Research On The Effect Of Drill String Movement On Annular Pressure Loss And Cuttings Transport In Riser

Deep water and ultra deep water are the future of oil exploration and development,but deep water drilling process pressure window is very narrow,so fine control of the pressure is needed.Deep water drilling riser is subjected to wave current,which will cause vibration response of the riser and drill string.As the size of the riser is larger than that of the wellbore,the relative movement between the riser and the drill string makes the annular flow more complicated than the annular flow field in wellbore and can affect the cuttings transport,but the characteristics of the annular flow field of the riser and the problem of cuttings transport are few studied.In order to study the influence of drill string movement on the annulus flow and cutting transport,the CFD software FLUENT and the dynamic grid technology were used to simulate the motion of the drill string in the riser.We obtain the effect of drill string movement(rotation,lateral vibration,vortex)on annular pressure loss and cuttings transport in riserThe results show that when the drill string rotates,if the drill string eccentricity is small,the drilling fluid spiral upward flow,the annular pressure loss change is not significant;when the drill string eccentricity is large,the ring may produce multiple and Drill string rotation in the opposite direction of the secondary flow vortex,which will increase the annular pressure loss,and will also affect the cuttings transport effect.When the drill string is vibrated laterally in the annulus of the riser,one or more secondary vortices will be generated in the annulus.The larger the amplitude of the drill string,the greater the disturbance of the annular flow field.The effect of different eccentricity and whirl direction on the annular flow field is different.On the whole,the disturbance of the annular flow field is stronger when the drill string is whirling.In the range of parameters studied in this paper,the cuttings transport ratio in the annular are smaller when drillstring movement in riser(rotation,lateral vibration,whirl)than those of the drill string when the drill string is concentric,but the decrease is smaller,On the whole,it can be considered that the drill string movement(rotation,lateral vibration,whirl)is not conducive to improve the efficiency of the cuttings transport.