Abstract:Deep reservoir gas reserves are abundant. However, due to complex geological conditions, such as the development of holes and fissures, the existence of weak bedding surface and other factors, shaft wall instability has always hindered the safe and efficient exploitation of deep oil and gas reservoirs. A series of problems such as stuck drilling, well collapse and leakage caused by shaft wall instability will bring huge losses to the project. Therefore, it is very important to have a comprehensive understanding of the mechanism and research progress of borehole instability. In this paper, starting from the stability of borehole, the mechanical mechanism and development history are summarized. It is found that the development of weak bedding surface, multi-factor ground stress, rock physical and mechanical parameters, the existence of pore cracks and other factors are the main factors that lead to the weakening of mechanical strength and the instability of deep reservoir wall. For strata with weak bedding surface, the wellbore instability is more obvious, and the mechanical strength of rocks at different inclination angles is greatly different, and the rocks are more prone to hydration expansion along the bedding surface. Therefore, drilling engineering parameters and drilling fluid density should be reasonably optimized. This paper systematically summarizes the research of borehole stability mechanics and related aspects, in order to better understand the mechanical mechanism of deep reservoir borehole stability, and provide reference for practical production and engineering practice.
