中文摘要：

水锁效应是油井作业过程中普遍存在的问题。在低孔、低渗透储层中,入井液水相的入侵对油相渗透率的影响尤为严重。针对海上埕岛油田东营组低渗岩心,通过恒压水侵物模实验评价了水相入侵对油相启动压力的影响,从而定量的表征了水锁的伤害程度。水侵实验表明,岩心中仅仅侵入0.3 PV的水,即可将油相启动压力由0.056 MPa提高到0.120 MPa。在水锁伤害研究的基础上,有针对性的研究了降滤失修井液体系,根据脂肪酸甲酯易于乳化的特点,研发了乳状液修井液体系。恒压水侵实验表明,该乳状液体系在水相和油相中均具有较好的降滤失能力;在2.89~8.78 MPa/m的压差梯度范围内,其降滤失率可达49.12%~88.67%。同时返排实验表明,水侵后恒压注油平衡压力为0.182 MPa,相比而言,乳状液侵入后恒压注油平衡压力则可降低至0.158 MPa。试验结果表明乳状液修井液体系降滤失效果较好,对储层岩心伤害较常规水相小。

英文摘要：

Water block effect exists throughout the oil-well operations.Oleic permeability is severely impacted by the invasion of aqueous working fluids,especially in low porosity and low permeability reservoirs.Targeted were studied mainly at low permeability core of Dongying Formation,Chengdao Offshore Oilfield.The effect of water invasion on oil threshold pressure was evaluated by establishing a water invasion physical model under constant pressure,which quantitatively characterized the damage degree of water block.According to the water invasion tests on cores,the oil threshold pressure could be increased from 0.056 MPa to 0.120 MPa only with a water influx of 0.3PV.Besides that,some pertinence research that related to filtration reducing workover fluid system had been conducted on the basis of the damage mechanism of water block.A new type of emulsion workover fluid system was developed based on the emulsification characteristic of fatty acid methyl ester（ FAME）.It was indicated by water invasion tests that the emulsion system performed well in reducing filtration both in water phase and oil phase.Its fluid loss rate could be 49.12% ～ 88.67% with the pressure gradient of 2.89 ～ 8.78 MPa/ m.Meanwhile flowback tests showed that,compared with the balance pressure of 0.182 MPa in constant-pressure oil displacement experiments after water invasion,the emulsion system could reduce this number to 0.158 MPa under the same condition.All above results demonstrate that the emulsion system has a better effect on reducing fluid loss,and also does less harm to reservoir cores.