SAGD循环预热割缝筛管参数影响规律研究

Study on the Influence Law of Slotted Liner Parameters During SAGD Cycle Preheating Period

为预测SAGD循环预热阶段井筒内蒸汽热力参数分布规律,提高地层受热均匀程度,考虑割缝筛管管柱结构特点,建立水平井井筒与储层耦合数值模型,采用全隐式有限差分法和迭代技术对模型进行求解,并验证模型的准确性。利用该模型可预测井筒内蒸汽压力、温度、干度和地层吸热率等参数分布规律,对比不同割缝宽度、长度和密度对循环预热效果的影响。结果表明:蒸汽压降和温度降主要发生在长油管内,蒸汽干度降主要发生在环空内。随割缝宽度、长度和密度的增加,水平段吸汽长度均减小;压力下降幅度均变缓;蒸汽干度下降幅度均增大;地层受热非均匀性均增强。优化割缝筛管参数,避免蒸汽冷凝成水,提高返回跟端处的蒸汽干度值,可提高地层受热均匀程度。

In order to accurately predict the steam thermo-physics parameters along the horizontal wellbore during SAGD cycle preheating period,and improve the uniformity of formation heating,considering the structural characteristics of slotted screen completion string.A coupled numerical model of horizontal wellbore and reservoir was developed.The model was solved with full implicit finite difference method and iteration algorithm,and the accuracy of the model was verified.The model can be used to predict the distribution of parameters include steam pressure,temperature,steam quality and formation heat absorption rate along the wellbore,and to compare the effects of different slot widths,lengths and densities on the cycle preheating effect.The results show that the steam pressure drop and temperature drop mainly occur in the long tubing,while the steam quality drop mainly arises in the annulus.With the increase of slot width,length and density,the length of steam absorption in horizontal section decreases;the slope of pressure decreases and the slope of steam quality rises from toe point to heel point in the annulus;and the heterogeneity of formation preheating increases.Optimizing the slotted liner parameters,avoiding the steam condensation into water and increasing the steam quality at the heel point of annulus,can improve the uniformity of formation heating.