Thermal Analysis of Offshore Buried Pipelines Through Experimental Investigations and Numerical Analysis

2016 ◽  
Author(s):  
Suvra Chakraborty ◽  
Vandad Talimi ◽  
Mohammad Haghighi ◽  
Yuri Muzychka ◽  
Rodney McAffee
Keyword(s):  
Numerical Analysis ◽  
Heat Loss ◽  
Transient Response ◽  
Oil And Gas ◽  
Burial Depth ◽  
Fluid Temperature ◽  
Buried Pipeline ◽  
Buried Pipelines ◽  
Arctic Regions ◽  
Backfill Soil

Modeling of heat loss from offshore buried pipelines is one of the prime concerns for Oil and Gas industries. Offshore Oil and Gas production and thermal modeling of buried pipelines in arctic regions are challenging tasks due to environmental conditions and hazards. Flow properties of Oil and Gas flowing through the pipelines in arctic regions are also affected due to freezing around pipelines. Solid formation in the production path can have serious implications on production. Heavy components of crude oil start to precipitate as wax crystal when the fluid temperature drops. Gas hydrates also form when natural gas combines with free water at high pressure and low temperature. Pipeline burial and trenching in some offshore developments are now one of the prime methods to avoid ice gouge, ice cover, icebergs, and other threats. Long pipelines require more thermal management to deliver production to the sea surface. Significant heat loss may occur from offshore buried pipelines in the forms of heat conduction and natural convection through the seabed. The later can become more prominent where the backfill soil is loose or sandy. The aim of this paper is to provide an insight of modeling and conducting the experiments using different parameters with numerical analysis results support to investigate the heat loss from offshore buried pipelines. This paper also provides validation of the outputs from benchmark tests with analytical models available for theoretical shape factor at constant temperature and constant heat flux boundary conditions. These theoretical models have limitations such as the assumption of uniform soil properties around the buried pipeline, isothermal outer surface of the buried pipeline and soil surface. Degree of saturation of surrounding medium can play a significant role in the thermal behavior of fluid travelling through the backfill soil. This paper presents several steady states and transient response analysis describing some influential geotechnical parameters along with test procedures and numerical simulations using CFD to model the heat loss for different parameters such as burial depth, backfill soil, trench geometries etc. This paper also shows the transient response for several shutdown (cooldown) tests performed in the saturated sand medium. The statistical and uncertainty analysis performed from the experimental outputs also ensure the legitimacy of the experimental model. The outcomes of this research will provide valuable experimental data and numerical predictions for offshore pipeline design, heat loss from buried pipelines in offshore conditions, and efficient model to mitigate the flow assurance issues e.g. wax and hydrates.

Design of Experiment and Validation of Model for Offshore Buried Pipeline Thermal Analysis

2016 ◽  
Author(s):  
Suvra Chakraborty ◽  
Vandad Talimi ◽  
Yuri Muzychka ◽  
Rodney McAffee ◽  
Gerry Piercey
Keyword(s):  
Heat Loss ◽  
Oil And Gas ◽  
Surrounding Medium ◽  
Soil Surface ◽  
Oil And Gas Industry ◽  
Cfd Modeling ◽  
Soil Conditions ◽  
Actual Behavior ◽  
Buried Pipeline ◽  
Backfill Materials

Buried pipeline heat transfer modeling has become an important topic in the Oil and Gas industry. The viscosity of fluid i.e. crude oil travelling through the buried pipeline largely depends on the flow temperature and pressure. The aim of this paper is to give an overview of designing the experiment for heat loss from offshore buried pipelines and validation of the experimental model using analytical solution and CFD modeling. Several benchmark tests have been performed to ensure the validity of the test using theoretical shape factor models which depend on the amount of heat flow, thermal conductivity and geometry of the surrounding medium. This theoretical model has limitations such as the assumption of uniform soil properties around the buried pipeline, isothermal outer surface of the buried pipeline and soil surface. This paper illustrates several steady state and transient experiments to simulate the mechanism of heat loss from an offshore buried pipeline along with the experimental procedures. This paper also shows the transient response for shutdown tests performed in dry sand medium with numerical runs as well. With the progress of the research, several investigations will be made using different burial depths and diameters of the buried pipeline with backfill materials and trenching for different soil conditions, affecting the actual behavior of the model.

Strategies for Isothermal, Real-Time, Transient Pipeline Models in Shut-In Conditions

2018 ◽  
Author(s):  
Norense Okungbowa ◽  
Trent Brown
Keyword(s):  
Real Time ◽  
Thermal Effects ◽  
Burial Depth ◽  
Fluid Temperature ◽  
Soil Density ◽  
Soil Thermal Conductivity ◽  
Buried Pipelines ◽  
Isothermal Model ◽  
Secondary Importance ◽  
Soil Heat Capacity

Onshore, liquid pipelines are often modeled with isothermal models. Ignoring thermal effects is justified because thermal effects are of secondary importance and because the data, such as burial depth, soil thermal conductivity, soil heat capacity, and soil density, required to accurately predict thermal behavior in buried pipelines is not known accurately. In addition, run speeds are faster for isothermal models than for rigorous thermal models, which is particularly important in real-time models. One condition where thermal effects become important is when a pipeline is shut-in. Pumps increase the temperature of the fluid, so the fluid temperature is, on average, greater than ambient temperature. When a pipeline is shut-in, the temperature decreases causing a corresponding decrease in pressure. Since an isothermal model does not account for this behavior, the decreasing pressure can be misinterpreted as a leak. This paper discusses a strategy for correcting the model to properly account for the behavior in shut-in conditions. The strategy is applied to real-time pipeline models using Synergi Pipeline Simulator (SPS), although the method is applicable to any isothermal model.

Numerical Simulation of Upheaval Buckling Using “Intelligent” Backfill Soil Springs

2015 ◽  
Author(s):  
Prigiarto Hokkal Yonatan ◽  
Filip Van den Abeele ◽  
Jean-Christophe Ballard
Keyword(s):  
Numerical Simulation ◽  
New Technique ◽  
Buried Pipeline ◽  
Buried Pipelines ◽  
Upheaval Buckling ◽  
Backfill Soil ◽  
Uplift Resistance ◽  
A New Technique ◽  
Force Equilibrium

Designing the cover height of buried pipelines to prevent them from buckling requires a method that can thoroughly and realistically model the phenomenon. This paper introduces a new technique to assess the risk of upheaval buckling (UHB) by using backfill soil springs (BFSS) to represent the uplift resistance provided by the backfill soil on top of a buried pipeline. This paper investigates the pre-buckling pipeline behavior related to UHB and highlights some of the key parameters governing the analysis. UHB assessment based on a case study was carried out and the results were then compared with those obtained from force-equilibrium methods generally used in the industry. The comparison shows that UHB assessment can be performed more rigorous using BFSS than using force-equilibrium methods. Therefore, using BFSS for UHB assessment improve the reliability in cover height design.

Inducing Frictional Force to Enhance the Transient Response in Beams

2019 ◽  
Vol 22 (2) ◽  
pp. 88-93
Author(s):  
Hamed Khanger Mina ◽  
Waleed K. Al-Ashtrai
Keyword(s):  
Numerical Analysis ◽  
Transient Response ◽  
Frictional Force ◽  
Damping Ratio ◽  
Experimental Results ◽  
Damping Capacity ◽  
Tightening Force ◽  
Contact Areas ◽  
Good Agreement ◽  
Ansys Workbench

This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.

Comparison of Buried Pipeline Crossing Assessments Using API RP 1102, Analytical Method and Finite Element Approach

2020 ◽  
Author(s):  
Nikhil Joshi ◽  
Pritha Ghosh ◽  
Jonathan Brewer ◽  
Lawrence Matta
Keyword(s):  
Finite Element ◽  
Analytical Method ◽  
Rapid Assessment ◽  
Buried Pipeline ◽  
The Finite Element Method ◽  
Buried Pipelines ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Element Approach ◽  
Multiple Loading

Abstract API RP 1102 provides a method to calculate stresses in buried pipelines due to surface loads resulting from the encroachment of roads and railroads. The API RP 1102 approach is commonly used in the industry, and widely available software allows for quick and easy implementation. However, the approach has several limitations on when it can be used, one of which is that it is limited to pipelines crossing as near to 90° (perpendicular crossing) as practicable. In no case can the crossing be less than 30° . In this paper, the stresses in the buried pipeline under standard highway vehicular loading calculated using the API RP 1102 method are compared with the results of two other methods; an analytical method that accounts for longitudinal and circumferential through wall bending effects, and the finite element method. The benefit of the alternate analytical method is that it is not subject to the limitations of API RP 1102 on crossing alignment or depth. However, this method is still subject to the limitation that the pipeline is straight and at a uniform depth. The fact that it is analytical in nature allows for rapid assessment of a number of pipes and load configurations. The finite element analysis using a 3D soil box approach offers the greatest flexibility in that pipes with bends or appurtenances can be assessed. However, this approach is time consuming and difficult to apply to multiple loading scenarios. Pipeline crossings between 0° (parallel) and 90° (perpendicular) are evaluated in the assessment reported here, even though these are beyond the scope of API RP 1102. A comparison across the three methods will provide a means to evaluate the level of conservatism, if any, in the API RP 1102 calculation for crossing between 30° and 90° . It also provides a rationale to evaluate whether the API RP 1102 calculation can potentially be extended for 0° (parallel) crossings.

Research on Simulation of Operation of DSG Collectors Based on Analysis of Scientific Materials

2011 ◽  
Vol 282-283 ◽  
pp. 710-715 ◽  
Author(s):  
Teng Gao ◽  
Jun Zhao ◽  
Bin Yang ◽  
Fu Wang
Keyword(s):  
Heat Transfer ◽  
Heat Loss ◽  
Energy Balance Equation ◽  
Basic Program ◽  
Transfer Model ◽  
Fluid Temperature ◽  
Steam Generation ◽  
Collector Efficiency ◽  
Steady State Heat Transfer ◽  
Fluid Parameters

In this paper, a direct steam generation (DSG) collector is researched. To determinate the DSG collector efficiency, a simplified heat loss correlation is applied. A one-dimensional steady state heat transfer model and an energy balance equation for DSG collector are developed. A Visual basic program coupled with fluid parameters is compiled to compute fluid temperature, heat transfer coefficient and heat loss along the absorber tube by iterations for given accuracy. The variation trends of many kinds of fluid parameters along the absorber tube are revealed. The effect of length of dry steam region on collector efficiency is accounted for also.

Estimation of Ice Load on a Ship Hull Based on Strain Measurements

2008 ◽  
Author(s):  
Bernt J. Leira ◽  
Lars Bo̸rsheim
Keyword(s):  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Element Model ◽  
Coast Guard ◽  
Ship Hull ◽  
Gas Industry ◽  
Arctic Regions ◽  
Lack Of Information ◽  
Measured Strain ◽  
Vessel Speed

The increased activity related to the oil and gas industry in polar waters implies that proper operation of ships such areas also will be in focus. The loading on a particular ship hull depends strongly on the route selection and vessel speed. Lack of information about the actual ice condition and the corresponding loads acting on the hull is identified to be among the most critical factors when operating in Arctic waters. This implies that there is a challenging interaction between strength-related design rules and schemes for operation of ships in arctic regions. In particular, the possibility of monitoring ice-induced stresses in order to provide assistance in relation to ship manoevering becomes highly relevant. The present paper is concerned with estimation of ice loads acting on the hull of the coast guard vessel KV Svalbard based on strains that were measured during the winter of 2007 as part of a project headed by DNV. Application of a finite element model of the bow structure is also applied in order to correlate the loading with the measured strains. The influence of ice thickness and vessel speed on the measured strain levels is also investigated.

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