含CO2天然气井井喷流场特征

为研究含CO2天然气井井喷后的流场特性进而为确定安全防护距离提供科学依据,采用流体力学理论与计算流体力学(CFD)技术相结合的方法分析了井喷的流场特征,阐述了井喷流场各个阶段的扩散机理,模拟所需的定解条件及数值计算方法.井喷整个过程可划分为临界流、等熵膨胀、可压缩射流、不可压缩射流、重气扩散和非重气扩散6个阶段.采用CFD模拟方法模拟得出含CO2天然气井井喷气体速度场,气体膨胀速度可达700 m/s以上;分析了CO2浓度分布规律,在等熵膨胀区的内层区域CO2气体质量浓度均匀分布,而在外层区域内,CO2 的质量浓度急剧降低,CO2质量浓度随扩散距离的变化符合高斯分布.理论预测与模拟结果具有很好的一致性,表明提出的井喷流场理论分析与CFD模拟方法是切实可行的.

Flow fields in the blowout of natural gas wells containing carbon dioxide

The flow fields of the blowout of natural gas containing carbon dioxide were analyzed by using fluid dynamics theory and computational fluid dynamics (CFD) technology so as to provide scientific foundation for safe distance determination. Dispersion mechanisms of blowout flow field at each stage, boundary conditions and numerical algorithm for simulation were presented as well. The process of well blowout can be divided into six stages. They are critical flux, equal entropy expanding, compressible ejection, incompressible ejection, heavy gas dispersion, and normal dispersion. The distribution of gas velocity field was got via CFD simulation, and the flux velocity can be more than 700 m/s. The concentration of CO2 was analyzed, indicating that in the inner layer of the equal entropy expanding area, the concentration is uniform, while in the external layer, the concentration declines sharply. The correlation between mass concentration of CO2 and dispersion distance obeys the Gauss formula. The theoretical predictions were consistent with the results of simulation, It shows that the theoretical analysis of flow field and the CFD simulation method are practical.