Different variants of preconditioning of wet and associated petroleum gases and controlling the characteristics of the resulting fuel gases have been considered. Introduction of an additional step of preliminary oxidative conversion (prereforming) of natural and associated petroleum gases makes it possible to oxidize selectively the "heavy" low-octane components of a complex hydrocarbon mixture and obtain fuel gas for power plants with a high methane number and a required lower heating value. Fuel characteristics of the gases obtained via partial oxidation can be further improved by admixture of gas-piston engine exhaust gas in an amount of about 100 m(3)/1000 m(3) to the air-fuel mixture. The version of controlling the fuel characteristics of complex gas mixtures, as described in the paper, is characterized by simplicity of engineering design, high feedstock flexibility, and the possibility to create simple-to-use modular automated systems for conditioning hydrocarbon gases in small gas fields or fields distant far from power plants.