Design Of Downhole Drilling Fluid Solid-Liquid Separating Device And Research On Flow Character

In the past petroleum drilling applications,slow response and difficult quantitative testing have been the major problems in the test of drilling fluids on the ground.For a long time,many companies at home and abroad are developing drilling gas testers,which are installed in the drill collar and able to test oil and gas in real-time.Detection device can not detect drilling fluid directly without removing the included large solid particles.To this end,the research of drilling fluid solid-liquid separating device was carried out in this paper.The goal is to design a solid-liquid separating device that can be installed in the drilling gas tester and achieve given separation size.Based on the methods of filtration and cyclone separation,the solid-liquid separating device is designed according to the working conditions.The device is comprised of a filtration structure and a cyclone separating structure,in which the filtration structure separates solid particles larger than 200?m in diameter and the cyclone separating structure separates the solid particles larger than 50?m in diameter.With the established fluid domain geometric models of filtration structure and cyclone separating structure,numerical simulation of downhole drilling fluid solid-liquid separating device is carried out using Euler multiphase flow model,RSM turbulence model,and porous media model.Characteristics of the flow field,pressure drop curve in porous media and distribution of solid phase in the filtration structure and cyclone separating structure are analyzed.The influence of structural parameters of cyclone separating structure upon separation efficiency is analyzed to determine the optimal parameter sets.The testing system for separating efficiency is established according to the simulation results,and experiments are conducted to find out the separation efficiency of sand with different particle sizes.Compared with the simulation results,it is found that the experiment results are consistent with the simulation results within the allowable error range.It is then proved that the designed downhole drilling fluid solid-liquid separating device can satisfy the separation requirements and the numerical simulation method can be used to guide the design of downhole solid-liquid separation device.