Study On Cementing Displacement Efficiency And Mud Cake Washing Ability

Well cementation is one of the most crucial parts in the process of oil and gas well development.The cementing quality has a direct impact on the pledging production lives of oil and gas wells.However,gas channeling with sustained pressure in annulus have been found in many oil and gas wells,which has increased the production risk.It is necessary to raise slurry displacement efficiency in order to ensure the quality of well cementation.Therefore,this paper studies the efficiency of cement displacement and the wash ability of mud cakes.The specific contents are as follows:(1)The model of drilling fluid retention is set up based on studying Herschel Bulkley rheological pattern by means of annulus fluid flow characteristics and stress distributions in drilling fluid elements.The retention of drilling fluid under different conditions is analyzed.Factor analysis shows that casing eccentricity is the main cause of retention of some drilling fluid.The reduction of the displacing fluid yield stress and the increase of the operational pressure gradient can prevent the overall retention of drilling fluid.(2)By using one-dimensional planar flow displacement model,this paper analyzes the dynamic changes of eccentric annulus displacement interface.The eccentric annular stable interface description model is derived by using Hel-Show model.The evolution process of displacement interface is simulated by Fluent software,and the variation of displacement interface is obtained.(3)Based on the wall shear stress theory,the distribution law of shear stress distribution in the eccentric annulus is obtained.The force of single mud cake particle is analyzed and the mud cake erosion model is established.Factor analysis indicates that when single mud cake diameter is less than 0.1 mm,the reduction of the pressure difference on mud cake and the increase of operational displacement contribute to washability.(4)Combining with drilling fluid retention model,interface displacement model and mud cake erosion model,this paper conduct a comprehensive evaluation of the cementing section displacement efficiency in virtue of programming with C# software.Through the study of cementing displacement efficiency and mud cake erosion,slurry displacement theory is improved,which helps to improve the wellbore integrity and cementing quality.This study can provide reference for on-situ displacement efficiency and cementing quality prediction.