SPE Journal
Volume 10, Number 4, December 2005, pp. 458-465

Summary

An approach was developed to extract the imbibition capillary pressure and the global mobility data from spontaneous water imbibition tests in oil/water/rock systems. Capillary pressure and global mobility data were calculated using this method with the experimental data of countercurrent spontaneous water imbibition tests in different rocks and at different interfacial tensions. The calculated capillary pressures were consistent with the change in interfacial tension. The oil/water/rock systems with greater interfacial tensions had greater capillary pressures. However the oil/water/rock systems with greater capillary pressure may not have greater imbibition rate. The calculated values of the global mobility and the imbibition index explain why the oil recovery or the imbibition rate in systems with high interfacial tension was smaller than that in systems with low interfacial tension, which has been considered a paradoxical result for many years.

Capillary pressure is of fundamental significance in reservoir engineering. Capillary pressure data are measured often using porous-plate, centrifuge, and mercury-injection techniques. These methods can suffer limitations in one or more aspects. For example, the porous-plate and centrifuge methods may have difficulty for core samples with a very low permeability; mercury intrusion technique cannot represent the true reservoir fluids. Spontaneous imbibition in porous media is a process dominated by the effect of capillary pressure. It would be useful if capillary pressure data could be extracted from spontaneous imbibition tests, because such tests are relatively simple, fast, and economical. Also, spontaneous imbibition tests are more representative of the fluid flow that happens in fractured reservoirs compared to the frequently used methods such as porous-plate, centrifuge, and mercury-injection approaches. However, it has been a challenge for a long time to extract capillary pressure from spontaneous imbibition tests.

© 2005. Society of Petroleum Engineers

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History

• Original manuscript received: 12 August 2003
• Revised manuscript received: 1 June 2005
• Manuscript approved: 4 August 2005
• Version of record: 15 December 2005