Two-phase slug flows are characterized by alternating packets of liquid and large gas bubbles in pipelines. Slugs are associated with high pressure drops, having a stochastic nature, since the spatial distribution of phases induces local intermittency in the pipe cross section, which leads to the temporal variation of the flow parameters. When slugs are formed, gas bubbles are entrained into the slug front, altering the physical properties of the flow. The correct prediction of this type of flow is critical to the proper design of pipelines and separation equipment. Therefore, a numerical tool is very useful to assist in the design and operation of pipelines. Particularly in the oil industry, the multiphase flow occurs during the production and transport of fluids (oil, water, gas and solids) from the reservoirs. This study aims to model the entrainment of gas into a slug using a 1D Two Fluid Model, with the Finite Volume Method, enabling higher resolution of the flow characteristics. Different empirical correlations for rate of gas bubble entrainment available in the literature were tested. The effectiveness of the developed model was validated using empirical correlations for the average bubble fraction within the slug.