| In the development of oil and gas fields,horizontal wells can increase the length of target layer,increase the oil drainage area and improve the oil and gas production;Therefore,horizontal well technology is widely used in oil and gas production;The length of horizontal section indicates the technical level of horizontal well drilling;The longer the horizontal section is,the more difficult it is to discharge rock cuttings and the worse the borehole purification effect is;Poor hole cleaning in the horizontal section will increase the additional load of the drilling rig and drill string,and seriously cause sticking and drill pipe fracture,which greatly increases the risk of drilling operation;Therefore,it is particularly important to improve the borehole purification effect,shorten the drilling cycle,improve the service life of drilling tools and ensure the drilling safety.Aiming at the drilling safety problems caused by poor horizontal wellbore purification,based on the principle of pipeline spiral flow,a new combined cyclone wellbore purification scheme is proposed,and the CFD-EDEM coupling method is used to visualize the flow field and particle motion law in the wellbore;The following research contents were completed:(1)Completed the basic theoretical analysis of the tool body;By establishing the axial force balance equation and circumferential torque balance equation of the tool body,the expressions of the axial velocity and angular velocity of the pipe spiral flow are obtained;The influencing factors of axial velocity and angular velocity of helical flow in pipeline are determined.(2)The determination of the initial structure of the tool body,the reliability verification of the numerical model and the feasibility verification of the scheme are completed;Based on the wellbore diameter and drill pipe diameter,according to the National Standard SY/t5051-2009,the structural parameters of cyclone borehole purification tool are preliminarily determined,and the calculation domain of tool body is established;The correctness of the numerical simulation method in this paper is verified by using the previous experimental data;By comparing the flow field distribution in rotating wellbore and non rotating wellbore,the feasibility of swirling wellbore purification scheme is determined.(3)The structural parameters of the tool body are optimized;The influence of the length and the thickness of the guide vane on the axial and radial direction of the well is analyzed;Orthogonal experiments were carried out on the two most influential quantities(blade number and blade lead).(4)Completed the exploration of the applicable scope of the working condition of the tool body;This paper mainly analyzes the influence of cuttings diameter,drilling fluid density,drilling speed,drilling fluid displacement,drill string eccentricity and drill string speed on borehole purification effect.(5)The theoretical calculation of the maximum effective working range of the tool body is completed;The visualization of long-distance original wellbore and long-distance rotating wellbore is studied by numerical simulation method.The cuttings migration efficiency and cuttings migration effect in the two kinds of wellbore are compared,which proves the feasibility of swirling wellbore purification scheme in long-distance wellbore.(6)The experimental verification of cyclone borehole cleaning tool is completed;By comparing the macroscopic phenomena and rock carrying efficiency between numerical simulation and experiment,the correctness of numerical simulation results is proved.Through the combination of numerical simulation and experimental verification,this paper fully discusses the specific structure of variable work,variable working conditions and the migration law of rock cuttings in long wellbore,so as to provide reference for the development of hydraulic borehole purification tools. |
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