延439井区气液混输管道瞬态变化规律及敏感性分析

Transient change law and sensitivity analysis on gas-liquid mixed transport pipeline in Y439 gas field

Y439井区采气管道为气液混输管道,地形起伏大导致积液严重,因此研究气液两相瞬态变化规律非常重要。以某采气管道为例,基于双流体模型建立多相流计算模型,研究管道积液动态规律和清管过程瞬态变化规律,提出采用井口压力峰值与最大清管段塞量相结合的方法确定管道清管时间,分析管道输气量、天然气含水量以及运行压力对井口压力峰值和最大清管段塞量的影响规律。研究结果表明:1)随着运行时间的延长,采气管道内积液逐渐向下游推移,当管道内积液量分布在全管段时,管道积液量和运行压力达到动态平衡;2)当管道入口投加清管器后,由于清管器上游气体被压缩,沿程摩阻损失增大,井口压力出现短暂的峰值变化,且管道出口排液主要集中在开始排液后0.5 h;3)敏感性分析结果显示,管道输气量越大,最大清管段塞量越小,井口压力峰值先降低后增大,在气相流速为1.2~3.1 m/s时增幅不明显;含水量上升,井口压力增幅明显,管道末端排液量显著增大;管道运行压力下降,对应的清管过程管道末端排液量显著增大。该成果可为气田气液混输管道的优化设计及清管操作提供理论依据。

The gas production pipeline is a gas-liquid mixed transport pipeline in Y439 gas field,which causes serious liquid accumulation because of the seriously undulating pipeline.Therefore,it is essential to study the gas-liquid two-phase transient change law.Taking a pipeline as an example,the author established a multiphase flow calculation model based on the two-fluid model and studied the pipeline’s liquid accumulation law and the pigging process’s transient law.Then,the author determined the pigging cycle by combining the peak wellhead pressure and the maximum pigging slug quantity and analyzed the influence of gas flow rate,water content,and operating pressure on the peak wellhead pressure and the maximum pigging slug volume.The research shows that:1)The liquid in the gas production pipeline gradually moves downstream with the extension of the operation time.The liquid in the pipeline and the operating pressure reach a dynamic balance when the liquid in the pipeline distributes in the whole pipe section.2)When the pig is added to the pipeline inlet,the friction loss along the pipeline increases,the wellhead pressure shows a short peak change,and the drain at the pipe outlet is mainly concentrated 0.5 h after the start of the drain because the gas upstream of the pig is compressed.3)The result of sensitivity analysis shows that the larger the gas volume of the pipeline,the lower the maximum pigging slug volume.The peak pressure at the wellhead first decreases and then increases,and the increase is not obvious when the gas phase velocity is 1.2~3.1 m/s;When the water content increases,the wellhead pressure increases significantly,and the liquid discharge at the end of the pipeline increases significantly;With the decrease operating pressure,the corresponding liquid discharge at the end of the pigging process increases significantly.The results can provide the theoretical basis for optimal design and pigging operation of the gas-liquid mixed transport pipeline in a gas field.