Contribution to a More Reproductible Method for Measuring Yield Stress of Waxy Crude Oil Emulsions

Abstract

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.

Bingham’s model in the oil and gas industry

“…Water-in-crude oil emulsions generally undergo a solgel transition as temperature is decreased, especially for waxy oils (Hemmingsen et al 2005;Visintin et al 2008;Paso et al 2009;Maia Filho et al 2012;Haj-shafiei et al 2013;Barbato et al 2014;Sun et al 2014). The yield stress of these gelled emulsions may be very high (of the order of 1000 Pa), and an accurate and reproducible method for its measurement still lacks (Barbato et al 2014).…”

“…Water-in-crude oil emulsions generally undergo a solgel transition as temperature is decreased, especially for waxy oils (Hemmingsen et al 2005;Visintin et al 2008;Paso et al 2009;Maia Filho et al 2012;Haj-shafiei et al 2013;Barbato et al 2014;Sun et al 2014). The yield stress of these gelled emulsions may be very high (of the order of 1000 Pa), and an accurate and reproducible method for its measurement still lacks (Barbato et al 2014). To the large number of difficulties already found in the determination of the rheological properties of waxy crude oils (Marchesini et al 2012), several other arise, due to many additional factors that influence the gel structure and hence the bulk rheology (Visintin et al 2008;Paso et al 2009;Maia Filho et al 2012;Sun et al 2014).…”

Avaliação Estatística Das Principais Variáveis Que Influenciam O Módulo De Armazenamento Elástico De Emulsões De Água Em Petróleo Parafínico

“…Área temática: Simulação, Otimização e Controle de Processosparafina na amostra (Barbato et al, 2014). Portanto, é necessário definir-se um tempo de condicionamento mínimo, porém suficientemente longo, capaz de garantir que medidas reológicas posteriores sejam imparciais.…”

Wax Chemical and Morphological Investigation of Brazilian Crude Oils

“…Since the solubility of high molecular weight waxes decreases sharply with the decrease in temperature, they precipitate out and crystallize. This result indicates that in low temperatures, it is more probably to have problems of flow assurance due to pipeline blockage occasioned by wax crystal depositions and to the formation of a highstrength gel, characterized by yield stress [35][36][37]. Another common factor studied on precipitation and morphology of waxy crystals is the aging time, which represents the influence of the time at a certainly constant temperature on the crystal wax.…”

“…This result can be attributed to the Ostwald ripening of wax crystals, a mechanism by which the large crystals grew at the expenses of smaller crystals of higher energy. Furthermore, oil uptake can also change the wax crystal distribution, leading to larger and softer wax crystals that can interpenetrate increasing intermolecular interactions between crystals [11,37,38]. Table 2 shows the wax crystal's average length at t = 0 h and after 1 h (t = 1 h) at temperatures 40, 20, and 5°C, as well as the crystal growth percentage in function of aging time.…”