Acta Petrolei Sinica ›› 2024, Vol. 45 ›› Issue (2): 390-402.DOI: 10.7623/syxb202402005

• OIL FIELD DEVELOPMENT • Previous Articles     Next Articles

High-pressure phase behavior and mass transfer law of Gulong shale oil and CO2 in Daqing oilfield

Song Zhaojie1, Deng Sen2,3, Song Yilei4, Liu Yong2,3, Xian Chenggang1, Zhang Jiang2,3, Han Xiao1, Cao Sheng2,3, Fu Lanqing2,3, Cui Huanqi2,3   

  1. 1. Unconventional Petroleum Research Institute, China University of Petroleum, Beijing 102249, China;
    2. Exploration and Development Research Institute, Daqing Oilfield Company Limited, Heilongjiang Daqing 163712, China;
    3. Heilongjiang Key Laboratory of Reservoir Physics and Fluid Mechanics, Heilongjiang Daqing 163712, China;
    4. China University of Petroleum-Beijing at Karamay, Xinjiang Karamay 834000, China
  • Received:2022-08-24 Revised:2023-08-27 Online:2024-02-25 Published:2024-03-07

大庆油田古龙页岩油-CO2高压相态及传质规律

宋兆杰1, 邓森2,3, 宋宜磊4, 刘勇2,3, 鲜成钢1, 张江2,3, 韩啸1, 曹胜2,3, 付兰清2,3, 崔焕琦2,3   

  1. 1. 中国石油大学(北京)非常规油气科学技术研究院 北京 102249;
    2. 大庆油田有限责任公司勘探开发研究院 黑龙江大庆 163712;
    3. 黑龙江省油层物理与渗流力学重点实验室 黑龙江大庆 163712;
    4. 中国石油大学(北京)克拉玛依校区 新疆克拉玛依 834000
  • 通讯作者: 宋宜磊,男,1996年4月生,2023年获中国石油大学(北京)博士学位,现为中国石油大学(北京)博士后,主要从事非常规油藏流体相态与渗流规律研究。Email:syl@cupk.edu.cn
  • 作者简介:宋兆杰,男,1985年11月生,2014年获中国地质大学(北京)博士学位,现为中国石油大学(北京)非常规油气科学技术研究院研究员、博士生导师,主要从事非常规油气提高采收率技术研究。Email:songz@cup.edu.cn
  • 基金资助:
    国家自然科学基金项目"页岩油储层纳微米孔喉中油-CO2-水多元体系相行为与流动机制研究"(No.52074319)、黑龙江省揭榜挂帅科技攻关项目"古龙页岩油提高采收率关键问题研究"(DQYT-2022-JS-761)和中国石油大学(北京)科研基金项目(2462021QNXZ008)资助。

Abstract: The light oil from Gulong shale is widely distributed, with favorable components and temperature-pressure conditions for miscibility with CO2. Pre-fracturing with CO2 injection and huff-and-puff can offer significant potential to enhance oil recovery. However, there is a lack of sufficient understanding of the high-pressure phase behavior of Gulong shale oil. Based on the equation of state and two-phase equilibrium theory, through verifying the results of constant mass expansion experiment and slim tube experiment for shale oil, the paper establishes a thermodynamic oil-CO2 two-phase equilibrium model considering the nano-confinement effect, and also a calculation method for the minimum miscibility pressure based on the two-phase equilibrium model. This paper is a case study of Gulong shale oils in Well Guye 2HC and Well Guye 9HC, and elucidates the interphase mass transfer behavior of Gulong shale oil and CO2, which is influenced by the factors such as maturity, oil/CO2 ratio, pressure, and nano-confinement effect. The results show that with an increase in CO2 mole fraction, the saturation pressure of Well Guye 2HC and Well Guye 9HC shale oils gradually decreases. Under reservoir temperature and pressure conditions, both Well Guye 2HC and Well Guye 9HC shale oils can be miscible with CO2. Under the same amount of CO2 injection, Well Guye 2HC shale oil exhibits a higher molecular weight and viscosity with a greater drop, and a lower saturation pressure and expansion coefficient with a smaller variation than Well Guye 9HC shale oil. The multilevel contact process of CO2 injection shows that the dissolution capacity and extraction effect of CO2 are similar in both Well Guye 2HC and Well Guye 9HC shale oils. After sufficient contact, C1-C6 components in the oil phase of Well Guye 2HC and Well Guye 9HC shale oils at the far end opposite to injection gas front are all extracted into the gas phase, and the mole fractions of CO2 in the oil phase increase to 86.63 % and 87.35 %, respectively. The presence of nano-confinement effect reduces the compositional differences between oil and gas inside nanopores, leading to a decrease in the interfacial tension and minimum miscibility pressure, which is beneficial to the mutual dissolution and miscibility between CO2 and shale oil. The impact of the nano-confinement effect on Well Guye 2HC and Well Guye 9HC shale oils is not significantly different. When the pore radius decreases from 100 nm to 10 nm, the minimum miscibility pressure of Well Guye 2HC and Well Guye 9HC shale oils with CO2 is decreased by 20.90 % and 21.31 %, respectively. Understanding the phase behavior of fluids in shale oil reservoirs can provide a theoretical guidance for the optimization of CO2 injection development.

Key words: Gulong shale oil, CO2 enhanced oil recovery, oil-gas phase behavior, minimum miscibility pressure, nano-confinement effect

摘要: 大庆油田古龙页岩油轻质油带分布广泛,具有与CO2形成混相的有利组分、温度和压力条件,注CO2前置压裂和吞吐提高采收率潜力较大,但目前对于古龙页岩油-CO2高压相行为的认识尚不充分。在状态方程和气液两相相平衡理论的基础上,通过与页岩油恒质膨胀实验、细管实验等结果校验,构建了考虑纳米限域效应的古龙页岩油-CO2两相相平衡热力学模型和基于相平衡模型的油气最小混相压力计算方法。以古页2HC井和古页9HC井页岩油为研究对象,阐明了成熟度、油/CO2比例、压力、纳米限域效应等因素影响的页岩油-CO2相间传质规律。研究结果表明,随着CO2摩尔分数的增加,古页2HC井和古页9HC井页岩油的饱和压力逐渐降低。在储层温度和压力条件下,古页2HC井和古页9HC井页岩油能够与CO2混相。在相同的CO2注入量条件下,古页2HC井页岩油的分子量和黏度更高,降幅也更大,饱和压力和膨胀系数更小,变化幅度也更小。注CO2多级接触过程显示,CO2在古页2HC井和古页9HC井页岩油中的溶解能力和抽提效果较为接近。在充分接触后,古页2HC井和古页9HC井注气后缘油相中C1—C6组分全部被抽提到气相中,油相中CO2的摩尔分数分别攀升至86.63%和87.35%。纳米限域效应的存在,减小了纳米孔内油气间组成差异,导致了界面张力和最小混相压力的降低,有利于CO2与页岩油相溶、混相。纳米限域效应对古页2HC井和古页9HC井页岩油的影响无明显差异,当孔隙半径由100 nm降低到10 nm时,古页2HC井和古页9HC井页岩油与CO2的最小混相压力分别降低20.90%和21.31%。通过明确页岩油藏流体相态变化规律,可为注CO2开发优化设计提供理论指导。

关键词: 古龙页岩油, 注CO2提高采收率, 油气相态, 最小混相压力, 纳米限域效应

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