The structure of thin, wavy falling films was studied to evaluate whether the random-appearing wave structure is a result of deterministic chaos or a purely stochastic process. The time-varying film thickness was obtained at different spatial locations near the point of wave inception for flow rates in the range of lntroduc t ionThe hydrodynamic behavior of thin wavy falling films has been a subject of intensive investigation for about forty years. These films are widely employed in equipment for heat transfer, mass transfer, and chemical reacting systems. In addition to the practical need for understanding the mechanics of this type of flow, there are challenging theoretical problems embedded in the task of modeling these wavy films. This combination has given rise to an extensive literature on this subject.The earliest work was based on the use of integral equations of the boundary layer type to solve the equations of motion (Kapitza and Kapitza, 1949;Shkadov, 1967). These approaches were based on the assumed existence of a periodic interface and produced first-order estimates for wavelength and velocity. A long series of papers including work by Benney (1966), Lin (1969), and Whitaker (1964), used linear stability analysis to find the wavelength and velocity of the fastest growing wave, again assuming a periodic perturbation. This initial periodic disturbance is thought to evolve into the more complex waveforms observed in experiments as a result of the nonlinear nature of the equations. Nonlinear stability analyses have also been pursued (Pumir, 1983). Recent work on the nonlinear But even a cursory examination of measured wave traces raises some doubts as to the usefulness of the idea of a smallamplitude periodic wave as the model for the initial phase of the wave motion or of isolated waves as a model for the developed ones. Figure Id shows a wave trace for a falling liquid film of water-glycerine solution taken with a conductivity probe mounted in a vertical pipe of 50.8 mm dia. as described below. The flow rate corresponds to a Reynolds number of 3.9. The probe was located 0.346 m below a carefully leveled, sharpedged overflow weir that served as the feed device. The film thickness data are shown after low-pass digital filtering at 25 Hz to remove noise. At this location the wave amplitude is less than 0.25% of the mean film thickness. At all positions closer to the feed the waves were so small that they could barely be detected even with the special circuitry used for this purpose. Note that while the period between successive waves is quite regular, the amplitude is very random. Kapitza and Kapitza (1949) in their classical study of waves on falling films found it necessary to pulse the feed to produce periodic waves. In the absence of pulsing they too reported that the waves were random in appearance. Thus one must question whether the

New slug flow data and closure relationships for heavy oils have recently become available in the literature for both horizontal and vertical flow. This laboratory data allows the testing of current modeling technology to understand what modeling gaps must be addressed and where more data is needed. Comparisons of the data with typical one-dimensional slug flow models were performed at conditions where the liquid flow in the liquid slug is either laminar, transition or weakly turbulent flow. The closure relationships such as distribution parameter, drift velocity, and holdup in liquid slug are discussed along with the impact of these choices.

In mature fields, wells and pipelines are often oversized for the current operating conditions. This is because they have been primarily designed to handle early and midlife production, which may lead to slugging issues in later field life. The resulting flow fluctuations frequently lead to liquid handling problems caused by excessive liquid levels and pressure surges in the first stage separator. This can be an important source of downtime due to facility trips and deferment from sub-optimal facility operations. Furthermore, slugs travelling through topside piping can cause integrity issues when they impact bends.In flowline-riser systems, riser-induced slugging can lead to large slugs, especially in deepwater systems. These can usually not be contained in a platform-based separator. In such cases gas lift and conventional choking are often used to mitigate slugging. These two methods have drawbacks, however. For gas lift a source of compressed lift gas must be connected to the riser base and the volumes required to mitigate slugging may cause constraints in gas handling. Conventional choking leads to production deferment due to the backpressure imposed by a partially closed choke.In recent years "active" slug control methods have been developed to overcome these drawbacks. One such system is a relatively inexpensive solution developed by Shell Global Solutions* known as the Smart Choke. This system has been installed at several locations worldwide and has been proven to be very effective in stabilizing slugging in flowlines and risers. Here, the topside choke is actively controlled to mitigate riser-induced slugging and acts only if flow surges are observed, reducing the peak flow rate into the separator. Between slugs, the choke opens, reducing the imposed backpressure. Since flow fluctuations are reduced, a flowline can be operated at higher average flow rate as the topside facilities can be operated at higher throughputs without risking excessive separator liquid levels. Field data from case histories in the GOM, Malaysia and Nigeria indicate that production gains of 10% are often possible.This paper presents the modeling, implementation and the data obtained from operations of the Smart Choke implementation for a deepwater facility in Nigeria. The objective of the Smart Choke is to stabilize * Shell Global Solutions is a network of independent technology companies in the Shell Group. In this document, the expressions "Shell" or "Shell Global Solutions" are sometimes used for convenience where reference is made to these companies in general, or where no useful purpose is served by identifying a particular company.the flow from the riser and to reduce the gas lift requirement. A feasibility study was performed to analyze the slugging behavior of the pipeline and the impact of no control, gas lift and, the combination of gas lift and Smart Choke. Upon favorable modeling results, the Smart Choke was moved to the project stage and implemented. Field data are presented to demonstrate how the Smart Choke was able ...

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