For deeply buried (> 2 500 m),special low porosity and low permeability sandstone gas reservoirs,in the process of drilling and completion,usually using 2% NaCl solution flush well,it does not consider the compatibility with reservoir fluid,and the density requirement of gas well about flushing fluid,which in the actual operation often have blowout and kick accident,coupled with the excessive fluid loss of the washing fluid will cause reservoir water lock damage.Through the screening evaluation of several kinds of surfactant,and according to the existing oilfield application effect,get new waterproof lock treatment agent.On the basis of the waterproof lock agent,adding fillers (KCl and HCOONa),research the flushing fluid system for ultra-low permeability and ultra-low permeability sandstone gas reservoir with well depth greater than 2 500 m,make its density in the range of 1.00 to 1.60 g/cm3 is adjustable.Get a formula as follows: 0.5% SATRO+0.05% sodium alkyl sulfonate+10% methanol+0.02%FX-02+fillers (KCl and HCOONa).The system not only has excellent performances of the new waterproof lock agent,but also to the density of low-permeability gas wells requirements,can slow down self-priming effect of reservoir core,has a good waterproof locking effect,the surface tension is small,the reservoir core permeability recovery rate is more than 95%.Using this system on the 5 wells in Jilin palace block (CS1-1,CS-1,CS-5,CS-6,CS-7) were washed well construction,determine the flushing fluid density is 1.05 g/cm3.After washing,5 gas-well production rise generally,and actual production were higher than forecast value,has significant to protect reservoir and increase production effect.%对于埋藏较深(>2 500 m)的特低孔、超低渗砂岩气藏,在钻完井过程中,通常使用2%NaCl溶液进行洗井施工;并没有考虑与储层流体的配伍性,以及气井对洗井液的密度要求,致使在实际作业中常有井喷、井涌的事故发生;加之该类洗井液的过度滤失会造成储层的水锁伤害.经过对多种活性剂的筛选评价,以及根据在已有油田的应用效果,得到一种新型防水锁处理剂,在此基础上,添加加重剂(KCl与HCOONa复配),研制适用于井深大于2 500 m的特低孔、超低渗砂岩气藏的洗井液体系,使其密度在1.00~1.60 g/cm3的范围可调.得到配方为:0.5%SATRO+0.05%烷基磺酸钠+10%甲醇+0.02%FX-02+加重剂(KCl与HCOONa复配).该体系不仅具有新型防水锁剂的各项优质性能;而且达到了低渗层气井对密度的要求,能减缓储层岩心自吸作用,具有良好的防水锁效果,表面张力较小,储层岩心渗透率恢复率大于95%.运用该体系对吉林王府区块的5口气井(CS1-1、CS-1、CS-5、CS-6、CS-7)进行了现场洗井施工,确定该井区内使用的洗井液密度为1.05 g/cm3,洗井后5口气井产气量普遍升高,且实际产量均高于投产预测值,具有显著的保护储层和增产的效果.
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