水气交替注入对CO_2驱油效果的影响

Effect of water and gas alternate injection on CO_2 flooding

延长油田靖边203区块是典型的低孔低渗油藏,该区块正在进行CO_2驱先导性试验。水气交替注入（WAG）能有效控制驱替前缘流度,抑制气窜并延长见气时间,从而改善CO_2驱油效果。通过与连续气驱对比实验,研究了WAG对CO_2驱油效果的影响,并探讨了注气速度、段塞尺寸和气水比等注入参数对CO_2驱油效果的影响规律。结果表明：对于非均质性油藏,WAG比连续气驱具有更明显的优势;渗透率级差为10~30时,WAG能有效地抑制气窜,改善驱油效果;渗透率级差过大或存在裂缝时,WAG驱油效果变差;WAG的注气速度、段塞尺寸和气水比分别为50 m L/min,0.10 PV和1∶1时,驱油效果最佳,采出程度在水驱基础上提高了20.95百分点,最终采出程度为44.70%。

The 203 well area is a typical low porosity and low permeability reservoir in Jingbian Oilfield. Pilot test of CO_2 flooding is in the early gas breakthrough in this block. WAG can effectively control the displacement front flow, inhibit gas channeling and extend the gas channeling time, thereby improving the effect of CO_2 flooding. By contrast with the continuous gas flooding experiments, the effects of WAG effect on CO_2 flooding was studied, and the influence of gas injection velocity, slug size and gaswater ratio on CO_2 flooding effects were explored. The results show that： for reservoir heterogeneity, WAG has more obvious advantages than the continuous gas flooding; when the permeability ratio is 10 to 30, WAG can effectively inhibit gas channeling and improve oil flooding efficiency; when the permeability ratio is too large or cracks exist, WAG flooding efficiency will be poor;with the gas injection velocity 50 m L/min, slug size 0.1 PV and gas-water ratio 1∶1, the flooding efficiency of WAG is the best. The reserves recovery has been improved 20.95% on the basis of water flooding, and the final recovery is 42.70%.