A Study on the Effect of Bottom-hole Differential Pressure on the Rock Stress Field

Abstract

Bottom-hole differential pressure is one of the most important factors that affects the drilling penetration rate. The purpose of the article is to study the effect of bottom-hole differential pressure on the vertical bottom-hole stress field. On the basis of mechanical analysis of the bottom-hole rock, the fluid-solid coupling model with the bottom-hole differential pressure is established under axisymmetry condition and is solved by using a numerical method. The comparison of the distribution of borehole wall stress between the numerical and theoretical solution is performed to verify the feasibility and rationality of the model. Then analysis of the stress state of the whole bottom-hole rock to break is carried out. The results show that the numerical solution is consistent with the theoretical solution and the fluid-solid coupling model is reasonable. With the increasing of the bottom-hole differential pressure, the bottom-hole tensile stress increases and compressive stress decreases and tensile region becomes larger. The whole bottom-hole rock to break is divided into three regions: triaxial tension region, biaxial compression and unidirectional tension region, and triaxial compression region. Qualitative and quantitative analysis of the bottom-hole stress field under different differential pressure provides the theoretical basis for rock breaking mechanism and faster and more efficient drilling.