Based on parameters forecast model of conventional horizontal injector wellbore, combined with coupling calculation of dual-tubing steam mass flow, the mass conservation equation, energy conservation equation and momentum conservation equation of steam flow within injector wellbore under different tubing combinations in preheating and production phases are formulated and the key parameters calculation model of dual-tubing injector wellbore is established. The temperature and pressure along the injector wellbore during the steam-assisted gravity drainage (SAGD) preheating phase of a SAGD well are calculated and compared with the downhole monitored data, which shows good match and verifies the accuracy of the model. Meanwhile, the model calculates that the minimal steam injection rate during SAGD preheating phase is 60 t/d, the longest horizontal length is 564 m under current configuration. Considering the current configuration has disadvantages of two sections of steam imbibition that may result in risk of section/point steam breakthrough at Point A during SAGD production phase, the combination of long tubing and short tubing is optimized: the short tubing is relocated 150 m from Point A and long tubing is located at Point B. Consequently, three sections of steam imbibition could be realized, and the risk of section/point steam breakthrough at Points is effectively reduced.%依据普通水平井注蒸汽井筒内参数预测模型,结合双油管质量流速耦合计算,推导出SAGD循环预热及生产过程中,不同管柱结构组合条件下注汽井筒内蒸汽流动的质量守恒、能量守恒及动量守恒方程,建立了双油管注汽井井筒沿程参数计算模型.利用该模型对某SAGD注汽井循环预热过程中井筒内沿程温度、压力等参数进行了计算,结果与现场监测结果吻合,证明了模型的准确性.利用该模型计算得出现有管柱结构下SAGD循环预热阶段最低注汽速度为60t/d,注汽井最大水平段长度为564m;针对现有管柱结构在SAGD生产过程中为两段式配汽,A点存在段通及点窜风险等缺点,对现有水平段内的长、短油管组合进行了优化,优化后的短油管下入水平段A点后150m,长油管下入水平段B点,数值模拟结果表明,采用优化后管柱结构组合,在SAGD生产阶段可实现三段式配汽,有效降低了A点段通及点窜风险.
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