Study On The Characteristics Of Liquid-solid Two-phase Flow In Drilling Wellbore Under Pulse Jet

In the process of oil extraction,the emergence of horizontal wells is of great significance to increase the recovery rate.However,because of their unique well structure,horizontal wells frequently result in cuttings accumulation and production accidents.Therefore,it is particularly important to study the flow characteristics of cuttings particles and drilling fluid in horizontal wells.Among them,pulse jet drilling is an efficient drilling technology,which can improve the bottom hole cuttings removal efficiency by enhancing the flow of cuttings downhole.The research of this subject is the application of complex fluid flow theory in the transportation of drilling cuttings in storage and transportation engineering,which belongs to the intersection of drilling engineering and storage and transportation engineering disciplines.In this paper,the Eulerian-Eulerian two-fluid model based on the kinetic theory of granular flow is used to simulate the flow behavior of cuttings and drilling fluid in a horizontal well under the pulsed jet.The k-?turbulence model is used to simulate the liquid-phase turbulence,and the Gidaspow drag model is used to calculate the liquid-solid interphase force.The effects of pulsed jet parameters(pulsed jet velocity,amplitude,and frequency)and the rheological parameters of Hershel-Bulkley drilling fluid(viscosity coefficient,rheological behavior index,and yield stress)on the liquid-solid two-phase flow characteristics in the wellbore and the impact of these parameters on the cuttings particle collision were analyzed.Increasing the velocity of the pulsed jet can generate high pressure and high-speed crossflow in the downhole area and remove bottom hole cuttings.When the jet velocity increased from 1.016m/s to 10.16m/s,the residual cuttings volume fraction in the bottom hole decreased from 2%to 0.006%.Increasing the pulse jet amplitude can produce obvious jet penetration at the bottom of the well,which is conducive to the migration of cuttings.And there is an optimal pulse jet amplitude,which is 1/2 of the average jet velocity.The pulse jet frequency has little effect on the bottom hole cuttings migration,but the increase in frequency can effectively reduce the height of the annulus cuttings bed.Turbulent kinetic energy and turbulent dissipation rate increase with the increase of pulse jet velocity and amplitude,and decrease with the increase of pulse jet frequency.The granular temperature of cuttings increases with the increase of the pulse amplitude and frequency.Non-Newtonian fluids have a positive effect on the migration of cuttings.With the increase of rheological parameters,cuttings are more distributed in the upper part of the annulus,which makes cuttings suspended,which is not conducive to the formation of cuttings bed.And the viscosity of the drilling fluid is low near the wall.The annulus pressure of the wellbore decreases as the distance from the bottom of the well increases,but the axial pressure curve of the wellbore increases as the fluid viscosity increases.By comparing parameter change factors,the rheological behavior index has the greatest impact on flow,especially in cuttings collision,energy transfer between drilling fluid and cuttings,followed by the viscosity coefficient and yield stress.With the increase of rheological parameters,the granular temperature of cuttings,particle pressure,and particle viscosity decrease,and the turbulent kinetic energy and turbulent dissipation rate increase.This paper also discusses the relationship between jet penetration length and pulse jet velocity.The jet penetration length change is not synchronized with the pulse jet velocity,but its period and frequency are almost the same.Under the jet velocity of u_in=10.16+5×sin(2?f×t)in this paper,the minimum jet penetration length is 16cm.