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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%Na Cl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/cm~3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/cm~3,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。
For ultra-low porosity and ultra-low permeability sandstone gas reservoirs buried deep (> 2 500 m), 2% NaCl solution is usually used for well washing during drilling and completion; the compatibility with reservoir fluid is not considered As well as the densities of gas wells in flushing fluid, resulting in frequent blowout and kick in actual operation. In addition, excessive filtration of this type of flushing fluid can cause water lock damage in the reservoir. After screening and evaluation of various active agents, and according to the application effect in the existing oilfield, a new waterproof lock treatment agent is obtained. On the basis of this, a weighting agent (KCl and HCOONa compounding) is added to develop a new waterproof lock treatment agent suitable for well depth greater than The ultra-low porosity and ultra-low permeability sandstone gas reservoirs with 2 500 m of wash fluid system make the density adjustable in the range of 1.00-1.60 g / cm 3. The formula is: 0.5% SATRO + 0.05% sodium alkyl sulfonate + 10% methanol + 0.02% FX-02 + weighting agent (KCl and HCOONa compound). The system not only has all the good properties of the new water-proofing agent, but also meets the requirements of density in low-permeability gas wells, can slow the self-absorption of reservoir core, has good waterproof lock effect, has small surface tension, Permeability recovery rate is greater than 95%. The system was used to clean the five gas wells (CS1-1, CS-1, CS-5, CS-6 and CS-7) in Wangfujing block in Jilin Province. The density of gas is 1.05 g / cm ~ 3. After gas well flushing, the gas production of the five gas wells generally increases, and the actual output is higher than the predicted value of production, which has significant effect on reservoir protection and stimulation.