改性栲胶在缝洞型碳酸盐岩油藏中的堵水实验研究

Experimental study on water shutoff of sulfonated larch tannin extract to aqueous layer in the fracture-cavity karst reservoir

根据塔河油田奥陶系缝洞型碳酸盐岩油藏条件,对耐高温改性栲胶堵剂在矿物组分相近的人造缝洞型岩心中的堵水机理进行了实验研究。在油井水层出水压力高于油层压力或者产油层裂缝大于出水层裂缝情况下,采用笼统注入方式堵水须进行暂堵处理,以封住产油层,使堵剂主剂选择性进入水层。改性栲胶堵剂可在水层中形成均匀的较强凝胶封堵带,而在油层中形成的是残余油与凝胶混合物,易被突破和形成流动通道;另外,改性栲胶凝胶具有极性,与碳酸盐岩表面结合比较稳固。因此,改性栲胶堵剂对水层的封堵能力更强。由于塔河油田地层水矿化度非常高,预冲洗既能隔离注入堵剂与地层水,又能降低溶胶聚沉,有利于提高改性栲胶凝胶对碳酸盐岩油藏出水层的封堵能力。

According to the conditions of the Ordovician fracture cavity karst reservoir in Tahe Oilfield, the mechanism of water shutoff of a kind of high temperature resistant gel made of sulfonated larch tannin extract was experimentally studied in the man-made fracture-cavity karst cores with the same mineral components. The experimental results show that it is necessary to treat the formation with the temporary plugging agent to seal the pay zones for selectively injecting gel into aqueous layers when the effluent water pressure is higher than that of pay zones, or the fractures in oil bearing zones are much wider than those in the aqueous layer. The water shutoff agent could form the uniform gelatinous zone with high intensity in the aqueous layers, But it could transfer to a kind of mixture containing residual oil and gel. The mixture could be penetrated to produce flow path in the pay zones. In addition, the gel with polarity could be firmly conjoined on the surface of karst rock. Therefore, it has so much capacity to seal the aqueous layers. The pre-flushing technology could either isolate the injection gelant from formation water or reduce coagulation and deposition of the gelant, which is favorable to improve the ability of the gel made of the sulfonated larch tannin extract to seal the aqueous layers in the fracture-cavity karst reservoir.