Hydrate dissociation induced by gas diffusion from pore water to drilling fluid in a cold wellbore

Youhong Sun, Hongfeng Lu, Cheng Lu, Shengli Li, Xiaoshu Lu-Tervola

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Abstract

It is a common view that the high temperature of the drilling fluid can lead to the dissociation of gas hydrate during drilling through hydrate-bearing sediments. This study indicates that the hydrate dissociation in wellbore can also be induced by gas diffusion from pore water to drilling fluid even if the temperature (and the pressure if necessary) of the drilling fluid is well controlled to keep the conditions of hydrate-bearing sediments along the hydrate equilibrium boundary. The dissociation of gas hydrate was modelled based on Fick's first law. It was found that the dissociation rate mainly depended on the temperature of the sediments. The locations of dissociation front of CH4 hydrate and CO2 hydrate in wellbore were calculated as a function of time. The impacts of the hydrate dissociation on the wellbore stability and the resistivity well logging in sediments were evaluated.
Original languageEnglish
Pages (from-to)410-417
JournalAdvances in Geo-Energy Research
Volume2
Issue number4
DOIs
Publication statusPublished - 24 Aug 2018
MoE publication typeA2 Review article in a scientific journal

Keywords

  • gas hydrage dissociation
  • model
  • gas diffusion
  • pore water
  • wellbore stability

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