Polytec Research Institute

Haugesund, Norway

Polytec Research Institute

Haugesund, Norway
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Soldal M.,NGI Inc | Park J.,NGI Inc | Lamech L.O.,University of Oslo | Tran T.,University of Oslo | And 3 more authors.
3rd EAGE Workshop on Rock Physics: From Rocks to Basin - Applying Rock Physics in Prospect Evaluation and Reservoir Characterization | Year: 2015

In this study, liquid CO2 is injected into fully brine saturated reservoir core samples in the laboratory, and consequently changes in electrical resistivity, acoustic velocities (ultrasonic frequency) and their anisotropy are measured. To enhance the spatial resolution, a system enabling velocity and resistivity measurements at different points and in different directions along the specimen's axial direction has been developed. Electrical resistivity and acoustic velocity and amplitude are all clearly influenced by porescale heterogeneity and fluid flow pattern and it is important to study this interaction. So far, focus has been related to CO2 geological storage, but the outline of the study is believed to also be applicable for CO2 injection for enhanced oil recovery (EOR). The study is still ongoing and some preliminary results are presented here and discussed.


Oosterkamp A.,Polytec Research Institute | Oosterkamp A.,Norwegian University of Science and Technology
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2015

Heat transfer between the fluid in a pipeline and the ambient soil is of importance for accurate modelling of flow hydraulic conditions. This work presents a study on the soil heat transfer from a buried natural gas pipeline. An export gas pipeline from Norway to the continent was subject to detail investigation. The aim was to improve the understanding of the heat exchange with the surrounding soil. The spatio-temporal development of soil temperatures in response to the presence of the warmer pipe was both measured and modelled. The thermal and hydraulic properties of the soil were determined through experimental methods and physical correlations/predictive modelling. The pipeline and the surrounding soil were instrumented with an array of temperature and soil moisture sensors providing the in-situ measurements. A CFD model of the experimental set-up was developed, applying the achieved soil thermal properties and local geology. In the model, measured soil surface and pipe wall temperatures were used as time dependent boundary conditions. The transient development of the thermal regime of the soil surrounding the pipeline was compared to the actual temperature measurement values. The model was used to assess the validity of the commonly used assumption that conduction is the prevailing heat transfer model. The contribution of natural convection heat transfer from ground water was also assessed. The results show that, given the thermal properties determined for the soil surrounding the instrumented section of the pipeline, a numerical calculation model using only heat conduction can represent the soil temperatures accurately at some distance to the pipe. Close to the pipe wall the predictions are less accurate. The role ground water plays in natural convection was demonstrated and found to be of minor significance for the case at hand. The cause of the temperature discrepancy close to the pipe wall warrants further investigation. Copyright © 2015 by the International Society of Offshore and Polar Engineers (ISOPE).


Sund F.,Polytec Research Institute | Oosterkamp A.,Polytec Research Institute | Oosterkamp A.,Norwegian University of Science and Technology | Hope S.M.,Polytec Research Institute | Hope S.M.,Norwegian University of Science and Technology
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2015

The impact of different methods for modelling heat transfer between a pipeline and the ambient is investigated. The differences in outlet temperatures between a steady and an unsteady heat transfer model are quantified, as well as the effects of simulating the annual oceanic temperature cycle over several years. A seasonal difference between measured and modeled outlet temperature is found. The results show that the absence of the heat storage term in the heat transfer model may only be a small contributing factor to this difference. Assuming the error is caused by inaccuracies in the ambient temperature, the impact on the capacity is found to be between 0.1 and 0.5 %. Copyright © 2015 by the International Society of Offshore and Polar Engineers (ISOPE).


Helgaker J.F.,Polytec Research Institute | Helgaker J.F.,Norwegian University of Science and Technology | Muller B.,Polytec Research Institute | Ytrehus T.,Polytec Research Institute
Journal of Offshore Mechanics and Arctic Engineering | Year: 2014

Transmission of natural gas through high pressure pipelines has been modeled by numerically solving the governing equations for one-dimensional compressible flow using implicit finite difference methods. In the first case the backward Euler method is considered using both standard first-order upwind and second-order centered differences for the spatial derivatives. The first-order upwind approximation, which is a one-sided approximation, is found to be unstable for CFL numbers less than 1, while the centered difference approximation is stable for any CFL number. In the second case a cell centered method is considered where flow values are calculated at the midpoint between grid points. This method is also stable for any CFL number. However, for a discontinuous change in inlet temperature, the method is observed to introduce unphysical oscillations in the temperature profile along the pipeline. A solution strategy where the hydraulic and thermal models are solved separately using different discretization techniques is suggested. Such a solution strategy does not introduce unphysical oscillations for discontinuous changes in inlet boundary conditions and is found to be stable for any CFL number. The one-dimensional flow model is validated using operational data from a high pressure natural gas pipeline. © 2014 by ASME.


Oosterkamp A.,Polytec Research Institute | Oosterkamp A.,Norwegian University of Science and Technology | Helgaker J.F.,Polytec Research Institute | Helgaker J.F.,Norwegian University of Science and Technology | Ytrehus T.,Norwegian University of Science and Technology
Energy Procedia | Year: 2015

The paper presents a study of gas pipeline to soil heat transfer. The effect of simplifications of the heat transfer model is investigated. Studied are steady, one dimensional unsteady and two dimensional unsteady models of the pipe wall and soil. Flow conditions at the pipeline inlet are varied. The effects of rapid changes in gas mass flow rate and temperature at the pipeline inlet are studied. The case presented is representative for export natural gas pipelines, containing offshore and buried sections along the route. Results are compared to experimental data from an existing export natural gas pipeline. © 2015 The Authors. Published by Elsevier Ltd.


Vevatne J.N.,Norwegian University of Science and Technology | Rimstad E.,Norwegian University of Science and Technology | Hope S.M.,Norwegian University of Science and Technology | Hope S.M.,Polytec Research Institute | And 2 more authors.
Frontiers of Physics | Year: 2014

Fracturing and refreezing of sea ice in the Kara sea are investigated using complex network analysis. By going to the dual network, where the fractures are nodes and their intersections links, we gain access to topological features which are easy to measure and hence compare with modeled networks. Resulting network reveal statistical properties of the fracturing process. The dual networks have a broad degree distribution, with a scale-free tail, high clustering and efficiency. The degree–degree correlation profile shows disassortative behavior, indicating preferential growth. This implies that long, dominating fractures appear earlier than shorter fractures, and that the short fractures which are created later tend to connect to the long fractures. The knowledge of the fracturing process is used to construct growing fracture network (GFN) model which provides insight into the generation of fracture networks. The GFN model is primarily based on the observation that fractures in sea ice are likely to end when hitting existing fractures. Based on an investigation of which fractures survive over time, a simple model for refreezing is also added to the GFN model, and the model is analyzed and compared to the real networks. © 2014 Vevatne, Rimstad, Hope, Korsnes and Hansen.


Ytrehus T.,Norwegian University of Science and Technology | Helgaker J.F.,Norwegian University of Science and Technology | Helgaker J.F.,Polytec Research Institute
Journal of Fluids Engineering, Transactions of the ASME | Year: 2013

The transportation of natural gas through high pressure transmission pipelines has been modeled by numerically solving the conservation equations for mass, momentum, and energy for one-dimensional compressible viscous heat conducting flow. Since the one-dimensional version is a result of averages over the pipe cross-section and the flow is normally turbulent, the order of averaging in space and time is an issue; in particular, for the dissipation term. The Reynolds decomposition and time averaging should be performed first, followed by the contraction to the one-dimensional version by the cross-sectional averaging. The result is a correction factor, which is close to unity, on the usual expression of the dissipation term in the energy equation. This factor will, to some extent, affect the temperature distribution along the pipeline. For low Reynolds numbers (Reâ‰104) it reduces the dissipation by as much as 7%, irrespective of roughness. For high Reynolds numbers (Re ≥ 107) and roughness in the high range of the micron decade, the dissipation is increased by 10%. If the pipeline is also thermally isolated such that the flow can be considered adiabatic, the effect of turbulent dissipation gains further importance. Copyright © 2013 by ASME.


Helgaker J.F.,Polytec Research Institute | Helgaker J.F.,Norwegian University of Science and Technology | Oosterkamp A.,Polytec Research Institute | Oosterkamp A.,Norwegian University of Science and Technology | And 2 more authors.
Journal of Natural Gas Science and Engineering | Year: 2014

Transportation of natural gas through high pressure large diameter offshore pipelines is modeled by numerically solving the governing equations for one-dimensional compressible pipe flow using an implicit finite difference method. The pipelines considered have a diameter of 1m and length of approximately 650km. The influence of different physical parameters which enter into the model are investigated in detail. These include the friction factor, equation of state and heat transfer model. For high pressure pipelines it is shown that the selection of the equation of state can have a considerable effect on the simulated flow results, with the recently developed GERG 2004 being compared to the more traditional SRK, Peng-Robinson and BWRS equations of state. Also, including heat accumulation in the ground is important in order to model the correct temperature at the outlet of the pipeline. The flow model is validated by comparing computed results to measured values for an offshore natural gas pipeline. © 2013 Elsevier B.V.


Stensholt S.,Polytec Research Institute
Computers and Mathematics with Applications | Year: 2015

We evaluate the Lattice-Boltzmann model that combines the free energy approach for multiphase flow with the bounce-back boundary condition. This method requires a virtual ordering parameter to be assigned to the wall nodes. Existing literature has assigned a single ordering parameter for the entire wall node, but this is too coarse to give accurate simulations since it allows for a spurious interaction of different phases through the wall nodes. The consequences are illustrated by examining rough and hydrophobic surfaces where contact angles can be predicted using the Cassie-Baxter equation. It is found that the single value approach gives a large systemic error in the measured contact angles. Considerable improvement can be obtained by assigning different values of the ordering parameter to each side of the wall node. © 2015 Elsevier Ltd.

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