Title: On concepts, strategies and techniques to the secondary development of China's high water-cut oilfields
Abstract: 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. : 中国油田基本为陆相储集层,非均质性严重,原油黏度偏高,注水开发采收率较低,提高采收率有很大潜力。在高含水后期剩余油呈"总体高度分散,局部相对富集"的格局,因此老油田提高采收率应该通过深化油藏描述、准确量化剩余油分布来重构油藏地下认识体系,结合油藏井网系统的重组,对剩余油相对富集区和分散的剩余油采取不同的挖潜对策和方法。提出"3个结合"综合治理方法,即:不均匀井网(在剩余油富集区钻高效调整井)与均匀井网(指整装油田)或相对均匀(断块油田)井网相结合;均匀或相对均匀井网与可动凝胶深部调驱或其他高效的剩余油驱替方式相结合;直井与水平井相结合。为此需要综合运用和发展地质、地震、测井、精细数值模拟等学科的新技术确定剩余油相对富集部位和规模,对此提出了比较系统、可行的技术路线和具体要求。参13