Residual oil distribution prediction and potential tapping in fractured-vuggy reservoirs

In the fractured-vuggy reservoirs in the Tahe Oilfield, oil production declined rapidly due to strong heterogeneity, and the recovery rate was low. Based on the geologic and developing features of fractured-vuggy reservoirs, we proposed a new concept, which divided flow unit in single well, to predict residual oil. Residual oil usually enriched in the partially-filled sealing formations with poor physical property and weak energy, the wings of water-flooded area, the regional higher position, low-efficiency oil-replacing area in reservoir after water-flooding, corner area in water-flooding, and the poorly-connected area among different flow units in single well. In the wells with decreasing fluid-supplying ability and energy, water-flooding and controllable massive cracking were still effective ways in residual oil exploration. For those wells failed in water-flooding, drainage recovery and hydraulic dilatancy were recommended. N₂ and CO₂ injections were economic and effective ways for EOR. Side-tracking and infill well could be deployed to extract residual oil accurately.