The paper presents the integrated reservoir simulation and optimization results of two onshore gas fields. The fields are tied to common separator node, and have the similar gas in place volumes and production potentials. The optimal production plan for each field is the goal of the simultaneous development planning. Usually, separate field development plane does not consider surface facilities constraints, so overestimates the gas production amount and project lifetime. However, integrated "reservoir-well-pipeline".model allows to optimize the production system and reach the maximum gas production from each field. This paper presents the two gas field production optimization algorithm, also several development strategies with common production facility constraints are discussed with results. The optimal two-field simultaneous development plan is calculated on integrated computer model taking into account production system constraints.