A NUMERICAL STUDY OF BOTTOM WATER DRAW-OFF OF STRATIFIED OIL-WATER PIPE FLOW

Abstract

In this study the problem of Bottom Water Draw-Off (BWDO) in stratified oil-water flow in pipelines is investigated using the finite-volume numerical method. This problem is frequently encountered in oil production pipelines with relatively high water cut. The conditions simulated are those obtained from field tests for a 68-cm I.D. pipeline. The flow conditions in this pipe result in stratified flow of relatively oil-free water at the bottom and oil-in-water dispersion at the top. The oil concentration in the oil-in-water dispersion layer was variable across the layer. The BWDO from a single 90° draw-off branch was simulated using a single fluid model coupled with particle tracking technique. Using the model the draw-off water quality was calculated for different draw-off flow rates and three different oil-in-water dispersion concentrations and three possible locations of the interface between the dispersion and water layers. The flow from two consecutive draw-off pipes 5-meter apart was also simulated under the same conditions. The two draw-off pipes flow rate combinations required to produce a desired draw-off water quality were calculated. Thus, threshold flow rates beyond which the quality of drawn-off water starts to deteriorate was established. The results obtained in this study should aid in proper design of BWDO systems in oil pipelines with high water cut under stratified flow conditions.