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厚油藏CO2驱气体超覆现象分析
赵凤兰,王强,宋黎光,娄小康,冯海如
0
(1.中国石油大学(北京)石油工程学院,北京102249;2.石油工程教育部重点实验室,北京102249;3.中国石油大学(北京)非常规油气科学技术研究院,北京102249)
摘要:
针对厚油藏CO2驱过程中气体发生超覆会造成垂向波及效率低的问题,为研究CO2的超覆运移距离,自主研制高温高压超覆模型,采用分层采集流体的方式,改变岩心长度(分别为60,50,40 cm)开展气驱实验,上、下出口端的产量分别表征岩心上、下部的开发效果以评价其超覆程度。实验结果表明,重力分异作用下CO2的运移过程可以分为3个主要阶段:气体均匀推进阶段(0~40 cm)、过渡阶段(40~50 cm)和超覆完成阶段(50~60 cm)。建立了比值法和面积法进行超覆程度的量化表征,气体运移距离越远,上、下出口端产油量差异越大,超覆程度指数增幅越大,总产油量降幅越大。因此,油田生产中,在保证经济利益最大化的前提下应尽可能减小井距以减弱气体超覆对开发效果的影响。
关键词:  厚油藏  重力超覆  CO2驱  运移距离  超覆程度
DOI:10.13673/j.cnki.cn37-1359/te.2020.04.015
基金项目:国家科技重大专项“低渗-致密油藏高效提高采收率新技术”(2017ZX05009-004)和“海外重点油气田开发钻采关键技术” (2017ZX05032-004)。
Analysis of gas overlap during CO2 flooding in thick oil reservoir
ZHAO Fenglan,WANG Qiang,SONG Liguang,LOU Xiaokang,FENG Hairu
(1.College of Petroleum Engineering,China University of Petroleum(Beijing),Beijing City,102249,China;2.Key Laboratory of Petroleum Engineering of the Ministry of Education,Beijing City,102249,China;3.Unconventional Oil and Gas Institute,China University of Petroleum(Beijing),Beijing City,102249,China)
Abstract:
Aiming at the problem of low vertical sweep efficiency caused by gas overlap during the CO2 flooding in thick oil reservoir,a high-temperature and high-pressure overlap model is independently developed to study the CO2 overlap migration distance. The fluid collection is completed in each layer,and the length of the core(60,50,40 cm)is changed to carry out the gas flooding experiment. The output of the upper and lower outlets characterize the development efficiency of the upper and lower parts of the core respectively to evaluate the overlap degree. The experimental results show that the migration process of CO2 under gravity segregation can be divided into three stages:the uniform gas advancement stage(0-40 cm),the transition stage(40-50 cm)and the overlap completion stage(50-60 cm). The ratio method and area method were established to quantitatively characterize the overlap degree. The farther gas migration distance shows the bigger difference in oil production between the upper and lower outlets,the higher increase of the overlap degree index shows the bigger decline in overall oil production. Therefore,the well spacing should be reduced as much as possible to minimize the impact of gas overlap on the development efficiency while ensuring maximum economic benefits in oilfield development.
Key words:  thick oil reservoir  gravity segregation  CO2 flooding  migration distance  overlap degree

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