ABSTRACT
This work considers the analysis of pressure transient data obtained from a restricted-entry well under multiphase flow conditions. In particular, we examine the pseudoskin factor caused by partial penetration in a reservoir with multiple flowing phases.
Only the total skin factor, which is a linear combination of the mechanical skin factor due to damage or stimulation and the pseudoskin factor due to partial penetration, can be obtained directly from semilog analysis of pseudoradial flow pressure data. In order to obtain the true mechanical skin factor, an independent estimate of the pseudoskin factor due to to restricted entry is required.
The pseudoskin factor correlations of Yeh and Reynolds1 and Ding and Reynolds2 for a restricted-entry well completed in a multilayer reservoir are extended to obtain a new correlation for computation of the pseudoskin factor caused by a restricted-entry well in a reservoir with multiple flowing phases. An extensive set of two-phase (oil-water, gas-water, oil-gas) and three-phase (oil-gas-water) examples are presented and indicate this correlation yields accurate estimates of the pseudoskin factor.
Because this correlation is dependent upon the analysis of pressure transient data obtained under multiphase flow conditions, conditions under which such analysis can be performed and procedures for that analysis are discussed. A new semi-theoretical procedure for analyzing solution-gas systems in which free gas is produced at the sandface is presented. Numerical results for all of the multiphase systems considered in this study indicate that the common practice of approximating a gas cap or aquifer as a constant pressure boundary cannot be justified.
