Steam properties such as steam pressure and steam quality are critical parameters to form integrated steam chamber and control steam consumption cost during SAGD process. However, steam property variation along steam injection well was not well understood yet. In this paper, a model describing steam flow behavior in steam injection wellbore was built and solved; accordingly steam property variation along steam injection wellbore can be calculated. In our model, both vertical and horizontal wellbores were further divided into several segments. Mass, momentum and energy balance equations have been applied to steam flow inside each segment. During the derivation of these equations, a void fraction correlation that is based on flow-pattern-independent drift-flux model was applied to describe steam flow in a non-uniform manner.

This model was validated by several sets of published field data and a series of general cases were studied to investigate the steam property variation inside wellbore. The computational results indicated that steam property distribution along vertical and horizontal wellbore portions have similar characteristics: steam pressure and steam quality tend to decrease along with wellbore trajectory in both vertical and horizontal wellbore portions during SAGD process; With the increase of steam injection pressure, steam quality decreases faster; with the increase of steam quality during injection, steam pressure decreases faster; With the increase of steam injection rate, steam pressure decrease faster while steam quality decrease slower. For horizontal wellbore, the increase of reservoir permeability tends to slow down the steam pressure decrease but accelerates steam quality deterioration; the increase of oil viscosity tends to slow down the steam quality deterioration but accelerate steam pressure decrease. The results from this study show the effects of steam properties varying along wellbore trajectory under different steam injection conditions and can be used as a design guidance to optimize the steam injection practice in SAGD process.

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