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Demulsifier selection is still considered an art that improves with experience; however, there are methods now available to eliminate some of the uncertainties involved in demulsifier screening and selection. The properties of a good demulsifier were addressed previously. How to select the best demulsifier and to optimize its usage is addressed here. Demulsifier selection should be made with the emulsion-treatment system in mind. Some of the questions to be asked include the following.
The International Gas Union's (IGU) recent report on world LNG markets found that the trade increased by only 1.4 mt to 356.1 mt compared to 2019 supported by increased exports from the US and Australia, together adding 13.4 mt of exports. Asia Pacific and Asia again imported the most volumes in 2020, together accounting for more than 70% of global LNG imports. Asia also accounted for the largest growth in imports in 2020--adding 9.5 mt of net LNG imports vs. 2019. While 20 mtpa in liquefaction capacity was brought on stream in 2020, all in the US, startup of several liquefaction trains in Russia, Indonesia, the US, and Malaysia were delayed as a result of the pandemic, according to the report. The only project that was sanctioned in 2020 was the 3.25-mtpa Energia Costa Azul facility in Mexico, and in early 2021 Qatar took final investment decision (FID) on four expansion trains totaling 32 mtpa.
Profile seating nipples and sliding sleeves have a special locking groove and a honed sealbore to allow a flow-control device to lock in the nipple and seal off when installed. By design, the sleeves and nipples will have a smaller inside diameter (ID) than that of the tubing string. For this reason, careful consideration must be given to the overall application and completion design when selecting and sizing the various models of profile seating nipples and sleeves. This is especially true in any case in which through-tubing operations or perforating are planned. Correct application of flow-control accessories can greatly reduce the time and money spent on diagnosing well problems (such as tubing or leaks) should they occur.
Shearing of production fluids creates tight oil/water emulsions, including small droplets of oil in water and small droplets of water in oil. Small droplets rise very slowly and are often not adequately separated in a given residence time. This can overwhelm downstream equipment unless additional steps are taken such as increasing chemical dosage, adding or increasing heat, or removal of the emulsion for separate treatment--all of which will increase operating and capital expenses. For our purposes, we consider only the removal of oil from water in a water treatment system. Removal of water from oil, as in oil dehydration, will be discussed elsewhere. The article is simply a review of basic droplet formation due to shearing from pipes, valves, and pumps. It is intended to remind engineers that the decisions made upstream can have a grave consequence on downstream separation equipment performance. The article focuses mostly on the sources of shear, the relative magnitude of shear, and the consequence on the oil droplet size. Details regarding oil droplet size distribution is outside the scope of this article. Instead, the focus is on just one parameter of the droplet diameter distribution, the maximum droplet diameter. Also, the effect of smaller oil droplets on water treatment equipment is not discussed in detail.
This article presents progress on modeling bubble entrainment and transport around ships using hybrid Reynolds-averaged Navier-Stokes/large eddy simulation (RANS/ LES) methods. Previous results using a Boltzmann-based polydisperse bubbly flow model show that LES perform better than RANS in predicting transport of bubbles to depth, a very important process to predict bubbly wakes. However, standard DES-type models fail to predict proper turbulent kinetic energy (TKE) and dissipation, needed by bubble entrainment, breakup, and coalescence models. We propose different approaches to obtain TKE and dissipation in LES regions and evaluate them for cases of increasing complexity, including decay of isotropic turbulence, a flat plate boundary layer, and the flow in the wake of the research vessel Athena. An exponential weighted average is used to estimate statistics and obtain the averaged quantities in regions with resolved turbulence. The TKE is satisfactorily predicted in the cases tested. A modified ω equation in the SST model is proposed to implicitly compute the dissipation, showing superior results than the standard DES models, although further improvements are necessary. A hybrid RANS/LES approach is proposed, which focused at conserving total TKE as the flow crosses RANS/LES interfaces, as previously performed for zonal approaches but attempting a DES-like detection of regions suitable for LES, critical for large-scale computations of bubbly flows involving complex geometries. A general form of a dynamic forcing term is derived to transfer the modeled TKE to resolved TKE with a controller to guarantee proper conservation of the energy transferred. It was verified that the model is not sensitive to grid size or time step. Improvements to DDES and the proposed TKE-conserving hybrid RANS/ LES method show encouraging results, although remaining challenges are discussed.
ABSTRACT The leg chord of truss type leg has a complex rack structure, and its hydrodynamic analysis is usually based on cylindrical approximation or experience, resulting in the deviation of the results from the reality. In order to improve the accuracy of the results, CFD is used to simulate the flow field around the chord with rack structure. The case study shows that the hydrodynamic coefficient Cd of chord is related to the form and size of chord rack and flow direction. This method can be also used to determine the hydrodynamic coefficients of other slender structures. INTRODUCTION Ship and offshore engineering structures are in the flow field which contains sea water and air. The effect of the fluid on the structure shows strong nonlinear characteristics. Among them, slender structures are common in the field of ship and marine engineering, such as marine risers, spar platforms, etc., which can be called blunt bodies. The wake characteristics produced by the flow around the bluff body are directly related to the stress state of the bluff body. Unreasonable design will reduce the engineering life and even lead to the occurrence of engineering accidents. Jack up platform is one of the most widely used offshore platforms. It depends on the pile leg to stand on the sea floor. The pile leg bears the weight of the platform main body and the external environmental load, which plays an important role in the safety of the whole platform. Compared with other types of pile legs, truss pile legs have higher safety and material utilization ratio, and are more commonly used in large-scale jack up platform. As shown in Fig. 1, a typical truss type pile leg of a jack up platform is shown on site. The truss type pile leg is composed of chords and braces. Among them, each brace is a regular cylinder, but the profile of chord is in the form of cylinder + rack as shown in Fig.2.
Over the last decades underwater radiated noise due to human shipping activities increased significantly, which has proven adverse effects on the perception of fish and marine mammals. To protect and preserve marine biology, regulations regarding acoustic emissions of ships and specifically underwater radiated noise, are continuing to be tightened by regulatory institutions. This development is urging the shipbuilding industry to improve sound prediction and analysis methods. With the propeller as the dominating acoustic source under water, in particular propulsion solution manufacturers need to act in order to meet future requirements not only for near field acoustics, which are primarily studied as pressure pulses on the ship hull, but also far field sound propagation.
CFD simulations allowing for scale resolved turbulence modelling and phase-transition are required to identify acoustic sources, which are usually accompanied by immense numerical resource demands. With an implicit Large Eddy Simulation (ILES) turbulence modelling approach a numerically relatively efficient and thus industry friendly way of resolving turbulent length scales is pursued and combined with the Schnerr-Sauer mass transfer model for cavitation simulation. The simulation method is benchmarked for hydrofoils, open water propeller tests and a propeller in behind ship condition, to evaluate the proposed setups accuracy of predicting turbulent flow structures and cavitation inception and extent, with the intention of ultimately confirming acoustic signatures in the near field. While tip vortex and cavitation structures are investigated for instance for the Arndt hydrofoil and the PPTC’11 test case, acoustics are analyzed with the Newcastle propeller test case, which leads to good agreement with experimental results reinforcing this approaches capabilities.
Turbulent flow consist of eddies of various size range, and the size range increases with increasing Reynolds number. At very small scale, the energy of the eddies dissipates into heat due to viscous forces. Energy dissipation rate is the parameter to determine the amount of energy lost by the viscous forces in the turbulent flow. Different approaches are used to calculate the energy dissipation rate, depending on the type of restrictions the fluid passes through. Turbulent flow is a complex phenomenon, which may seem highly unpredictable.
An emulsion treating unit or system will use one or more of the methods listed in Table 1 to aid in destabilizing, coalescence, gravity separation. Heating oil emulsions has four basic benefits; It reduces viscosity, increases droplets, dissolves paraffin crystals, and increases density between oil and water. Crude oil emulsions with similar viscosity ranges do not always require the same type of treating equipment or the same treating temperature. Emulsions that are produced from different wells on the same lease or from the same formation in the same field might require different treating temperatures. For this reason, treating temperatures should be tested so that the lowest practical treating temperature for each emulsion and treating unit or system can be determined by trial.
Samples of an oil emulsion may be required for several reasons, including crude specification verification, performance evaluation of the emulsion treating system, or simply, laboratory testing. Invariably, the emulsion to be sampled is under pressure, and special procedures must be used to obtain representative samples. For crude specification testing, it is not important to maintain the integrity of the water droplets; however, the sample location point may be critical. In general, samples should not be withdrawn from the bottom of the pipe or vessel. Free water may be present and accumulate at the bottom of the pipe or vessel, affecting the basic sediment and water (BS&W) reading.