Modern well testing is marked by the introduction of pressure derivative in analyzing well test data. The improvement of exploiting the shape and the particular points of the pressure derivative curve made a great progress in reservoir characterization and development. In certain circumstances the quality of measured pressure data can be affected by extern or intern noises. Consequently, errors may be amplified while computing pressure derivative and the out put data of the well and the reservoir such as wellbore storage, flow regimes, reservoir permeability, boundary limits can be unreliable.

This paper present a new method for reducing model error by adjusting the derivative pressure in cases of homogeneous and naturally fractured reservoirs. A WTS software is developed for providing permeability, skin factor and well bore storage for homogeneous reservoir and interporosity flow parameter and storage coefficient for naturally fractured reservoir as reliable as possible.

The formulation of numerical model of interpretation in this software is based upon Tiab's Direct Synthesis, where the boundary conditions of the newly developed algorithm to fit pressure derivative is adapted to Golub method. Some field applications on Hassi Messaoud Algerian oil reservoir are presented to illustrate the adjustment of pressure derivative for both cases homogeneous and naturally fractured systems.


The first research in the domain of well testing started in 1930. The conventional methods had been put into practice in thirties and were the only available methods till seventies. Horner1 presented in 1951 a new method to interpret Build Up test using semi-log technique. The use of type curve matching started in 1970 by Ramey2 who established the first type curves to overcome the shortcoming in case of not developed tests most significantly tests while drilling. In the same era other methods of type curve matching were developed by Agrawal and al. 3, Earlougher and al. 4...

The introduction of pressure derivative in 1975 by Tiab5 was marked the starting point of modern well testing. He demonstrated that the plot of pressure and its derivative in log-log plot is an important tool for identifying flow regimes and boundary limits. In eighties, Bourdet and al. 6 combined the pressure and its derivative with type curve matching for different reservoir models in order to improve the quality of well test interpretation. Although this improvement is recognized by analysts as a great progress however the method of matching still suffers from errors that can be shown on the non-unique solution. Horne7 showed that curve type matching in loglog plot is less efficient than conventional semi-log.

In nineties, Tiab8 introduced the so-called TDS "Tiab's Direct Synthesis" for interpreting well test data without recourse to type matching. Originalities of this technique can be pointed on the following points:

  1. Rapidity of data treatment,

  2. It provides a unique solution.

  3. It has means for verification, and.

  4. It provides facility to construct certain flow regimes while tests are not developed.

All these features can be directly handled without type curve matching.

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