Critical quantities on the yielding process of waxy crude oils

Tarcha, B. A.; Forte, Bárbara P. P.; Soares, Edson J.; Thompson, Roney L.

doi:10.1007/s00397-015-0835-1

Cited by 51 publications

(19 citation statements)

References 22 publications

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“…In fact, the attempt to find the critical stress is very common for the case of waxy crude oils, which is a very complex elasto-viscoplastic gel. Typically, the critical stress for a waxy oil is the yield stress, the stress necessary to break the material's viscoplastic structure [9,10,24,32,35]. Here, the critical stress is that necessary to overcome the adhesive force between the gel and the wall, as stated in [24].…”

Section: Resultsmentioning

confidence: 99%

Rheological properties of a cross-linked gel based on guar gum for hydraulic fracture of oil wells

Vargas

Andrade

Loureiro

et al. 2020

J Braz. Soc. Mech. Sci. Eng.

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The hydraulic fracturing of oil wells is, supposedly, the first technique used to upgrade the oil and gas production. The main idea of this technique is to inject a fluid containing any kind of proppant into the well at a high flow rate and high pressure. One kind of fluid quite used as fracturing material is a cross-linked water-based guar gum gel. It seems that the rheological character of this kind of gel has not yet received the attention it deserves. This material is highly non-Newtonian and must be carefully analysed for further improvement in the fracturing process. We carried out different rheometric tests, which are presented in terms of the shear stress versus shear rate. The material seems to behave like a visco-elastic fluid, reasonably well described by the Jeffrey model. In addition, it is worth noting that the gel is very slippery, even on a rough surface. For this reason, we paid great attention to the maximum stress (a critical stress), above which the gel slips. We strongly believe that this stress has great practical importance for flow assurance and could be used to estimate the total pressure drop in the fracturing process.

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Section: Resultsmentioning

confidence: 99%

Rheological properties of a cross-linked gel based on guar gum for hydraulic fracture of oil wells

Vargas

Andrade

Loureiro

et al. 2020

J Braz. Soc. Mech. Sci. Eng.

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“…For low values of applied stress, the shear rate develops a trajectory in time that ends in a negligible shear rate. For high stress values, this phenomenon can also be detected in a deformation versus time plotting where an almost constant plateau is reached for low stress values ( Tarcha, Forte, Soares, & Thompson, 2015 ). The difficulties in experimentally determining the yield stress of a material are known in the literature and are more pronounced in thixotropic and other time-dependent systems as discussed in Møller et al (2006) and Soares, Thompson, and Machado (2013) .…”

Section: Viscoplastic Time-dependent Phenomenamentioning

confidence: 86%

Transient motions of elasto-viscoplastic thixotropic materials subjected to an imposed stress field and to stress-based free-surface boundary conditions

Oishi

Thompson

Martins

2016

International Journal of Engineering Science

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In the present work, we present an approach to handle transient flows of elastoviscoplastic thixotropic (EVPT) materials under the action of the gravity force field and subjected to free-surface boundary conditions that are stress-based. This kind of conditions are common in problems where the motion is unknown a priori , i.e. the motion is treated as a consequence while the forces are the cause. The model for the EVPT material employed is within the scope of a recently developed thermodynamic backbone for elastoviscoplastic thixotropic materials. The finite difference Marker and Cell method is used to investigate effects of elasticity, thixotropy, and plasticity varying the Weissenberg number, the dimensionless thixotropic equilibrium time, and the yield number, respectively. The Cartesian Poiseuille flow is used to test the main features of the numerical scheme. The evolution in time of an initially square and fully-structured block is captured. The structure level and shape evolutions of the block reveal the capability of the present numerical approach to handle the complexity of the material and the free-surface motion.

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“…The instrument used was the MCR 301 controlled stress rheometer from Anton Paar operating in the shear stress range 10 -7 -10 5 Pa and shear rate range 10 -6 -10 4 s -1 with Peltier temperature control of ±0.5 o C and cooling rates in a range varying from 0.01 to 6.5 o C/min. The recommended (see Tarcha et al (2015) study with different geometries) cone and plate geometry (stainless steel plate, diameter 25 mm and cone angle 0.991 0 ) was used as this provided no slip, a uniform shear rate and uses a small sample (0.60ml) suitable for effective temperature control. The critical difference between this and earlier work (Chang et al, 1998) is the resolution in the shear stress/rate achievable, enabling to zoom into the elastic region and probing the creep-fracture region in very small steps and rates.…”

Section: Rheometry Methodologymentioning

confidence: 99%

“…Restarting a gelled pipeline is thus a common problem in the oil industry which can be very expensive without a good understanding of the rheology of the cooled static gel to enable a correct prediction of an appropriate re-start pressure to be made. Because of the importance of the problem, gelled waxy crude oils have been extensively studied and from several perspectives, morphology (Kok et al, 1996, Singh et al, 2001, Chen et al, 2004, Visintin et al, 2008, Yi and Zhang, 2011, Lin et al, 2011, rheology (Wardhaugh and Boger, 1991a, 1991b, Rønningsen, 1992, Chang et al, 1998, Chang et al, 2000, da Silva and Coutinho, 2004, Kane et al, 2004, Venkatesan et al, 2005, Visintin et al, 2005, Visintin et al, 2008, Magda et al, 2009, Hou and Zhang, 2010, Dimitriou et al, 2011, Rønningsen, 2012, Marchesini et al, 2012, Tarcha et al, 2015, Andrade et al, 2015, Van Der Geest et al, 2017, Andrade et al, 2018 and modelling of pipe flow restart (Chang et al, 1999, Davidson et al, 2004, Vinay et al, 2006, Huang et al, 2011, Van Der Geest et al, 2015, Oliveira et al, 2015.…”

Section: Introductionmentioning

confidence: 99%

Rheology of waxy crude oils in relation to restart of gelled pipelines

Fakroun

Benkreira

2020

Chemical Engineering Science

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Waxy crude oils are pumped hot but upon power cut, pumping stops, the oil cools leading below the wax appearance temperature to precipitation of the wax and the formation of a gel throughout the pipe. In such a situation, what is the minimum pressure required to restart flow, not to merely deform the gel or break it? This paper provides a solution to this problem using microscopic observations under controlled cooling conditions and rheological data conducted in constant stress mode under controlled temperature and cooling conditions and restart experiments in laboratory pipelines replicating the rheometric conditions and deviations from them to inform large diameter operation in the field. Three important findings derive from the experimental data collected: (i) A fragmentation stress τ f , rather than the static stress τ s that precedes it, is found to be the more accurate predictor of flow restart pressures; (ii) Waxy crude oils gels exhibit true yield stress and yielding process but also show flow on application of the slightest stress below yielding; (iii) This flow, in the elastic region, is jagged rather than continuous suggesting a consolidation process of the crystals and their agglomerates forming the gel. In the broader context of the existence of a yield stress, the data presented here show that there is such a thing as a yield stress and the concepts of a yield stress and that everything flows are not mutually exclusive.

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Critical quantities on the yielding process of waxy crude oils

Cited by 51 publications

References 22 publications

Rheological properties of a cross-linked gel based on guar gum for hydraulic fracture of oil wells

Rheological properties of a cross-linked gel based on guar gum for hydraulic fracture of oil wells

Transient motions of elasto-viscoplastic thixotropic materials subjected to an imposed stress field and to stress-based free-surface boundary conditions

Rheology of waxy crude oils in relation to restart of gelled pipelines

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