Loading...

Mathematical Modeling of Diffusion in Fractured Media for Gas Injection

Saki, Mohammad | 2012

726 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43324 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Masihi, Mohsen; Shadizadeh, Reza; Ayatollahi, Shahabeddin
  7. Abstract:
  8. It is common to inject gas in naturally fractured reservoirs to maintain the reservoir pressure. Recovery will be the result of the complex interplay of several mechanisms such as viscous flow, extraction by molecular diffusion, gravity drainage, oil swelling and capillary force. Generally the main mechanism is gravity drainage However in many cases like low permeability of matrix, small matrix block size and high capillary pressure; gravity drainage may be very low or ineffective. Low permeability results inefficient viscous displacement too. Therefore in these cases the main mechanism is diffusion. The parameters influences the diffusion are: The nature of the injected gas, the composition of the oil in place, the presence of water, the fracture intensity, The rate of injected gas and The geometry of matrix blocks. The main objective of this study is to develop a mathematical model which describes the mass transfer between a gas flowing in the fracture and resident fluid in a matrix block. The injected gas diffuses into the porous matrix through gas and liquid phases causing the vaporization of oil in the porous matrix which is transported by convection and diffusion to the gas flowing in the fracture. Mass transfer between the fracture and the matrix is assumed to occur by diffusion mass transfer and fluid flow between the matrix and the fracture. The model most be accounts for diffusion and convection mechanisms in both gas and oil phases in the porous matrix. In this study, initially four different models are proposed and the system is simulated by them separately. Then the results are compared to the data extracted from PHD dissertation of Jamili (2010), the experiment of nitrogen injection into the fracture whenever the core is saturated with binary compound of methane and n-pentane. Finally the best model is selected that was fourth model. The simulation of the systems of 1D, two phase, three component and 1D, two phase, four component and 1D, three phase, three component and 2D, two phase, three component are done successfully. The results are given by the simulations shows that the molecular diffusion is a main mechanism and play an important role in recovery in the case of tight and small matrix block size that is saturated by light and intermediate hydrocarbons.
  9. Keywords:
  10. Gas Injection ; Simulation ; Fractured Reservoirs

 Digital Object List

 Bookmark

No TOC