The article describes the optimizing of the gas field development system parameters. Optimization criterion is the net present value (NPV). Existing approaches are analyzed such as numerical integrated models using hydrodynamic simulators as a reservoir model; semi-analytical balance models based on the standard nonlinear flow equation to a gas well; the material balance equation and empirical correlations for calculating pressure losses in tubing lifts and surface arrangement. These approaches provide optimal solutions in particular cases, however, the design of a general solution to the optimization problem and the analysis of factors affecting the optimal values of the parameters of the development system is extremely difficult due to the significant time spent on calculations and relatively large number of variables. An analytical technical and economic model for the gas field development is proposed. The following assumptions are made: the gas is perfect; pseudo-stationary inflow of gas; properties of the reservoir are uniform over the area; condensate-gas factor is constant. Above listed assumptions let us to calculate a NPV value in analytical form. Cases outside boundaries of assumptions can be compensated by evaluating the range of optimal parameters of the development system corresponding to the range of input parameters. The main dimensionless control parameters were determined: coefficients of the gas well flow equation, cost of well construction, cost of transport and gas treatment infrastructure per unit of increase in throughput capability, wellhead pressure, limit of tubing head velocity. Optimization parameters are number of wells and dimensionless rate of production. The optimization problem of calculating optimal values of number of wells and dimensionless rate of production was solved for a wide range of control parameters. The solution is presented in a graphical form - values of the optimal parameters form dimensionless coefficients of the inflow equation. Dependences on the other dimensionless control parameters are presented in the form of analytical correlations obtained by deep analysis of optimization solutions.
Results of the work can be used to assess the optimal parameters of the gas field development system at the early design stages, to assess the sensitivity of the optimal parameters of the gas field development system to changes in the values of the most uncertain geological and economic parameters, as well as to assess the range of optimal parameters of the gas field development system to narrow the number of options planned for calculation on detailed numerical integrated models.
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