Phase Splitting of Wet Steam in Annular Flow Through a Horizontal Impacting Tee Junction

Chien, Sze-Foo (Texaco Inc.) | Rubel, Mark T. (Texaco Inc.)

OnePetro 

Summary

Phase splitting occurs during gas/liquid two-phase flow through pipe junctions and causes a gas/liquid mass ratio in the outlet legs of the junction that is different from that at the inlet. In steamflood distribution networks, this results in different steam qualities at the outlets of a junction than at the inlet. This, in turn, results in a heat distribution not in accordance with the mass distribution in the outlets of the tee. Because heat management of a steamflood project is important for both economic incentives and ultimate recovery, phase splitting must be understood and controlled. This paper presents the results of an experimental investigation conducted on phase splitting of wet steam during annular flow through a horizontal 2-in. impacting tee. The experimental operating range included inlet pressures of 400 and 600 psig, inlet mass fluxes from 1,180 to 10,150 lbm/(in.2-hr), inlet steam qualities from 0.2 to 0.8, and outlet vapor extraction ratios for one outlet leg from 0.2 to 0.5. From these experimental data, the relative importance of these variables on phase splitting was determined and correlations to predict the outlet steam qualities were established. These correlations predicted the experimental results of the present investigation and of Azzopardi et al. to within acceptable limits.

Introduction

Most large steam EOR projects incorporate a complex steam distribution system involving a multitude of junctions to transport steam to injection wells. The junctions used to distribute the steam can be impacting or branching tees. An impacting tee divides the incoming flow into two coaxial outlet branches perpendicular to the inlet (Fig. 1). A branching tee diverts part of the incoming flow through a branch perpendicular to the inlet while the remainder flows straight through the tee (Fig. 2). In branching tee junctions, the vapor/liquid mass ratio at the outlets can be substantially different from that at the inlet. This phenomenon is known as phase splitting of two-phase flow. Because the vapor phase of a wet steam has a much higher heat content per unit mass than the liquid phase, the difference in the vapor/liquid ratio leads to a heat distribution to each outlet that is not proportional to the mass distribution of the steam. Because of the symmetric geometry of an impacting tee, it was felt that phase splitting may not occur. Therefore, many steam distribution systems of steamflood projects have used impacting tees as junctions. Recent studies have shown, however, that the phase splitting in impacting tees can be as severe as in branching tees, especially when the inlet quality and the extraction ratio are low.