Effect of friction work on key parameters of steam at different state in toe-point injection horizontal wellbores

When modeling of steam flow in wellbores, the effect of friction work on temperature/ steam quality of both fluid in wellbores and reservoir should be considered. A model that can describe the energy re-distribution in the system should be built. In this paper, new energy balance equations for steam flow in inner tubing (IT) and annuli are developed with consideration of the effect of frction work on the energy re-distribution process in the system. The heat energy caused by shear stress has an obvious influence on the increase of steam quality or superheated steam temperature, especially under high injection speed condition. Firstly, a model for steam flow is developed in wellbores based on the energy and momentum balance equations. The energy balance equation controlls the predicted values of steam quality or superheated steam temperature, and the momentum balance equation controlls mainly the steam pressure. Secondly, coupled with the seepage model in oil layer, a comprehensive mathematical model is establiehed for single, two-phase flow of steam in horizontal wells with toe-point injection technique. Results show that: ( a) when the effect of friction work was neglected, the predicted steam quality or superheated steam temperature were obviously smaller than field data. (b) While seam quality decreases with distance when wet steam flows in wellbores, superheated steam temperature in annuli has an increase at the heel-point in annuli. This is because the fluid with lower temperature in annuli absorbs heat from steam with higher temperature in IT. (c). In order to obtain a satisfactory oil recovery ratio, field engineers are suggested to increase the injection pressure to a reasonable level based on the rock fracture pressure experiment.