Study On The Theory And Technology Of Influencing The Flushing Efficiency Of The Wellbore Mud Cake

The flushing efficiency of mud cake is one of the key factors affecting the wellbore interface cementing strength,because there are few theoretical researches on the mud cake flushing efficiency in cementing operation,and the technical measures in field application are undefined,the paper based on the theorise of engineering fluid mechanics and hydrology,to theoretical analysis and experimental study on the influence of three main factors on the flushing efficiency of mud cake,and put forward the property requirements of mud cake and flushing fluid for improving the flushing efficiency,on the research,through the laboratory experiment analysis,put forward the specific methodology and technology which to enhance mud cake flushing efficiency for three kind of drilling fluids(formate drilling fluid,poly sulfide drilling fluid,oil-base drilling fluid),and develop a new fluishing system to solve the oil mud cake.The paper main contents and achievement are as follows.(1)Using for reference in the theory of viscous sediment starting,to analysis of the mainly mud cake performance which are influence on the mud cake washing efficiency,and combined with the mud cake performance evaluation experiment and grey model to research the influence rule of performance for washing efficiency.the research achievement are turn out that,mud cake performance mainly through the strength and thickness to affects the mud cake damage time,and then affects the washing efficiency,the samller strength and thickness of mud cake,it's have shorter damage time and higher washing efficiency.(2)By using the calculation model of turbulent wall shear force and combining with the laboratory simulation experiment,to research the effects of the roughness of the well wall and the properties of the flushing fluid on the mud cake flushing efficiency,the results shaow that larger and density roughness of the wall,the mud cake flushing effiency is lower;in turbulent flow condition,the higher density and smaller plastic viscosity.the efficiency of mud cake is higher,in addition to addition of certain amount solid material is also to improving the washing efficiency of the mud cake.(3)Through adjusting formate drilling fliud,polysulfide drilling,oil-base drilling fluid pH and thinners add quantity in a certain range,are optimize drilling fluiud rheological properties and filtration properties,for formate drilling fluid and polysulfonate drilling fluid,both mud cake flushing efficiency and displacement efficiency of drilling fluid can be improved,but for oil-based drilling fluid,mud cake flushing efficiency cannot be improved.(4)Base on the the component characteristics of oil-base drilling fluid and the performance requirements of the flushing fluid to improve the flushing efficiency of the mud cake,a washing fluid system CNZ suitable for improving the flushing efficiency of the mud cake of the oil-base drilling fluid was developed through experiments by optimizing the surface active agent,liquid weighting agent and solid phase material.The results of laboratory experiments show that the system can not only effectively improve the flushing efficiency of mud cake in rough shaft wall,but also can make the oil-wet interface turn into water-wet interface,which is beneficial to improve the interface cementation.