通过扩大波及体积提高聚驱采收率

Enhancing Polymer Flooding Recovery Factor by Expanding Sweep Volume

为实现杏南油田新增N13聚驱区块的开发效果,满足采收率不低于老试验区和小井距区、达到或超过抗盐试验区的既定开发目标,有必要对其扩大波及体积技术进行研究。通过对不同类型井组进行高浓低速阶段参数分析、应用降浓提速、改注及深度调剖等一系列扩大波及体积技术研究及应用来提高采收率。A、B、C、D 4类井高浓低速注入阶段适宜的注入浓度分别为1800~2100mg/L、1500~1800mg/L、1200~1500mg/L和1 200mg/L及以下;区块以注水时指示曲线的拐点压力为依据,确定降浓提速的压力界限为8.0 Mpa,措施前后吸液厚度比例和薄差层相对吸液量均表现为先升后降趋势;根据压力上升空间制定改注措施,改注后各类井注入压力均有所下降,吸水剖面得到改善,C、D类井效果好于A、B类;从调剖层位视吸水指数降幅、吸液厚度提高幅度、连通采出井最大含水下降值、单井累计增油上来看,注聚前水驱阶段期深调效果最好、含水下降期次之、含水回升期较差。

In order to achieve the development effect of polymer flooding block N13 in Xingnan Oilfield,make its recovery factor not lower than that of old test area,small well spacing area and salt resistance test area,it is necessary to study the extending sweep volume technologies suitable for the block.A series of extending sweep volume techniques,such as analyzing polymer injection parameters in high concentration and low injection speed stage,reducing polymer concentration and increasing injection speed,replacing original polymer solution by salt resistant polymer solution at appropriate time,and deep profile control,are applied in different types of well groups in order to improve the recovery factor of this block.In the high concentration and low velocity injection stage,the suitable injection concentrations of Class A,B,C and D wells are 1 800~2 100 mg/L,1 500~1 800 mg/L,1 200~1 500 mg/L and≦1 200 mg/L respectively.The pressure when decreasing concentration and increasing injection speed is determined based on the inflection point pressure(8.0 MPa)of the water injection curve.The ratio of suction thicknesses before and after the measures and the relative suction volume of thin and poor layers show the trend of first rising and then falling.Polymer replacing measure is determined according to pressure rise space.After implementing the polymer replacing measure,the injection pressure of all kinds of wells is decreased,the injection profile is improved,and the improvement effect of Class C and D wells is better than that of Class A and B wells.From the decrease of apparent water absorption index,the increase of suction thickness,the decrease of maximum water cut value of connected production wells and the cumulative oil increase of single well,the implementing effect of deep profile control is the best in water flooding stage before polymer flooding,it is secondary in water cut decrease period,and it is the worst in water cut rising stage.