Petroleum Science >2022,??lssue 1:??- DOI: https://doi.org/10.1016/j.petsci.2021.10.026
Effects of creep characteristics of natural gas hydrate-bearing sediments on wellbore stability Open?Access
文章信息
作者：Yang Li, Yuan-Fang Cheng, Chuan-Liang Yan, Zhi-Yuan Wang, Li-Fang Song,
作者单位：
投稿时间：
引用方式：Yang Li, Yuan-Fang Cheng, Chuan-Liang Yan, Zhi-Yuan Wang, Li-Fang Song, Effects of creep characteristics of natural gas hydrate-bearing sediments on wellbore stability, Petroleum Science, Volume 19, Issue 1, Pages 220-233, https://doi.org/10.1016/j.petsci.2021.10.026.
文章摘要
Abstract
Natural gas hydrate (NGH) reservoirs consist of the types of sediments with weak cementation, low strength, high plasticity, and high creep. Based on the kinetics and thermodynamic characteristics of NGH decomposition, herein a heat-fluid-solid coupling model was established for studying the wellbore stability in an NGH-bearing formation to analyze the effects of the creep characteristics of NGH-bearing sediments during long-term drilling. The results demonstrated that the creep characteristics of sediments resulted in larger plastic yield range, thus aggravating the plastic strain accumulation around the wellbore. Furthermore, the creep characteristics of NGH-bearing sediments could enhance the effects induced by the difference in horizontal in situ stress, as a result, the plastic strain in the formation around the wellbore increased nonlinearly with increasing difference in in situ stress. The lower the pore pressure, the greater the stress concentration effects and the higher the plastic strain at the wellbore. Moreover, the lower the initial NGH saturation, the greater the initial plastic strain and yield range and the higher the equivalent creep stress. The plastic strain at the wellbore increased nonlinearly with decreasing initial saturation.
Natural gas hydrate (NGH) reservoirs consist of the types of sediments with weak cementation, low strength, high plasticity, and high creep. Based on the kinetics and thermodynamic characteristics of NGH decomposition, herein a heat-fluid-solid coupling model was established for studying the wellbore stability in an NGH-bearing formation to analyze the effects of the creep characteristics of NGH-bearing sediments during long-term drilling. The results demonstrated that the creep characteristics of sediments resulted in larger plastic yield range, thus aggravating the plastic strain accumulation around the wellbore. Furthermore, the creep characteristics of NGH-bearing sediments could enhance the effects induced by the difference in horizontal in situ stress, as a result, the plastic strain in the formation around the wellbore increased nonlinearly with increasing difference in in situ stress. The lower the pore pressure, the greater the stress concentration effects and the higher the plastic strain at the wellbore. Moreover, the lower the initial NGH saturation, the greater the initial plastic strain and yield range and the higher the equivalent creep stress. The plastic strain at the wellbore increased nonlinearly with decreasing initial saturation.
关键词
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Natural gas hydrates; Wellbore stability; Creep; Plastic yield