Separator design in petroleum engineering is so important because of its important role in the evaluation of optimum parameters and also to achieve to maximum stock tank liquid. However, no simulator exists that simultaneously and directly optimizes the parameters "pressure", "temperature", and so on. On the other hands, Commercial simulators fix one parameter and vary another parameter to achieve the optimum conditions. So, they need long-time simulation. Moreover, gas condensate reservoirs, like another reservoirs, have this problem as well. In present paper, a self-developed simulator applied in the optimized design of gas condensate reservoir's separators by determining optimized pressure, temperature, and number of separators in order to obtain maximized tank liquid volume and minimized tank liquid density utilizing Matlab software and other commercial simulators such as Aspen-Plus, Aspen-Hysys, and PVTi to do a comparison. Also, each software was separately tested with one, two, and three separators to obtain the optimum number of separators. Additionally, Peng-Robinson equation of state (PR EOS) has been applied in the simulation. For simulation input, a set of field data of gas condensate reservoir has been utilized, as well. The results show a good compatibility of this simulator with other simulators but in so little runtime (this simulator calculates the optimum pressure and temperature in a wide range of pressures and temperatures with the help of a simultaneous optimization algorithm in one stage) and the highest stock tank liquid is calculated with this simulator in comparison to other simulators. Also, with the help of this simulator, we are able to obtain the optimum pressure, temperature, and the number of separators in the gas condensate reservoir's separators with any desired properties. Finally, this simulator optimizes the temperatures for each separator and obtains very good results despite the other simulators that fix temperatures for all separators in most times.

Wells performance is evaluated by IPR curves that show the relationship between bottomhole pressure and inflow rate. This curve and its outcome equation can be applied for production schedule and maintenance management of well and reservoir. But, the measuring of bottomhole pressure to approach these curves needs much time and high expenses and also running special tools in wells. In these operations, the probability of catastrophic failure such as well damage or well complete lost may exist. However, these difficulties in offshore wells like production platform in the South Pars gas field that are installed tens kilometers far from lands are harder than any places. Therefore, nowadays by considering these difficulties, there is a high tendency for using wellhead test data that are very inexpensive as well as these data are less accurate than in well data. Moreover, pressure drop due to the existence of gas condensate in well fluid causes the flow regime to be more complicated. Wide researches have been applied to two-phase flow pressure drop in the wellbore and a lot of equations are considered. Anyhow, these equations and their accuracy should be studied in each special case. In this study that is on the south Pars gas condensate field wells, widespread of equations are utilized for calculation of pressure drop in the tubing and they are applied for tubing performance curve as well. In the south pars field wells, the well data of bottomhole pressure are not being measured during production. In this paper, we try to calculate bottomhole pressure by using PIPESIM software and simulating re-