* <math>\text{Change in gas volume} = (GB_{gi} - GB_g) + [N_p R_p (N - N_p) - NR_{si}] B_g</math> due to gas produced, evolved, and encroached from a gas cap | * <math>\text{Change in gas volume} = (GB_{gi} - GB_g) + [N_p R_p (N - N_p) - NR_{si}] B_g</math> due to gas produced, evolved, and encroached from a gas cap |