The analysis and interpretation of well test data usually depends on the assumptions of a constant reservoir flowrate and single phase flow in the reservoir. These assumptions are usually not valid for field data. This work proposes new methods to "correct" variable-rate pressure data to yield the pressure data that would have existed had the reservoir flowrate been constant. These methods are verified using analytical (single phase) solutions and are then applied to multiphase flow pressure-time data, rather than the more complex pseudopressure and pseudotime approaches.;These new "correction" methods were successfully applied to simulated data from homogeneous, naturally fractured, and vertically fractured reservoirs for both infinite and finite outer boundary conditions. The wellbore storage inner boundary condition was generally used, but in some cases specific rate schemes were also used. The error analyses obtained when these methods were applied to simulated data were excellent. Also, each of the new methods proposed has advantages over current methods in the literature. These advantages include speed, accuracy, and stability.;One practical problem encountered was the generally poor quality of the measured or calculated sandface flowrate data. The solution proposed in this work computes the sandface flowrate using the assumption of a wellbore storage inner boundary condition. Several schemes were developed and verified for the computation of the sandface flowrate.;In summary, this work presents new methods to correct pressure data from well tests where variable-rate flow conditions occur. Methods to compute the sandface flowrate were also developed and verified. Then these methods were successfully applied to field data where variable-rate, multiphase flow was observed.
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