The Evaluation Methods Of Spacer In The Condition Of Oil-base Drilling Fluid

Oil-base drilling fluid had stable performance,strong ability to resist pollution as well as the inhibitive ability,and many other advantages,so widely used at home.And spacer had a greater influence on the cementing quality under the condition of oil-base drilling fluid.Nevertheless,at present evaluation of the effect of spacer had no unified evaluation criteria,and most methods were based on water-based drilling fluid to evaluation the flushing effect of spacer,but the research which of reverse wetting phenomenon in the two phase interface between the oil-based drilling fluid and spacer fluid is less.Therefore,it is necessary to establish a set of comprehensive effecting evaluation method of the spacer under the condition of the oil-base drilling fluid,and explore the relationship between flushing efficiency and displacement,so that the scope of reasonable dosage of spacer were obtained.On the basis of a large number of literature investigation,this paper summarized the current spacer effects,including wetting effect and flushing effect.Firstly,using the experimental apparatus,two flushing fluid A and B were choosed to determine the flushing fluid surface tension,interfacial tension and wetting Angle.Secondly,combining with the process of underground displacement to simulate the reverse wetting process,and evaluating compound of two system;Lastly to simulate down hole the processing which is in the condition of high temperature and pressure,based on the principle of the shear rate,the filtration apparatus were transformed,the device which make the the mud cake and equipment to flushing were developed.And the experimental displacement,washing time,permeability,concentration of flushing fluid to formulate the experimental scheme were considered;we considered annulus pressure and temperature on drilling fluid rheological parameter and combined the displacement efficiency mathematical model with annulus friction pressure model,so that the relationship between the displacement efficiency and dosage of spacer were established,the result of the experiment was verified.Results show that if type A rinses surfactant concentration was 25%-30%,the reverse wetting ability is best;Mixed liquor is lower than the flushing fluid of A;Under the same conditions,flushing effect of A is better than that of B.The core permeability was greater,the washing effect is poorer.The flushing effect is better with the displacement increasing;Under the same capacity of slurry,the thickness of the drilling fluid was greater than that of the casing wall,the effect which of spacer fluid and drilling fluid density difference of 0.4 g/cm3 and dynamic shear difference 4 Pa was worse than the method which change the capacity of slurry.