Since the birth of the oil industry, flaring has been used upstream to depressurize eruptive wells and downstream to burn excess gases in refining and petrochemical plants and also in associated and natural gas treatment plants. Unfortunately, flaring produces a great number of harmful by-products such as dangerous particles, volatile organic compounds, polycyclic aromatic and many other compounds just as harmful. The separation of gas and oil phases remains the most important stage in the so-called surface production. Given the high gas oil ratio (GOR) of Algerian crude oil, the separation of this gas is carried out in three or four stages. However, the choice of the optimal number of stages of separation and intermediate values of pressure requires a rigorous computation wherein the use of a simulator is more than necessary to make possible the optimization of the separation process. The present work was performed on a new separation and compression unit in an area where all the associated gas production is being flared despite the new environmental laws. Our approach consists of first simulating the separation process with the most appropriate thermo dynamical model. The intermediate separation pressure values can be determined by empirical correlations such as the method of equal pressure ratio. In our computations we have opted for a graphical method, specifically the method of minimum compression energy, that requires rigorous calculations entailing therefore the use of the Hysis simulator. This treated gas may be valorized as a raw material for the petrochemical industry or compressed and reinjected into the reservoir in order to maintain the rate of oil production. It remains that one important way of valorizing this associated gas is to transform it into liquid through a process known as gas to liquid (GTL) technology.