CHARACTERISTICS OF BREAKTHROUGH PRESSURE OF MESOZOIC-PALEOZOIC COVER IN JIANGSU LOWER YANGTZE AREA
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摘要: 江苏下扬子区震旦系—第三系发育多套盖层,包括寒武系下统幕府山组、志留系下统高家边组、白垩系上统浦口组区域性盖层等。泥岩盖层的突破压力主要受泥岩孔隙中微孔隙和小喉道分布的控制;统计表明,盖层的突破压力随埋深的增加先是由小变大,埋深继续增加又由大变小,说明突破压力受成岩演化控制。利用吸附法获得的吸附—脱附等温线来测定微孔结构的研究表明,盖层突破压力的变化与泥岩在不同演化阶段的微孔隙结构有关。在较低的演化阶段,泥岩具有孔隙型毛细孔结构特征,在压实作用下,孔隙度逐渐变小,突破压力不断增加。当到达较高演化阶段时,泥岩脆性增加,在地应力作用和抬升作用下,产生微裂隙,突破压力不断变小,封盖能力逐步降低。Abstract: Sets of cap formations have generated from Sinian to Tertiary in the Jiangsu Lower Yangtze area,such as-C1mu,S1g and K2p.Breakthrough pressure of mudstone caprock is mainly controlled by distribution of micropores and small throats.Statistics have shown that as burial depth increases,breakthrough pressure increases at first and then decreases,indicating the controlling effect of diagenesis on breakthrough pressure.Adsorption and desorption isotherms of microporosity have proved that caprock breakthrough pressure changes due to micropores structures of mudstone during different evolution stages.During the lower stage,mudstone is characterized by pore-type structure and breakthrough pressure increases with depth.During the higher stage,mudstone brittle increases and micro-fissures come into being,resulting in decreases of breakthrough pressure and sealing ability.
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Key words:
- breakthrough pressure /
- diagenesis /
- mudstone caprock /
- Mesozoic-Paleozoic /
- Lower Yangtze area /
- Jiangsu Province
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