This study looked to improve reproducibility in the procedure to determine the yield stress of water-in-oil (W/O) emulsions prepared with waxy crude oil. The influence of various experimental variables was studied: measurement geometry, emulsion cooling rate, shear stress during the cooling step, gap reduction (parallel plates), final gap (parallel plates), and conditioning steps. The measured yield stress varied significantly depending upon the measuring geometry used (from 100 to 500 Pa). The geometries cross-hatched parallel plate (D = 60 mm) and grooved coaxial cylinder measured the highest yield stress, and it was observed that the shear stress during cooling was the most important measurement variable in the emulsion yield stress.

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Hydrate blockage in subsea systems is responsible for a portion of lost profits in several deepwater oil fields. This problem tends to worsen in the fields recently discovered in Brazilian Pre-Salt layer due to greater water depth, higher pressure, lower temperature, and oil more prone to agglomerate. Additionally, in this scenario, the logistic for hydrate remediation, if a rig is required, is even more complex due to the greater distance from shore. The overall conditions found in Brazil offshore fields prior to Pre-Salt development allowed applying a less conservative hydrate prevention design when compared to other areas throughout the world. Now, while the global trend is to reduce the safety margin to manage hydrate risk rather than simply avoid them, it may be interesting to increase flow assurance design robustness for some critical fields. This paper presents some suggestions in order to meet this goal.

Flow assurance is a multidiscipline process involving sampling, laboratory analysis, and production and facilities engineering to ensure uninterrupted optimum well productivity. Laboratory testing provides necessary data to assess the flow assurance risk because it defines phase behavior and the properties of the waxes, asphaltenes, emulsions and hydrates known to be principal causes of flow problems. In deep- and ultra-deepwaters scenarios the precipitation, deposition, and gelling of organic solids in hydrocarbon fluids constitute critical production concerns. Understanding the crude oil behavior can help to avoid high costs resulting from production reductions or stoppages or, conversely, from system overdesign. This paper shows an effort to establish correlations between Brazilian crude oils properties and flow assurance related issues.

Turbulent flow in d-type corrugated pipes of various aspect ratios has been numerically investigated in terms of flow pattern and friction factor, for Reynolds numbers ranging from 5000 to 100,000. The present numerical model was verified by comparing the friction factor with experimental and numerical results from the literature. The numerical analysis suggested that d-type behavior exists for groove aspect ratios up to w/k = (groove width/rib height) = 2 independent of the pitch. However, for a ratio of w/k = 3 an important change in the flow pattern occurs so that the pressure drag exerted by the groove walls becomes important. It is shown that the friction factor is independent of the groove height as long as the flow is similar to a flow in a d-type corrugated pipe. Moreover, the friction factor curve for d-type pipes shows a logarithmic behavior as function of the Reynolds number, so that a simple method can be used to derive an expression for the friction factor as a function of the Reynolds number and the relative groove width only. The results may be useful to engineering projects that require a better prediction of the friction factor in d-type corrugated pipes.