关键词: 泥质岩层, 孔隙流体, 超压, 启动压力, 启动阻力, 低速渗流, 欠压实

Abstract: The water in pores of mudstone flowing outward follows the law of low-velocity non-Darcy seepage.After mud-sediment changed into stone,the water flowing in pores of middle layer of mudstone has to overcome the starting resistance resulted from the water film forming in pores.Water is easily preserved in the pores and forms the undercompaction of the mudstone layer.The water in the pores of the undercompaction layer undertook a part weight of the super jacent stratum and resulted in the ultra-pressure of fluid in the pores.The starting resistance is a fundamental factor for causing the ultra-pressure of fluid in pores of mudstone layers.In the early stage of diagenesis,the starting resistance was small,and the fluid was easily flowing in pores.The ultra-pressure of fluid was made up starting resistance and viscous resistance.In the middle to later period of diagenesis,the starting resistance of mudstone layer increased,and the fluid was hard or impossible to flow in the pores.The viscous resistance is equal to zero,and the ultra-pressure value is equal to the starting resistance.Because the starting resistance can express the characteristics of the mudstone,the ultra-pressure of fluid must exist in the pores if there are neither cracks nor faults.The starting resistance increased with rising thickness of mudstone layer,buried depth and heightening of diagenesis degree and with the decrease of sandy content.The ultra-pressure value of fluid in pores increased as much as the starting resistance with the change of above factors.

Key words: mudstone layer, porous fluid, ultra-pressure, starting pressure, starting resistance, low-velocity seepage, undercompaction