Entropy Production of Hydrate Transport in Subsea Multiphase Pipeline Flows

Volume 5B: Pipeline and Riser Technology ◽

10.1115/omae2015-42272 ◽

2015 ◽

Author(s):

Adedoyin Odukoya ◽

Greg F. Naterer

Keyword(s):

Heat Transfer ◽

Numerical Model ◽

Entropy Production ◽

Gas Flow ◽

Oil And Gas ◽

Fluid Layer ◽

Hydrate Formation ◽

Internal Diameter ◽

Environment Temperature ◽

Subsea Pipelines

A numerical model is developed to examine the flow conditions of multiphase heat transfer and entropy production during hydrate formation in subsea pipelines. The temperature and pressure gradients of the oil and gas flow in subsea pipelines lead to entropy generation. This paper examines the impacts and effects of thermodynamic irreversibilities on the nucleation and growth processes of hydrate crystals in the pipeline flows. The effects of heat transfer ratio, internal diameter of the pipe, molar gas density, and environment temperature on entropy production in subsea pipelines are predicted and discussed in this paper. The numerical model accounts for the temperature distribution along the axial length of the pipe, reaction kinetics, and mass transfer between the solid and fluid layer. The kinetic energy of the hydrate particles during the coagulation process is analyzed in the numerical model. The results indicate that entropy production is highest at the beginning of the nucleation process. Pipelines with smaller internal radii have a lower rate of hydrate formation in subsea pipelines. The results from the numerical model are verified by comparison with experimental results for structure type II natural gas hydrates.

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Challenges in Hydrate Plug Prevention in Pipelines Seen Over the Lifetime of a Field

Volume 7: Offshore Geotechnics; Petroleum Technology ◽

10.1115/omae2009-79446 ◽

2009 ◽

Author(s):

Casper Hadsbjerg ◽

Kristian Krejbjerg

Keyword(s):

Oil And Gas ◽

Formation Rate ◽

Hydrate Formation ◽

Extended Period ◽

Oil And Gas Industry ◽

High Water ◽

Point Of View ◽

Field Development ◽

Hydrate Plug ◽

Subsea Pipelines

When the oil and gas industry explores subsea resources in remote areas and at high water depths, it is important to have advanced simulation tools available in order to assess the risks associated with these expensive projects. A major issue is whether hydrates will form when the hydrocarbons are transported to shore in subsea pipelines, since the formation of a hydrate plug might shut down a pipeline for an extended period of time, leading to severe losses. The industry practices a conservative approach to hydrate plug prevention, which is the addition of inhibitors to ensure that hydrates cannot form under pipeline pressure and temperature conditions. The addition of inhibitors to subsea pipelines is environmentally unfriendly and also a very costly procedure. Recent efforts has therefore focused on developing models for the hydrate formation rate (hydrate kinetics models), which can help determine how fast hydrates might form a plug in a pipeline, and whether the amount of inhibitor can be reduced without increasing the risk of hydrate plug formation. The main variables determining whether hydrate plugs form in a pipeline are: 1) the ratio of hydrocarbons to water, 2) the composition of the hydrocarbons, 3) the flowrates/flow regimes in the pipeline, 4) the amount of inhibitor in the system. Over the lifetime of a field, all 4 variables will change, and so will the challenge of hydrate plug prevention. This paper will examine the prevention of hydrate plugs in a pipeline, seen from a hydrate kinetics point of view. Different scenarios that can occur over the lifetime of a field will be investigated. Exemplified through a subsea field development, a pipeline simulator that considers hydrate formation in a pipeline is used to carry out a study to shed light on the most important issues to consider as conditions change. The information gained from this study can be used to cut down on inhibitor dosage, or possibly completely remove the need for inhibitor.

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Natural Convection Flow and Heat Transfer Between a Fluid Layer and a Porous Layer Inside a Rectangular Enclosure

Journal of Heat Transfer ◽

10.1115/1.3248089 ◽

1987 ◽

Vol 109 (2) ◽

pp. 363-370 ◽

Cited By ~ 160

Author(s):

C. Beckermann ◽

S. Ramadhyani ◽

R. Viskanta

Keyword(s):

Heat Transfer ◽

Porous Medium ◽

Natural Convection ◽

Numerical Model ◽

Porous Layer ◽

Fluid Layer ◽

Convection Flow ◽

Natural Convection Flow ◽

Rectangular Enclosure ◽

Flow And Heat Transfer

A numerical and experimental study is performed to analyze the steady-state natural convection fluid flow and heat transfer in a vertical rectangular enclosure that is partially filled with a vertical layer of a fluid-saturated porous medium. The flow in the porous layer is modeled utilizing the Brinkman–Forchheimer–extended Darcy equations. The numerical model is verified by conducting a number of experiments, with spherical glass beads as the porous medium and water and glycerin as the fluids, in rectangular test cells. The agreement between the flow visualization results and temperature measurements and the numerical model is, in general, good. It is found that the amount of fluid penetrating from the fluid region into the porous layer depends strongly on the Darcy (Da) and Rayleigh (Ra) numbers. For a relatively low product of Ra × Da, the flow takes place primarily in the fluid layer, and heat transfer in the porous layer is by conduction only. On other hand, fluid penetrating into a relatively highly permeable porous layer has a significant impact on the natural convection flow patterns in the entire enclosure.

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Mathematical model of natural gas flow in pipelines in the presence of hydrate formation

Proceedings of the Mavlyutov Institute of Mechanics ◽

10.21662/uim2008.1.030 ◽

2008 ◽

Vol 6 ◽

pp. 205-209

Author(s):

V.Sh. Shagapov ◽

R.R. Urazov

Keyword(s):

Heat Transfer ◽

Mathematical Model ◽

Mass Transfer ◽

Natural Gas ◽

Phase Transformations ◽

Gas Hydrates ◽

Heat Conductivity ◽

Gas Flow ◽

Hydrate Formation ◽

Natural Gas Flow

The flow of wet natural gas in the pipeline is considered in the presence of the formation of gas hydrates on the internal walls of the channel. In the description of the phenomenon, such interrelated processes as phase transformations and mass transfer of water into the composition of gas hydrates, heat transfer between the gas stream and the environment, heat conductivity in the ground are taken into account.

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Problem of conjugate heat transfer between main gas pipeline and frozen ground

E3S Web of Conferences ◽

10.1051/e3sconf/201910201001 ◽

2019 ◽

Vol 102 ◽

pp. 01001

Author(s):

Edward Bondarev ◽

Igor Rozhin ◽

Kira Argunova

Keyword(s):

Heat Transfer ◽

Mathematical Model ◽

Gas Flow ◽

Hydrate Formation ◽

Conjugate Problem ◽

Gas Pipeline ◽

Frozen Ground ◽

Flow Area ◽

Tube Cross Section ◽

Main Gas Pipeline

Mathematical model of non-isothermal gas flow within the framework of tube hydraulics including change of tube cross-section due to hydrate formation and the dependence of coefficient of heat transfer between gas and hydrate layer on varying flow area is proposed. The corresponding conjugate problem of heat exchange between imperfect gas in the pipeline and the environment is reduced to the solution of differential equations describing non-isothermal flow of gas in pipes and heat transfer equations in ground with the corresponding conjugation conditions. In the quasi-stationary mathematical model of hydrate formation (dissociation), the dependence of gas-hydrate transition temperature on gas pressure is taken into account. Some decisions taken in the design of the first section of the main gas pipeline «Power of Siberia» have been analyzed. It has been shown that if gas is not sufficiently dried, outlet pressure may drop below the technological limit in about 6-7 hours. At the same time, for completely dry gas ,it is possible to reduce the cost of thermal insulation of the pipeline at least two fold.

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