Effects of cooling regime on the formation of voids in statically cooled waxy crude oil

Chala, Girma T.; Sulaiman, Shaharin Anwar; Japper-Jaafar, Azuraien; Abdullah, Wan Ahmad Kamil Wan

doi:10.1016/j.ijmultiphaseflow.2015.08.016

Cited by 19 publications

(5 citation statements)

References 28 publications

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“…During gelation, thermal shrinkage of waxy crude oil results in void formation. , Recently, many studies have focused on the formation and measurement of voids. − A sudden volume contraction is observed at the gelation temperature during the cooling of waxy crude oil. Due to a contraction in the waxy oil sample, the wax crystal network formed during gelation tries to pull (tensile force) the shear cell’s surface.…”

Section: Introductionmentioning

confidence: 99%

New Method for Gelation Temperature Measurement without Disturbing the Crystal Network

Shinde

Kumar

2021

Ind. Eng. Chem. Res.

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The present study proposes a new nonoscillatory nonrotary (NONR) method to measure gelation temperature based on a temperature-dependent normal force. A variation in the normal force signal is observed due to the combined effect of volume shrinkage and wax crystal network. The sample retains fluidity above the gelation temperature, in the absence of a gel network. The proposed method shows good repeatability for a model waxy oil and real crude oils. The results of the NONR method are consistent with the results from earlier methods. Gelation temperature measurement using the NONR method does not require gel movement. However, all of the existing rheological methods use either shear stress or shear rate, which participates in the gelation process. The gelation temperatures of 15% macrocrystalline wax in the dodecane sample measured using constant shear stress, constant shear rate, oscillatory, and NONR methods are 26.6, 27.5, 26.8, and 27.0 °C, respectively.

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Section: Introductionmentioning

confidence: 99%

New Method for Gelation Temperature Measurement without Disturbing the Crystal Network

Shinde

Kumar

2021

Ind. Eng. Chem. Res.

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“…The main advantages of MRI stem from the fact that the NMR signal is very sensitive to any small alterations of the chemical composition, physical structure, and temperature in the systems under study. Thus, MRI being a well-known noninvasive visualization technique has been successfully applied in many areas of research such as materials science, chemical engineering, petroleum science, etc. − Recently, NMR imaging has been demonstrated to be an informative tool for studying the phase behavior in crude oils. − …”

Section: Introductionmentioning

confidence: 99%

New Insight into the Wax Precipitation Process: In Situ NMR Imaging Study in a Cold Finger Cell

2016

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A cold finger cell intended for the wax deposition measurements was fabricated and integrated into an NMR imaging probe for the noninvasive study of wax precipitation processes in situ. The cell was first tested with a model system; then, a series of experiments with different thermal gradients applied to the cell were performed for a waxy crude oil. NMR imaging of the operating cell revealed the formation of a deposit with the morphology and dynamics strongly correlating with the temperature regime. At higher temperatures of cold finger, the incipient wax gel ages uniformly, giving rise to the hard and thin inner layer of deposit accompanied by a branched loosely consolidated outer layer. Conversely, the lower temperatures facilitate formation of a thick deposit which no longer ages uniformly and slow down the diffusion-controlled growth of the branched deposit structure. The results obtained are consistent with the majority of the data previously reported. Thus, gelation of the wax at temperatures below the cloud point and subsequent thermal-driven diffusion processes are considered to be the dominant mechanisms of the deposit formation. The counter diffusion and Ostwald ripening aging concepts were found to be relevant in the case of the cold finger study and account for the phenomena observed in this work. The information obtained via NMR imaging is highly complementary to the results obtained by other techniques that can aid in understanding the essential processes behind the wax precipitation phenomena. The approach developed can be effectively extended to study any thermal-driven phase separation process.

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“…Remarkably, thermal analysis could help to understand and develop control strategies alleviating flow problems [25][26][27]. Thermal shrinkage experienced during cooling of waxy crude oil produces an intra-gel void, and this reduces the strength of the gel structure [28][29][30]. On the other hand, flow assurance could be maintained by injecting non-reacting gas into production pipelines to ease the restarting of the pumping of waxy crude oil.…”

Section: Introductionmentioning

confidence: 99%

Artificial Neural Network and Regression Models for Predicting Intrusion of Non-Reacting Gases into Production Pipelines

Chala¹,

Negash

2022

Energies

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Wax deposition and gelation of waxy crude oil in production pipelines are detrimental to crude oil transportation from offshore fields. A waxy crude oil forms intra-gel voids in pipelines under cooling mode, particularly below the pour point temperature. Consequently, intrusion of non-reacting gas into production pipelines has become a promising method to lessen the restart pressure required and clear the clogged gel. A trial-and-error method is currently employed to determine the required restart pressure and restart time in response to injected gas volume. However, this method is not always accurate and requires expert knowledge. In this study, predictive models based on an Artificial Neural Network (ANN) and multilinear regression are developed to predict restart pressure and time as a function of seabed temperature and non-reacting gas injected volume. The models’ outcomes are compared against experimental results available from the literature. The empirical models predicted the response variables with an absolute error of below 5% compared to the experimental studies. Thus, such models would allow accurate estimation of restart pressure, thereby improving transportation efficiency in offshore fields.

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Effects of cooling regime on the formation of voids in statically cooled waxy crude oil

Cited by 19 publications

References 28 publications

New Method for Gelation Temperature Measurement without Disturbing the Crystal Network

New Method for Gelation Temperature Measurement without Disturbing the Crystal Network

New Insight into the Wax Precipitation Process: In Situ NMR Imaging Study in a Cold Finger Cell

Artificial Neural Network and Regression Models for Predicting Intrusion of Non-Reacting Gases into Production Pipelines

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