【摘要】 致密砂岩地层是油气钻井中常见的难钻层段，其难钻本质在于岩石矿物组成复杂，胶结致密，加之赋存环境受原地温压耦合的多尺度交互作用，使其力学特征更加复杂，现有实验手段难以有效表征。为此，从骨架/胶结矿物的细观热膨胀特征入手，结合多晶离散元方法，建立了一种考虑温度作用的非均质细观力学建模方法，并用于揭示其三轴压缩特性。研究结果表明：不同于骨架矿物的热胀冷缩特性，黏土矿物晶面间距随温度升高表现出不可逆的热膨胀性，是局部强化致密砂岩力学性质的根本原因；黏土矿物受热膨胀增加了粒间的接触强度，局部致密化，使三轴压缩过程中粒间更难破坏，粒内拉伸裂纹占比随温度的升高而升高；常温～200℃,抗压强度与弹性模量随温升递增，围压的增加使得弹性模量的增长趋势由“下凸状”转至“上凸状”。30 MPa时，常温升至200℃,抗压强度增长了21.6%。200℃时，围压从0.1增至30 MPa,抗压强度增长了26.6%。研究结果可为深层致密砂岩钻井的钻前力学预测提供理论工具。更多还原

【Abstract】 Dense sandstone formation is a common difficult-to-drill section in oil and gas drilling, and its difficult-to-drill nature lies in the complex composition of rock minerals and dense cementation, coupled with the multiscale interaction of in situ temperature and pressure coupling in the endowment environment, which makes its mechanical characteristics more complex and difficult to be effectively characterized by existing experimental means. For this reason, starting from the fine-scale thermal expansion characteristics of the skeleton/cemented minerals, combined with the polycrystalline discrete element method, a non-homogeneous fine-scale mechanical modeling method considering the temperature effect was established and used to reveal its triaxial compression characteristics. The results show these as follows. Unlike the thermal expansion and contraction characteristics of skeleton minerals, the spacing of clay mineral grain surfaces shows irreversible thermal expansion with increasing temperature, which is the fundamental reason for the mechanical properties of locally strengthened dense sandstones; the thermal expansion of clay minerals increases the contact strength of intergranularity, and the localized densification makes the intergranularity more difficult to be damaged during triaxial compression, and the percentage of intragranular tensile cracks rises with the temperature; the compressive strength and elastic modulus of clay minerals increase with the temperature at room temperature～200 ℃, compressive strength and modulus of elasticity increases with temperature, the increase of peripheral pressure makes the elastic modulus growth trend from “lower convex” to “upper convex”. 30 MPa, room temperature to 200 ℃, the compressive strength increased by 21.6%. At 200 ℃, the compressive strength increased by 26.6% from 0.1 to 30 MPa. The results provide a theoretical tool for prediction of pre-drilling mechanics for drilling wells in deep dense sandstones.更多还原