西南石油大学学报(自然科学版) ›› 2018, Vol. 40 ›› Issue (3): 121-128.DOI: 10.11885/j.issn.1674-5086.2017.02.28.06

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Law of CO2 Immiscible Front Movement in Low-permeability Oil Reservoir

MENG Fankun1,2, LEI Qun1, SU Yuliang2, HE Dongbo1   

  1. 1. PetroChina Research Institute of Petroleum Exploration & Development, Haidian, Beijing 100083, China;
    2. School of Petroleum Engineering, China University of Petroleum(East China), Qingdao, Shandong 266580, China
  • Received:2017-02-28 Online:2018-06-01 Published:2018-06-01

Abstract: The interaction of different fluids in carbon dioxide (CO2) immiscible flooding in a low-permeability oil reservoir is complex, and the description of the front is difficult. Therefore, the fractional flow model for the CO2 immiscible flooding in a low-permeability oil reservoir was derived herein based on an improved relative permeability model for CO2 flooding, considering the CO2 dissolution in crude oil and the influence of the pressure gradient of the oil phase. The computing method of the front movement speed of CO2 flooding and the saturation profile was established by introducing the seepage retardation factor to correct the B-L equation. The veracity of this computing method was verified by comparing with the gas saturation profile obtained from the CO2 flooding empirical data. The CO2 dissolution, viscosity of different crude oils, and influence of the injection pressure on the front movement speed of CO2 flooding were analyzed. The results indicated that the front movement speed was reduced by more than 50% considering the CO2 dissolution in crude oil. Moreover, the higher the crudeoil viscosity, the greater the front movement speed. The front movement speed decreased with the increase in the injection pressure and inflected at the point of minimum miscible pressure. The adaptability of the CO2 flooding of three typical test sites in the Jilin, Shengli, and Yanchang oil fields was evaluated by comparing the distributions of their gas saturation profile.

Key words: low permeability oil reservoir, CO2 immiscible flooding, B-L equation, front movement speed, saturation profile

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