【摘要】 以温压组合条件模拟地层埋深状态,对16块储层砂岩进行了三轴压缩试验,并对试件中不同尺度的应力裂缝（stress-induced cracks）进行了宏、微观相结合的研究,观察统计了裂缝的长度、方向、密度等几何参数的变化.结果表明:应力裂缝的形态特征与岩石变形时的温、压组合条件之间存在着相关关系;当外加载荷不超过岩石抗压强度的50%时,数量有限的微裂缝都是尺度与岩石颗粒相当的粒内或粒间裂缝;穿粒裂缝仅出现在80%峰值应力以上的应力区间中,且主要由粒内裂缝连通形成,随着穿粒裂缝尺度的增大,裂面与σ₁方向夹角在统计分布上有增大趋势,并逐级趋于未来的宏观破裂角;65℃、75 MPa 以上的温、压组合条件下,试件中最终形成的宏观裂面上皆以反阶步为特征.基于以上结果,本文建立了微裂缝演化的逐级连通模型,为复杂的构造应力裂缝预测工作,提供了一条新的思路.更多还原

【Abstract】 A series triaxial compressional tests of a reservoir sandstone（J₂s）were made at different temperatureand pressure.The stress—induced cracks generated in the tested samples were studied both macroscopicallyand microscopically,and some geometrical parameters of those cracks such as the lenth,the direction andthe density were measured carefully.The observed data show that there is an instinct relation between thegeometrical characteristics of the cracks and the TP conditions under which the specimens were tested.When the applied stress is lower then 50% of the compressional strength of the rock,almost all of thecracks in the samples are intragranular or intergranular microcracks with the same or smaller size of thegrain and the absolute number of the cracks is also small.the across—granular cracks occure only when theapplied stress is increased to 80% of the compressional strength,and the angles between the crack planeand （?） in thin sections gradually approach to the final macroscopical fracture angle when the cracks aregetting larger and larger.Antisteps were found on each of the macrocrack surfaces of the samples tested at the TP conditionsnot less than 65℃,75MPa.Based on the observed results,a mechanism is proposed for the transition from microcracks（?）roliferation to the formation of the mainfracture.更多还原