Matrix-fracture interface cleanup protocol for tight sandstone and carbonate reservoirs

In tight sandstone and carbonate reservoirs, the hydrocarbon recovery is mainly governed by the matrixfracture interface mass transfer efficiency. To improve the matrix-fracture interface mass transfer in tight sandstone and carbonate reservoirs, we propose the following protocol to clean up the matrix-fracture interface and improve hydrocarbon production: (1) Inject one of the following - CO2 followed by anionic or non-ionic surfactant, Anionic or non-ionic surfactant followed by CO2, miscible or near miscible CO2 gas, low concentration anionic or non-ionic surfactant. (2) Repeat the process when another cycle of treatment is needed. The same procedure can be applied into injection well to improve injectivity. The proposed cleanup protocol improves production because - wettability alteration, reduction of IFT, swelling of the oil leading to lower viscosity, and molecular diffusion among other thermodynamic effects-all acting at the matrix-fracture interface. To assess the proposed matrix-facture interface clean up protocol, IFT and contact angle measurements that mimic the proposed processes were conducted. Favorable wettability alteration of tight carbonate and sandstone crude-aged cores and oil-brine IFT reduction were observed.