Identification and Classification of New Three-Phase Gas/Oil/Water Flow Patterns
- Cengizhan Keskin (SPT Group) | Hong-Quan Zhang | Cem Sarica (U. of Tulsa)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 11-14 November, Anaheim, California, U.S.A.
- Publication Date
- Document Type
- Conference Paper
- 2007. Society of Petroleum Engineers
- 4.6 Natural Gas, 4.2.3 Materials and Corrosion, 4.3.1 Hydrates, 4.1.5 Processing Equipment, 5.3.2 Multiphase Flow, 4.3.3 Aspaltenes, 3.1.6 Gas Lift, 5.2 Reservoir Fluid Dynamics, 4.2 Pipelines, Flowlines and Risers, 4.1.2 Separation and Treating, 4.2.2 Pipeline Transient Behavior
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Three-phase gas-oil-water experiments have been conducted in horizontal pipes at various flow rates and water cuts. Three-phase flow patterns have been observed and identified using a high speed video system and a new classification of three-phase flow patterns is proposed. Twelve new three-phase gas-oil-water flow patterns are: Stratified-Stratified, Stratified-Dual Continuous, Stratified-Oil Continuous, Stratified-Water Continuous, Intermittent-Stratified, Intermittent-Dual Continuous, Intermittent-Oil Continuous, Intermittent-Water Continuous, Annular-Oil Continuous, Annular-Water Continuous, Dispersed Bubble-Oil Continuous and Dispersed Bubble-Water Continuous. The flow pattern maps are presented based on the new three-phase flow pattern classification. Comparisons made with the available two-phase flow pattern model predictions show the inadequacy of the two-phase flow models in characterization of three-phase flow.
Three-phase flow is the flow of three different phases in a pipe at the same time. Three-phase gas-oil-water flow is a common occurrence in the petroleum industry. Most of the gas and oil reservoirs naturally contain water or due to the pressure decrease with production, the natural pressure of an oil reservoir is maintained by injecting water. Therefore, water is produced along with oil and gas which results in three-phase gas-oil-water flow in wellbore and surface gathering systems of many flowing and gas lift wells, and in sub-sea production lines, pumping systems and in surface gathering lines. Perhaps, the most relevant practice is the transportation of natural gas-oil-water mixtures through pipelines.
A gas-oil-water mixture presents complex problems in both transportation and production stages due to its complicated flow behavior. The pipeline design parameters, such as; pressure gradients and holdups strongly depend on the flow pattern. The flow pattern also has an effect on the corrosion of the pipeline which is caused by the free water in contact the pipe wall. The other problems related to gas-oil-water flow patterns are wax and asphaltene deposition, and formation of hydrates and emulsions.
In gas-oil-water flow, both gas-liquid and oil-water flow patterns are observed at the same time. Very well-known horizontal gas-liquid flow patterns are: stratified, stratified wavy, elongated bubble, slug, dispersed bubble and annular flow. The horizontal oil-water flow patterns based on Trallero's1 classification are: stratified flow (ST), stratified with mixing at the interface (ST & MI), dispersion of oil in water over a water layer (Do/w & w), emulsion of oil in water (o/w), emulsion of water in oil (w/o) and dual type of dispersions (Dw/o & Do/w).
However, there is no consensus on three-phase gas-oil-water flow patterns. Some researchers, such as Malinowsky2 and, Laflin and Oglesby3used only two-phase gas-liquid flow patterns to present their three-phase test results. In all of these studies oil-water mixture was considered as a single phase liquid for the dispersed flows. Therefore, they did not need to identify new flow patterns for three-phase flow.
On the other hand, some other researchers made new classifications and identified new three-phase flow patterns. One of these researchers is Sobocinski4 who conducted three-phase flow experiments in an 11.6 m long horizontal transparent plastic tube with a 0.079 m ID. The experiments were carried out at atmospheric conditions and the superficial velocities were between 2.4-16.3 m/s for air, 0.006-0.09 m/s for oil and 0.002-0.088 m/s for water. Sobocinski4 was the first researcher in the literature to classify three-phase flow patterns and identified nine flow patterns based on gas-liquid and oil-water status. The flow patterns are: Stratified-No liquid mixing, Ripple-No liquid mixing, Surface waves-Inception of oil and water mixing, Light waves-Incipient emulsion, Waves-Incipient emulsion, Waves-Partial emulsion, Heavy waves-Partial emulsion, Light crests-Emulsion, and Semi annular-Emulsion. The first part of the flow pattern names indicates gas-liquid status and the second part indicates oil-water status of the flow. It can be seen that Sobocinski4 did not make a classification depending on the continuous liquid phase and his three-phase flow patterns included only stratified and stratified wavy gas-liquid flow patterns. Therefore, this classification is far from complete.
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