分流控制提高低渗平面非均质油藏的 CO₂波及效率

Improving CO₂ Sweeping Efficiency of a Areal Heterogeneity Model by Diffluence Management

王志兴 赵凤兰 吕广忠 侯吉瑞 张 蒙 王 鹏 郝宏达

WANG Zhixing ZHAO Fenglan LV Guangzhong HOU Jirui ZHANG Meng WANG Peng HAO Hongda

针对低渗透油藏 CO2驱由平面非均质性导致的产液不均、气窜早和波及效率低等问题，采用室内物理模拟实验方法，研究分流控制方法改善 CO2驱效果的可行性。根据实际油藏非均质条件，建立了级差为 5的平面非均质径向流物理模型及相应的实验流程，模拟五点井网 CO2驱过程，分析定生产压力、低渗优先和低渗高压差三种生产方式下 CO2驱油效果。其中，定生产压力模拟常规井网气驱方式，低渗优先则为调整生产井投产时间，低渗高压差则为平衡井组产液量的生产方式。研究结果表明，定生产压力方式下，注入气沿高渗透方向生产井突破并窜逸，生产井产液量不均衡，模型整体气驱采收率仅为 23.11%。而采用低渗优先和低渗高压差的方式，生产井见气时间延长，各生产井产液量增加，采收率分别为 42.50%和 46.42%。可见，通过生产井的分流控制方法，能一定程度上延缓气窜通道的形成，提高波及效率。分流控制方法操作成本低，有望成为低渗平面非均质油藏 CO2驱油效果的改善措施之一。图 10表 3参 17

CO2 flooding is greatly affected by areal heterogeneity in low permeability reservoirs，causing uneven pressure distribution，early gas breakthrough and low recovery factor. This study explored the applicability of diffluence management to improve CO2 flooding under laboratory condition using physical experiment simulation. Based on the permeability ratio of the actual reservoir block，a radius model with areal heterogeneity was made to simulate CO2 flooding as five spots pattern and relative experimental methods were designed. Three production patterns，including constant pressure，preproduction in low permeability well and high producing pressure differential in low permeability well，were introduced to evaluate the gas flooding effects. Results showed that under constant pressure production pattern，there was a significant gas breakthrough in only one production well located in high permeability area，and a huge production difference over the other four production wells，and only 23.11% oil was recovered. The latter two methods produced more oil and delayed gas breakthrough time，achieving oil recovery 42.50% and 46.42% ，respectively. By high producing pressure differential in low permeability well，the injected gas was evenly distributed across the radius model，leading to a lager gas sweeping volume，a higher gas utility and more oil production. Because of low operational cost，diffluence management method is expected to be an effective way to improve CO2 flooding efficiency in low permeability reservoirs with areal heterogeneity