- This paper addresses the problem of treating the pressure-sensitive viscosity/compressibility ( mu C//t) product while analyzing the prefracture test data. A large variation of mu C//t with pressure occurs in a typical low-flow capacity (kh) well. These pressure-sensitive gas properties lead to a nonlinear gas flow equation. Use of the pseudopressure function partially linearizes the gas flow equation, while introduction of pseudotime and pseudopressure functions causes the complete linearization. This linearization permits a valide type-curve analysis. However, a semianalytical solution of the diffusivity equation that considers only the pseudopressure function suggests that the problem of nonlinearity is insignificant. We show that both the contentions presented in the literature are correct: complete linearization is required when the data are affected by wellbore storage, whereas partial linearization is quite adequate for a valid semilog analysis.