Geomechanical Numerical Modeling of Well Wall in Underbalanced Drilling with Finite Difference Method in Flac ۲D

Well instability is one of the most fundamental challenges faced by the oil and gas industry. This imposes high annual costs for oil companies. Thus, well wall stability analysis is a gap to be filled in the oil industry. Collection of data on elements such as in-situ stress, reservoir and well pressure, mechanical rock properties and drilling fluid leads to the construction of a geomechanical numerical model, which will help in assessing the probable risks in futuredrilling. When a geomechanical model is designed, the magnitude and principal stress directions, pore pressure, and mechanical properties of the rock are determined at all points of the model. In this case, it is possible to investigate the amount of well instability as a function of weight and properties of drilling fluid. In this paper, the safe mud window was determined and the minimum and maximum mud pressures were determined in the ranges of ۷۰-۶۰ MPa and ۱۱۰-۱۰۰ MPa respectively in relation to different depths. A modeling of well stability in underbalanced drilling was made by entering the mechanical properties in FLAC software.