The leakages in pipelines have been raising serious environmental concerns; various systems have been developed to detect leakages in a pipeline. Hence, there is a need for early leakage detection, as well as a leakage prevention system. A detailed analysis of two-phase flows using transient modeling prior to leak detection using transient modeling is much required. This paper focuses on validating the two-phase flows using transient modeling with the help of OLGA, a multiphase software. The software was able to validate both steady-state pressure drop calculations and transient simulations in two-phase flows using a black oil model. A pipeline with 18,000 ft length with varying various other parameters such as inlet flow rates, diameters, and Gas Liquid Ratio (GLR) are studied and validated. The validation was based on the study which was analyzed for the purpose of operating and planning of new oil field in Saudi Arabia. The current paper was able to validate the study both in steady-state and transient flow simulations. © Institute of Technology PETRONAS Sdn Bhd (Universiti Teknologi PETRONAS) 2024.