关键词: 缝洞型碳酸盐岩油藏, 选择性堵水, 改性栲胶, 封堵能力, 实验研究

Abstract: 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.

Key words: fracture-cavity karst reservoir, selective water shutoff, sulfonated larch tannin extract, sealing capacity, experimental study