Pore-Scale Analysis of WAG & Development of a New Empirical Model Centre for Petroleum Studies Department of Earth Science and Engineering Imperial College London Vural Sander Suicmez Dr. Mohammad Piri Prof. Martin J. Blunt 20 January 2006

Motivation Pore Network Modelling (Fatt, 1956). Wide range of 3-phase flow scenarios. Improvement in computational power. A physically motivated three-phase relative permeability model (Blunt, 2000).

Outline Introduction to WAG What has already been done? (Piri and Blunt, 2005) Two- and three-phase pore-scale fluid configurations Displacement mechanisms New work on Cyclic Injection (WAG) New displacement mechanisms Validating the model Effects of Wettability A New Relative Permeability Model Isoperm Curves & Effect of Displacement Path Oil & Gas Trapping Conclusions

(Christensen et al., 1998) SPE 39833 What is the problem? (Christensen et al., 1998) SPE 39833

What do we have? Piri, 2004 A three-phase flow simulator (incorporating geologically realistic network model) with full extension of possible generic configurations for any wettability. A robust clustering algorithm incorporating coalescence and break of trapped clusters. Point-by-point comparison with data using saturation path tracking algorithm.

One- and Two-Phase Configurations Water Oil Gas

Three-Phase Configurations Water Oil Gas

Connectivity and Clustering (Hoshen & Kopelman, 1976) * Dead End Inlet Outlet Cluster is Connected Periodic Boundary Condition

Example Displacement Sequence Gas Water Oil Configuration B Configuration B Configuration A Primary Drainage Water Flooding Gas Injection Configuration F Configuration C Layer Collapsing Gas Injection Configuration A

Mobilising Oil by Double Displacement Water Oil Gas Trapped Oil

Multiple Displacements (Van Dijke & Sorbie, 2003) For a better connected network, double displacements are sufficient

Double Displacements Gas Injection Gas Oil Water Water Injection Gas Water Oil Water Injection Water Oil Gas Water Gas Oil Oil Injection Oil Gas Water Oil Water Gas

Model Validation (Oak, 1990) Water2 Gas1 Water1

Gas Relative Permeability

Oil Reconnection

Water Relative Permeabilty

Pore Occupancy

Oil/Water Capillary Pressure

Model Validation (Egermann et al, 2000) Spreading Oil Layers Water-Wet

Model Validation (Egermann et al, 2000) Water Gas

Gas Relative Permeability

Water Relative Permeability

Generic WAG Study (Strongly Oil-Wet) Spreading Oil Layers Strongly Oil-Wet

Generic WAG Study (Strongly Oil-Wet) Gas1 Gas2 Water1 Water2

Oil Relative Permeability

Gas Relative Permeability

Pore Occupancies

Krw Comparison

Kro Comparison

Oil Isoperm (Spiteri & Juanes, 2004) SPE 89921 Stone I Stone II

Oil Isoperm Water-wet Oil-wet

Displacement Path Water-gas Water-gas-water

Hydrocarbon Trapping (Jerauld, 1996) SPE 36178 weakly wat-wet water wet

Hydrocarbon Trapping

Conclusions Double displacement mechanism plays an important role in a water-wet system. Impact of WAG cycles on oil recovery lessened in an oil-wet medium. Gas behaviour is complex, depends whether it is the most non-wetting phase or not. Rel perms for different displacement paths are similar as a function of flowing saturation. Further work on oil and gas trapping is necessary.

Acknowledgments Shell Schlumberger Statoil BHP BG Saudi Aramco Eni We are thankful to the members of the Imperial College Consortium on Pore-Scale Network Modelling; Shell Schlumberger Statoil BHP BG Saudi Aramco Eni Total Japan Oil, Gas and Metals National Corp. (JOGMEC) Department of Trade and Industry (DTI) EPSRC