A new simplified fully implicit compositional simulator has been developed. This simulator is different from existing models because it combines the conventional black oil equations with a compositional injection component equation. Sets of two dimensional pvt and injection component K value tables at constant pressure and variable mole fraction injection component are generated using a cubic equation of state used in the compositional simulator. The data are generated from a series of cells loaded with the initial composition of the reservoir. Pore volume increments of injection gas are cycled through the cells in sequence, with oil and gas volumes passing downstream in proportions calculated by the relative permeability curves. This pvt test replicates a one dimensional compositional cycling process at fixed pressure. The resulting data describes a unique compositional path through the phase diagram for constant pressure and variable mole fraction injection gas, and this path is independent of cell position in the simulator. The simulator runs at speeds that far exceed the speeds in current compositional simulators, primarily because the speed is independent of the number of components. Small problems with several hundred cells typically run about 10 times faster, and larger speed increases are realized for bigger problems. The simulator has been tested successfully for gas cycling projects including the Third SPE Comparative Solution Project and CO2 flooding projects. Results for constant and variable pressure cycling, with and without vertical crossflow were in good agreement with a compositional model.