Quantitative evaluation of water-alternative-natural gas flooding in enhancing oil recovery of fractured tight cores by NMR

Abstract As the associated gas of tight reservoirs, natural is abundant and noncorrosive, which more suitable for development oil reservoirs in China. However, mechanism injection unclear, channeling serious after fracturing. The water-alternating-gas (WAG) flooding an effective means to delay improve recovery. Therefore, it significant clarify preventing recovering by water-alternation-natural (WANG) flooding. WANG experiments with different water–gas slugs were conducted non-fracture fractured cores. Besides, distribution pore spaces cores before displacement main contribution on recovery quantitatively analyzed using nuclear magnetic resonance core mercury porosimetry techniques. results indicate that compared flooding, can retard channeling, increase formation energy, enhance up 14.1%, especially Under resistance water slugs, was allowed enter smaller pores its swept volume expanded. Oil mainly stored mesopores (0.1–1 μm) small (0.01–0.1 μm), accounting over 90% total volume. recovered comes from mesopores, accounts 75% amount. Moreover, strengthens macropores (1–10 but also squeezes into micropores (0.001–0.01 μm).