党海龙,肖前华,高瑞民,等.延长油田长7致密油储层CO2驱替特征[J].深圳大学学报理工版,2019,36(No.3(221-330)):298-303.[doi:10.3724/SP.J.1249.2019.03298]
DANG Hailong,XIAO Qianhua,GAO Ruimin,et al.Characteristics of CO2 displacement for Chang 7 tight reservoir in Yanchang oilfield[J].Journal of Shenzhen University Science and Engineering,2019,36(No.3(221-330)):298-303.[doi:10.3724/SP.J.1249.2019.03298]
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延长油田长7致密油储层CO2驱替特征
党海龙1,2,肖前华3,高瑞民2,戚志林3,畅 斌2

1)中国石油大学(北京)石油工程学院,北京 102249; 2)陕西延长石油(集团)有限责任公司,陕西西安710075; 3)重庆科技学院石油与天然气工程学院,重庆401331

致密油; CO2驱替; CO2-水交替驱替; 可动流体; 核磁共振; 纳米空间可动用量

Characteristics of CO2 displacement for Chang 7 tight reservoir in Yanchang oilfield
DANG Hailong1,2, XIAO Qianhua3, GAO Ruimin2, QI Zhilin3, and CHANG Bin2

1)School of Petroleum Engineering, China University of Petroleum, Beijing 102249, P.R.China2)Shaanxi Yanchang Petroleum(Group)Co. Ltd., Xi'an 710075, Shaanxi Province, P.R.China3)School of Petroleum Engineering, Chongqing University of Science and Technology, Chongqing 401331, P.R.China

tight reservoirs; CO2 displacement; CO2 water-alternating-gas injection(CO2-WAG ); mobile fluids; nuclear magnetic resonance(NMR); mobile fluids in nanopores

DOI: 10.3724/SP.J.1249.2019.03298

备注

常规开发方式难以动用致密油储层流体,原油采出程度低.为探索更高效的驱油方式,以延长油田长7致密油储层为研究对象,选取实际储层样品,对比研究了单纯CO2驱替与水驱替至含水率(体积分数)为60%时转CO2-水交替驱替的长岩心驱替的实验研究.结果发现,单纯CO2驱替和CO2-水交替驱替2种方式的驱油效率明显高于单纯水驱替效率.其中,CO2驱替效率可达50%以上; 水驱替至含水率为60%时转CO2-水交替驱替,驱油效率可达60%以上.通过核磁共振结合高速离心等测试手段对储层流体可动用性分析发现,储层中60%以上的流体赋存于纳米级空间,纳米级空间的可动用量仅有7%左右,储层流体极难动用.CO2与原油间的物理化学作用起到了原位改质的效果,驱油效率得到了提升.CO2-水交替存在造成贾敏效应,减缓水驱突进,强化纳米级低速渗流通道向储层必然渗流通道转变,驱油效率同样可得到提升.研究结果可为延长油田长7致密油储层CO2驱替先导试验提供参考.

It is very difficult to recover oil from tight reservoirs through conventional methods. This study aims to explore more effective methods of oil extraction for an example of Chang 7 tight reservoir in Yanchang oil field. Core samples are selected for testing two different oil extraction methods using in-house experiments, including CO2 displacement and CO2 water-alternating-gas injection(CO2-WAG)displacement after water-cut reaches 60% after water flooding. The experimental results show that the oil recovery of both of the two methods are apparently higher than that of pure water flooding, that is, the oil recovery by using CO2 displacement is 50% higher than that of water flooding, and the oil recovery using CO2-WAG displacement is 60% higher than that of water flooding. The analysis of the range of moveable fluids using nuclear magnetic resonance(NMR)and high speed centrifugation reveals that over 60% of reservior fluid exists in nanopores, and among which only 7% is mobile. Because of the physicochemical reactions between CO2 and crude oil, the flowing capacity of crude oil could be improved at in-situ, thus the oil displacement efficiency enhanced. In addition, as CO2-WAG can lead to the Jiamin effect, the fingering of water flow can be mitigated. Therefore, the nano-scale pores can be forced to be the flowing channels, so that the fluids in nanopores can be recovered. This research provides the basis for developing CO2 displacement project for Chang 7 tight oil reservoir in Yanchang oil field.

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