克拉玛依油田九_(6)区稠油油藏蒸汽-CO_(2)复合驱实验评价

Steam-CO_(2) Flooding for Heavy Oil in District 9-6,Karamay Oilfield:Experiment and Evaluation

克拉玛依油田九6区齐古组稠油油藏上油层蒸汽驱采出程度达60%,而下油层采出程度仅为32%,存在油藏原油动用程度差异大,部分储集层未被波及等开发问题,需要探索新的开发方式来进一步提高开发效果。通过室内物理模拟实验,研究了九6区蒸汽-CO_2复合驱油效率及其驱油机理,优化了复合驱最佳注入参数。实验结果表明,蒸汽-CO_2复合驱过程中CO_2可为蒸汽驱打开渗流通道,降低注蒸汽压力,还可以抑制蒸汽驱造成的高黏度油包水乳状液的形成,降低了原油黏度;蒸汽冷凝水形成水气交替段塞,减缓了CO_2气窜发生,增大了波及体积,形成了良好的协同作用,蒸汽-CO_2复合驱比蒸汽驱驱油效率提高35%左右,实验优选了最佳注入方式为交替注入,在蒸汽温度为220℃,蒸汽与CO_2注入比为10∶1～25∶1时,最终驱油效率可达80%以上。

The recovery percent of reserves by steam flooding in the heavy oil reservoirs of the upper Qigu formation in District 9-6 of Karamay oilfield is 60%, but the recovery percent of reserves of the lower Qigu formation is only 32%. New development methods are needed tosolve the problems of partial unswept reservoirs and large differences in reservoir producing degree, and further to improve development effect. Based on the indoor physical simulation experiments, this article studies the steam-CO2 flooding effect and oil displacement mechanism in District 9-6 and optimizes the injection parameters of the combined flooding. The experiment results show that CO2 can open theflowing channel for steam flooding and reduce the steam injection pressure, meanwhile it can inhibit the forming of the high-viscosity water-in-oil emulsion resulted from steam flooding and reduce crude oil viscosity;the water from steam condensation forms a water-alternating-gasslug, which can slow down the CO2 channeling and increase the swept volume. The enhanced oil recovery of steam-CO2 flooding is 35.0%higher than that of steam flooding and it is proved that the steam-CO2 alternating injection is the best injection mode. When the steam temperature is at 220 ℃ and the steam-CO2 volume ratio ranges from 10:1 to 25:1, the final oil displacement efficiency can reach 80%.