Loading...

Gravity Drainage and Capillary Imbibition in Iranian Fractured Carbonate Reservoirs

Darvishi, Hamid Reza | 2010

912 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 42567 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Goodarznia, Iraj; Esmaeilzadeh, Fereidoon; kharrat, Riaz
  7. Abstract:
  8. Gravity Drainage and Capillary Imbibition are among the most important mechanisms in oil production from carbonate fractured reservoirs. In order to investigate the feasibility and effects of these mechanisms in oil recovery from carbonate cores, some different experiments were carried out at Sharif University Laboratories. Carbonate cores were taken away from the well-known Asmari outcrop, Asmari Mountain in south east of M.I.S. city and used in these experiments. Oil and gas samples were collected from field separators and recombined to reservoir composition. The Gas-Oil ratio was adjusted to obtain the reservoir fluid properties. A core flooding apparatus with various capabilities was designed and installed to run these experiments. This apparatus was equipped with a high pressure pump, core holder, air bath, temperature and pressure high accurate transmitters, gas amplifier, oil-gas separator, back pressure valve, and computer controlling panel. A number of free and forced imbibition tests at reservoir condition were carried out using cores with various permeability and porosity. First, one of the cores was selected for water flooding at injection rates of 0.1, 0.2, 0.5 cc/min at reservoir temperature and pressure. This test was also repeated for gas flooding. After flooding tests, five cores with different permeability and porosity were selected for free imbibition and gravity drainage tests. The recovery factor was between 54-59 percent for water flooding and 50-58 percent for gas flooding showing a relative improvement with increasing injection rate. The main reason for this recovery increase was due to higher capillary number resulting in a decrease in residual oil saturation and has been discussed in Conclusion section in more detail. The results of imbibitions showed that in addition to flooding, these tests are also feasible at laboratory conditions using small cores. The free imbibitions recovery factor was evaluated between 12-23 percent of original oil in place. Gravity drainage was observed on these cores, but there was no oil production even after two days. A five spot section of a real fractured carbonate reservoir simulation model were extracted to run water and gas flooding tests on it. The results of this simulation showed a recovery factor of 46 percent from water flooding which was close to core flooding results. The small decrease in recovery factor was for sweep efficiency which is lower with respect to linear flooding. In gas flooding of the five-spot pattern, the gas segregation phenomena was clearly realized resulting in a very low recovery. In evaluation of imbibition results, a dimensionless definition of time was introduced. A unique relationship for different cores could be attained by plotting the recovery factor versus the defined dimensionless time. From this relationship, it is possible to predict the behavior of free water imbibitions on large blocks at reservoir scale
  9. Keywords:
  10. Simulation ; Core Holder ; Amplification ; Fractured Reservoirs ; Imbibition Process ; Water Flooding ; Gravity Drainage Mechanism

 Digital Object List

 Bookmark

No TOC