems of rapid reaction speed and small action radius of conventional in-situ CO 2 generation,the sustained-release system with NH4Cl and acetic acid as gas release agent and Na2CO3 as gas release agent was optimized.Experimental results showed that this sustained-release system had the advantages of long reaction time,high gas generation efficiency,temperature and salt resistance,safety and reliability,and effectively overcame the shortcomings of existing technologies.The system has the best sustained release effect when the mass ratio of NH4Cl to acetic acid was 4:1,the reaction time can be extended to 50min and the final gas generation efficiency was as high as 91.5%.The reaction time of the system gradually decreased with the increase of temperature,and the applicable temperature range was lower than 100°C.Gas generation efficiency of the system decreased slightly with the increase of salinity.When salinity was 20000ppm,gas generation efficiency can still maintain 85%.Under the same conditions,the plugging rate of the sustained release system was 20.83~23.08%higher than that of the conventional system.Compared with the conventional system,the recovery rate of low-permeability core can be improved by 4.48%with the slow release system,and the overall recovery rate can be further improved by 2.25%.