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<p>High Shale content, a high sedimentation rate, and a sequence of initially slow followed by rapid sediment deposition are widely considered favorable conditions for the formation of overpressure. These conditions are also applicable in layers containing halite. The role of halite in the formation and evolution of overpressure remains unclear. This study relies on mathematical and numerical simulations to investigate the overpressure phenomenon in simplified geometric structures of shale-sandstone layers with halite. Our findings confirm that the basic mechanism involves the influence of halite on rock properties within the shale-sandstone layers. The occurrence of halite in rock layers alters the compaction curve of the rocks, causing a reduction in rock permeability. These findings not only advance the timing of overpressure occurrence in the layer but also intensify its magnitude. Due to the presence of halite, the threshold of mudstone content that forms overpressure in the layer decreases compared with non-saline layers. As a result, overpressure phenomena may occur in layers that previously did not meet the conditions for overpressure formation. We also found that the higher the halite content, the less influence of sedimentation rate and sedimentation mode on overpressure formation. In addition, this study also clarifies the role of gypsum in the formation of overpressure, and believes that the thickness of gypsum is the key factor in determining the magnitude of overpressure.</p>

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Mechanisms for overpressure generated by the undercompaction involving halite in Shale-sand layers

  • 期刊论文

  • 发表日期：

    2025年4月2日

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  • Taozheng Yang,
  • Chenglin Liu,
  • Jixian Tian,
  • Rizwan Sarwar Awan,
  • Guoxiong Li,
  • Zhengang Ding,
  • Hongliang Huo,
  • Yubo He,
  • Haidong Wang,
  • Tong Qiao

摘要

High Shale content, a high sedimentation rate, and a sequence of initially slow followed by rapid sediment deposition are widely considered favorable conditions for the formation of overpressure. These conditions are also applicable in layers containing halite. The role of halite in the formation and evolution of overpressure remains unclear. This study relies on mathematical and numerical simulations to investigate the overpressure phenomenon in simplified geometric structures of shale-sandstone layers with halite. Our findings confirm that the basic mechanism involves the influence of halite on rock properties within the shale-sandstone layers. The occurrence of halite in rock layers alters the compaction curve of the rocks, causing a reduction in rock permeability. These findings not only advance the timing of overpressure occurrence in the layer but also intensify its magnitude. Due to the presence of halite, the threshold of mudstone content that forms overpressure in the layer decreases compared with non-saline layers. As a result, overpressure phenomena may occur in layers that previously did not meet the conditions for overpressure formation. We also found that the higher the halite content, the less influence of sedimentation rate and sedimentation mode on overpressure formation. In addition, this study also clarifies the role of gypsum in the formation of overpressure, and believes that the thickness of gypsum is the key factor in determining the magnitude of overpressure.