Response of oceanic hydrate-bearing sediments to thermalstresses

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In this study, we evaluate the response of oceanicsubsurface systems to thermal stresses caused by the flow of warm fluidsthrough noninsulated well systems crossing hydrate-bearing sediments.Heat transport from warm fluids, originating from deeper reservoirs underproduction, into the geologic media can cause dissociation of the gashydrates. The objective of this study is to determine whether gasevolution from hydrate dissociation can lead to excessive pressurebuildup, and possibly to fracturing of hydrate-bearing formations andtheir confining layers, with potentially adverse consequences on thestability of the suboceanic subsurface. This study also aims to determinewhether the loss of the hydrate--known to have a strong cementing effecton ... continued below

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Moridis, G.J. & Kowalsky, M.B. May 1, 2006.

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In this study, we evaluate the response of oceanicsubsurface systems to thermal stresses caused by the flow of warm fluidsthrough noninsulated well systems crossing hydrate-bearing sediments.Heat transport from warm fluids, originating from deeper reservoirs underproduction, into the geologic media can cause dissociation of the gashydrates. The objective of this study is to determine whether gasevolution from hydrate dissociation can lead to excessive pressurebuildup, and possibly to fracturing of hydrate-bearing formations andtheir confining layers, with potentially adverse consequences on thestability of the suboceanic subsurface. This study also aims to determinewhether the loss of the hydrate--known to have a strong cementing effecton the porous media--in the vicinity of the well, coupled with thesignificant pressure increases, can undermine the structural stability ofthe well assembly.Scoping 1D simulations indicated that the formationintrinsic permeability, the pore compressibility, the temperature of theproduced fluids andthe initial hydrate saturation are the most importantfactors affecting the system response, while the thermal conductivity andporosity (above a certain level) appear to have a secondary effect.Large-scale simulations of realistic systems were also conducted,involving complex well designs and multilayered geologic media withnonuniform distribution of properties and initial hydrate saturationsthat are typical of those expected in natural oceanic systems. Theresults of the 2D study indicate that although the dissociation radiusremains rather limited even after long-term production, low intrinsicpermeability and/or high hydrate saturation can lead to the evolution ofhigh pressures that can threaten the formation and its boundaries withfracturing. Although lower maximum pressures are observed in the absenceof bottom confining layers and in deeper (and thus warmer and morepressurized) systems, the reduction is limited. Wellbore designs withgravel packs that allow gas venting and pressure relief result insubstantially lower pressures.

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  • Journal Name: SPE Journal; Journal Volume: 12; Journal Issue: 2; Related Information: Journal Publication Date: 2007

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  • Report No.: LBNL--60150-JArt
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 925585
  • Archival Resource Key: ark:/67531/metadc893765

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  • May 1, 2006

Added to The UNT Digital Library

  • Sept. 27, 2016, 1:39 a.m.

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  • Dec. 1, 2016, 4:31 p.m.

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Moridis, G.J. & Kowalsky, M.B. Response of oceanic hydrate-bearing sediments to thermalstresses, article, May 1, 2006; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc893765/: accessed November 14, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.