Is there a way to MATHEMATICALLY ensure that the liquid and gaseous phases of the hydrocarbon remain in "THERMODYNAMIC EQUILIBRIUM", when the reservoir pressure falls below Bubble Point Pressure during a water flooding (or Secondary Oil Recovery)?

Despite the known fact that

(a) the mass exchange will take place between the liquid and gaseous phases of the hydrocarbon (during secondary recovery);

and

(b) the number of phases and the composition of each phase for all the concerned chemical species will depend on the thermodynamic conditions and the overall concentration of each species (during tertiary recovery).