New Correlations for Critical and Subcritical Two-Phase Flow Through Surface Chokes in High-Rate Oil Wells

Abstract

Summary The critical and subcritical multiphase flow through wellhead restrictions of a prolific oil field in the Middle East is investigated, and two sets of new correlations are presented. The first set of correlations is developed by using 40 field tests representing critical flow conditions. The second set of correlations is based on 139 field tests representing subcritical flow conditions of gas/liquid mixtures through wellhead chokes. For the critical multiphase flow condition, the predicted oil flow rates by the new set of correlations are in excellent agreement with the measured ones. The absolute average percent difference (AAPD) is between 1.88 and 4.37, and the corresponding standard of deviation (SD) is between 2.52 and 6.52. These results are found to be statistically superior to those predicted by other published correlations considered in this work. During the subcritical gas/ liquid flow conditions through surface chokes, the accuracy of oil flow rates predicted by the new set of correlations seems to be sensitive to the type and size of the choke being used. For Cameron LD type and 144/64-in. choke, the oil flow rates predicted by the proposed correlation are superior to those predicted by other methods available in the literature, with AAPD of 8.5. However, for smaller choke sizes of 96/64 and 64/64 in., the oil flow rates predicted by the new correlations and other methods are found to be close to each other. For Cameron F type and 144/64-in. choke size, the oil flow rates predicted by the new correlation are closely matched by those predicted by other published methods, with AAPD of 13.7. For smaller choke sizes of 80/64 and 64/64 in., few field tests are available, and the predications of all methods, including the proposed ones, show similar statistical results. The above findings for Cameron F choke also seem to apply to beaned wellhead assemblies for this particular oil field.