热采环境泥岩热-流-力耦合破裂行为试验与理论研究

Mudstone interbeds in heavy oil reservoir severely hampered normal expansion of steam chamber and effective recovery of heavy oil in thermal recovery technology (steam assisted gravity drainage), especially in western oil field of China, which has a great heavy oil reserve. Field trials found that the temperature and pressure in thermal recovery process can promote mudstone interlayer failure, improving heavy oil recovery. Based on this, this study intends to investigate the failure behavior of mudstone in thermal recovery process through physical experiments and theoretical analysis, within the framework of mechanics considering the interaction between temperature, pore pressure, stress and failure. The main contents include: (1) Based on the similarity theory, test of mudstone is carried out and the failure characteristics in thermal recovery process are studied; (2) Based on high-temperature high-pressure triaxial tests of mudstone samples, a thermo-hydro-mechanical-damage model describing the failure evolution of mudstone is established; and the transfer of temperature, pressure and stress in thermal recovery process is studied. (3) By combining numerical simulation and physical tests, the failure mechanisms of mudstone in thermal recovery process are revealed. This study helps us to understand the phenomenon of thermal failure in thermal recovery process, providing experimental and theoretical basis for thermal recovery optimization and other related engineering problems.

复杂稠油储层中的泥岩夹层严重阻碍了蒸汽驱界面（蒸汽腔）的扩展和原油的有效动用，是我国西部稠油油藏注蒸汽热采（蒸汽辅助重力驱）开发面临的主要问题。现场试验发现，某种热采温度压力环境可促进泥岩夹层破裂，改善稠油开发效果。基于此，本项目拟在综合考虑温度、孔隙压力、应力与破裂相互作用关系的力学框架体系内，采用物理试验与理论分析相结合的方法系统研究泥岩在热采环境中的破裂行为。主要研究内容包括：（1）基于相似理论，开展泥岩热破裂物理模拟试验，还原泥岩在热采环境下的破裂行为；（2）基于高温高压三轴岩石力学试验，建立泥岩的热-流-力-损伤耦合数学模型，模拟热破裂过程泥岩的温度场、压力场及应力场转移规律；（3）综合物理相似试验与数值模拟，揭示泥岩在热采环境下的破裂机理。本项目研究成果有助于深入认识泥岩在热采环境中的破裂现象，为稠油热采方案优化及相关工程问题研究提供试验及理论依据。

研究泥岩在热采环境下的热-流-力耦合破裂规律及机理，有助于深入认识热采油藏中泥岩层的破裂行为，从而制定合理的注汽方案，对于避免泥岩盖层的完整性破坏、打通泥岩隔夹层渗流通道，提高稠油油藏开发效果具有重要意义。本项目采用理论分析、室内物理试验与细观数值模拟相结合的方法系统的研究泥岩在热采环境中的力学性能和破裂特征，获取了与泥岩破裂行为相关的关键力学参数，还原了热采工况下泥岩从细观损伤到宏观破裂的全过程，定量分析了围压、温度、升温速度等因素对热破裂的影响。在此基础上，综合考虑温度、孔隙压力、应力与泥岩破裂之间的相互作用关系，应用损伤力学、热力学和渗流力学理论，建立了描述泥岩热破裂过程的热-流-力-损伤耦合数学模型，采用MATLAB与COMSOL联合仿真方法模拟热采工况下泥岩层的破裂演化过程，定量分析了泥岩破裂过程中温度场、压力场、应力场及破裂带的时空演化规律及相互作用关系，揭示了热采环境泥岩的破裂机理。