Low temperature rheological behavior of Umbarka waxy crude and influence of flow improver

El‐Gamal, I. M.; Gad, E. A. M.

doi:10.1016/s0927-7757(97)00079-4

Cited by 18 publications

(11 citation statements)

References 6 publications

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“…Davenport and Somper (1971), for example, showed that the reduction of temperature enlarges significantly the material yield stress. The increase of yield stress, the storage modulus, G′, the loss modulus, G″, and the viscosity with the temperature reduction was also observed by several authors (Wardhaugh and Boger 1987;El-Gamal and Gad 1998;El-Gamal 1998;Remizov et al 2000;Chang et al 2000, Webber 2001Venkatesan et al 2003;Kané et al 2004;Visintin et al 2005;Chen et al 2006;Zhang 2007, 2010;Lopes-da-Silva and Coutinho 2007;Lee et al 2008;Li et al 2009;Oh et al 2009;Hasan et al 2010;Dimitriou et al 2011;Ghannam et al 2012;Rønningsen 2012). The rise of such properties was attributed to wax solubility reduction in oil as the temperature decreases (Venkatesan et al 2003).…”

Section: Introductionsupporting

confidence: 66%

Influence of the initial cooling temperature on the gelation and yield stress of waxy crude oils

et al. 2014

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One of the major problems in waxy crude oil production and transportation is oil gelation that takes place within pipelines as a result of wax crystallization at low temperatures. In such cases, the pressure needed to restart the oil flow in subsea pipelines can be much larger than the usual steady-state pressure, as the temperature in such environment can be as low as 4°C. The literature has shown that not only the temperature itself but also the fluid shear and thermal histories have significant influence on the yield stress of waxy crude oils. This paper investigates the effect of the initial cooling temperature on the waxy crude oil viscosity, gelation temperature, and yield stress. In order to accomplish that, rheological tests were carried out under static and dynamic cooling conditions. The results show that there is a critical range for the initial cooling temperature that provides maximum values for viscosity, gelation temperature, and yield stress. In other words, the highest values of those properties are observed when the cooling started within this temperature range. The effect of a thermal pretreatment usually used to remove light ends was also investigated. In spite of not changing the initial temperature critical range, the yield stress was slightly affected by the thermal treatment. It is worth noting that the yield stress varies from approximately zero to hundreds after dynamic cooling or to thousands after static cooling within the tested range of the initial cooling temperatures.

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Section: Introductionsupporting

confidence: 66%

Influence of the initial cooling temperature on the gelation and yield stress of waxy crude oils

et al. 2014

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“…20 Then, the crude oil was left at room temperature for 48 hr before any further utilization. 21 The wax precipitation characteristics of Oil M, including the wax precipitation curve, wax content, and WAT were determined by using a differential scanning calorimeter (TA Q20), which has a heat flux controlling accuracy of ±0.1 μW and a temperature controlling accuracy of ±0.05 C. The test specimen (a crucible with waxy crude oil) was first heated to 80 C and held for 1 min to resolve all precipitated wax. Then, the specimen was cooled to −25 C at a cooling rate of 5 C/min.…”

Section: Besides Zhang Et Al Liang Et Al and Wang Et Al Investigatmentioning

confidence: 99%

Investigation of thickness and wax content of wax deposits in polyethylene pipe using a flow loop

Huang

Zhang

et al. 2020

AIChE Journal

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In this study, the thickness and wax content of wax deposits were found to be thinner and lower in the polyethylene (PE) pipe than in the stainless steel (SS) pipe using a flow loop apparatus. The diffusivity of wax, radial thermal gradient, and wax precipitation rate in the PE and SS pipes were calculated and compared. It was found the diffusivity of wax in the PE pipe was higher and tended to enhance the wax deposition in the PE pipe, while the radial thermal gradient and wax precipitation rate were lower in the PE pipe and had the opposite effects. These factors are shown to be comparable with each other and the effect of the thermal gradient dominates the mass flux of wax from bulk to the oil‐deposit interface and into the deposits finally, thus causing differences in thickness and wax content of deposits between the PE and SS pipes.

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“…It is also known that the flow behaviors of wax crude oils are also characterized by their shear and thermal history dependence, called the shear and thermal history effect. [5][6][7][8][9] This effect is mainly shown at temperatures below the abnormal temperature. This shear and thermal effect can be attributed to the effect of shear and heating/cooling on the morphology and structure of wax crystals.…”

Section: Introductionmentioning

confidence: 99%

“…It is also known that the flow behaviors of wax crude oils are also characterized by their shear and thermal history dependence, called the shear and thermal history effect. − This effect is mainly shown at temperatures below the abnormal temperature. This shear and thermal effect can be attributed to the effect of shear and heating/cooling on the morphology and structure of wax crystals. ,, Wardhaugh and Boger 5 studied the shear history effect of waxy crude oils and suggested a so-called locus of equilibrium viscosities to replace the rheological model in hydraulic calculations of steadily operating pipelines.…”

Section: Introductionmentioning

confidence: 99%

Flow Behavior of Daqing Waxy Crude Oil under Simulated Pipelining Conditions

Ding

Zhang

et al. 2006

Energy Fuels

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Daqing oilfield is the largest oilfield in China. This crude oil is a typical waxy crude oil, with a wax content of 26% and a gel point of 32 °C. Flow behaviors of waxy crude oils at temperatures near the gel point/pour point are vital for both pipeline hydraulic calculation and evaluation on restartability of a shutdown pipeline. In this study, experimental simulation was conducted by using a stirred vessel with the energy dissipation of viscous flow as the shear simulation parameter. Crude oil specimens were taken from the stirred vessel at different temperatures during flow simulation, and the DSC (differential scanning calorimetry) curves and rheological properties, such as viscosity, gel point, yield stress, and thixotropy, were measured. The viscosity under simulated pipelining conditions was found to be much less than that measured under quiescent cooling conditions, and the gel point decreased with decreasing temperature of sampling, i.e., the end temperature of the dynamic cooling process. The DSC curves of crude oil specimen captured at different sampling temperatures and from different positions such as the bulk of crude oil and the wall of the stirred vessel showed no difference, which indicated the depletion of wax due to wax deposition during the shear simulation was not responsible for viscosity and gel point reduction in the dynamic cooling measurement. Therefore, this reduction is attributed to shear disturbance on the developing wax crystal structure, called the shear history effect. At sampling temperatures above 35 °C, which is 3 °C above the gel point measured under quiescent cooling conditions, both the yield stresses and the thixotropic parameters showed little dependence on the shear history. However, at lower sampling temperatures, remarkable shear history dependence was found. Empirical correlations were developed between the yield stress and the sampling temperature as well as the measurement temperature and between the thixotropic parameters and the sampling temperature. These correlations provide not only quantitative information on the shear history effect of waxy crude but also accurate rheological properties for assessment of the operation state and restartability of pipelines transporting this crude oil.

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Low temperature rheological behavior of Umbarka waxy crude and influence of flow improver

Cited by 18 publications

References 6 publications

Influence of the initial cooling temperature on the gelation and yield stress of waxy crude oils

Influence of the initial cooling temperature on the gelation and yield stress of waxy crude oils

Investigation of thickness and wax content of wax deposits in polyethylene pipe using a flow loop

Flow Behavior of Daqing Waxy Crude Oil under Simulated Pipelining Conditions

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