[1] |
B. J. Bourblaux and F. J. Kalaydjian, “Experimental study of cocurrent and countercurrent flows in natural porous media,” SPE Reservoir Engineering, vol. 5, no. 3, pp. 361-368, 1990. |

[2] |
M. E. Chimienti, S. N. Illiano, and H. L. Najurieta, “Influence of temperature and interfacial tension on spontaneous imbibition process,” in Proceedings of the Latin American and Caribbean Petroleum Engineering Conference, vol. 53668, SPE, Caracas, Venezuela, April 1999. |

[3] |
M. Pooladi-Darvish and A. Firoozabadi, “Cocurrent and countercurrent imbibition in a water-wet matrix block,” SPE Journal, vol. 5, no. 1, pp. 3-11, 2000. |

[4] |
H. L. Najurieta, N. Galacho, M. E. Chimienti, and S. N. Illiano, “Effects of temperature and interfacial tension in different production mechanisms,” in Proceedings of the Latin American and Caribbean Petroleum Engineering Conference, vol. 69398, SPE, Buenos Aires, Argentina, 2001. |

[5] |
G. Q. Tang and A. Firoozabadi, “Effect of pressure gradient and initial water saturation on water injection in water-wet and mixed-wet fractured porous media,” SPE Reservoir Evaluation and Engineering, vol. 4, no. 6, pp. 516-524, 2001. |

[6] |
R. W. Parsons and P. R. Chaney, “Imbibition model studies on water-wet carbonate rocks,” SPE Journal, pp. 26-34, 1966. |

[7] |
R. Iffly, D. C. Rousselet, and J. L. Vermeulen, “Fundamental study of imbibition in fissured oil fields,” in Proceedings of the Annual Technical Conference, vol. 4102, SPE, Dallas, Tex, USA, 1972. |

[8] |
G. Hamon and J. Vidal, “Scaling-up the capillary imbibition process from laboratory experiments on homogeneous samples,” in Proceedings of the SPE European Petroleum Conferenc, vol. 15852, London, UK, October 1986. |

[9] |
S. Al-Lawati and S. Saleh, “Oil recovery in fractured oil reservoirs by low IFT imbibition process,” in Proceedings of the Annual Technical Conference and Exhibition, vol. 36688, SPE, Denver, Colo, USA, 1996. |

[10] |
J. C. Reis and M. Cil, “A model for oil expulsion by counter-current water imbibition in rocks: one-dimensional geometry,” Journal of Petroleum Science and Engineering, vol. 10, no. 2, pp. 97-107, 1993. |

[11] |
T. Babadagli, “Scaling of cocurrent and countercurrent capillary imbibition for surfactant and polymer injection in naturally fractured reservoirs,” SPE Journal, vol. 6, no. 4, pp. 465-478, 2001. |

[12] |
D. Zhou, L. Jia, J. Kamath, and A. R. Kovscek, “Scaling of counter-current imbibition processes in low-permeability porous media,” Journal of Petroleum Science and Engineering, vol. 33, no. 1-3, pp. 61-74, 2002.
· doi:10.1016/S0920-4105(01)00176-0 |

[13] |
M. F. El-Amin and S. Sun, “Scaling of a two-phase countercurrent imbibition using characteristic velocity,” Transport in Porous Media. Submitted. |

[14] |
N. R. Morrow and G. Mason, “Recovery of oil by spontaneous imbibition,” Current Opinion in Colloid and Interface Science, vol. 6, no. 4, pp. 321-337, 2001.
· doi:10.1016/S1359-0294(01)00100-5 |

[15] |
D. Kashchiev and A. Firoozabadi, “Analytic solutions for 1D countercurrent imbibition in water-wet media,” SPE Journal, vol. 8, no. 4, pp. 401-408, 2003. |

[16] |
Z. Tavassoli, R. W. Zimmerman, and M. J. Blunt, “Analytic analysis for oil recovery during counter-current imbibition in strongly water-wet systems,” Transport in Porous Media, vol. 58, no. 1-2, pp. 173-189, 2005.
· doi:10.1007/s11242-004-5474-4 |

[17] |
D. Silin and T. Patzek, “On Barenblatt’s model of spontaneous countercurrent imbibition,” Transport in Porous Media, vol. 54, no. 3, pp. 297-322, 2004.
· doi:10.1023/B:TIPM.0000003678.85526.b1 |

[18] |
H. S. Behbahani, G. D. Donato, and M. J. Blunt, “Simulation of counter-current imbibition in water-wet fractured reservoirs,” Journal of Petroleum Science and Engineering, vol. 50, no. 1, pp. 21-39, 2006.
· doi:10.1016/j.petrol.2005.08.001 |

[19] |
D. Wilkinson, “Percolation model of immiscible displacement in the presence of buoyancy forces,” Physical Review A, vol. 30, no. 1, pp. 520-531, 1984.
· doi:10.1103/PhysRevA.30.520 |

[20] |
N. Bech, O. K. Jensen, and B. Nielsen, “Modeling of gravity-imbibition and gravity-drainage processes: analytic and numerical solutions,” SPE Reservoir Engineering, vol. 6, no. 1, pp. 129-136, 1991. |

[21] |
Z. Tavassoli, R. W. Zimmerman, and M. J. Blunt, “Analysis of counter-current imbibition with gravity in weakly water-wet systems,” Journal of Petroleum Science and Engineering, vol. 48, no. 1-2, pp. 94-104, 2005.
· doi:10.1016/j.petrol.2005.04.003 |

[22] |
G. Løvoll, Y. Méheust, K. J. Måløy, E. Aker, and J. Schmittbuhl, “Competition of gravity, capillary and viscous forces during drainage in a two-dimensional porous medium, a pore scale study,” Energy, vol. 30, no. 6, pp. 861-872, 2005.
· doi:10.1016/j.energy.2004.03.100 |

[23] |
H. Karimaie and O. Torsæter, “Effect of injection rate, initial water saturation and gravity on water injection in slightly water-wet fractured porous media,” Journal of Petroleum Science and Engineering, vol. 58, no. 1-2, pp. 293-308, 2007.
· doi:10.1016/j.petrol.2007.02.002 |

[24] |
D. W. Ruth, Y. Li, G. Mason, and N. R. Morrow, “An approximate analytical solution for counter-current spontaneous imbibition,” Transport in Porous Media, vol. 66, no. 3, pp. 373-390, 2007.
· doi:10.1007/s11242-006-0019-7 |

[25] |
D. Silin, T. Patzek, and S. M. Benson, “A model of buoyancy-driven two-phase countercurrent fluid flow,” Transport in Porous Media, vol. 76, no. 3, pp. 449-469, 2009.
· doi:10.1007/s11242-008-9257-1 |

[26] |
S. Akin and A. R. Kovscek, “Imbibition studies of low-permeability porous media,” in Proceedings of the Western Regional Meeting, vol. 54590, SPE, Anchorage, Ala, USA, May 1999. |

[27] |
J. Cai, B. Yu, M. Zou, and L. Luo, “Fractal characterization of spontaneous co-current imbibition in porous media,” Energy and Fuels, vol. 24, no. 3, pp. 1860-1867, 2010.
· doi:10.1021/ef901413p |

[28] |
M. F. El-Amin and S. Sun, “Effects of gravity and open-boundary location on a two-phase countercurrent imbibition in porous media,” Journal of Porous Media. Submitted. · Zbl 1213.76191 |

[29] |
Z. Chen, Reservoir Simulation: Mathematical Techniques in Oil Recovery, SIAM, Philadelphia, Pa, USA, 2007. · Zbl 1167.86001 |