TY - BOOK

T1 - Three Dimensional Investigation of Hydrate Formation in Natural Gas Pipelines

AU - Naseer, Mohammad

N1 - no embargo

PY - 2012

Y1 - 2012

N2 - Gas hydrates can undermine the flow assurance programs by blocking the pipelines. The stoppage in the production results in wastage of time and resources. A gas pipeline may pass through regions with topographic variations and elevation differences. In winters the ground temperatures may fall resulting in colder pipelines walls. If water vapour concentration in the natural gas mixture is such that temperature of the gas at the walls falls below the saturation temperature, condensation of water vapour may ensue. The condensed water flows along the pipe and tends to accumulate at the bottom section of the pipe. In addition to being accumulated at the bottom section of the pipeline, the water also gets entrapped at the sagging/ uphill sections, or trap-like portions of the pipelines. During the winter season, the deposition may be at different sections along the pipeline separated by large distances. The deposits may be circumferential and axial, reducing the effective flow rate of the gas. At the start of summers or during transient pipeline operations, the deposited hydrates may sloughen at the walls and travel along the pipe to eventually get trapped at pipe bends (for example) plugging the cross-section completely. The deposition in this manner has an appearance of packed ice \cite{DendySloan2011}. While one dimensional (1-D) Computational Fluid Dynamics (CFD) codes can identify the hydrate prone zones along the length of the pipeline, the effects of condensation, hydrate formation and deposition along axial-radial directions (growth morphology) can only be ascertained with a three-dimensional (3-D) analysis. However, hydrate formation, deposition and blockage are complex multifaceted phenomena and require a synergistic approach, including various submodels to capture the whole phenomenon in totality. The work presented is an effort to model the mechanisms that lead to hydrate formation so that temporal and spatial phenomena related to hydrate formation can be understood. This in turn can help to ascertain critical sections of the pipe line with respect to hydrate deposition and blockage.

AB - Gas hydrates can undermine the flow assurance programs by blocking the pipelines. The stoppage in the production results in wastage of time and resources. A gas pipeline may pass through regions with topographic variations and elevation differences. In winters the ground temperatures may fall resulting in colder pipelines walls. If water vapour concentration in the natural gas mixture is such that temperature of the gas at the walls falls below the saturation temperature, condensation of water vapour may ensue. The condensed water flows along the pipe and tends to accumulate at the bottom section of the pipe. In addition to being accumulated at the bottom section of the pipeline, the water also gets entrapped at the sagging/ uphill sections, or trap-like portions of the pipelines. During the winter season, the deposition may be at different sections along the pipeline separated by large distances. The deposits may be circumferential and axial, reducing the effective flow rate of the gas. At the start of summers or during transient pipeline operations, the deposited hydrates may sloughen at the walls and travel along the pipe to eventually get trapped at pipe bends (for example) plugging the cross-section completely. The deposition in this manner has an appearance of packed ice \cite{DendySloan2011}. While one dimensional (1-D) Computational Fluid Dynamics (CFD) codes can identify the hydrate prone zones along the length of the pipeline, the effects of condensation, hydrate formation and deposition along axial-radial directions (growth morphology) can only be ascertained with a three-dimensional (3-D) analysis. However, hydrate formation, deposition and blockage are complex multifaceted phenomena and require a synergistic approach, including various submodels to capture the whole phenomenon in totality. The work presented is an effort to model the mechanisms that lead to hydrate formation so that temporal and spatial phenomena related to hydrate formation can be understood. This in turn can help to ascertain critical sections of the pipe line with respect to hydrate deposition and blockage.

KW - Hydrare

KW - Pipeline

KW - clathrates

KW - condensation

M3 - Doctoral Thesis

ER -