Laboratory Validation of Critical Flow Choke Rate Equations for Wet Steam at Field Operating Conditions

Abstract

ABSTRACT In recent years, the effort put forth toward the advancement of steamflood technology for improved heavy oil - recovery has seen considerable growth. A significant portion of the costs associated with a steamflood operation may be attributed to the generation of the steam required for injection. It is extremely important, therefore, that a high degree of accuracy is maintained in the measurement and control of the resulting steam-water mixture at each individual well. In fields where the required injection pressures are relatively low, the most common method of controlling the flow rate utilizes critical flow static chokes. New data are presented for the flow of steam-water through critical flow static chokes at conditions representative of a typical steam flood operation. The experimental data are a result of testing in Texaco’s new Steam Flow Research Facility. The experimental data covers a wide range of inlet qualities (20 to 100%) and inlet pressures (400 to 800 psig) for static choke bean diameters of 24/64 and 28/64 inch. The Thornhill-Craver empirical correlation predicts all of the experimentally measured values of critical mass flow rate within ± 10%. For inlet qualities ≥ 40%, all data is predicted within ±5%; below 40%, the equation over-predicts the critical flow data. The Napier equation modified for wet steam by King and Crocker over-predicts the critical mass flow rate at the present range of operating conditions.