A computer-implemented method of identifying a plurality of operating points for an oil and/or gas producing system, the oil and/or gas producing system comprising a well, a flow line and riser unit and a separator unit, said well, flow line and riser unit being arranged to output fluid to said separator unit on the basis of a plurality of independent variables and the separator unit being arranged to separate liquid and gas from the fluid output thereto, wherein operation of the oil and/or gas producing system is simulated by means of a producing system model, the producing system model being arranged to generate values for a plurality of dependent variables corresponding to pressure and/or flow rates achieved by respective units of the oil and/or gas producing system under control of said independent variables, the method comprising: generating one or more sets of values of said independent variables corresponding to one or more operating points, respectively; performing a process in respect of said generated one or more sets of values of independent variables, the process comprising: operating the producing system model in accordance with each set of values of independent variables so as to generate a corresponding set of values of said dependent variables; for each set of values of dependent variables, evaluating the values of at least one of said dependent variables in accordance with a predetermined evaluation criterion, a value of the evaluation criterion being included in the set of dependent variables; storing the evaluated set of values of dependent variables in association with the corresponding set of values of independent variables; using the evaluated set of values of dependent variables to generate one or more further sets of values of said independent variables and applying the process to the one or more further sets of values of said independent variables; and repeating the process for successively generated further sets of values of independent variables until a predetermined criterion has been reached; characterized in that the process further comprises the steps of: forming an operability map using stored sets of independent variables and corresponding sets of dependent variables; and selecting one or more potential operating points from the operability map and/or a preferred path to manoeuvre between operating points. generating one or more sets of values of said independent variables corresponding to one or more operating points, respectively; performing a process in respect of said generated one or more sets of values of independent variables, the process comprising: operating the producing system model in accordance with each set of values of independent variables so as to generate a corresponding set of values of said dependent variables; for each set of values of dependent variables, evaluating the values of at least one of said dependent variables in accordance with a predetermined evaluation criterion, a value of the evaluation criterion being included in the set of dependent variables; storing the evaluated set of values of dependent variables in association with the corresponding set of values of independent variables; using the evaluated set of values of dependent variables to generate one or more further sets of values of said independent variables and applying the process to the one or more further sets of values of said independent variables; and repeating the process for successively generated further sets of values of independent variables until a predetermined criterion has been reached; characterized in that the process further comprises the steps of: forming an operability map using stored sets of independent variables and corresponding sets of dependent variables; and selecting one or more potential operating points from the operability map and/or a preferred path to manoeuvre between operating points. operating the producing system model in accordance with each set of values of independent variables so as to generate a corresponding set of values of said dependent variables; for each set of values of dependent variables, evaluating the values of at least one of said dependent variables in accordance with a predetermined evaluation criterion, a value of the evaluation criterion being included in the set of dependent variables; storing the evaluated set of values of dependent variables in association with the corresponding set of values of independent variables; using the evaluated set of values of dependent variables to generate one or more further sets of values of said independent variables and applying the process to the one or more further sets of values of said independent variables; and repeating the process for successively generated further sets of values of independent variables until a predetermined criterion has been reached; characterized in that the process further comprises the steps of: forming an operability map using stored sets of independent variables and corresponding sets of dependent variables; and forming an operability map using stored sets of independent variables and corresponding sets of dependent variables; and selecting one or more potential operating points from the operability map and/or a preferred path to manoeuvre between operating points.