Wellbore dynamics are essential in reservoir testing, acting as a vital connection between the reservoir and surface measurements. This study addresses the challenges in well control and emphasizes the advantages of utilizing wellbore dynamic simulation to enhance the safety of formation tester (FT) sampling and deep transient tests (DTT). The research particularly focuses on pre-job simulations and multi-parameter sensitivity analysis to improve our understanding of how hydrocarbons interact with wellbore mud during and after FT pump-out operations, thereby addressing the critical challenges of well control in the oil and gas industry. FT typically involves the use of specialized tools to extract fluid samples from the formation, allowing for the analysis of pressure, temperature, and fluid properties. DTT, on the other hand, involves isolating a section of the wellbore and flowing fluids to the surface, providing real-time data on the reservoir's productivity. Both FT and DTT are complex operations that require precise control over various parameters to ensure accurate data collection and to avoid operational hazards. One of the most critical aspects of these operations is well control, which involves maintaining the balance between formation pressure and wellbore pressure to prevent uncontrolled fluid flow. Well control is particularly challenging during DTT due to the dynamic nature of the wellbore environment. Well control is a fundamental aspect of safe and efficient drilling operations. It involves managing the pressure in the wellbore to prevent kicks (influx of formation fluids) and blowouts (uncontrolled release of fluids). This paper examines 3 case studies that explore different types of hydrocarbons and overbalance conditions. In these cases, cloud-based wellbore fluid simulations were performed under various flow rate scenarios to predict potential well control issues. Emphasis is placed on near-critical hydrocarbon fluids, including condensate, volatile oil, and wet gas.