| For a gas well at the center of a circular reservoir, the use of pseudo-pressure and either pseudotime or normalized time, adequately linearizes the gas flow equation. Thus, accurate estimates of permeability, skin factor and average reservoir pressure can be obtained from a buildup test. Because of the non-linearity of the gas equation, however, superposition used in the analysis of the buildup test data for a gas well has to be verified for reservoir geometries other than circular.;By analyzing pressure data generated by a numerical simulator, Homer plots, using pseudo-pressure and modified Horner times, and MDH graphs, using pseudo-pressure and modified MDH times, provide accurate estimates of permeability, skin factor and average reservoir pressure for a well situated in a closed, rectangular reservoir.;Buildup data from a gas reservoir containing gas contaminants can be accurately analyzed using pseudo-pressure and either modified Horner time ratios or MDH times, provided that the gas properties used are corrected for the presence of the contaminants. Failure to correct for the contaminants significantly affects the accuracy of the estimate for permeability.;The time to the end of the semi-log straight line on Horner and MDH plots is approximately the same for the gas and liquid flow. The correlations developed for the liquid flow can be used as a guideline to estimate the time to the end of the semi-log straight line for the gas flow. |
