Approximately linear or exponential flow rate decline is often reported at the conventional DST or Flow Test.
At the present study, a new practical method based on theoretical considerations is brought forward for pressure build-up analysis in such cases. Its characteristic feature exists in plotting the observed pressure data vs the appropriate functions different from that of logarithmic type as in the conventional methods, which are derived, taking the flow period, shut-in period and decline rate into considerations, and the numerical values of which can be easily known on the prepared charts.
This new method provides with the simultaneous evaluation of prevailing reservoir pressure, transmissibility and flow decline rate, even though the last is previously unkown, and it seems to the author that better results can be obtained by the new method than by other conventional ones.
The evaluation of skin factor is also treated at the present study. As a matter of course, the skin factor formula for variable rate case differs from the conventional one for constant rate case and the accuracy of results by the latter is theoretically discussed. It is considered that the modification for the skin factor formula has its practical meaning especially at DST, because the final flow rate can't generally be known.
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