高压含硫天然气对井口节流橇冲蚀的数值模拟及现场验证

Numerical simulation and field verification of high-pressure sour natural gas erosion within wellhead skid-mounted choke manifold

[目的]高压含硫天然气节流过程对节流橇有明显的冲蚀破坏作用,因此采取合理的检测手段非常重要。[方法]以川西北气矿双鱼石下二叠统气藏L004-X1井口节流橇为研究对象,采用Fluent软件建立数值模型,模拟井口压力103MPa的高压条件下的流场及冲蚀过程。分析了现场工况下节流橇内的压力场与速度场,研究了天然气中固体杂质颗粒的质量流量、入口速度、直径及节流橇前后压降对节流阀体冲蚀的影响,并采用超声波相控阵技术对现场L004-X1井出口段测温测压套开展了在线、离线壁厚检测,以验证节流橇冲蚀数值模拟及现场不停产在线检测的可行性。[结果]阀芯内壁面的冲蚀形貌以点状分布为主,出口段测温测压套的冲蚀形貌为连续片状分布,并且由于重力原因导致出口段测温测压套中位于下方的C面冲蚀最为严重。阀芯冲蚀最严重部位为阀芯内壁面,其次为阀芯出口处。冲蚀速率随颗粒的质量流量、入口速度的增加而增大,随颗粒直径的增大而逐渐减小并趋于平稳。对比数值模拟结果与超声波相控阵现场离线检测结果发现,出口段测温测压套4个面最小壁厚的平均相对误差为4.1%,验证了数值模拟的可行性。超声波相控阵现场在线、离线两种检测方法得到的最小壁厚基本一致,为便于现场操作,推荐使用在线检测方式。[结论]研究成果可为现场节流方案制定与节流橇的检测提供理论参考,但数值模拟研究中并未考虑H2S腐蚀的影响,后续可结合不同气体压力与速度的H2S腐蚀实验来进行更准确的冲蚀速率预测。(图12,表2,参20)

[Objective]Notable erosion damages occur in skid-mounted choke manifolds during the choking process of high-pressure sour natural gas,thus necessitating effective detection methods.[Methods]Taking the wellhead skid-mounted choke manifold L004-X1 in the Shuangyushi Lower Permian Gas Reservoir of Northwest Sichuan Gas Mine as the study object,a numerical model was developed using Fluent software to simulate the flow field and erosion process under high-pressure conditions(103 MPa)at the wellhead.The comprehensive analysis focused on the pressure field and velocity field within the choke skid under on-site operating conditions.Factors influencing the erosion of choke valve body,including mass flow rate,inlet velocity,diameter of solid impurity particles in natural gas,and pressure drop before and after the choke skid,were thoroughly investigated.Additionally,ultrasonic phased array technology was employed for on-site online and offline wall thickness detection of the temperature/pressure measuring casing at the outlet section of Well L004-X1.This study aimed to verify the feasibility of the proposed numerical simulation and on-site online detection method for choke skid erosion without requiring shutdown.[Results]From a morphological standpoint,the inner wall surface of the valve spool exhibited a predominant distribution of dotted erosion.The temperature/pressure measuring casing at the outlet section showed continuous sheet erosion,with the most severe erosion observed on the lower face C,attributed to the force of gravity.The valve spool displayed the most significant erosion on its inner wall surface,followed by its outlet.The erosion rate increased with higher mass flow rates and inlet velocities of particles,while gradually decreasing and stabilizing with increasing particle diameters.A comparison of results between numerical simulation and on-site offline detection using ultrasonic phased array technology revealed an average relative error of 4.1%in the minimum wall thickness of the four faces of the temperature/pressure measuring casing at the outlet section.This finding verified the feasibility of the proposed numerical simulation.The on-site online and offline ultrasonic phased array detection methods demonstrated consistent results for the minimum wall thickness.Therefore,the online detection method is recommended to facilitate on-site operations.[Conclusion]The findings of this study provide valuable theoretical guidance for the safe detection of field facilities in high-pressure sour gas reservoirs.However,the effect of H2S corrosion was not considered in the numerical simulation study.It is suggested to conduct H2S corrosion experiments under different gas pressures and velocities in further researches for more accurate prediction of erosion rate.(12 Figures,2 Tables,20 References)