| Title | PARAMETRIC AND STATISTICAL ANALYSIS OF STIMULATION OF GEOTHERMAL WELLS THRU DEFLAGRATION |
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| Authors | A. Aspiras, R. Archer, J. OSullivan |
| Year | 2018 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Geothermal stimulation, Permeability enhancement, Deflagration, Propellant stimulation |
| Abstract | Stimulation through deflagration aims to use the energy generated from the combustion of a propellant to enhance permeability of a feed zone by generating fractures around the well bore. Given the success of the technology in oil and gas industry, this study was conducted to check if the technique has potential in addressing geothermal permeability issues. Both the short and long-term enhancement of production were investigated. A radial model was developed using AUTOUGH2 and PyTOUGH to act as a deflagration simulator for testing different reservoir conditions and stimulation parameters. This simulator was satisfactorily calibrated to data from an actual well that had been deflagrated. Results showed that two-phase medium and high enthalpy reservoirs react more favorably to the deflagration stimulation compared to low enthalpy and vapour dominated reservoirs. In terms of sustainability, both the medium and high enthalpy reservoirs showed positive long-term permeability enhancement, while the vapour dominated and low enthalpy reservoirs returned to their pre-deflag conditions after less than five years of production. All cases showed a minimal change in enthalpy, indicating that deflagration does not significantly affect the enthalpy of the reservoir. This paper focuses on the first of two levels of analysis (Level 1), which investigates combinations of different permeability, reservoir pressure and temperature, wellbore pressure, productivity index, and number of shots to determine the conditions suitable for deflagration. The second level of analysis that tests the sensitivity and robustness of the scenarios by checking the varying effects of Permeability Enhancement Factor and Radius of Influence which are both a function of the size/volume of propellant and the breakability of the rock around the well, will not be discussed in this paper. |