Loading...

Mathematical Modeling of Molecular Diffusion for Gas Injection of Fractured Gas Condensate Reservoir – Single Block Approach

Kazemi Nia Korrani, Aboulghasem | 2009

945 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39936 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ghotbi, Cyrus; Gerami, Shahab; Hashemi, Abdonabi
  7. Abstract:
  8. Gas condensate reservoirs show very complex behavior as wellbore pressure falls below the reservoir fluid dew point pressure and consequently liquid phase appears near the wellbore. Since pressure drawdown is the largest near the wellbore, therefore, this region is the first that experience the liquid dropouts. With continuing the production, reservoir pressures at the other parts of the reservoir fall below the dew point pressure and as a result, condensate appears at these regions. The more the condensate accumulates near the wellbore the more decreasing the gas relative permeability occurs. Condensate accumulating does as a liquid barrier and causes not only decreasing the gas production; but also causes remaining of the most significant part of the fluid in the reservoir. Gas condensate reservoirs are often simulated with multi-component and multi-phase simulators. In the other hand, fractured reservoir pressure behavior with their complexities has gained wide interest in the petroleum industry during the last few decades and poses a challenge for the reservoir modelers. The presence of a retrograde gas-condensate fluid incorporates an additional layer of complexity to the fractured reservoirs in such a way that the study of naturally fractured gas condensate reservoirs inherently brings together one of the most complex thermodynamic and hydrodynamic phenomena in the solution domain. When production starts from a gas condensate fractured reservoir; depletion results due to fluid withdrawal. The fracture network and the external edges of the matrix blocks are prone to subject to faster depletion and one can say that condensate dropout will occur in the fracture network first and then in the external edges of the matrix block. In fractured reservoir with tight matrix blocks, significant pressure difference occurs between fracture gas and matrix block gas; which eventually results to significant concentration difference or diffusive flow between two these medium gases in condensate fluids. Therefore, it is believed that the interplay of the Darcian-flow and Fickian-flow (multi-mechanistic flow) is the key to answer the questions about depletion performance and ultimate recovery in these reservoirs. As the entire fractured reservoir is depicted as a stack of several single blocks of matrix rock, ultimate recovery is controlled by the behavior of each of the single matrix block in the stack. The objective of this study is the development of numerical simulator that can capture the dominant flow processes and recovery mechanism in the injection of natural gas in gas condensate fractured reservoirs. The results show that, in natural gas injection into gas condensate fractured reservoirs; the contribution of Fickian flow can largely surpass the Darcian flow when the matrix block permeabilities are less than 0.01 md in the case of one phase flow. This occurs in the fractured reservoirs with the matrix block permeabilities of one greater order of magnitude (i.e., less 0.1 md) in the case of two-phase flow; which is also one order of magnitude greater than that of when natural depletion occurs in the gas condensate fractured reservoirs. In addition, simulation results show that the greater the diffusion coefficient the greater the pressure pulse speed in the reservoir. Fracture permeabilities of greater than 500 md don’t affect the molecular diffusion at all and for fracture permeabilities of less than 500 md this effect is no more important that can be ignored.

  9. Keywords:
  10. Gas Condensate Reservoirs ; Relative Permeability ; Fractured Reservoirs ; Dew Point Pressure ; Molecular Diffusion ; Multi Mechanistic

 Digital Object List

  • محتواي پايان نامه
  •   view

 Bookmark