On concepts, strategies and techniques to the secondary development of Chinaʹs high water-cut oilfields

Most oil fields in China are reservoirs with strong heterogeneity and relatively viscous crude in continental sediments. Due to the low waterflooding oil recovery factor, there is still a great potential to improve the oil recovery. The remaining oil in high water-cut mature oilfields has the characteristics of “highly scattered in general, but locally abundant”. As a result, a sophisticated reservoir characterization and an accurate quantification of the remaining oil distribution are necessary in rebuilding knowledge to the reservoir. Different strategies and measures including well pattern realignments should be applied to the area with varying abundance level of remaining oil. Three integrated measures are proposed: (1) the combination of non-uniform well patterns (infill drilling of efficient wells in area with abundant remaining oil), and uniform well patterns (in un-compartmentalized reservoir) or relatively uniform well patterns (in fault-block reservoir); (2) combination of uniform or relatively uniform well patterns and measures of more efficient recovery techniques such as moveable gel displacement for recovering the scattered remaining oil; and (3) combination of vertical and horizontal wells. Therefore, new technologies in multiple disciplines of geology, seismology, well-logging and advanced reservoir simulation are needed to be developed and applied in determining the location and abundance level of remaining oil. In this paper, a systematic and feasible technical approach as well as specific requirements is proposed.