Economic pigging cycles for low-throughput pipelines

Wax deposition occurs frequently in waxy crude oil pipelines when the level of flow decreases, and pigging is needed at regular intervals. An economic pigging model is established in accordance with the objective function based on the sum of thermal costs, power costs, and single piping costs. Thus, by compiling a program, the most economical pigging cycle will be determined. Furthermore, the calculation methods for hydraulic and thermal constraints are given. Taking the example of the distance between the central processing platform and the land terminal external piping line of the M-field cluster, the effects of different inlet temperatures, throughput, and remnant wax thicknesses on the economic pigging cycle will be analyzed. The results show that with an increase in the inlet temperature, the total costs of the pipeline operation increase, while the pigging cycle will prolong. As throughput increases, total costs will decrease, while the pigging cycle also extends. When throughput is fixed, a remnant wax thickness of 0.4 mm helps reduce the total operating costs of the pipeline at different inlet temperatures. While throughput varies, a remnant wax thickness from 0.2 to 0.4 mm can reduce total costs at a fixed inlet temperature.

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Study of the causes for wax deposition under the operating conditions of main oil pipelines

SCIENCE & TECHNOLOGIES OIL AND OIL PRODUCTS PIPELINE TRANSPORTATION ◽

10.28999/2541-9595-2020-10-6-610-619 ◽

2020 ◽

Vol 10 (6) ◽

pp. 610-619

Author(s):

Rustam Z. Sunagatullin ◽

◽

Rinat M. Karimov ◽

Radmir R. Tashbulatov ◽

Boris N. Mastobaev ◽

...

Keyword(s):

Phase Diagrams ◽

Total Content ◽

Operating Conditions ◽

Wax Deposition ◽

Oil Saturation ◽

Oil Pipelines ◽

Thermobaric Conditions ◽

Wall Zone ◽

Significant Factors ◽

Commercial Oil

The results of investigations of the main causes and the most significant factors of intensification of paraffin deposition in main oil pipelines are presented. A comprehensive analysis of the composition and properties of commercial oils and their sediments was carried out, according to which phase diagrams of equilibrium of oil dispersed systems were obtained using the example of commercial oils from Bashkir fields. Based on the phase diagrams, a curve of wax oil saturation was constructed, the analysis of which confirms that the existing thermobaric conditions during the operation of main oil pipelines do not allow transporting oil without the risk of waxing. It was noted a special influence of the value of the temperature gradient in the near-wall zone and the imbalance of the ratio of high-molecular oil components in commercial batches formed in the process of joint pumping on the intensity of waxing of sections of oil pipelines complicated by deposits, which was confirmed by statistical data on the frequency of pigging. The regularities obtained in this way are proposed to be used as an express method for predicting complications associated with intensive waxing of main oil pipelines. In order to quickly assess the risks of waxing of sections of main oil pipelines, an indicator is introduced that characterizes the ratio of the content of solid paraffins to the total content of resins and asphaltenes of oil, called the criterion of instability of a commercial oil batch.

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Role of Shearing Dispersion and Stripping in Wax Deposition in Crude Oil Pipelines

Energies ◽

10.3390/en12224325 ◽

2019 ◽

Vol 12 (22) ◽

pp. 4325

Author(s):

Zhihua Wang ◽

Yunfei Xu ◽

Yi Zhao ◽

Zhimin Li ◽

Yang Liu ◽

...

Keyword(s):

Crude Oil ◽

Flow Rate ◽

Critical Flow ◽

Wax Deposition ◽

Dominant Effect ◽

Critical Flow Rate ◽

Oil Pipelines ◽

Oil Flow ◽

Shearing Mechanism

Wax deposition during crude oil transmission can cause a series of negative effects and lead to problems associated with pipeline safety. A considerable number of previous works have investigated the wax deposition mechanism, inhibition technology, and remediation methods. However, studies on the shearing mechanism of wax deposition have focused largely on the characterization of this phenomena. The role of the shearing mechanism on wax deposition has not been completely clarified. This mechanism can be divided into the shearing dispersion effect caused by radial migration of wax particles and the shearing stripping effect caused by hydrodynamic scouring. From the perspective of energy analysis, a novel wax deposition model was proposed that considered the flow parameters of waxy crude oil in pipelines instead of its rheological parameters. Considering the two effects of shearing dispersion and shearing stripping coexist, with either one of them being the dominant mechanism, a shearing dispersion flux model and a shearing stripping model were established. Furthermore, a quantitative method to distinguish between the roles of shearing dispersion and shearing stripping in wax deposition was developed. The results indicated that the shearing mechanism can contribute an average of approximately 10% and a maximum of nearly 30% to the wax deposition process. With an increase in the oil flow rate, the effect of the shearing mechanism on wax deposition is enhanced, and its contribution was demonstrated to be negative; shear stripping was observed to be the dominant mechanism. A critical flow rate was observed when the dominant effect changes. When the oil flow rate is lower than the critical flow rate, the shearing dispersion effect is the dominant effect; its contribution rate increases with an increase in the oil flow temperature. When the oil flow rate is higher than the critical flow rate, the shearing stripping effect is the dominant effect; its contribution rate increases with an increase in the oil flow temperature. This understanding can be used to design operational parameters of the actual crude oil pipelines and address the potential flow assurance problems. The results of this study are of great significance for understanding the wax deposition theory of crude oil and accelerating the development of petroleum industry pipelines.

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Effect of Thermal Treatment Temperature on the Flowability and Wax Deposition Characteristics of Changqing Waxy Crude Oil

Energy & Fuels ◽

10.1021/acs.energyfuels.8b02552 ◽

2018 ◽

Vol 32 (10) ◽

pp. 10605-10615 ◽

Cited By ~ 11

Author(s):

Haoran Zhu ◽

Chuanxian Li ◽

Fei Yang ◽

Hongye Liu ◽

Dinghong Liu ◽

...

Keyword(s):

Thermal Treatment ◽

Crude Oil ◽

Treatment Temperature ◽

Wax Deposition ◽

Waxy Crude Oil ◽

Thermal Treatment Temperature ◽

Waxy Crude

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Experimental Study on Wax Deposition Characteristics of a Waxy Crude Oil Under Single Phase Turbulent Flow Conditions

10.4043/22953-ms ◽

2012 ◽

Cited By ~ 1

Author(s):

Priyank Dwivedi ◽

Cem Sarica ◽

Wei Shang

Keyword(s):

Experimental Study ◽

Turbulent Flow ◽

Crude Oil ◽

Single Phase ◽

Flow Conditions ◽

Wax Deposition ◽

Waxy Crude Oil ◽

Waxy Crude ◽

Turbulent Flow Conditions

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Study on Optimizing Operation of Preheating Commissioning for Waxy Crude Oil Pipelines

Advances in Mechanical Engineering ◽

10.1155/2014/894256 ◽

2014 ◽

Vol 6 ◽

pp. 894256

Author(s):

Jian Zhang ◽

Yi Wang ◽

Xinran Wang ◽

Handu Dong ◽

Jinping Huang ◽

...

Keyword(s):

Crude Oil ◽

Outlet Temperature ◽

Fluid Temperature ◽

Governing Equations ◽

Waxy Crude Oil ◽

Waxy Crude ◽

Oil Pipeline ◽

Single Station ◽

Oil Pipelines ◽

Volume Method

A mathematical model is established for the preheating commissioning process of waxy crude oil pipelines. The governing equations are solved by the finite volume method and the finite difference method. Accordingly, numerical computations are made for the Niger crude oil pipeline and the Daqing-Tieling 3rd pipeline. The computational results agree well with the field test data. On this basis, fluid temperature in the process of the preheating commissioning is studied for single station-to-station pipeline. By comparing different preheating modes, it is found that the effect of forward preheating is the best. Under different preheating commissioning conditions, the optimal combination of outlet temperature and flow rate is given.

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Wax deposition during production of waxy crude oil and its remediation

Petroleum Science and Technology ◽

10.1080/10916466.2017.1363776 ◽

2017 ◽

Vol 35 (18) ◽

pp. 1831-1838 ◽

Cited By ~ 2

Author(s):

Ashish Dewangan ◽

Ashok Kumar Yadav

Keyword(s):

Crude Oil ◽

Wax Deposition ◽

Waxy Crude Oil ◽

Waxy Crude

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The Use of Biobased Surfactant Obtained by Enzymatic Syntheses for Wax Deposition Inhibition and Drag Reduction in Crude Oil Pipelines

Catalysts ◽

10.3390/catal6050061 ◽

2016 ◽

Vol 6 (5) ◽

pp. 61 ◽

Cited By ~ 9

Author(s):

Zhihua Wang ◽

Xueying Yu ◽

Jiaxu Li ◽

Jigang Wang ◽

Lei Zhang

Keyword(s):

Drag Reduction ◽

Crude Oil ◽

Wax Deposition ◽

Biobased Surfactant ◽

Oil Pipelines

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Unavoidable Destroyed Exergy in Crude Oil Pipelines due to Wax Precipitation

Entropy ◽

10.3390/e21010058 ◽

2019 ◽

Vol 21 (1) ◽

pp. 58

Author(s):

Qinglin Cheng ◽

JinWei Yang ◽

Anbo Zheng ◽

Lu Yang ◽

Yifan Gan ◽

...

Keyword(s):

Crude Oil ◽

Design Parameters ◽

Burial Depth ◽

Outlet Temperature ◽

Waxy Crude Oil ◽

Wax Precipitation ◽

Waxy Crude ◽

Oil Pipeline ◽

Oil Pipelines ◽

Operation Parameters

Based on the technological requirements related to waxy crude oil pipeline transportation, both unavoidable and avoidable destroyed exergy are defined. Considering the changing characteristics of flow pattern and flow regime over the course of the oil transportation process, a method of dividing station oil pipelines into transportation intervals is suggested according to characteristic temperatures, such as the wax precipitation point and abnormal point. The critical transition temperature and the specific heat capacity of waxy crude oil are calculated, and an unavoidable destroyed exergy formula is derived. Then, taking the Daqing oil pipeline as an example, unavoidable destroyed exergy in various transportation intervals are calculated during the actual processes. Furthermore, the influential rules under various design and operation parameters are further analyzed. The maximum and minimum unavoidable destroyed exergy are 381.128 kJ/s and 30.259 kJ/s. When the design parameters are simulated, and the maximum unavoidable destroyed exergy is 625 kJ/s at the diameter about 250 mm. With the increase of insulation layer thickness, the unavoidable destroyed exergy decreases continuously, and the minimum unavoidable destroyed exergy is 22 kJ/s at 30 mm. And the burial depth has little effect on the unavoidable destroyed exergy. When the operation parameters are simulated, the destroyed exergy increases, but it is less affected by the outlet pressure. The increase amplitude of unavoidable destroyed exergy will not exceed 2% after the throughput rises to 80 m3/h. When the outlet temperature increases until 65 °C, the loss increase range will not exceed 4%. Thus, this study provides a theoretical basis for the safe and economical transportation of waxy crude oil.

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