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

Advances in Geo-Energy Research

article

Youhong Sun¹  Hongfeng Lu²  Cheng Lu²  Shengli Li¹  Xiaoshu Lv³ 

[1] Key Laboratory of Drilling and Exploitation Technology in Complex Conditions of Ministry of Land and Resources, College of Construction Engineering, Jilin University;Guangzhou Marine Geological Survey, China Geological Survey;Department of Civil and Structural Engineering, School of Engineering, Aalto University

关键词: Gas hydrate dissociation;    model;    gas diffusion;    pore water;    wellbore stability;   

DOI  :  10.26804/ager.2018.04.06

来源: Yandy Scientific Press

【 摘 要 】

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.

【 授权许可】

Unknown