I. Introduction The ever - increasing energy demand makes the development of deep - seated reservoir oil and gas reservoirs increasingly important. However, the complex geological conditions and engineering factors in deep - seated strata bring great challenges to drilling engineering. Among them, the problem of wellbore instability seriously affects the safety and efficiency of drilling, causing a series of problems such as pipe sticking, well collapse and well leakage, and causing huge losses to drilling engineering. Therefore, in - depth research on the wellbore instability mechanical mechanism in deep - seated bedded weak - plane reservoirs has important theoretical and practical significance.
II. Analysis of Wellbore Instability Mechanism in Deep - seated Strata The wellbore instability mechanism is complex and mainly related to rock mechanical characteristics, formation stress state, drilling fluid action and other aspects. In deep - seated strata, the formation pressure is high and the temperature is high, and the rock mechanical properties change significantly, which increases the risk of wellbore instability. Moreover, the bedded weak - planes in the formation will reduce the rock strength and make the wellbore more prone to instability.
III. Research on Characteristics of Deep - seated Bedded Strata Research on Physical Characteristics of Deep - seated Strata The physical characteristics of deep - seated strata (such as density, porosity, permeability, etc.) are significantly different from those of shallow - seated strata. The changes of these characteristics will affect the rock mechanical behavior and then affect the wellbore stability. Research on Mechanical Characteristics of Deep - seated Strata The mechanical characteristics of deep - seated strata (such as elastic modulus, Poisson's ratio, compressive strength, etc.) are different from those of shallow - seated strata. In a high - temperature and high - pressure environment, the rock mechanical characteristics will be softened and weakened, which makes the wellbore instability problem in deep - seated strata more serious. Rock Mechanics Constitutive Equation of Bedded Weak - plane The bedded weak - plane is an important feature of deep - seated bedded strata, and its influence on rock mechanical behavior cannot be ignored. Establishing the rock mechanics constitutive equation of bedded weak - plane can better describe its mechanical characteristics and provide a theoretical basis for studying wellbore instability.
IV. Research on Wellbore Stability under Multi - field Coupling Mechanics - Chemistry Research Theory The mechanics - chemistry coupling effect is of great significance in the wellbore instability of deep - seated bedded weak - plane reservoirs. The hydration of rocks will reduce their mechanical strength and increase the risk of wellbore instability. Therefore, studying the mechanics - chemistry coupling action mechanism is important for understanding the wellbore instability mechanism. Evaluating Wellbore Stability under Multi - field Coupling Multi - field coupling includes the multi - field interactions such as mechanical field, temperature field and chemical field. Establishing a multi - field coupling model can comprehensively consider the influence of various factors on wellbore stability, so as to more accurately evaluate wellbore stability.
V. Conclusions and Prospects This paper systematically summarizes the research progress on wellbore instability mechanics in deep - seated bedded weak - plane reservoirs, and reveals the influence mechanism of factors such as the development of bedded weak - planes on wellbore instability. However, there are still some deficiencies in the current research, such as the insufficient in - depth research on the wellbore instability mechanism under complex geological conditions, and the accuracy of the multi - field coupling model needs to be improved. Future research should further strengthen the research on the wellbore instability mechanism under complex geological conditions, improve the accuracy and reliability of the multi - field coupling model, and provide stronger theoretical support and technical guarantee for the safe and efficient exploitation of deep - seated bedded weak - plane reservoirs.