二氧化碳连续管井筒流动传热规律研究

基于二氧化碳在井筒内流动时的传热过程,考察二氧化碳在井筒内的热量和压力传递方式及其对相态和物性变化的影响规律。建立二氧化碳井筒内热传递模型,采用交替方向推进法进行求解,分析二氧化碳在井筒内流动过程中温度、压力和相态的变化规律。结果表明:二氧化碳在连续管内热交换效率较高,温度上升幅度随着井深的增大逐渐减小;二氧化碳沿环空上返过程中,温度逐渐降低,在靠近井口处温度显著下降;随着井深的增大,连续管内的液态二氧化碳逐渐转变为超临界态,在沿环空上返的过程中再次转变为液态,继而变为气液两相至出口。

Wellbore heat transfer law of carbon dioxide coiled tubing drilling

Based on heat transfer process of carbon dioxide wellbore flow, the heat and pressure transfer mechanism of carbon dioxide in the wellbore, as well as the carbon dioxide property variation and phase change were investigated. The wellbore heat transfer model of carbon dioxide was developed, through which the wellbore temperature and pressure profiles were analyzed using alternate direction method. The results show that heat transfer efficiency is relatively high in wellbore. The increase extent of temperature for carbon dioxide reduces with the well depth gradually. Annular temperature of carbon dioxide decreases along the flow, and the temperature decreases significantly near the wellhead. The phase of carbon dioxide changes from liquid to supercritical state along the flow, then to liquid phase in the annular area. It changes to liquid-gas state at last.