酸性气井关井后重组分沉降对井筒组分变化的影响  

Impact of heavy constituent precipitation on gas component variations in a sour gas well during the shut-in period

作　　者：郭肖[1] 杜志敏[1] 付德奎[1] 

机构地区：[1]"油气藏地质及开发工程"国家重点实验室.西南石油大学

出　　处：《天然气工业》2010年第3期60-62,共3页Natural Gas Industry

基　　金：国家高技术研究发展计划(863计划)(编号:2007AA06Z209);国家自然科学基金项目(编号:50974104;50774062);四川省青年基金项目(编号:09ZQ026-048)

摘　　要：目前经典的井筒稳态多相流流动模型没有考虑关井后重组分沉降作用,可能导致井筒压力—温度预测不准。针对酸性气井井筒复杂流动特征,基于热动力学平衡原理和热扩散理论,考虑酸性气井关井后H2S及CO2重组分在重力、化学势变化以及热扩散作用下向下沉降,建立了重组分沉降过程中组分梯度方程和扩散模型,模拟计算了井筒压力分布和组分变化。研究表明:关井后井筒中H2S和CO2重组分沉降导致流体密度、H2S、CO2摩尔浓度从井口到井底逐渐增大,而C1、C2组分含量逐渐减少。实例井5000m井深井口样和井底样H2S含量差别近10%,建议酸性气井流样分析宜采用井底样。这也解释了为什么酸性气井井底一般腐蚀更为严重。At present, classical steady-state multiphase flow models are built without the consideration of the heavy constituent precipitation during the shut-in period, which may lead to the inaccuracy in predicting pressure and temperature. In this paper, in view of the complicated wellbore flow characteristics in a sour gas well, and based on the thermodynamic equilibrium and thermal diffusion theories, a compositional gradient equation and a thermal diffusion model were developed taking into account of the precipitation of H2S and CO2 under the action of gravity, chemical potential variation and thermal diffusion. An analog calculation for pressure distribution and component variations of wellbore was performed. The results show that the heavy constituent precipitation (H2S and CO2) causes the fluid density and molar concentration of H2S and CO2 to increase gradually from the wellhead to the bottom, and to decrease in the component concentration of C1 and C2. The difference of H2S content between the wellhead and the bottom is approximately 10% in a sour gas well with 5000 m in depth. This can interpret why serious corrosion often happens at the bottom of a sour gas well. In addition, it is suggested that fluid samples should be selected from the well bottom for the fluid analysis.

关 键 词：酸性气体 气井 关井 组分 腐蚀 数学模拟 影响 分析 

分 类 号：TE37[石油与天然气工程—油气田开发工程]