Recently, the development of tight oil reservoirs of PetroChina is mainly in the stage of large-scale production. Among them, hydraulic fracturing technology of horizontal well is a relatively very effective way to realize the economic development of unconventional oil and gas resources. The lack of systematic analysis and research on the overpressure mechanism of unconventional resources and the characteristics of wellbore stability has led to frequent occurrences of drilling accidents such as practical lost circulation, inflows, pack off and connection gas in horizontal well drilling operation. This greatly restricts the development and production of unconventional resources. In addition, the instability of the wellbore can easily lead to serious drilling complex accidents and greatly increase drilling costs. Among them, the geomechanical evaluation method is the focus of optimizing the drilling schemes. And accurate geomechanical models can provide technical support for drilling. On this basis, according to its reasonable optimization process measures to control potential drilling risks. Although the improvement and perfection of the evaluation method of geomechanical characteristics is a major focus of optimizing the drilling plan. However, one-dimensional geomechanics is often limited to the study of stress characteristics around the wellbore. As a result, it can't accurately characterize the distribution of its stress characteristics in three-dimensional space. Furthermore, the spatial overpressure distribution law is clarified, and the integrated research can carry out pre-drilling early warning, actual drilling tracking and post-drilling evaluation of horizontal wellbore stability. According to its research results, reasonable optimization of process measures to control potential drilling risks. Based on geomechanical research to optimize mud weight, thereby improving wellbore stability, and reducing the risks of drilling operation. The experience and knowledge gained from the research results of this study will provide guidance and reference for the efficient development of unconventional oil and gas reservoirs in other basins as much as possible.