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<p>Using fixed well patterns and constant water injection rates over extended periods in multilayered sandstone reservoirs often leads to uneven performance across different layers. Some layers may be over-saturated with water, while others may not be sufficiently swept, resulting in inefficient oil recovery. Furthermore, this causes poor overall utilization of the reservoir, with certain areas left upswept. To improve waterflooding efficiency and improve oil recovery, this study presents two well pattern adjustment methods that employ variable injection and production rates constraints: Rotational Injection and Rotational Production (RIRP) and Zonal Injection and Rotational Production (ZIRP). The effectiveness of these methods was demonstrated through pore-scale experiments and numerical reservoir simulations. Results show that at a reservoir scale, RIRP changes how water flows by creating pressure changes over time, facilitating fluid movement between and within each layer more effectively. At pore scale, both RIRP and ZIRP increase capillary forces, which help redistribute oil and water in the rock pores. Compared to the traditional commingled injection and zonal production (CIZP) method, RIRP and ZIRP perform better, increasing oil recovery by 3–7.6% and reducing water cut by 1.6–11.5%. This study also presents three operating cycles for each of the RIRP and ZIRP methods. Field data show that these techniques can significantly increase oil production, making them effective options for improving oil recovery in mature reservoirs during high water cut periods.</p>

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Well pattern adjustment of variable-injection-production-rate waterflooding in high water-cut oilfields

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2025年9月11日

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  • Wang Jincai,
  • Zhao Lun,
  • Zhang Angang,
  • Zhang Xiangzhong,
  • Guo Xuejing,
  • Li Yi,
  • Zhao Wenqi

摘要

Using fixed well patterns and constant water injection rates over extended periods in multilayered sandstone reservoirs often leads to uneven performance across different layers. Some layers may be over-saturated with water, while others may not be sufficiently swept, resulting in inefficient oil recovery. Furthermore, this causes poor overall utilization of the reservoir, with certain areas left upswept. To improve waterflooding efficiency and improve oil recovery, this study presents two well pattern adjustment methods that employ variable injection and production rates constraints: Rotational Injection and Rotational Production (RIRP) and Zonal Injection and Rotational Production (ZIRP). The effectiveness of these methods was demonstrated through pore-scale experiments and numerical reservoir simulations. Results show that at a reservoir scale, RIRP changes how water flows by creating pressure changes over time, facilitating fluid movement between and within each layer more effectively. At pore scale, both RIRP and ZIRP increase capillary forces, which help redistribute oil and water in the rock pores. Compared to the traditional commingled injection and zonal production (CIZP) method, RIRP and ZIRP perform better, increasing oil recovery by 3–7.6% and reducing water cut by 1.6–11.5%. This study also presents three operating cycles for each of the RIRP and ZIRP methods. Field data show that these techniques can significantly increase oil production, making them effective options for improving oil recovery in mature reservoirs during high water cut periods.