Aside from liquid hydrocarbon, oil exploration also produces associated petroleum gas and wet gas. The use of associated petroleum and wet gas adversely affects gas turbine performance and gas line operation in several ways such as low gas quality, unstable heating value, and high H 2 S content. This research develops an integrated gas-combined heat and power optimal power flow with associated petroleum and wet gas utilization constraint. Thermodynamic equations are used to model gas turbine and gas network operation when subjected to low-quality fuels. To meet the fuel quality standard, additional constraints are considered. These constraints include the Modified Wobbe Index, a critical parameter for gas turbines, and H 2 S content, a critical parameter for pipelines. The results show that the proposed model can optimize combined heat and power cost by determining the most efficient power-steam dispatch, optimal fuel mixture and gas line pressure settings, while still meeting operational constraints.