Structural Design And Performance Evaluation Of Wellhead Tubular Desander In Condensate Gas Field

Sand production at wellhead of gas wells will affect wellhead equipment and downstream oil and gas gathering and transportation system.It may occur severe cases such as pipeline sand plugging and valve penetration and leakage.The offshore wellhead platform has some characteristics of limited space,far away from land,no permanent personnel,high maintenance cost,which poses a higher challenge to the sand removal equipment and related technology.In this paper,we analyzed and compared the traditional multi-phase flow sand control technology,reformed the structure of the tubular desander.The working characteristics of the desander are studied by Fluent.We also tested the separation efficiency of the desander under different structures through laboratory experiments,and put forward the evaluation method of the applicability of the desander.The main content and conclusion are as below:The desander is divided into five modules:inlet pipeline,tee,outlet pipeline,inertial migration section and sand storage tank.From the numerical simulation results,we found that the pressure in the desander decreases gradually from the entrance pipeline to the three-way section,and the velocity value hardly changes compared with the entrance velocity;at the three-way section,the continuous phase flow state changes most obviously;at the three-way section to the exit pipeline,a strong gas core zone is generated,local velocity increases,and a vortex is generated on the other side,and the pressure is generated along the axial direction of the exit pipeline.Continuous fluctuations cause turbulent flow energy dissipation and increase the energy loss in the separator.In the inertial migration section and the sand storage tank area,the continuous phase velocity gradually drops to 0,and the static pressure value jumps.When the gravel enters the area,it moves forward only by its own inertia and deposits at the bottom of the sand storage tank under the action of gravity.The separation efficiency of desander with different structures is compared by numerical simulation,which provides a theoretical basis for the selection of solid machine.The natural gas condensate wellhead sand control experiment system is designed and built,and the sand-adding method is improved to ensure the uniformity of multiphase flow gravel addition.Based on this experimental system,the influence of working condition parameters and structural parameters on the separation performance of the desander is studied.The range analysis method shows that the factors affecting the separation performance of the desander are particle size,superficial gas velocity and apparent liquid velocity.Among them,the influence of gravel particle size is the most significant,while the other two factors are similar,and the particle size is not obvious.Experiments show that the separation chamber enlargement and two-stage structure can effectively improve the separation efficiency of the desander.When the diameter of separation chamber expands from D₁ to 2D₁,the continuous phase flow state changes from the gas-liquid two-phase interface above the direct impact sand storage cylinder to swirl flow,and the separation efficiency of large-size gravel increases obviously.The pressure drop in the separator increases sharply when the diameter increases again,and the separation efficiency almost does not increase.Using two-stage structure instead of single-stage structure will increase the area of the desander,but the area of the desander is larger than that of the separation chamber.The diameter enlargement results in lower overall pressure drop and better separation performance.Considering the experimental results comprehensively,this paper had given the basic structure of the wellhead tubular desander.Through investigation and numerical calculation,it put out the applicability judgment method of natural gas condensate wellhead desander,which provides guidance for desander design with similar application requirements.