The heavy oil reservoirs of Duo 1 Member in Xingbei Oilfield are thin with active bottom water.To prevent the bottom water breakthrough during its development of and increase its recovery factor, the concentration of viscosity reducer was screened in laboratory and the CO2 huff and puff parameters of horizontal wells were optimized.Then, CO2 huff and puff was tested on site based on the development situations of 4 horizontal wells.It is indicated that the key to improve the CO2 huff and puff effects of horizontal wells is to select viscosity reducers, optimize CO2 injection rate and control oil production intensity.When CO2 huff and puff of horizontal well is tested, it is necessary to injection viscosity reducer first and then CO2 to reduce the damage of bitumen deposit to oil layers in the process of CO2 injection.When sucker rod pumps are used, the bottom water coning can be controlled by decreasing the pumping rate.By October 2016, this technology had been conducted in 4 wells 5 times with cumulative viscosity reducer injection of 23 t, cumulative CO2 injection of 5 627.45 t, cumulative incremental oil 2 560.17 t and oil replacement ratio of 0.31-0.85, averaging 0.45.By virtue of this technology, the damage of CO2 to reservoirs, the injection pressure of CO2 and the undirected CO2 injection volume are decreased, the effective period of CO2 huff and puff of horizontal wells are prolonged, and the oil replacement ratio is increased.The research results can be used as the reference for the horizontal-well CO2 huff and puff in similar thin heavy oil reservoirs with bottom water.%兴北油田垛一段稠油油藏油层厚度薄,底水活跃,为解决开发过程中底水突进、采收率低的问题,在室内进行降黏剂浓度筛选和水平井CO2吞吐参数优化的基础上,结合4口水平井的开采现状,开展了CO2吞吐现场试验.研究表明:提高水平井CO2吞吐效果的关键是降黏剂筛选、优选CO2合理的注入量和控制采油强度;在水平井CO2吞吐试验中先注入降黏剂,后注入CO2,可降低注CO2过程中沥青沉淀对油层的伤害;水平井CO2吞吐转抽后,通过降低抽油泵排量,可控制底水锥进.截至2016年10月,4口井5井次累计注入降黏剂为23 t,累计注入CO2为5 627.45 t,累计增产原油为2 560.17 t,换油率为0.31~0.85 ,平均为0.45.该项研究有效降低了CO2对储层的伤害和CO2的注入压力,减少了CO2注入的盲目性,延长了水平井CO2吞吐的有效期,提高了换油率,对同类薄层稠油底水油藏开展水平井CO2吞吐具有一定的借鉴意义.
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