水平井过热蒸汽循环预热井筒传热模拟

Simulation of Superheated Steam Circulating in Sealed Wellbores

蒸汽辅助重力泄油(SAGD)被矿场实践证明是稠油开发的有效手段,为了在生产阶段获得满意的开发效果,矿场往往在正式开发前采取蒸汽循环预热的方式对近井地区进行加热。在预热阶段,由于近井地带稠油黏度为原始地层条件下的黏度,因此流动性很差,可以忽略蒸汽注入量。为了矿场应用方便,需要针对该物理过程进行建模,对井口操作参数进行优化,并对近井地带加热效果进行评估。基于质量、能量和动量守恒方程,建立了井筒内管流数学模型,并与地层中瞬态导热模型耦合,建立水平井SAGD井筒预热数学模型,并采用有限差分方法获得数值解。研究表明,当注汽压力过高时,过热蒸汽容易流入地层,降低循环热效率。随着过热蒸汽压力的升高,长油管和环形空间内过热蒸汽的温度升高。随着过热蒸汽压力的升高,长油管向环形空间的导热速率下降,而地层吸热速率不断升高。

The steam assisted gravity drainage (SAGD) has been proved effective in heavy oil recovery. In the field practice, the pre-steam circulating method is always adopted to obtain satisfactory oil recovery efficiency. During the pre-heating process, the amount of injected steam into reservoir can be neglected due to the poor mobility of heavy oil. It is needed to model the physical circulating process so that the optimal injection parameters at wellhead can be obtained, and the heating performance can be evaluated. Based on the mass, energy and momentum balance equations, a wellbore model is established. By coupling with the transient heat transfer model in formation, a comprehensive model is established. The model is solved with numerical methods. Results show that: the heating efficiency is reduced when more steam is injected into the reservoir;the temperature of superheated steam increases with rising of superheated steam pressure;the reservoir heat absorption rate increases with rising of superheated steam pressure.