QL1井井底突发性岩爆动力学机理及动态演化过程

氮气钻井钻遇致密砂岩高压裂缝圈闭导致井底岩爆是四川盆地西部白马庙构造QL1井恶性井喷事故的根本诱因。利用研究井壁失稳的理论方法来进行井底岩爆的动力学机理分析,并借助Visual Basic语言和Matlab软件编程,进行了岩爆的动态演化模拟。研究认为,当井底逐渐接近高压裂缝圈闭的过程中,裂缝面周向应力和径向应力差值逐渐增大,主应力之间的差值所引起的剪应力增长使裂缝面产生压剪破坏及压剪-拉伸复合破坏,直至破坏区连通井筒,高压气体携带大量碎屑喷入井内,释放大量能量,产生井底岩爆。该研究成果系统解释了QL1井录井监测参数的异常变化,其研究结果不仅可为岩爆的防治提供理论基础,而且在石油工程领域为深部岩体动力学失稳研究提供了一个新的视角。

Dynamic mechanism and dynamic evolution process of abrupt bottom-hole rock burst in Well QL1

Bottom-hole rock burst occurred in high-pressure fracture traps consisting of tight sandstones drilled in nitrogen drilling, basically resulting in the malignant blowout accident in Well QL1. The dynamic mechanism of bottom-hole rock burst was analyzed using the theoretical method for the study of wellbore instability, and the dynamic evolution simulation of rock burst was performed by means of Visual Basic and Matlab programming. The research suggests when the bottom hole is gradually approaching the high-pressure fracture trap, the difference between circumferential stress and radial stress of the crack face gradually increases, and the increasing shear stress caused by the difference between principal stresses leads to the compression-shear failure and the composite failure resulted from compression, shear and tension. Until the wellbore is communicated with the failure zone and the high pressure gas carrying plenty of debris is injected into the well, a large amount of energy is released to trigger bottom-hole rock burst. The research results systematically explain the abnormal changes of logging monitoring parameters in the well QL1. The results not only provide a theoretical basis for the prevention and control of rock burst, but also provide a new perspective for studying the dynamic instability of deep rock in the field of petroleum engineering.