| A major problem in the drilling process of horizontal wells and extended reach wells is how to ensure that the borehole is sufficiently clean when drilling in highly deviated and horizontal wells.If the borehole is not sufficiently cleaned,it will lead to many drilling problems,such as sticking,supporting pressure,burying the borehole and so on.There are many factors affecting the cuttings carrying efficiency of drilling fluid,which are classified according to the action source:first,it is affected by the movement of circulating medium(drilling fluid,etc.);The second is the influence of mechanical movement,such as drill pipe rotation,lateral movement,axial movement,high-frequency vibration and chip carrying tool blade rotation.Cuttings migration is a highly complex solid-liquid flow problem affected by the coupling of circulating medium and drilling tool mechanical motion.Therefore,it is of great significance to study the failure law of cuttings bed and the redistribution law of cuttings in annulus after failure under the combined action of axial movement of drill pipe in horizontal well section and circulating medium.In order to deeply study the typical liquid-solid two-phase flow problem of cuttings migration affected by the combined action of axial mechanical movement and circulating medium when the drill pipe moves axially in horizontal well section,this paper uses Euler two fluid model(TFM)and particle dynamics theory(KTGF)to carry out targeted research.The interphase force between liquid and solid is calculated by Huilin gidaspow model,and the axial movement of drill pipe is defined by profile program,so as to realize the three-dimensional numerical simulation and analysis of annulus flow field and cuttings movement during the axial movement of drill pipe in horizontal well section.According to different hydraulic parameters,the simulation work is carried out under the conditions of different axial movement speed of drill pipe,different consistency coefficient and different particle diameter.In order to effectively verify the numerical simulation results,a set of axial tripping out experimental equipment is designed according to the geometric proportion of the numerical simulation model.The experimental equipment includes four parts:pressurization part,axial power part,wellbore annulus part and fixed support.The verification experiments of several simulated hydraulic parameters are carried out under the same pressure environment as the simulation conditions.The results show that the chip carrying effect of drill pipe joint is particularly obvious when the tripping speed is in the range of 0.1 m/s-0.25 m/s;When the tripping speed is greater than 0.25 m/s,it will cause intense pressure fluctuation in the wellbore,resulting in the redistribution of rock cuttings in the wellbore and the accumulation of rock cuttings to form a locally thicker rock cuttings bed than the initial rock cuttings bed.When the speed is too high,the intense pressure fluctuation may lead to wellbore collapse and overflow;At the same tripping speed,increasing the consistency coefficient can make more cuttings in suspension and increase the settling time of cuttings,with the consistency coefficient of 30 m Pa.s~n is the boundary,less than 30 m Pa.s~n annulus cuttings are high in front and low in back along the axial direction,which is greater than 30 m Pa.s~n is distributed in the form of low before and high after;Moreover,when the consistency coefficient is low(k<30 m Pa.s~n),the range of matching tripping speed can be appropriately relaxed to 0.25 m/s-0.75 m/s,which can effectively control the thickness of cuttings bed and reduce the risk of sticking.While the drilling fluid with high consistency coefficient(k>30 m Pa.s~n)has strict requirements for tripping speed and should be strictly controlled between 0.1 m/s-0.25 m/s;Under the same hydraulic parameters,the experimental results are consistent with the simulation results,and the error is small. |
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