Crude Oil Pipeline Research Articles

The Potential Impacts of the East African Crude Oil Pipeline (EACOP) on Human Rights in Uganda

The Potential Impacts of the East African Crude Oil Pipeline (EACOP) on Human Rights in Uganda

Polysiloxane-Based Liquid-like Layers for Reducing Polymer and Wax Fouling

Surface fouling occurs when undesired matter adheres and accumulates on a surface, resulting in a decrease or loss of functionality. Polymer and wax fouling can cause costly blockages to crude oil pipelines, clog jet fuel injectors, foul chemical reaction vessels, and significantly decrease the efficiency of heat exchangers. Fouling occurs in many forms but can be segmented based on adherent size, modulus, and chemical functionality. Depending on the foulant, surface design strategies can vary greatly. Few strategies exist to prevent the buildup of wax and polymers on surfaces. In this report, we investigate the potential of highly disordered, siloxane liquid-like layers as a strategy for reducing wax and polymer deposition. In our tests, it was found that the liquid-like layers developed here were able to reduce postadsorption roughness for polymer and wax by as much as 35- and 47-fold, respectively, when compared to the control. SFG was utilized to investigate the molecular-level interfacial properties for each of the modified surfaces to help understand the antifouling mechanism. The data showed that the likely higher grafting density and a large degree of random conformational freedom at the liquid-surface interface make the developed siloxane-covered surfaces energetically unfavorable for polymer and wax accretion.

Crude oil pipeline constraints: A tale of two shales

Permian and Williston Basins are both experiencing takeaway pipeline bottlenecks. The price of Bakken sweet crude in Williston is still cointegrating with the national West Texas Intermediate (WTI) benchmark and downstream gasoline market while the Midland crude price in Permian Basin is not. The Midland price only reintegrated with WTI as well as regional gasoline price after the takeaway bottleneck is alleviated. This is because of the rail system developed in the Williston Basin that allows Bakken crude to reach other trading hubs and downstream markets even when pipeline bottlenecks occur. Blocking the constructions of pipelines will not prevent the flow of oil because more oil will be moved by trucks, railways, and barges. These shipping modes are more expensive and are not as safe and efficient as pipelines.

Mathematical Modeling of Wax Deposition in Field-Scale Crude Oil Pipeline Systems

The formation of solid wax crystals, which interlock and form a gel-like layer on the inner wall of the crude oil pipeline, influences the transportation of waxy crude oil. The deposited layer grows continuously and hardens during the oil transportation, reducing the effective inside diameter of the crude oil pipeline and the flow rate. In extreme cases, the deposited layer may block the crude oil pipeline leading to a loss of production and capital investment. In this paper, wax deposition from multiphase flow in field-scale oil pipeline transport systems has been studied. The novelty of this work is to develop a mathematical model that incorporates water-in-oil emulsions, wax precipitation kinetics, molecular diffusion, and shear dispersion to enable accurate predictions of both the wax deposit growth rate and aging of the deposit. The coupled nonlinear partial differential equations governing the flow are discretized in time by a second-order semi-implicit time discretization scheme based on the Adams-Bashforth and Crank-Nicolson methods, which completely decouples the computation of the governing equations. The resulting temporal schemes are discretized in space by the bivariate spectral collocation method based on Chebyshev-Gauss-Lobatto grid points and simulated in MATLAB software to obtain the profiles of the flow variables. The simulation results are presented in graphical and in tabular forms and discussed. This study found that the deposit thickness is directly proportional to the Reynolds number and inversely proportional to the mass Grashof number, Schmidt number, and Weber number. Deposit aging is rampant during the early stages of wax deposition, after which it stabilizes at a specific value as time elapses. A deposition model to predict the wax deposit thickness and aging is proposed in this study. The findings of this study will help in making informed decisions on the planning of pigging operations, thermal insulation, and other remediation techniques to be applied in controlling wax deposition in field-scale crude oil pipeline systems.

Assessment of permafrost disturbances caused by two parallel buried warm-oil pipelines: A case study at a high-latitude wetland site in Northeast China

Multiple studies demonstrate that narrow-linear strong disturbances triggered by pipeline engineering activities have resulted in rapid permafrost degradation. However, the extent, duration, and severity of permafrost disturbances induced by two parallel buried warm-oil pipelines remain unclear. Here, we examine the thermal disturbances of the China-Russia crude oil pipelines (CRCOPs I and II) on the surrounding permafrost. Ground temperature measurements on and off the right-of-way of the CRCOPs and an electrical resistivity tomography survey were conducted at a selected high-latitude wetland site in northeastern China. The observations showed that warm oil flow in pipelines dissipated heat to the surrounding soil, resulting in the thawing of underlying permafrost accompanied by the formation and development of thaw bulbs around the pipes. Currently, the thaw bulb of CRCOP-I was about four times as large as that of CRCOP-II, mainly due to the longer 7-year working duration of CRCOP-I. To quantify the permafrost disturbances around the pipeline, a conductive heat transfer model was established. A numerical simulation of the soil thermal regime around the pipeline suggested the initial growth of the thaw bulb was quite fast but gradually slowed with time, of which the shape was modified to ellipse from a semicircle. The existence of CRCOP-II would accelerate the warming of permafrost on the CRCOP-I right-of-way due to the small separation distance between them. We expect that the thaw bulbs of the two pipelines will expand larger than previously estimated due to the adverse effects of pipeline settlement and surface water flow, sparking a wider permafrost disturbance.

Prediction of wax deposit thickness in waxy crude oil pipelines using improved GM(1,1) model

In this paper, the GM(1,1) model with function arccosx transformation and GM(1,1) model with function transformation are established by using arccosine function transformation method and aarccosx function transformation method, and the GM(1,1) model with function cosx2 transformation is established by using function transformation theory, and GM(1,1) model with function cosx2+c transformation is established by using translational transformation theory on the basis of this model. The prediction accuracy of GM(1,1) model, GM(1,1) model with function arccosx transformation, GM(1,1) model with function aarccosx transformation, GM(1,1) model with function cosx2 transformation, and GM(1,1) model with function cosx2+c transformation are compared by modeling with the field pipeline data and the indoor loop data. The influence of a value in GM(1,1) model with function aarccosx transformation on prediction accuracy is discussed, and the influence of c value in GM(1,1) model with function cosx2+c transformation on prediction accuracy is discussed. With the increase of a and c values, the average relative error show a trend of decreasing and then increasing, by comparing the average relative errors under different a and c values, the optimal a value and c value and the optimal prediction accuracy are obtained. The results show that the GM(1,1) model with function cosx2+c transformation in the indoor loop has an average relative error of 0.6490% when c=0.114, which is the minimum average relative error compared to other models and achieves the highest prediction accuracy. The GM(1,1) model with function cosx2+c transformation in the field pipeline has an average relative error of 1.94156% when c=−0.555, which is the minimum average relative error compared to other models and achieves the highest prediction accuracy. Among the five models, only the GM(1,1) model with function cosx2+c transformation has fitted and predicted values that are closer to the actual thickness values in the indoor loop experimental data and the field pipeline data, and the predicted values are more consistent with the actual conditions in the field pipeline. This paper verifies the feasibility of using the GM(1,1) model with function cosx2+c transformation to predict the wax deposition thickness of the pipe wall, and provides a reference for subsequent research on accurate prediction of wax deposition thickness.

A newly integrated ground temperature dataset of permafrost along the China–Russia crude oil pipeline route in Northeast China

Abstract. The thermal state of permafrost in the present and future is fundamental to ecosystem evolution, hydrological processes, carbon release and infrastructure integrity in cold regions. In 2011, we initiated a permafrost monitoring network along the China–Russia crude oil pipeline (CRCOP) route at the eastern flank of the northern Da Xing'anling Mountains in Northeast China. We compiled an integrated dataset of the ground thermal state along the CRCOP route consisting of meteorological data near the southern limit of latitudinal permafrost, ground temperature (GT) data in 20 boreholes with depths of 10.0–60.6 m, soil volumetric liquid water contents (VWCs) and 2D electrical resistivity tomography (ERT) data at different sites. Results demonstrate a permafrost warming during 2011–2020 in the vicinity of the southern limit of latitudinal permafrost, as manifested by rising GTs at almost all depths in response to climate warming. Local thermal disturbances triggered by the construction and operation of CRCOPs have resulted in significant permafrost warming and subsequent thawing on the right-of-way (ROW) of the pipelines. This permafrost thaw will persist, but it can be alleviated by adopting mitigative measures, such as an insulation layer and thermosyphons. The in situ observational dataset is of great value for assessing the variability of permafrost under the linear disturbances of the CRCOPs and related environmental effects, for understanding hydro–thermal–mechanical interactions between the buried pipelines and permafrost foundation soils, and for evaluating the operational and structural integrity of the pipeline systems in the future. The dataset is available at the National Tibetan Plateau/Third Pole Environment Data Center (https://doi.org/10.11888/Cryos.tpdc.272357; Li, 2022).

Application of Magnetic Flux Leakage Internal Detection Technology in Evaluation and Analysis of Crude Oil Pipeline Corrosion

There are many abnormal points in the magnetic flux leakage internal inspection results of a crude oil pipeline. For 20 of the more serious metal loss anomalies Internal corrosion evaluation standard specification, corrosion evaluation and pressure analysis. The results of corrosion evaluation and pressure analysis are taken as the basis for theoretical screening, and the final selection is preferred. The excavation verification and defect repair were carried out at 3 abnormal points of internal inspection. The accuracy of magnetic flux leakage internal detection results is verified through excavation verification, which proves the magnetic flux leakage internal detection. The measurement technology can play a role in the evaluation and analysis of pipeline corrosion.

Modeling transient cavitating flow in large drop crude oil pipelines

Transient cavitating flow is a dangerous condition in the operation of large drop crude oil pipelines. Accurately predicting the high pressure generated by cavity collapse is the premise of analyzing and formulating pipeline safety management and control strategies. A new numerical simulation method for one dimension cavitating flow in crude oil pipelines considering the effect of unsteady friction was proposed. The unsteady friction (UF) term is coupled to the classical discrete gas cavity model (DGCM) for modeling the cavitating flow, and the proposed model is called UF-DGCM. The method of characteristics (MOC) is used to solve the UF-DGCM. The validity of the model has been verified with experimental data. The pipeline length of the two test cases is 37.23 m and 15.22 m, respectively, and the pipeline diameter is 22.1 mm and 20.0 mm, respectively. For the two test cases, the accuracy of the prediction results is improved by 6.7% and 4.4%, respectively. A case study of cavitating flow caused by pump shutdown in a pipeline with a length of 35 km and a diameter of 738 mm was performed using UF-DGCM, and the effects of water hammer wave speed, crude oil vapor pressure, and pump shutdown time on cavitating flow were analyzed. The results show that the maximum pressure peak is dependent on the water hammer wave speed. About the increase in the wave speed value of 200 m/s will lead to an increase in the maximum pressure head value of 10.1 m. The increase of pump shutdown time will inhibit the growth of cavities, and increasing the pump shutdown time by 4 s will shorten the existence time of cavities by about 3 s. The extension of the pump shutdown time will prevent cavitating flow. The proposed improved model is more suitable for transient cavitating flow analysis, and the results of flow parameters research will be helpful to prevent cavitating flow in crude oil pipelines.

Doubling down on DAPL: the contentious politics of pipeline governance in Illinois

ABSTRACT This article analyzes the permitting proceeding for the capacity expansion of the Dakota Access and Energy Transfer Crude Oil Pipelines in Illinois. Drawing on field research undertaken between 2018–2021, we examine how a grassroots-led coalition of climate activists – Save Our Illinois Land (SOIL) – navigated the Illinois Commerce Commission’s institutional context to oppose regulatory approval. We argue that SOIL mobilized procedural aspects of the regulatory process to politicize a highly path-dependent and techno-managerial administrative proceeding. SOIL did so to open political space for greater consideration of and deliberation around socio-ecological challenges like climate change in pipeline governance. While U.S. focused, our findings highlight the difficulties inherent to employing institutionalized participation as a mechanism to politicize energy governance and engage in contentious energy politics. Climate advocates face complex challenges that inhibit their ability to unsettle the power structures that reinforce carbon-intensive systems and promote inclusive and climate-driven energy infrastructure governance.

Optimal diameter of liquid-phase ethane transportation pipeline considering the liquid-vapor phase change

The liquid-phase pipeline is the optimal choice for large-amount and long-distance ethane transportation. Selecting the optimal diameter is necessary for the economical design of the pipeline. However, the special critical temperature 32.2 °C and critical pressure 4.87 MPa of ethane makes it easy to become liquid-vapor phase change, which is not considered in the traditional natural gas or crude oil pipeline design. In this paper, a new mathematical model is built to calculate the optimal diameter of the ethane pipe by using the ‘pump station + pipeline’ unit as the research object. The model selects the lowest total pipeline construction and operation costs as the objective function, and the constraints include the ethane liquid-vapor phase change, the pipe maximum allowable stress, and pipe specifications. In particular, the liquid-vapor phase change constraint is added to the traditional model to avoid the ethane liquid-vapor phase change, which is obtained by quantitatively analyzing the variation of physical parameters of ethane close to the pressure-temperature phase boundary. The optimization model is solved by use of the genetic algorithm. Finally, optimal pipe diameters are calculated for the conditions of transmission capacity from 1000 t/d to 10,000 t/d. Comparisons of calculated pipe diameter with eight actual cases show that the results are feasible with the average and maximum deviations being less than 5% and 8%, respectively. The effects of pipe materials and electricity prices on the pipe diameter are analyzed. It is demonstrated that the pipe material has a negligible effect on the optimal diameter, whereas increasing the electricity price will lead to the increase of the optimal diameter in the case of large transmission volumes.

Application of Superparamagnetic Nanoparticle (SPM-NP) Heating in Wax Removal during Crude Oil Pipeline Pigging

Mechanical pigging is a major wax removal technique in crude oil pipeline transportation. To lower the risk of pig stalling accidents in pigging, a superparamagnetic nanoparticle (SPM-NP) pigging system that consists of an electromagnetic pig and nanopaint is designed to soften the wax deposit and reduce the wax resistive force. During pigging, the induction coil on the pig generates an alternating magnetic field, which induces heat production of the nanopaint on the pipe wall. The COMSOL software is used to simulate the temperature distribution of the wax layer. Yield stress measurements reveal that the wax layer yield stress is nearly linearly correlated to temperature. Compared with a regular pig, the SPM-NP pigging system reduces the wax resistive force by up to 20~40%, with an acceptable electrical current intensity of about 20 A in the given cases. Multiple factors affecting the wax layer temperature were analyzed. SPM-NP heating could be a promising technique for wax remediation and hydrate prevention.

The Conundrums of Illicit Crude Oil Refineries in Nigeria and Its Debilitating Effects on Nigeria’s Economy: A Legal Approach

Nigeria’s oil industry encounters crude oil theft in commercial quantities, which is often exported to neighbouring countries. This has occasioned a loss of revenue and has caused environmental pollution due to oil spillages. There is a need for a stringent legal framework to combat the menace caused by incessant crude oil thefts, pipeline vandalisation by militants, and inadequate maintenance of existing crude oil refineries. The study adopts doctrinal legal research methods and a conceptual approach with the consideration of primary and secondary sources of law, for instance, the Petroleum Industry Act 2021, the Nigeria Extractive Industry Transparency Initiative (NEITI Act 2007, International Conventions, law textbooks and peer-reviewed journals. The justification for using the method was to establish the trustworthiness of the findings on illicit crude oil refineries. The findings reveal that the Nigerian government has lost more than 150,000 barrels of crude oil daily valued at USD six billion as a result of crude oil theft. This has reduced oil revenues, which ought to have added to the national treasury. The Petroleum Production and Distribution (Anti-Sabotage Act) 2007, which proscribes disruption of petroleum products in Nigeria, has not been diligently enforced. There is also an absence of a specific oil and gas legal framework criminalising crude oil theft. Section 3(e)(f)(iv) of the Nigeria Security and Civil Defence Corps Act only offers pipeline security as one of the functions of the corps, without distinctly stating the penalties to be imposed on those damaging crude oil pipelines. The study designs a hybrid model for the renovation of the country’s crude oil refineries. It also advocates the need to redefine legal regimes on illegal oil refineries by amending the Petroleum Industry Act to include specifically illegal oil refineries provision and to effectively criminalise crude oil theft. The implications of the main results are as follows: criminalising crude oil theft and pipeline vandalisation with vigorous punishments will serve as deterrence to others in the sector, increase revenues for the government and reduce environmental pollution.

Three-Dimensional CFD Modeling on the Thermal Characteristics of Buried Oil Pipeline Involving the Heat Transfer of Wax Layer

It is common to have a wax layer on the inner wall of waxy crude oil pipeline. However, the study of the wax layer on the heat transfer of buried pipeline systems is inadequate due to its instability of composition and properties; it may lead to the inaccurate prediction of the pipeline temperature field. Based on the finite element simulation technology, a three-dimensional heat transfer model of buried crude oil pipeline involving wax layer was proposed and solved. The thermal effect of the wax layer on pipeline system was analyzed quantitatively. Numerical results show that the average deviation of soil temperature near the pipeline reach 1.42 K when there is a 4 mm wax layer. Among different thermal conductivity models of heterogeneous materials, the EMT model plays best in predicting the conductivity of a waxy layer. By setting different working conditions, the influence mechanisms of several thermal influencing factors are discussed. The results show that the thermal influence range of heated pipe is positively associated with oil temperature and velocity. The core thermal response zone is about 12 m along the X-axis. Beyond 8 m depth from ground surface, the temperature fluctuation of soil is almost unaffected by the oil pipeline.

Pressure Drop Prediction of Crude Oil Pipeline Based on PSO-BP Neural Network

Pipeline transportation of crude oil has great advantages over traditional oil transmission methods, in terms of economic and environmental protection. The main costs in the oilfield surface system are the fuel costs for heating the crude oil during transportation and the electricity costs for the pumping units. In the northeast of China, where winter temperatures are extremely low and the oil has a high freezing point and high viscosity, higher temperatures, and pressures are required to transport crude oil. With machine learning widely used in many industries and achieving better results, the digital management of oil pipelines has stored a large amount of production and operation data, which has laid the foundation for the research of oil pipeline process calculation using machine learning methods. In this paper, a crude oil pressure drop calculation of an oil pipeline in Northeast China is carried out based on a neural network. For pipeline pressure drop calculation, the back propagation neural network (BP) pressure drop calculation model and particle swarm optimization for back propagation neuron network (PSO-BP) pressure drop calculation model are established. Two models were used to calculate and compare the measured data, and the average absolute error of the PSO-BP model was the smallest, which was 0.015%. Compared with the BP model, the average relative error is reduced by 13.16%. Therefore, The PSO-BP pressure drop calculation model has high accuracy and is of practical significance for predicting pipeline pressure drop.

Risk assessment of interstate pipelines using a fuzzy-clustering approach

Interstate pipelines are the most efficient and feasible mean of transport for crude oil and gas within boarders. Assessing the risks of these pipelines is challenging despite the evolution of computational fuzzy inference systems (FIS). The computational intricacy increases with the dimensions of the system variables especially in the typical Takagi–Sugeno (T–S) fuzzy-model. Typically, the number of rules rises exponentially as the number of system variables increases and hence, it is unfeasible to specify the rules entirely for pipeline risk assessments. This work proposes the significance of indexing pipeline risk assessment approach that is integrated with subtractive clustering fuzzy logic to address the uncertainty of the real-world circumstances. Hypothetical data is used to setup the subtractive clustering fuzzy-model using the fundamental rules and scores of the pipeline risk assessment indexing method. An interstate crude-oil pipeline in Egypt is used as a case study to demonstrate the proposed approach.

A demonstration of sustainable pipeline routing optimization using detailed financial and environmental assessment

The selection of optimal pipeline routes should consider the costs for the design, construction, operation and maintenance of all the routing alternatives. The cost analysis of each alternative route requires substantial geospatial information on slopes and elevations, land use, soil types and other features. In addition to financial costs it is necessary to consider the sustainability aspects, including public safety and environmental impacts, if the pipeline passes near populated areas or if it crosses with natural habitats. This work uses an available computer-aided design tool to automate the routing optimization process. The optimal search follows Simulated Annealing to obtain a set of near-optimal pipeline routes and designs. This optimizer is able to consider a large variety of static geospatial features, conduct detailed hydraulic and cost calculations, and accommodate models for the evaluation of environmental impacts. Cost calculations are in accordance to widely recognized procedures used in pipeline design practice. For the quantification of environmental impacts, this study defines a cost function and proposes a simple implementation using geospatial data from CDDA and the Natura. The above are herein applied on the routing optimization of a crude oil pipeline, to demonstrate how financial and environmental criteria can be considered jointly at the early design phases of a real scale project. The pipeline is over 110 km long. The considered terrain involves areas of different land use, protected areas, cities and other infrastructures, seismic faults and Seveso plants. The data needed for these calculations are obtained from many geospatial data layers. The paper describes in detail the fusion procedures to pretreat the data and facilitate calculations of financial costs and environmental impacts. Results are obtained over a range of control variables to depict the trade-offs between the two criteria and other design options. The obtained results compare favorably with the routing proposed by the pipeline company.

Effect of Wax Composition and Shear Force on Wax Aggregation Behavior in Crude Oil: A Molecular Dynamics Simulation Study.

To explore the influence of different wax components and the shear effect exerted by the pump and pipe wall in the process of crude oil pipeline transportation on the microbehavior of wax aggregation in crude oil at low temperatures, molecular dynamics models of binary and multivariate systems of crude oil with different wax components are established in this paper. The simulation results are compared with the existing experimental results and the NIST database to verify the rationality and accuracy of the models. By using the established binary model to simulate four crude oil systems containing different wax components, it can be found that the longer the wax molecular chain, the more easily the wax molecules aggregate. The influence of temperature on the aggregation process of wax molecules with different chain lengths is also studied. The lower the temperature, the greater the difference in wax molecular aggregation degree caused by the difference in molecular chain length. Nonequilibrium molecular dynamics is used to simulate the shear process of a multivariate system of crude oil, and the micromechanisms of the shear effect on the aggregation process of wax molecules are studied. Shearing can destroy the stable structure of crude oil, resulting in the orientation and conformational transformation of wax molecules, and obtaining the region of wax molecules sensitive to temperature and shear effects, the temperatures of which are below the wax precipitation point and the shear rate of which is lower than the maximum shear rate to prevent the molecular structure from being destroyed. At the same time, the sensitivity of wax components with different chain lengths to the shear effect is studied. The research results provide theoretical guidance for ensuring the safe and economic operation of waxy crude oil production.

Whose jobs face transition risk in Alberta? Understanding sectoral employment precarity in an oil-rich Canadian province

ABSTRACT Labour markets of oil-exporting regions will be impacted by a global transition to low-carbon energy as oil demand reduces to meet the aims of the Paris Agreement. Together with direct job losses in the oil and gas industry, indirect employment effects on other sectors should also be considered to ensure a just transition. We explore these direct and indirect employment impacts that could result from the low-carbon transition by analysing the effect of oil price fluctuations on the labour market of Alberta, a Canadian province economically reliant on oil sands extraction. We employ a mixed methods approach, contextualizing our quantitative analysis with first-hand experiences of career transitions using interviews with oil sands workers. We estimate a vector autoregression for province-wide insights and explore sector-specific dynamics using time series regressions. We find that the price discount on Canadian oil sands, which is determined by local factors like crude oil quality and pipeline capacity, does not significantly affect employment, while the global oil price does. This finding puts in doubt claims of long-term employment benefits from new pipelines. We find that at a provincial scale, oil price fluctuations lead to employment levels also fluctuating. Our analysis at the sectoral level shows that these job fluctuations extend beyond oil and gas to other sectors, such as construction and some service sectors. These findings suggest that the province’s current economic dependence on oil creates job precarity because employment in various sectors is sensitive to a volatile oil market. Furthermore, due to this sectoral sensitivity to oil price changes, workers in these sectors may be especially at risk in a low-carbon transition and warrant special attention in the development of provincial and national just transition policies. Transitional assistance can support workers directly, while economic diversification in Alberta can reduce reliance on international oil markets and thereby ensure stable opportunities in existing and new sectors. Key policy insights Decreased global oil demand is likely to create employment risks for workers in Alberta and other fossil fuel producing regions of the world. Current economic dependence on oil sands extraction in Alberta leads to job precarity across sectors, including in those seemingly unrelated to extraction. Proactive economic diversification in anticipation of the low-carbon transition could reduce precarity by mitigating the effects of oil price fluctuations on employment levels in the long term. Workers in sectors with higher oil price sensitivity (i.e. oil and gas, construction, professional services, manufacturing, accommodations, and food services sectors) could be prioritized in coordinated just transition policies at the local, provincial, and national scales. The details of career transitions gleaned from our interviews suggest that tripartite social dialogue would contribute meaningfully to just transition policy development.

Lateral Buckling of Pipe-in-Pipe Systems under Sleeper-Distributed Buoyancy—A Numerical Investigation

The crude oil in pipelines should remain at high temperature and pressure to satisfy the fluidity requirement of deep-sea oil transportation and consequently lead to the global buckling of pipelines. Uncontrolled global buckling is accompanied by pipeline damage and oil leakage; therefore, active buckling control of pipelines is needed. Pipe-in-pipe (PIP) systems have been widely used in deep-sea oil pipelines because of the protection and insulation characteristics of the outer pipe to the inner pipe. In this study, sleeper-distributed buoyancy is used as an active buckling control method for the global buckling of PIP systems with initial imperfections. The accuracy of this technique is verified by comparing the finite element model of a 3D pipeline with experimental data. The effects of buoyancy density, pipe–soil friction coefficient, initial imperfection, stiffness ratio of inner and outer pipes, and buoyancy unit interval on the global buckling performance are also analyzed. The critical buckling force and lateral displacement of this method are studied using an analytic solution, and the relevant calculation formulas are obtained and verified to provide a basis for its engineering application.