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<p>Hydraulic fracturing is an important stimulation measure for tight sandstone oil reservoirs. CO<sub>2</sub>, as an effective energizing gas and displacement agent, can improve hydraulic fracturing and oil production performance. A comprehensive model capable of simulating hydraulic fracturing and oil production as a continuous process is valuable for evaluating the role of CO<sub>2</sub> in different stages. In this paper, a novel integrated mechanism model was established to simulate fracturing and production. The model incorporates mechanisms such as fracture opening and closing, fracturing fluid imbibition, CO<sub>2</sub>–crude oil interaction, and asphaltene deposition damage. These mechanisms were further characterized and coupled in the numerical model developed by the software CMG-STARS to conduct simulation works. To verify the model’s reliability, a sensitivity analysis was carried out based on a single fracture to assess the influence of various factors on fracturing and EOR performance. The simulation results indicate that hydraulic fracturing, CO<sub>2</sub> energization, CO<sub>2</sub> huff and puff, and fracturing fluid imbibition can enhance oil recovery (EOR), except for asphaltene deposition. CO<sub>2</sub>-energized fracturing followed by depletion production requires less CO<sub>2</sub> injection as a front slug and results in longer fractures, a wider imbibition area, and lower asphaltene deposition risk. Under the basic conditions, the EOR factors contributed by hydraulic fracturing, CO<sub>2</sub> energization, fluid imbibition and asphaltene deposition are 23.06%, 3.92%, 3.44%, and  −1.25%, respectively, and the CO<sub>2</sub> cannot be stored effectively. In contrast, conventional fracturing followed by CO<sub>2</sub> huff and puff requires more CO<sub>2</sub> with a storage efficiency of 44.4%, but results in poorer hydraulic fracturing performance, general CO<sub>2</sub> huff and puff, a smaller imbibition area, and more severe asphaltene deposition damage. The corresponding EOR factors are 17.60%, 3.97%, 2.47%, and -2.22%, respectively. This model can be applied to optimize fracturing and production parameters, providing deeper insights into the fracturing stimulation process.</p>

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Study on Rock–Fluid Interactions and Influencing Factors in the Fracture During the CO2-Energized Fracturing and Production Process in Tight Sandstone Oil Reservoirs

  • 期刊论文

  • 发表日期：

    2025年6月5日

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  • Liang Zhang,
  • Xing-shun Yao,
  • Rong-hua Wen,
  • Li-xing Li,
  • Zi-lin Zhang,
  • Hong-bin Yang,
  • Lin-chao Yang

摘要

Hydraulic fracturing is an important stimulation measure for tight sandstone oil reservoirs. CO2, as an effective energizing gas and displacement agent, can improve hydraulic fracturing and oil production performance. A comprehensive model capable of simulating hydraulic fracturing and oil production as a continuous process is valuable for evaluating the role of CO2 in different stages. In this paper, a novel integrated mechanism model was established to simulate fracturing and production. The model incorporates mechanisms such as fracture opening and closing, fracturing fluid imbibition, CO2–crude oil interaction, and asphaltene deposition damage. These mechanisms were further characterized and coupled in the numerical model developed by the software CMG-STARS to conduct simulation works. To verify the model’s reliability, a sensitivity analysis was carried out based on a single fracture to assess the influence of various factors on fracturing and EOR performance. The simulation results indicate that hydraulic fracturing, CO2 energization, CO2 huff and puff, and fracturing fluid imbibition can enhance oil recovery (EOR), except for asphaltene deposition. CO2-energized fracturing followed by depletion production requires less CO2 injection as a front slug and results in longer fractures, a wider imbibition area, and lower asphaltene deposition risk. Under the basic conditions, the EOR factors contributed by hydraulic fracturing, CO2 energization, fluid imbibition and asphaltene deposition are 23.06%, 3.92%, 3.44%, and  −1.25%, respectively, and the CO2 cannot be stored effectively. In contrast, conventional fracturing followed by CO2 huff and puff requires more CO2 with a storage efficiency of 44.4%, but results in poorer hydraulic fracturing performance, general CO2 huff and puff, a smaller imbibition area, and more severe asphaltene deposition damage. The corresponding EOR factors are 17.60%, 3.97%, 2.47%, and -2.22%, respectively. This model can be applied to optimize fracturing and production parameters, providing deeper insights into the fracturing stimulation process.