多轮次调剖的室内实验研究与现场应用

Laboratory Experimental Study and Field Implementation of Rotational Profile Control Operations in Water Injection Wells

采用沿一条对角线设置高渗区、两端设注入、采出口的厚平板模型和可视化薄平板模型及高、中、低渗三填砂管并联模型,实验研究了水驱后(含水95%)多轮次调剖的效果。在厚平板模型上用水玻璃/氯化钙堵剂调剖三轮次,在薄平板模型上用聚合物铬冻胶调剖八轮次,均出现了调剖效果(采收率增值)递减现象。提出了效果递减的五个机理及相应对策:①前后两次调剖注入的堵剂影响面部分重叠,应使用强度不同、凝胶化时间不同的堵剂,建立多轮次调剖堵剂系列;②堵剂的作用随径向距离增加而减弱;应逐轮次增加堵剂量;③封堵时机不当,含水越低则调剖效果越好;④注入压力欠当,高注入压力下堵剂可进入欲启动层;⑤注入的堵剂部分失效,如有机冻胶发生氧化降解,粘土内滤饼被冲刷。在综合含水高达96.3%的坨11南沙二11-3试验区,采用PI和FD决策技术选调剖井,选择堵剂并优化堵剂配方,从1999年10月到2002年10月对全区6口注水井进行5轮次共21井次调剖,使试验区年自然递减率(1999年为11.65%)大幅度减小,含水受到控制(2003年8月为96.1%),采收率提高2.0%,可采储量增加。图5表3参3。

The efficiency of rotational, repeated round by round, profile modification （PM） operations after 95% water cut reached in water flood is experimentally studied on thick and thin, videogenic , platelike physical models and on parallel three sandpacks of diferent permeability. A progressive decrease in efficiency （in enhancement in oil recovery） is observed for three PM treatments with a water glass/CaCl2 fluid on the thick model and for eight PM treatments with a polymer/Cr^3＋ gelling fluid on the thin model. Five mechanics involved in the progressive decrease and the countermeasures to be taken are suggested： ①the influencing zones of the plugging agents （PAs） placed in successive 2 rounds of PM are overlapped therefor PAs of different strength and gelafion （setting） time should be used and series PAs for rotational PM be established; ② the function of equal volume of PAs placed weakens with enlarging radial distance thus the volume of PAs injected should be increased round by round; ③ the PM is performed in unproper time as the lower the water cut the more effective the PM operation is; ④the injecting pressure is undue as the plugging fluid might invade into the zones to be mobilized under high injecting pressures; ⑤ the pluggings and blockages created undergo failure partially as a result, for example, of oxidative destruction of organic gels or washout of filtrate clay cakes. In experimental area of southern Tuo- 11 in Shengtuo, Shengli, where the composite water cut reached 96.3%, the well selection for PM is made by using PI and FD decision procedures, the proper plugging fluids are chosen, their recepts are optimized, the PM operations are performed in all six water injection wells in 5 rounds, 21 well-times totally from Oct 1999 to Oct 2002 and following results are obtained： significant reduction in annual productivity decline rate （11.65% in 1999） ; composite water cut being under control （96.1% in Aug 2003） ; oil recovery enhanced by 2.0% ; and increase in recoverable oil reserve.