【摘要】 在围压2~40MPa变化范围内,以恒流法多次变化上游压力测量了以断层岩为主的样品的气体(N2)渗透率,将实验结果进行了Klinkenberg效应校正。对实验数据的拟合分析表明,滑脱因子b值与绝对渗透率kl存在b=λkl-d形式的幂律关系,断层岩符合b=0.004 6kl-0.476的变化关系。与沉积岩相比,断层岩的气体滑脱效应更强,采用气体测量渗透率时,其滑脱效应不能忽略。断层岩气体渗透率和绝对渗透率与测量所用的孔隙压力间的关系为kg/kl=1+(0.009 2kl-0.476)/(Pu+Pd)。结果表明样品渗透率越低,滑脱效应越强,提高孔隙压力,滑脱效应逐渐减小;对于高渗(10-15m2~10-18m2)的样品,高孔隙压力下(4MPa以上)的气体渗透率与绝对渗透率基本一致,对于超低渗(10-22m2~10-20m2)的样品,即使提高孔隙压力亦很难避免滑脱效应。在40MPa有效压力下断层泥样品的绝对渗透率为4.54×10-19m2~2.43×10-17m2,角砾岩的绝对渗透率较断层泥高出1~2个数量级,为2.25×10-17m2~7.94×10-16m2,表明汶川地震断层带具有核部低、破碎带高的渗透结构,断层带核部具备热压作用发生所要求的低渗条件。更多还原

【Abstract】 The nitrogen gas permeabilities of fault rocks were measured under confining pressure ranging from 4 to 40 MPa. At each confining pressure step,we changed the upstream pressure several times and measured the permeability. The measured gas results were then corrected by Klinkenberg’s equation. Relationship between slippage factor b and intrinsic permeability klcan be described by a power law correlation expressed as b = 0. 004 6kl- 0. 476. Compared with sedimentary rocks,the gas slippage effect of fault rocks is stronger,which should not be ignored when using gas as a medium for permeability experiments. The relationship between gas permeability,intrinsic permeability and pore pressure is expressed as kg/ kl= 1 +( 0. 009 2kl- 0. 476) /( Pu+ Pd). Results show that the lower the permeability of rocks is,the stronger the Klinkenberg effect is. Additionally,the slippage effect decreases as pore pressure increases. For the relative permeable( 10- 15m2~ 10- 18m2) samples,their gas permeabilities are almost identical to intrinsic permeabilities under relative higher pore pressure condition( higher than 4MPa). However,for the ultra-low permeable( 10- 22m2~ 10- 20m2) samples,it’s difficult to avoid the slippage effect although under high pore pressure condition. The intrinsic permeability of fault gouge samples ranges between 4. 54 × 10- 19m2 and 2. 43 × 10- 17m2,and those of the breccia samples are higher by 1 ~ 2 orders of magnitude which range between 2. 25 × 10- 17m2and7. 94 × 10- 16m2. These results demonstrate that the permeability structure of Wenchuan earthquake fault zone is characterized by a low permeable fault core and relative higher permeable damaged zone.The fault zone has the characteristics of low permeability for thermal pressurization.更多还原