【摘要】 在页岩气开采中,脆性不仅直接影响页岩的压裂效果和井壁的稳定性,也是储层甜点评价的重要指标。结合页岩的受载变形特性（应力-应变曲线）及其矿物组分对页岩脆性的变化规律进行了分析,并对采用3种不同指标得到的页岩脆性系数进行了比较。页岩的应力-应变曲线通过单轴和常规三轴压缩实验获取,页岩矿物组分采用XRD,XRF技术进行测定。结果表明:页岩脆性系数均随围压增大而减小,围压越大,破裂面越少,并呈现出由脆性向延性转变的趋势;脆性矿物含量越高,脆度越高。在进行储层压裂层位选择以及可压性评价的时候,要综合考虑现场地应力状态以及矿物组分的影响。脆性系数B₃与B₁的相关性更好,与北美普遍采用石英组分进行脆性系数评价相比,对于矿物组分复杂的我国南方古生界页岩,宜采用石英、方解石、白云石作为脆性矿物组分进行页岩脆性评价。更多还原

【Abstract】 In the exploitation of shale gas,the brittleness not only directly influences the fracturing effect of shale and the stability of wellbore,but also is an important index for the evaluation of the sweet pot of shale reservoir.Deformation characteristic（ stress-strain curve） of shale was combined with the mineral components of shale to analyze the change rule of shale brittleness,and brittleness index obtained by three kinds of different indexes was compared.The shale deformation characteristic was obtained by uniaxial and conventional tri-axial compression tests,and the shale mineral components was determined by the XRD and XRF techniques.The results show that the brittleness index of shale decreases with the increase of confining pressure,the fracture surface presents a decreasing trend with the increase of confining pressure,and the trend of brittle to ductile transition. The brittleness index presents a linear increasing change rule with the brittle mineral content.During the reservoir fracturing layer selection and the evaluation of fraccability,the influence of in-situ stress state and mineral composition should be comprehensively considered. Brittleness index B₃ and B₁ have a better correlation than B₂ and B₁.In comparison with North America,which widely uses the content of quartz to evaluate brittleness index,the complex of mineral components in southern China Paleozoic shale,thequartz,calcite and dolomite used as brittle mineral content for brittleness evaluation is more suitable.更多还原