NMR-Based Shale Core Imbibition Performance Study

Shale gas reservoirs are unconventional resources with great potential to help meet energy demands. Horizontal drilling and hydraulic fracturing have been extensively used for the exploitation of these resources. According engineering practice, some shale wells low flowback rate fluids may obtain high yield which is different from case conventional sandstone reservoirs, fluid absorbed into formation by spontaneous imbibition an important mechanism production. This paper integrates NMR experiment examine effects fractures, salinity, surfactant concentration on recovery performance core samples pore-throat sizes acquired Longmaxi Formation in Luzhou area, Sichuan Basin. The research shows that right peak T2 spectrum increases rapidly during process imbibition, left at initial stage changes gently later stage, shifting right. result indicates water first enters fracture system quickly, then small pores near wall due effect capillary force, gradually sucks deep large pores. Both capacity increase increased density, decreased solution concentration. After flowback, permeability generally 8.70–17.88 times average 13.83 times. There also many microcracks occurring end face surface sample after absorption, function as new flowing channels further improve reservoir properties. demonstrates characteristics several relevant affecting factors, providing crucial theory foundations development reservoirs.