Special Oil & Gas Reservoirs >

2022 , Vol. 29 >Issue 1: 134 - 140

DOI: https://doi.org/10.3969/j.issn.1006-6535.2022.01.020

Reservoir Engineering

Experiment on the Mechanism of Enhancing Oil Recovery by CO2 Flooding with Gas-soluble Demixing Agent

  • Sun Dalong ,
  • Zhang Guangdong ,
  • Peng Xu ,
  • Jing Hao ,
  • Lyu Hua ,
  • Ren Chaofeng ,
  • Wang Ning
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  • 1. Southwest Petroleum University, Chengdu, Sichuan 610500, China;
    2. Keyuan Engineering Technology Testing Center of Sichuan Province, Chengdu, Sichuan 610091, China;
    3. PetroChina Changqing Oilfield Company, Jingbian, Shaanxi 718500, China;
    4. PetroChina Changqing Oilfield Company, Xi′an, Shaanxi 710000, China

Received date: 2020-05-11

  Revised date: 2021-11-04

  Online published: 2023-01-10

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Abstract

In view of unclear understanding of the mechanism of reducing mixed-phase pressure and enhancing oil recovery by CO2 flooding with soluble demixing agent, the demixing mechanism of gas-soluble demixing agent was clarified by analyzing the changes in crude oil composition, crude oil viscosity, oil-gas interfacial tension and crude oil phase characteristics in combination with laboratory experiment, numerical simulation and weight analysis. The experimental results showed that after injecting the gas-soluble demixing agents of 3% and 20% volume fraction, the content of heavy components in crude oil was reduced by 25.07% and 48.21%, the average crude oil viscosity reduced by 61.51% and 96.88%, the interfacial tension between crude oil and CO2 reduced by 30.36% and 91.16% at the same pressure, and the saturation pressure reduced by 6.22% and 15.90%, respectively. The dominant demixing mechanism of gas-soluble demixing agent was to crack the heavy components of crude oil, reduce the crude oil viscosity and decrease the oil-gas interfacial tension. The study also analyzed the oil displacement mechanism for oil recovery enhancement by mixed injection and plug injection of gas-soluble demixing agent and CO2, and clarified the seepage characteristics of different affected areas in the formation, namely there was two-phase seepage of CO2 or gas-soluble demixing agent and formation crude oil in the mixed injection area, and three-phase seepage of CO2, gas-soluble demixing agent and formation crude oil in the mixed-phased area. This study provides a basis for the optimization and field practice of the gas-soluble demixing agent for CO2 flooding.

Key words： gas-soluble demixing agent; CO2 flooding; enhance oil recovery; seepage characteristics; mechanism

Cite this article

Sun Dalong , Zhang Guangdong , Peng Xu , Jing Hao , Lyu Hua , Ren Chaofeng , Wang Ning . Experiment on the Mechanism of Enhancing Oil Recovery by CO2 Flooding with Gas-soluble Demixing Agent[J]. Special Oil & Gas Reservoirs, 2022 , 29(1) : 134 -140 . DOI: 10.3969/j.issn.1006-6535.2022.01.020

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