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基于Comsol Multiphysics 5.2和Matlab软件,构建材料参数服从Weibull分布的非均质花岗岩钻井,分析了3000m和4000m埋深下,不同温度对花岗岩蠕变特性的影响。实验结果表明:在相同埋深下,当温度在300℃~480℃区间内,花岗岩钻井围岩稳态蠕变率基本保持不变,当温度超过480℃~500℃时,稳态蠕变率明显增大,即温度阈值为480℃~500℃。在轴压、围压一定的情况下,随着温度升高,钻井围岩初始蠕变应变值明显增大,但在不同埋深下初始蠕变应变值基本相同,体现为热弹性应变。在相同埋深下,花岗岩钻井沿其径向蠕变应变,受温度影响显著,随着温度的升高,钻井围岩的蠕变应变增大。在3000,4000 m埋深下,高温对花岗岩钻井围岩蠕变性能影响显著,在500℃时随时间推移,钻井围岩蠕变应变明显加快,即钻井围岩高温失稳阈值在500℃左右。高温使花岗岩力学性能弱化,在花岗岩内部造成损伤,随着温度的升高损伤不断积累,在500℃左右发生突变,致使钻井围岩失稳破坏。
Based on Comsol Multiphysics 5.2 and Matlab software, heterogeneous granite drilling with Weibull distribution with material parameters was constructed. The effects of different temperatures on the creep characteristics of granite were analyzed under the depth of 3000m and 4000m. The experimental results show that at the same depth, the steady-state creep rate of granite surrounding rock remains basically unchanged when the temperature is in the range of 300 ℃ ~ 480 ℃. When the temperature exceeds 480 ℃ ~ 500 ℃, the steady-state creep rate Significantly increased, that is, the temperature threshold is 480 ℃ ~ 500 ℃. Under the condition of constant axial pressure and confining pressure, the initial creep strain of surrounding rock increases obviously with the increase of temperature. However, the initial creep strain at different depths is basically the same, which is shown as thermoelastic strain. Under the same depth, the creep strain of granite along its radial direction is affected by the temperature. As the temperature increases, the creep strain of the surrounding rock increases. Under the depth of 3000 and 4000 m, the creep behavior of granite surrounding rock is significantly affected by the high temperature. The creep strain of the surrounding rock is obviously accelerated with the passage of time at 500 ℃, that is, the high temperature instability threshold of surrounding rock is about 500 ℃ . The high temperature makes the mechanical properties of granite weakened, causing damage in the granite. As the temperature increases, the damage continues to accumulate, causing a sudden change at about 500 ℃, causing the failure of the surrounding rock of the drilling.