CO2驱开发后期防气窜综合治理方法研究

室内实验得到的CO2混相驱油效率往往可达90％以上,但现场却难以达到室内实验的驱油效果.限制采收率提高的主要原因是CO2的黏性指进、重力超覆和油层的非均质性等因素对注入CO2波及效率的影响.针对注CO2驱开发后期油藏气窜现象逐渐加重、开发矛盾不断加剧等问题,从开发层系、注采结构、注入方式以及注入剖面4个方面开展了改善CO2驱开发效果的研究,并提出了细分层系、高部位注气、水气交替注入、聚合物调剖及CO2＋泡沫驱防气窜等技术对策.现场实施结果显示,油藏整体气油比从2 733.1 m3/m3下降到63.84 m3/m3,日产油从注气前的30.72 t上升到注气后的81.68 t.该项防气窜综合治理技术及经验可为类似油藏注气驱开发方案设计和后期防气窜提供借鉴.

Comprehensive treatment of gas channeling at the later stage of CO2 flooding

It is difficult for the field to achieve the CO2 miscible flooding efficiency of indoor experiments which could reach more than 90%. Recovery factor is limited mainly by several aspects, namely, CO2 viscous fingering, gravity overlap and reservoir heterogeneity, which exert negative influence on CO2 sweep efficiency. On the other hand, gas channeling aggravates gradually and development conflicts intensify continuously at the later stage of production. This paper analyzed development effect of CO2 flooding, regarding layer series of development, injection-production structure, way of injection and injection profile, moreover, proposed technologies of strata subdivision, injection in the top, water alternating gas （WAG）, polymer profile control and CO2 ＋ foam flooding. Good response has been observed after the onsite implementation. Reservoir overall gas-oil ratio decreased from 2 733.1 m3/m3 to 63.84 m3/m3, and daily oil production increased from 30.72 t （before gas injection） to 81.68 t （after gas injection）. Generally, this anti-gas channeling comprehensive technology is of great significance for similar reservoir scenario design and gas channeling prevention.