Numerical Analysis for Geomechanical Deformation of Sea Bed due to
Gas Hydrate Dissociation

doi:10.12972/ksmer.2015.52.2.148

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2015 Vol.52, Issue 2 Preview Page Next Page

Research Paper

Numerical Analysis for Geomechanical Deformation of Sea Bed due to Gas Hydrate Dissociation 가스하이드레이트 해리에 따른 해저지반의 역학적 변형 해석: 김형목
Hyung-Mok Kim

30 April 2015. pp. 148-157

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Abstract

In this study, we examined the influence of in-situ stress and bottom hole pressure ondissociation-induced geomechanical deformation of hydrate-bearing formation in a numerical manner. Thesequentially coupled analysis of TOUGH+Hydrate and FLAC3D was employed for the simulation of hydratedissociation and subsequent dissociated gas flow as well as stress/deformation analysis of the surroundingformations, respectively. The simulation model was constructed using the information of the Ulleung basin fromthe recently published work (Lim, 2013; Moridis et al., 2013). We could observe that subsidence may occur ina homogeneous way and was sensitive to stiffness properties of sea beds. The subsidence was more substantialwhen initial stress condition is anisotropic, but depressurization level at the bottom hole was more influentialto the subsidence rather than the initial stress condition. The potential for shear failure in hydrate-bearing formationand surrounding ground induced by effective stress change was predicted to be little.

Keywords

Hydrate bearing sediments

Sea bed

Gas hydrate

Geomechanical deformation

Dissociation

본 연구에서는 수치해석을 통해 가스하이드레이트 함유층 내 초기응력분포 및 가스 생산을 위한 감압압력이 해저 지반의 역학적 변형에 미치는 영향을 살펴보았다. 해석기법으로는 가스하이드레이트의 해리 및해리 가스와 공극 유체의 열유동뿐만 아니라 주변 지반 내 응력 및 변형을 동시에 시뮬레이션할 수 있는TOUGH+Hydrate와 FLAC3D를 순차해석하는 방식을 사용하였다. 동해 울릉분지 시추조사 결과에 근거한 기존해석사례(Lim, 2013; Moridis et al., 2013)를 이용한 모델 해석 결과, 침하는 균등한 양상으로 발생하였으며,침하량은 해저 지반의 강성 특성에 매우 민감한 반응을 보였다. 수평응력에 비해 수직응력이 우세한 이방성응력조건에서 침하량이 다소 증가하는 결과를 보였으며 초기응력분포보다 감압 시 공저 압력 수준에 상대적으로민감한 결과를 보였다. 가스하이드레이트 해리에 따른 상부 지층 및 주변 해저 지반의 유효 응력 변화에 의한전단파괴는 일어나지 않는 것으로 예측되었다.

키워드

하이드레이트 함유퇴적층

해저지반

가스하이드레이트

역학적 변형

해리

References

Huh, D.G., 2005, “Status of gas hydrate research in Korea,” J. the Korean Society of Mineral and Energy Resources Engineers, Vol. 42, No. 3, pp.206-213.
Hyodo, M,, Li, Y., Yoneda, J., Nakata, Y., Yoshimoto, N., Nishimura, A., 2014, “Effects of dissociation on the shear strength and deformation behavior of methane hydrate- bearing sediments,” Marine and Petroleum Geology Vol. 51, pp.52-62.
Itasca, 2009, FLAC3D: Fast Lagrangian Analysis of Continua in 3 Dimensions, Version 4.0, Minneapolis, Minnesota, Itasca Consulting Group, pp.438. 2009.
KIGAM, 2011, “Studies on gas hydrate development & production technology,” Ministry of Knowledge and Economy, p.239
Kim, A.R., Cho, G.C., Kim, S.J., Lee, J.Y., 2014, “Geomechanical response of hydrate-bearing sediments in the Ulleung basin,” Proc. 8th Int. Conf. Gas Hydrates, July 2014, Beijing, China
Kim, H. M., Rutqvist, J., 2014, “Geomechanical model analysis for the evaluation of mechanical stability of unconsolidated sediments during gas hydrate development and production,” Tunnel & Underground Space, Vol. 24, No.2, pp. 143-154
Kim, J.S., Lee, R.S., Lim, J.S., Kim, S.J., Moridis, G.J., 2014, “Numerical investigation to assess the gas hydrate production potential of the UBGH2-6 site in the Ulleung basin, Republic of Korea,” Proc. 8th Int. Conf. Gas Hydrates, July 2014, Beijing, China
Kwon, T.H., Cho, K.C., 2008, “Excess pore pressure generation in gas hydrate-bearing sediments by thermal changes,” Proceedings of Korean Society of Civil Engineers, pp.937-940
Lee, J., 2009, “The development status and prospect for the production technology of gas hydrate,” J. the Korean Society of Mineral and Energy Resources Engineers, Vol. 46, No. 3, pp.387-401.
Lee, J.Y., Lee. J., Kim S., 2011, “Experimental research trends on gas hydrate production,” Proc. of the Korean Society for New and Renewable Energy, 2011 May, pp.147-2.
Lim, Dae-hee, 2013, “Numerical analysis for prediction of mechanical behavior of marine sediment during depressurization process of gas hydrate,” Msc Thesis, Seoul National University.
Matsui, A., Haneda, H., Ogata, Y., Aoki, K., 2005, “The effect of saturation degree of methane hydrate on the shaer strength of synthetic methane hydrate sediments,” Proceedings of the 5th International Conference on Gas Hydrates, Tronheim, Norway, pp.657-663.
Moridis, G.J. Kowalsky, M.B., Pruess, K., 2008, “TOUGH +HYDRATE v1.0 USER’S MANUAL: A code for the simulation of system behavior in hydrate bearing geologic media,” LBNL-149E, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
Moridis, G.J., Kim, J.H., Reagan, M.T., Kim, S.J., 2013, “Feasibility of gas production from a gas hydrate accumulation at the UBGH2-6 site of the Ulleung basin in the Korean East Sea,” J. Petroleum Science and Engineering, Vol. 108, pp.180-210.
Park, S.S., 2008, “A study on submarine slope failure due to gas hydrate dissociation,” J. of the Korean Society for Geosystem Engineering, Vol. 45, No. 2, pp.164-173.
Rutqvist, J., Moridis, G.J., 2007, “Numerical stuides of geomechanical stability of hydrate-bearing sediments,” Offshore technology conference, 2007 May, Houston, Texas, U.S.A.
Rutqvist, J., Moridis, G.J., Grover, T., Collett, T., 2009, “Geomechanical response of permafrost-associated hydrate deposits to depressurization-induced gas production,” J. Petroleum Science and Engineering, Vol. 67, pp.1-12.
Rutqvist, J., Moridis, G.J., Grover, T., Silpnagarmert, S., Collett, T., Holdich, S.A., 2012, “Coupled multiphase fluid flow and wellbore stability analysis associated with gas production from oceanic hydrate-bearing sediments,” J. Petroleum Science and Engineering, Vol. 92-93, pp.65-81.
Shin, H.J., Lim, J.S., Kim, S.J., 2012, “Estimation of porosity and saturation in gas hydrate bearing sediments using well logs and core analysis data of the 2nd wells in Ulleung basin, East Sea, Korea,” J. the Korean Society of Mineral and Energy Resources Engineers, Vol. 49, No. 2, pp.175-185.
Song, Y., Zhu, Y., Liu, W., Zhao, J., Li, Y., Chen, Y., Shen, Z., Lu, Y., Ji, C., 2014, “Experimental research on the mechanical properties of methane hydrate-bearing sediments during hydrate dissociation,” Marine and Petroleum Geology, Vol., 51, pp.70-78.
van Genuchten, M.T., 1980, “A closed-form equation for predicting the hydraulic conductivity of unsaturated soils,” Soil Sci Soc Am J., Vol. 44, pp.892-898.
Yamamoto, K., 2014, “Methane hydrate offshore production test in the eastern Nankai trough: a milestone on the path to the real energy resource,” Proc. 8th Int. Conf. Gas Hydrates, July 2014, Beijing, China.

Information

Publisher :The Korean Society of Mineral and Energy Resources Engineers
Publisher(Ko) :한국자원공학회
Journal Title :Journal of the Korean Society of Mineral and Energy Resources Engineers
Journal Title(Ko) :한국자원공학회지
Volume : 52
No :2
Pages :148-157
DOI :https://doi.org/10.12972/ksmer.2015.52.2.148

[1] Huh, D.G., 2005, “Status of gas hydrate research in Korea,” J. the Korean Society of Mineral and Energy Resources Engineers, Vol. 42, No. 3, pp.206-213.

[2] Hyodo, M,, Li, Y., Yoneda, J., Nakata, Y., Yoshimoto, N., Nishimura, A., 2014, “Effects of dissociation on the shear strength and deformation behavior of methane hydrate- bearing sediments,” Marine and Petroleum Geology Vol. 51, pp.52-62.

[3] Itasca, 2009, FLAC3D: Fast Lagrangian Analysis of Continua in 3 Dimensions, Version 4.0, Minneapolis, Minnesota, Itasca Consulting Group, pp.438. 2009.

[4] KIGAM, 2011, “Studies on gas hydrate development & production technology,” Ministry of Knowledge and Economy, p.239

[5] Kim, A.R., Cho, G.C., Kim, S.J., Lee, J.Y., 2014, “Geomechanical response of hydrate-bearing sediments in the Ulleung basin,” Proc. 8th Int. Conf. Gas Hydrates, July 2014, Beijing, China

[6] Kim, H. M., Rutqvist, J., 2014, “Geomechanical model analysis for the evaluation of mechanical stability of unconsolidated sediments during gas hydrate development and production,” Tunnel & Underground Space, Vol. 24, No.2, pp. 143-154

[7] Kim, J.S., Lee, R.S., Lim, J.S., Kim, S.J., Moridis, G.J., 2014, “Numerical investigation to assess the gas hydrate production potential of the UBGH2-6 site in the Ulleung basin, Republic of Korea,” Proc. 8th Int. Conf. Gas Hydrates, July 2014, Beijing, China

[8] Kwon, T.H., Cho, K.C., 2008, “Excess pore pressure generation in gas hydrate-bearing sediments by thermal changes,” Proceedings of Korean Society of Civil Engineers, pp.937-940

[9] Lee, J., 2009, “The development status and prospect for the production technology of gas hydrate,” J. the Korean Society of Mineral and Energy Resources Engineers, Vol. 46, No. 3, pp.387-401.

[10] Lee, J.Y., Lee. J., Kim S., 2011, “Experimental research trends on gas hydrate production,” Proc. of the Korean Society for New and Renewable Energy, 2011 May, pp.147-2.

[11] Lim, Dae-hee, 2013, “Numerical analysis for prediction of mechanical behavior of marine sediment during depressurization process of gas hydrate,” Msc Thesis, Seoul National University.

[12] Matsui, A., Haneda, H., Ogata, Y., Aoki, K., 2005, “The effect of saturation degree of methane hydrate on the shaer strength of synthetic methane hydrate sediments,” Proceedings of the 5th International Conference on Gas Hydrates, Tronheim, Norway, pp.657-663.

[13] Moridis, G.J. Kowalsky, M.B., Pruess, K., 2008, “TOUGH +HYDRATE v1.0 USER’S MANUAL: A code for the simulation of system behavior in hydrate bearing geologic media,” LBNL-149E, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.

[14] Moridis, G.J., Kim, J.H., Reagan, M.T., Kim, S.J., 2013, “Feasibility of gas production from a gas hydrate accumulation at the UBGH2-6 site of the Ulleung basin in the Korean East Sea,” J. Petroleum Science and Engineering, Vol. 108, pp.180-210.

[15] Park, S.S., 2008, “A study on submarine slope failure due to gas hydrate dissociation,” J. of the Korean Society for Geosystem Engineering, Vol. 45, No. 2, pp.164-173.

[16] Rutqvist, J., Moridis, G.J., 2007, “Numerical stuides of geomechanical stability of hydrate-bearing sediments,” Offshore technology conference, 2007 May, Houston, Texas, U.S.A.

[17] Rutqvist, J., Moridis, G.J., Grover, T., Collett, T., 2009, “Geomechanical response of permafrost-associated hydrate deposits to depressurization-induced gas production,” J. Petroleum Science and Engineering, Vol. 67, pp.1-12.

[18] Rutqvist, J., Moridis, G.J., Grover, T., Silpnagarmert, S., Collett, T., Holdich, S.A., 2012, “Coupled multiphase fluid flow and wellbore stability analysis associated with gas production from oceanic hydrate-bearing sediments,” J. Petroleum Science and Engineering, Vol. 92-93, pp.65-81.

[19] Shin, H.J., Lim, J.S., Kim, S.J., 2012, “Estimation of porosity and saturation in gas hydrate bearing sediments using well logs and core analysis data of the 2nd wells in Ulleung basin, East Sea, Korea,” J. the Korean Society of Mineral and Energy Resources Engineers, Vol. 49, No. 2, pp.175-185.

[20] Song, Y., Zhu, Y., Liu, W., Zhao, J., Li, Y., Chen, Y., Shen, Z., Lu, Y., Ji, C., 2014, “Experimental research on the mechanical properties of methane hydrate-bearing sediments during hydrate dissociation,” Marine and Petroleum Geology, Vol., 51, pp.70-78.

[21] van Genuchten, M.T., 1980, “A closed-form equation for predicting the hydraulic conductivity of unsaturated soils,” Soil Sci Soc Am J., Vol. 44, pp.892-898.

[22] Yamamoto, K., 2014, “Methane hydrate offshore production test in the eastern Nankai trough: a milestone on the path to the real energy resource,” Proc. 8th Int. Conf. Gas Hydrates, July 2014, Beijing, China.

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