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The AAPG/Datapages Combined Publications Database

Indonesian Petroleum Association


25th Annual Convention Proceedings (Volume 2), 1996
Pages 137-149

Multi-Layer Test Analysis for Dissolved Gas Reservoirs

W. Jatmiko, T. S. Daltaban, J. S. Archer


This research investigates the performance of a well under multi-phase flow conditions when the reservoir pressure falls below the bubble point pressure. In this paper, the performance of dissolved gas reservoirs is studied. The reservoir consists of a two-layer commingled system, where the test production comes from a fully perforated interval. The water phase is assumed immobile. The main objective of this study is to interpret the flowing well pressure response and predict the reservoir character based on its performance.

This method proposes procedures to predict transient pressure and saturation distributions by applying the line source solution and a pseudopressure function from a drawdown test. This function relates reservoir pressure and saturation, and hence the governing equation can be solved analytically. Once the pressure distribution is obtained, the two-phase flow region can be identified by comparing the radial pressure distribution with the bubble point pressure. The wellbore saturation is calculated from the flowing pressure data. The saturation distribution within the two-phase flow region is then determined using a quadratic equation. Several iterative procedures will be used until the material balance error agrees within the specified tolerance.

This method has been tested using simulated data obtained from a numerical simulator. In general the analytical solutions agree with the simulated data. Compared with the numerical simulator, this method has reduced the cpu time significantly. This method can be used to determine the reservoir capacity (k.h) from multi-phase well testing during the early life of reservoirs.

One of the important contributions of this method is its ability to estimate the in-situ two phase flow boundary dynamically because this boundary keeps expanding with continuously decreasing reservoir pressure. In this way, it is now possible to determine the radius of investigation to which the derived multi-phase characteristics correspond.

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