二连低渗透油藏采油过程中储层伤害研究

An Analysis on Formation Damage of Erlian Low Permeable Reservoirs during Oil Recovery

探讨了二连地区低渗透的阿南、哈南两油田储层在注水开发过程中受到的伤害。由两油藏地质和油藏特征及 7年 ( 1 990— 1 996)高注采比、高注水压力条件下采液指数和采油指数的变化 ,得出两油藏的伤害主要是应力敏感和有机结垢并作了详细分析论证。室内岩心围压 孔隙度、围压 渗透率关系数据证实了两油藏储层的强应力敏感性。从原油中石蜡、胶质沥青质存在状态及对原油组成变化和外界条件变化的感受性得出了两油田储层有机结垢的必然性。1 0年 ( 1 988— 1 998)来两油田采出原油初馏点、石蜡和胶质沥青质含量上升 (生产数据 ) ,岩心孔隙压力下降时油相渗透率下降幅度大、孔隙压力不变时油相渗透率下降幅度小 (岩心实验数据 ) ,采出原油含水量低时 ( 0 %— 3 0 % )蜡沉淀加快 ,1 995— 1 998年针对有机结垢采取的 92井次、9种解堵方法中复合解堵法效率最高 ,井底管柱附着物中石蜡含量高而无机盐少 ,均说明有机结垢是两油藏伤害的另一主要因素。两油藏储层均属弱速敏性。

The formation danage of low permeable Oil Fields Ana and Hanan in Erlian is analysed and discussed. From the geological and the reservoir characteristics and the data of fluid and oil productivity indexes at the two Oil Fields in 1990-1998 under the regime of high water injection to oil production ratios and high water injection pressures it is concluded that the two main demageing factors are stress sensibility of and organic scaling in the reservoir formations. The strong stress sensibility is evidenced by the laboratory data of confined pressure core porosity and core permeability relationships. The certainty of organic scaling is originated from the state and the responsibility of waxes and resin-asphaltenes to the changes in crude composition and environment. Being another damageing factor, organic scaling is evidenced by: the increase in initial boiling point, wax and resin-asphaltene contents of the produced crude in 1988-1998; large interval of decrease in core permeabilily for oil when the pore pressure decreasing and little interval-when the pore pressure being constant; the fact of fast wax precipitation at the stage of low water cut(0-30%); a combinational method of blockage releasing being the most effective of 9 on the basis of 92 treatments; high wax and low salts contents of the deposit on pipe strings at well bottom. The two reservoirs are of weak sensibility to stream velocity.