地形起伏对凝析气集输管道工况的影响

Influence of undulating terrains on operation conditions of condensate gas gathering lines

地形起伏不均是造成凝析气单管气液混输管道生产不稳定的一个重要因素。为了了解地形起伏对凝析气单管气液混输管内流体压力、温度、持液率、持液量、流体流型、天然气水合物形成情况等的具体影响,借助于PIPEPHASE工艺流程模拟软件,选用由组分热物性模型、BWRST状态方程及MBE水力学模型共同构成的经验组合模型,以某凝析气田的一个集输管网系统为研究对象,模拟计算和分析了不同程度地形起伏下凝析气管网运行工况的变化情况。分析结果表明,管内流体压力、持液率的波动幅度以及管路总压降均随着地形起伏程度的增加而增大,但管路沿程温降和总持液量受地形起伏的影响较小;此外,地形起伏还容易导致管内流体流型出现不稳定情况,也易使管内形成天然气水合物,且地形起伏程度越大,天然气水合物生成的可能性就越大。该分析结果对地形起伏地区凝析气集输管道的工艺设计和生产运行管理具有一定的指导作用。

Undulating terrains often cause the unsteadiness of condensate gas flow in the gathering and transport lines and thus affects the pipeline operation. To solve this problem ultimately, it is necessary to analyze the parameters influenced by undulating terrains in detail including fluid pressure, temperature, liquid holdup, flow regime, hydrate formation, and so on. With the help of the PIPEPHASE simulation software, this paper adopted the empirical models composed of the thermal physical modeling components, the BWRS equation of state and the MBE hydraulic model is adopted. Then, taking the gas gathering line system in a certain condensate gas field as an example, the changing operating conditions of this line system under variable topographic relief terrains is simulated and analyzed. The analysis shows that, the sharper the terrain incline is, the greater the fluid pressure, liquidholdup fluctuation and cumulative pressure drop in linepipes. However, the parameters, such as temperature drop and total liquid holdup, are less likely to be influenced by undulating terrains. Besides, undulating terrains easily lead to the unsteadiness of fluid flow regime and the easy occurrence of hydrate formation in the linepipes. And the fiercer the fluctuation is, the greater the chance of hydrate formation is. In conclusion, this study provides guidance for the process design, operation and management of condensate gas gathering lines in undulating terrains.