Seal mechanism of cap rocks
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摘要: 利用自行研制的气驱法突破压力仪,对盖层封闭机理进行研究。通过测试不同长度粉砂岩样品,发现相同样品具有较一致的突破压力值,且与样品长度无关,由此认为在封闭能力评价中,盖层厚度与其毛细管封闭能力无关。同时,实验中在样品一端恒定不同的水压值,发现气体突破样品所需的压力均增加,并且增加的压力值等于所恒定的水压值。对比超压形成模式,认为超压之所以能够增强盖层封闭能力,主要是因为它提高了气体突破下致密层泥岩所需的压力,并且提高的压力值等于欠压实段超压值。Abstract: Seal mechanism of cap rocks was analyzed with self-designed instrument for gas breakthrough pressure experiment.As to the same siltstone sample,breakthrough pressure was the same even though the sample length was different.Therefore,cap rock thickness does not affect capillary seal capacity in geology application.In experiment,different water pressure was imposed constantly to one end of the sample,resulting in the increase of gas breakthrough pressure,which was equivalent to the imposed water pressure.According to illustrations of overpressure formation mechanism,the overpressure had made it more difficult for gas to break through the lower tight formation and the extra pressure was equivalent to overpressure of the undercompacted formation.
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Key words:
- breakthrough pressure /
- cap formation /
- overpressure seal /
- capillary pressure seal
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