Well Testing for Gas Condensate Reservoirs

Abstract

Abstract The analysis of well-testing pressure data obtained at a well producing a gas condensate reservoir is considered. It is assumed that a liquid bank forms in the vicinity of the well. Only radial flow problems are considered; thus, our objective is to find semilog analysis procedures that can be applied to our two-phase flow problem. The contributions and results of this research work can be summarized as follows: (i) We present theoretical results for drawdown and buildup semilog analysis equations based on the single-phase real gas pseudopressure of Al-Hussainy. (ii) A theoretical equation for the apparent skin factor observed during buildup is derived. The apparent skin factor is a linear combination of the mechanical skin factor and a pseudoskin factor due to the existence of a two-phase Zone near the wellbore. The value of the pseudoskin factor depends on the size of the liquid bank and the near-wellbore value of effective gas permeability with the two-phase Zone, (iii) It is shown that by combining results of drawdown and buildup analysis or by analyzing buildup data from a a modified isochronal test, we can separate the components of the skin factor, i.e., to determine the mechanical skin factor, the radial extent of the liquid zone and the average effective gas permeability within the liquid zone. The determination of the individual components is based on the theoretical equation for the buildup apparent skin factor.