Problems and possibilities with combined analyses of PLT and pressure-transient data from layered reservoirs are discussed, with standard single-layer methods used to estimate parameters, and model verification based on matches of available PLT and pressure-transient data used to complete analyses.

For commingled reservoirs it is shown that if the total flow capacity can be obtained from a direct analysis, then the flow capacity and skin of each layer from stable and short-time PLT profiles can also be obtained by simple two-rate methods. Assuming repeatability of the data, the PLT profile after shut-in can be determined from another test. Also, the rate of crossflow after shut-in relative to the production is shown not to be relevant for the success of this approach.

The main problem with layered-reservoir data is contrasts in skin values, both for commingled and crossflow reservoirs. With severe contrasts in skin values, analyses can become highly uncertain regardless of method used. This is shown by closedform approximations of infinite-acting solutions for commingled reservoirs and illustrated with synthetic data. A field case from the Norwegian sector of the North Sea has also been included to highlight the problems.

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