吉林特低渗透油藏CO_2驱油开发效果探讨

TECHNICAL DISCUSSION ON DEVELOPMENT EFFECTS OF CO_2 FLOODING IN JILIN EXTRA-LOW PERMEABILITY RESERVOIR

特低渗透油藏的自身特征决定了其开发难度大于常规油藏,存在"注不进,采不出"等问题。注CO_2提高采收率技术应用于特低渗透油藏潜力巨大,如何改善其驱油效果是合理高效开发的关键。通过室内特低渗透长岩心物理模拟实验,采用12种方案进行CO_2驱油效果评价。研究表明,超前注气相对于同步注气可以提高采收率4. 69%,驱油效果优于同步注气,其CO_2气体突破早于同步注气。不同注气时机实验采收率与转CO_2驱油时产出液含水率呈负对数关系,总压力梯度变化呈M型,转注CO_2驱油后存在滞后效应,采用小流量可以达到增产目的。不同注气段塞实验采收率与总注入流体中CO_2所占体积比例呈正相关关系。不同气水比和CO_2驱油实验CO_2突破时间较为一致,水驱油和CO_2驱油实验总压力梯度变化较为一致。应用于特低渗透油藏开发,提出超前低速注气、气水交替和后期水驱策略,多种注采方案,进行分区试验。

The characteristics of extra-low permeability reservoirs determine its development more difficult than that of conventional reservoirs.There is “no injection allowed, no output” and other issues.CO 2 injection is a potential technology to enhance oil recovery fromextra-low permeability reservoirs, how to improve its flooding effects is the key to rational and efficient development.Physical simulation experiments were done indoor by long extra-low permeability cores, 12 plans used to evaluate the CO 2 flooding effects.Studies show that the advance gas injection can improve recovery more than the synchronous gas injection by 4.69 %, and the CO 2 gas breaks earlier in advance gas injection.In experiments with different gas injection timing, the relationship between ultimate recovery and water content of produced fluid is negative logarithmic, and the curves of total pressure gradient and injection volume are M-type changed.There is a lag effect after CO 2 injection flooding, and the ultimate recovery can be improved by using a small flooding rate.The different gas injection slug experiments show that the relationship between ultimate recovery and CO 2 proportion of total injection is positive.The breakthrough time of different gas injection slug experiments and CO 2 flooding experiment are similar, and the total pressure gradient of water flooding and CO 2 flooding are more consistent.The development mode of low-speed advance gas injection, then alternated gas/ water and later water flooding is recommended for the extra-low permeability reservoirs, adopting various injection solutions at different blocks.