SAGD循环预热水平段注汽参数规律

SAGD循环预热效果是影响SAGD开发技术的项重要因素，循环预热水平段与油层直接接触，循环预热过程中由于注汽参数选取不匹配易造成水平段加热不均匀，针对该问题提出以蒸汽返回某点时蒸汽干度大于等于0为目标的水平段注汽参数优化方案。以现场实际管柱结构、油藏特点为基础，建立水平段循环预热流动传热数学模型，采用差分法对模型进行编程求解，分析蒸汽压力、干度、散热量等参数沿程分布规律，对比不同注汽速度、注汽干度组合对预热效果的影响。并得到加热均匀和经济有效的SAGD水平段循环预热最优参数图版。结果表明：循环预热阶段，沿程压降、温降主要发生在长油管中，在环空中蒸汽主要消耗汽化潜热加热油层；注汽流速越小、干度越低越有利于环空与油层换热。
The circulation preheating effect of SAGD is an important factor affecting the development of SAGD Technology. The horizontal section is in direct contact with the reservoir, and it is easy to cause uneven heating of the horizontal section due to the unmatched steam injection parameters.Aiming at this problem, in this paper we put forward the optimization scheme of the steam injection parameter with the steam dryness not less than 0 when the steam returns to the point. The mathematical model of steam flow based on the real structures of column site and reservoir characteristicsis is established for steam cycle preheating. The finite difference method is used to solve the model, and the distributions of the steam pressure, dryness and heat dissipation along the wellbore are discussed. The influence of the steam injection rate and steam injection dryness on the preheating effect is discussed, and the optimum parameter chart of SAGD cyclic pre-heating with uniform heating and economy is obtained. The results show that the pressure drop and temperature drop along the wellbore mainly occur in the long tubing during the preheating cycle, and the steam in the annulus mainly consumes the vaporized latent heat to heat the oil layer. Moreover, the steam injection rate is smaller and the dryness is lower, it is more favorable to the heat transfer between the annulus and reservoir