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<p>After more than 20&#xa0;years of exploration and research, China's shale gas resources are the largest globally in terms of recoverable resources and exhibit significant development potential. Shale gas condensate reservoirs exhibit complex fluid phase changes during development, where condensate obstructs seepage channels and affects oil and gas recovery. Limited research exists on enhanced oil recovery from shale gas condensate reservoirs, with a gap in laboratory experiments. There is an urgent need to investigate gas injection mechanisms for enhanced oil recovery in shale gas condensate reservoirs. This study uses a shale gas condensate reservoir in China as a case study to evaluate the characteristics of depletion-drive development and elucidate the mechanism of huff-n-puff gas injection for enhanced oil recovery through laboratory experiments. Initially, PVT phase state tests were conducted on the condensate gas to determine fundamental parameters. Subsequently, starting pressure and depletion-drive development tests were conducted. Finally, a long-core huff-and-puff gas injection test was conducted. The results indicated that the dew point pressure is 45.1&#xa0;MPa and the maximum retrograde condensate oil saturation is 27.61%, with fracturing technology identified as the primary method for developing shale reservoirs, particularly as fractured shale shows high stress sensitivity. Additionally, the faster the natural depletion rate, the more favorable it is for condensate production. CO<sub>2</sub> was found to be the optimal injection medium, as it effectively reduces the dew point pressure of the condensate gas and inhibits condensate oil formation. Furthermore, the optimal timing for huff-n-puff gas injection occurs near the maximum retrograde condensation pressure, and an appropriately extended shut-in time enhances the recovery rate of condensate oil. These findings provide a theoretical foundation for the efficient development of shale gas condensate reservoirs in China and carry substantial significance for the broader application and advancement of huff-n-puff gas injection-enhanced oil recovery technology in similar gas reservoir settings.</p>

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Experimental Study on the Mechanism of Enhanced Oil Recovery of Shale Gas Condensate Reservoirs

  • 期刊论文

  • 发表日期：

    2025年4月13日

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  • Yong Tang,
  • Minmao Cheng,
  • Yong Wang,
  • Jiazheng Qin,
  • Youwei He,
  • Senlin Zhang,
  • Chengang Yuan,
  • Kun Chen,
  • Yinghe Hong

摘要

After more than 20 years of exploration and research, China's shale gas resources are the largest globally in terms of recoverable resources and exhibit significant development potential. Shale gas condensate reservoirs exhibit complex fluid phase changes during development, where condensate obstructs seepage channels and affects oil and gas recovery. Limited research exists on enhanced oil recovery from shale gas condensate reservoirs, with a gap in laboratory experiments. There is an urgent need to investigate gas injection mechanisms for enhanced oil recovery in shale gas condensate reservoirs. This study uses a shale gas condensate reservoir in China as a case study to evaluate the characteristics of depletion-drive development and elucidate the mechanism of huff-n-puff gas injection for enhanced oil recovery through laboratory experiments. Initially, PVT phase state tests were conducted on the condensate gas to determine fundamental parameters. Subsequently, starting pressure and depletion-drive development tests were conducted. Finally, a long-core huff-and-puff gas injection test was conducted. The results indicated that the dew point pressure is 45.1 MPa and the maximum retrograde condensate oil saturation is 27.61%, with fracturing technology identified as the primary method for developing shale reservoirs, particularly as fractured shale shows high stress sensitivity. Additionally, the faster the natural depletion rate, the more favorable it is for condensate production. CO2 was found to be the optimal injection medium, as it effectively reduces the dew point pressure of the condensate gas and inhibits condensate oil formation. Furthermore, the optimal timing for huff-n-puff gas injection occurs near the maximum retrograde condensation pressure, and an appropriately extended shut-in time enhances the recovery rate of condensate oil. These findings provide a theoretical foundation for the efficient development of shale gas condensate reservoirs in China and carry substantial significance for the broader application and advancement of huff-n-puff gas injection-enhanced oil recovery technology in similar gas reservoir settings.