Detailed Characterization of the Remaining Oil in Matured Water Drive Reservoir

Most of the water-drive oil reservoirs in the western South China Sea had stepped in the middle and high water-cut stage. By the influence of reservoir heterogeneity, fault distribution, well pattern deployment and variation of reservoir flow parameters during long-term natural water drive and water flooding, the remaining oil distribution forecast is not accurate enough, increasing the difficulty of making effective adjustment and potential tapping measures. Through years of tackling key technical problems and field practice, the detailed characterization technique of the remaining oil in matured water drive reservoir was presented. Based on water displacement mechanism, variation of relative permeability curves are derived from Zhang’s water-drive characteristic curve during long-term water displacement. In addition, dynamic monitoring data matching was adopted to improve the forecast accuracy of the remaining oil distribution in water flooding oil reservoirs. By combination of flow field, remaining oil saturation field, and remaining oil reserves abundance, comprehensive characterization of water drive dynamic state was realized. The remaining oil enriched areas were quantitatively classified into four levels of potential regions, and corresponding adjustment and potential tapping measures were proposed. This technique had been successfully applied in the middle and high water-cut oilfields in the western South China Sea, with remarkable estimated incremental oil production of approximately 204,000 m 3 .