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Pressure Transient Analysis of Variable-rate Well Test Data

Mansoori Habib Abadi, Mehdi | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 48245 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Rashtchian, Davood; Van den Hof, Paul; Jansen, Jan Dirk
  7. Abstract:
  8. This study presents a novel perspective on pressure-transient analysis (PTA) of downhole-pressure and flow-rate data by use of system-identification (SI) techniques as widely used in advanced process engineering. Key features of the algorithm are that it considers the classic PTA process from a system-theoretical perspective; derives the causal structure of the flow dynamics; proposes a method to deal with continuously varying pressure and flow-rate signals contaminated with correlated noise, which estimates physical reservoir parameters through a systematic matching procedure in the frequency domain; and can cope with arbitrary (i.e., not necessarily piecewise constant) flow-rate signals. To this end, the wellbore and the reservoir are modeled as two distinct two-port power-transmitting systems that are bilaterally coupled at their common boundary. This structure reveals that, from an SI perspective, the wellbore dynamics affect the bottomhole data as a feedback mechanism. Because of this feedback structure, it is necessary to use closed-loop SI techniques, and, because of the presence of sensor noise, the reservoir model cannot be identified solely from the bottomhole measurements. Therefore, an auxiliary signal is needed. For different auxiliary signals, the suitable closed-loop SI technique has been developed. Thereafter, the usual physical reservoir parameters (e.g., averaged permeability and skin factor) are obtained through matching the results of the identified reservoir model and those of typical analytical reservoir models in the frequency domain. Numerical experiments, by use of a synthetic data set, and field examples, by use of data from a real gas well, illustrate the key aspects of the proposed methods. Regarding the successful results of the SI algorithm on the data with variable flow rate, the possibility of experiment design for estimating the porous media properties on a core scale has also been investigated that shows acceptable results
  9. Keywords:
  10. Well Testing ; Experimental Design ; System Identification ; Deconvolution ; Reservoir Pressure Transient Respons ; Causal Structure

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