| The oil and gas well can be as shallow as hundreds of meters,or can be as deep as thousands of meters,even ten thousands of meters.The casing and cementing slurry undergo various tests of measures which can increase production,such as severe environment of high temperature and pressure,the corrosion and harassment of underground oil and gas water and other medium,and the acidification and fracture in the oil operation.The purpose of cementing is to seal complex formation which is loose,easy to collapse and leak,and seal layer of oil,gas and water to prevent leakage.Therefore,the performance of cementing slurry has a direct impact on the quality of cementing,and ultimately has high requirements of cementing slurry.As a result,improving the mixing quality and efficiency of cementing slurry has great practical significance to cementing operations.As the requirement on the quality of cementing slurry becomes increasingly stringent,the thesis explores and designs the mixing head which is in favor of premixing of cementing slurry by studying domestic and foreign cementing system and researches on the multiphase flow.The thesis has conducted CFD stimulations respectively on the size and velocity of the mixing head,the speed of the dry ash,the angle of the diversion thimble,the distance between the diversion thimble and the water outlet.Thus,thepreferred plan of mixing cementing slurry is confirmed.Then,it has carried out the stimulations on the operating parameter,dimension parameter and location parameter of the rotation speed of agitator,of the distance between two blades on the coaxial axis,and of the distance between two agitating shafts,which has optimized the structure of agitator thus it can be benefit to the stirring and mixing of cementing slurry.Finally,it carries out the CFD numerical simulation of the flow field between the mixing head and the agitator,and compares it with the stirring and mixing of cementing slurry alone in the agitator,analyzes and explores the mixing of cementing slurry and its' impact on mixing efficiency when the mixing time is 1 minute and 1.5 minute respectively.Through the CFD stimulations on mixing and agitator,the thesis has reached the following conclusion:(1)FLUENT can establish the following three models in the Euler-Euler coordinate system: the Volume of Fluid model,the Mixture model and the Eulerian model.Through a comprehensive analysis of the applicable conditions of three multiphase flow models,the Eulerian model is selected for the multiphase flow simulation of the mixing head while the Mixture model is selected for the agitator.Forthe selection of the turbulence model,the thesis selects the standard k-? model because the turbulence intensity of the mixing head and the agitator is relativelyhigh,the Reynolds number is high and the calculative ability of the computer should be taken into consideration at the same time.As for dealing with the mixing slurry zone in the agitator tank,the method of multiple reference frames is selected.(2)The thesis designs the overall structure of the mixing head and uses CFD fluid software to conduct numerical simulation calculation.It simulated the effect of inlet diameter on mixing result while the diameter is 50 mm,60mm,and 70 mm respectively.Finally,the 60 mm is selected as the best one.The same simulation is carried out to explore the effect of different angles of diversion thimble on mixing result of cementing slurry at the angles of 30°,45°,and 60° respectively.The optimal angle of 45 ° is selected at last.Then the simulation of the distance between the diversion thimble and the water outlet is conducted when the distance is 5mm,10 mm,and 15 mm respectively.The distance of 5mm is taken as the final option.Thus,the water inlet diameter is 60 mm,and the angle of diversion thimble is 45 ° while the distance between the diversion thimble and the water outlet is 5mm.Under the premise of choosing the above combination and ensuring the processing capacity of the mixing head,the inlet operating parameter is that the speed of the water inlet and the dry ash inlet is 8m/s?2m/s respectively.(3)The numerical simulation of the flow field of the existing structural agitators in SJ is carried out to explore the influence of different rotation speed on the mixing performance at the speed of 100 rpm,150rpm,200 rpm,250rpm and 300 rpm respectively.When the rotation speed is between 100 rpm and 200 rpm,the influence on mixing of cementing slurry is significant;the influence has no obvious change when the rotation speed is between 200 rpm and 250rpm;there is no influence when the speed is between 250 rpm and 300 rpm.After taking the mixing efficiency and energy consumption into full consideration,the normal working rotation speed is between 150 rpm and 200 rpm,the maximum speed is 250 rpm.Then,the thesis researches the distance between two blades on the coaxial axis when the distance is 150 mm,170mm,190 mm and 210 mm respectively.Through simulation,the mixing result of cementing slurry is relatively good when the optimum distance is 190 mm.Finally,the influence of different distance of two agitating shafts on mixing is analyzed.The simulation is analyzed when the distance is 575 mm,555mm,535 mm,515mm,495 mm and 475 mm respectively.Through the handling of simulation result,the mixing result of cementing slurry is the best when the distance is 575 mm.(4)Through the analysis of simulation on the premixed cementing slurry by mixing head in agitator,the thesis comprehensively analyzes the flow field between the mixing head and agitator.Then,it makes a comparison on the simulation results between the cementing slurry which has been premixed by mixing head and cementing slurry without premixing when the stirring time is 1 min and 1.5 min respectively.The final result shows that the mixing result of cementing slurry with premixing by mixing head is much better,and thus proves the function of mixing head in the mixing of cementing slurry. |
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