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This In order to improve the oil well cementing interface strength, the removing agent (JCJ) and cleaning agent (QXJ) were used from the perspective of clearing the mud cake on the borehole wall and wellbore casing. The factors influencing the effect of JCJ and QXJ were researched through metal plate immersion test, cleaning test and cementing strength simulation experiments. The results showed that the removal rate of mud cake could reach to 88% when the metal plate was first soaked in the drilling fluid at 55 °C for 40 min when 1% (weight) of JCJ was added into the drilling fluid and then was cleaned in the aqueous solutions within 1% JCJ at 45 °C for 25 min. The cementing strength simulation experiments showed that the cementing strengths of the interfaces between the cement and the wellbore casing (the first interface), the cement and the borehole wall (the second interface) could be enhanced to 10.3 and 8 times respectively which indicated the well cementing quality could be improved effectively. Besides, the main properties of drilling fluid did not changed greatly after adding JCJ into the drilling fluid. Materials The drilling fluid and well cement were obtained from Daqing Drilling Company of China National Petroleum Corporation (CNPC) . The removing agent (JCJ) was a non-ionic surface active agent, and the cleaning agent (QXJ) was alcohols mixture. Metal plate immersion test The effect of JCJ was tested by the metal plate immersion test. The less residue of the oil-based drilling fluid on the metal plate, the better removing effect of JCJ. In the test, the metal plate (70 mm×50 mm×1 mm) was first immersed in the JCJ-containing drilling fluid at constant temperature for a period of time, and then the mud cake formed on the plate, the plate with mud cake was taken out and weighed. The weight-growth of the metal plate defined as the difference of its weight before and after impregnation was used to evaluate the effect of JCJ. The lower the weight difference of the plate, the better the effect of LPP. Cleaning test In order to improve the removing effect further the cleaning test was carried out. After the metal plate immersion test the metal plate with drilling fluid was then cleaned in the aqueous

Mud Cake Removing to Improve the Well Cementing Quality