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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。
In order to study the flow field characteristics of CO2 natural gas well after blowout and to provide a scientific basis for the determination of safety protection distance, the fluid field characteristics of well blowout are analyzed by combining fluid mechanics theory and computational fluid dynamics (CFD) technology. The diffusion mechanism of the various stages of the field, the conditions for the solution to the simulations and the numerical calculation methods. The whole process of blowout can be divided into six stages: critical flow, isentropic expansion, compressible jet, incompressible jet, heavy gas diffusion and non-heavy gas diffusion. The CFD simulation method was used to simulate the velocity field of gas jet with CO2 natural gas well and the gas expansion rate was up to 700 m / s. The distribution of CO2 concentration was analyzed. The CO2 gas concentration in the inner region of isentropic expansion zone was uniformly distributed, In the outer region, the mass concentration of CO2 decreases sharply, and the variation of CO2 mass concentration with the diffusion distance accords with the Gaussian distribution. The theoretical predictions and simulation results are in good agreement, indicating that the theoretical analysis and CFD simulation of well blowout flow field are feasible.