| Until the end of 2007, the number of polymer flooding blocks in Daqing Oilfield has been larger than 30 and the annual output was 1000×10~4 tons. 14 blocks of them have already arrived at water flooding stage after the polymer flooding, facing a problem of potential tapping continuously. There is more than 40% of residual oil in high-quality reservoir can not be pumped out after polymer flooding. The critical problems of potential tapping after the polymer flooding are the accurate identification of residual oil type, potential and its distribution regulation.This article has finished the evaluation for the development status of the polymer flooding blocks. The remaining oil distribution of Beierxidong Block was studied by numerical simulation method, and based on numerical simulation; the multi-level fuzzy comprehensive evaluation method was used to evaluate the residual oil potential after polymer flooding of Beierxidong Block. The results show that there still exists many residual oil underground after polymer flooding with great potential. After polymer flooding, residual oil saturation is low in the thick oil reservoir with middle and high permeability. But the thin reservoir with low permeability was developed poorly, and the remaining oil saturation is still high; channel sand has a high recovery and low residual oil saturation, and the channel-between sand was developed poorly, sheet sand body was developed very little. Moderate washed regions have the largest remaining reserves; the remaining geological reserves of the regions whose effective thickness are greater than 2m account for an absolute large proportion; the surplus reserves in the middle-and high-permeability regions is relatively large. The remaining recoverable reserves is relatively large in the cell medium with larger thickness and middle permeability after the polymer flooding, and the one in strong washed and poor conditioned oil layer is relatively small. the potential distribution in the two-stage of water flooding and polymer flooding is given for the six sedimentary units of Group I in Beierxidong block, the potential after polymer flooding have a distinct downward trend compared with water flooding. The potential after polymer flooding increases as the permeability, reservoir thickness, and the residual oil saturation increases. The river channel sand still has a high potential, and then is the channel-between sand.On the basis of potential evaluation, the potential countermeasures after polymer flooding are supplied corresponding to different units, locations and types of remaining oil. |
