基于泡沫携液实验的压降携液量CFD数值模拟

CFD numerical simulation of pressure drop liquid carrying capacity based on foam carrying liquid experiment

为了研究流体动力学(CFD)方法对泡沫排水采气的可行性及在实际井筒中的流动规律,通过分析直井在不同质量分数泡排剂的流型、压降和携液量,得到最优泡排剂质量分数,基于室内实验模型建立相同的CFD物理模型,并对多相流模型(Eulerian模型、VOF模型和Mixture模型)和紊流模型(Reynolds Stress、k-ε和k-ω模型)进行优选得到最适合泡沫排水采气的数学模型,最后在实际井筒温度压力条件下进行CFD模拟得到流型压降携液量规律。结果表明:泡排剂质量分数为0.3%时携液效果最好;优选得到的最优CFD数学模型为“VOF+k-ω”,模拟结果与实验结果对比,压降、携液量误差均在10%以内;在实际井筒条件下,随着温度和压力增至40℃和15 MPa,液、气量分别低于0.2 m^(3)/h、30 m^(3)/h时,流型转为弹状流,压降增加1.8倍,携液量减少0.72倍,泡排效果减弱。该计算方法计算简单、准确性高,可以为泡沫排水采气工艺技术的高效实施和方案优化提供理论指导。

In order to study the feasibility of computational fluid dynamics(CFD)method for foam drainage gas recovery and the flow law in actual wellbore,the flow regime,pressure drop and liquid carrying capacity of vertical wells with different foam drainage agent mass fractions are analyzed to obtain optimal foam drainage agent mass fraction.The same CFD physical model is established based on lab experiment model,and multiphase flow models(Euler model,VOF model and Mixture model)and turbulence models(Reynolds Stress,k⁃εand k⁃ωmodels)are optimized to obtain the most suitable mathematical model for foam drainage gas recovery.Finally,the CFD simulation is carried out at actual wellbore temperature and pressure to obtain the law of flow regime pressure drop and liquid volume.The results show that foaming agent with mass fraction of 0.3%has the best liquid carrying effect.The optimal CFD mathematical model is“VOF+k⁃ω”.Comparison between simulation and experiment results shows the errors of pressure drop and liquid carrying capacity both less than 10%.Under actual wellbore conditions,with temperature and pressure increase to 40℃and 15 MPa,and liquid and gas volume are lower than 0.2 m^(3)/h and 30 m^(3)/h respectively,flow regime turns to slug flow,pressure drop increases by 1.8 times,liquid carrying capacity decreases by 0.72 times,and foaming drainage effect is weakened.The calculation method is simple and accurate,and provides theoretical guidance for efficient implementation and optimization of foam drainage gas recovery technique.