Analysis of physical properties of gas hydrate-bearing unconsolidated sediment samples from the ultra-deepwater area in the South China Sea

Abstract

Marine natural gas hydrate has recently attracted global attention as a potential new clean energy source. Laboratory measurements of various physical properties of gas hydrate-bearing marine sediments can provide valuable information for developing efficient and safe extraction technology of natural gas hydrates. This study presents comprehensive measurement results and analysis of drilled hydrate-bearing sediments samples recovered from Qiongdongnan Basin in the South China Sea. The results show that the gas hydrate in the core samples is mainly methane hydrate with a methane content of approximately 95%, and the other components are ethane and carbon dioxide. The saturation of the samples fluctuates from 2%–60%, the porosity is approximately 38%–43%, and the water content is approximately 30%–50%, which indicate that high water saturation means that timely drainage should be paid attention to during hydrate extraction. In addition, the median diameter of the sediment samples is mainly distributed in the range of 15 to 34 μm, and attention should be paid to the prevention and control of sand production in the mining process. Moreover, the thermal conductivity is distributed in the range of 0.75 to 0.96 W/(m∙K) as measured by the flat plate heat source method. The relatively low thermal conductivity of hydrates at this study site indicates that a combined approach is encouraged for natural gas production technologies. It is also found that clay flakes and fine particles are attached to the surface of large particles in large numbers. Such characteristics will lead to insufficient permeability during the production process.

Key words： natural gas hydrates; physical properties analysis; hydrate-bearing sediments

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Grant No. U19B2005).

References

1 Sloan E D Jr. Fundamental principles and applications of natural gas hydrates. Nature, 2003, 426(6964): 353–359

2 Milkov A V. Global estimates of hydrate-bound gas in marine sediments: how much is really out there? Earth-Science Reviews, 2004, 66(3–4): 183–197

3 Zhao J, Liu Y, Guo X, Gas production behavior from hydrate-bearing fine natural sediments through optimized step-wise depressurization. Applied Energy, 2020, 260: 114275

4 Gao Q, Yin Z, Zhao J, Tuning the fluid production behaviour of hydrate-bearing sediments by multi-stage depressurization. Chemical Engineering Journal, 2021, 406: 127174

5 Liang H, Yang L, Song Y, New approach for determining the reaction rate constant of hydrate formation via X-ray computed tomography. Journal of Physical Chemistry C, 2021, 125(1): 42–48

6 Zhao J, Guo X, Sun M, N₂O hydrate formation in porous media: a potential method to mitigate N₂O emissions. Chemical Engineering Journal, 2019, 361: 12–20

7 Zhou S, Li Q, Lv X, Key issues in development of offshore natural gas hydrate. Frontiers in Energy, 2020, 14(3): 433–442

8 Lee J H, Baek Y S, Ryu B J, A seismic survey to detect natural gas hydrate in the East Sea of Korea. Marine Geophysical Researches, 2005, 26(1): 51–59

9 Wu S, Zhang G, Huang Y, Gas hydrate occurrence on the continental slope of the northern South China Sea. Marine and Petroleum Geology, 2005, 22(3): 403–412

10 Zhang Z, McConnell D R, Han D. Rock physics-based seismic trace analysis of unconsolidated sediments containing gas hydrate and free gas in Green Canyon 955, Northern Gulf of Mexico. Marine and Petroleum Geology, 2012, 34(1): 119–133

11 Lu Y, Luan X, Lyu F, Seismic evidence and formation mechanism of gas hydrates in the Zhongjiannan Basin, Western margin of the South China Sea. Marine and Petroleum Geology, 2017, 84: 274–288

12 Kuang Y, Yang L, Li Q, Physical characteristic analysis of unconsolidated sediments containing gas hydrate recovered from the Shenhu Area of the South China sea. Journal of Petroleum Science Engineering, 2019, 181: 106173

13 Liu C, Ye Y, Meng Q, The characteristics of gas hydrates recovered from Shenhu area in the South China sea. Marine Geology, 2012, 307–310: 22–27

14 Liu C, Meng Q, He X, Characterization of natural gas hydrate recovered from Pearl River Mouth basin in South China Sea. Marine and Petroleum Geology, 2015, 61: 14–21

15 Guo X, Xu L, Wang B, Optimized gas and water production from water-saturated hydrate-bearing sediment through step-wise depressurization combined with thermal stimulation. Applied Energy, 2020, 276: 115438

16 Liu C, Meng Q, Hu G, Characterization of hydrate-bearing sediments recovered from the Shenhu area of the South China Sea. Interpretation (Tulsa), 2017, 5(3): 13–23

17 Yang L, Falenty A, Chaouachi M, Synchrotron X-ray computed microtomography study on gas hydrate decomposition in a sedimentary matrix. Geochemistry Geophysics Geosystems, 2016, 17(9): 3717–3732

18 Kneafsey T J, Lu H, Winters W, Examination of core samples from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: effects of retrieval and preservation. Marine and Petroleum Geology, 2011, 28(2): 381–393

19 Lee J Y, Kim G Y, Kang N K, Physical properties of sediments from the ulleung basin, East Sea: results from second ulleung basin gas hydrate drilling expedition, East Sea (Korea). Marine and Petroleum Geology, 2013, 47: 43–55

20 Chong Z, Zhao J, Chan J H R, Effect of horizontal wellbore on the production behavior from marine hydrate bearing sediment. Applied Energy, 2018, 214: 117–130

21 Chong Z, Moh J W R, Yin Z, Effect of vertical wellbore incorporation on energy recovery from aqueous rich hydrate sediments. Applied Energy, 2018, 229: 637–647

22 Song Y, Kuang Y, Fan Z, Influence of core scale permeability on gas production from methane hydrate by thermal stimulation. International Journal of Heat and Mass Transfer, 2018, 121: 207–214

23 Wang L, Sun X, Shen S, Undrained triaxial tests on water-saturated methane hydrate–bearing clayey-silty sediments of the South China Sea. Canadian Geotechnical Journal, 2021, 58(3): 351–366

24 Wang L, Li Y, Wu P, Physical and mechanical properties of the overburden layer on gas hydrate-bearing sediments of the South China Sea. Journal of Petroleum Science Engineering, 2020, 189: 107020

25 Lee C, Yun T S, Lee J S, Geotechnical characterization of marine sediments in the Ulleung Basin, East Sea. Engineering Geology, 2011, 117(1–2): 151–158

26 Pooladi-Darvish M, Hong H. Effect of conductive and convective heat flow on gas production from natural hydrates by depressurization. In: Taylor C E, Kwan J T, eds. Advances in the Study of Gas Hydrates. Boston: Springer, 2004

27 Yang L, Zhao J, Wang B, Effective thermal conductivity of methane hydrate-bearing sediments: experiments and correlations. Fuel, 2016, 179: 87–96

28 Wang B, Fan Z, Lv P, Measurement of effective thermal conductivity of hydrate-bearing sediments and evaluation of existing prediction models. International Journal of Heat and Mass Transfer, 2017, 110: 142–150

29 Liu Y, Zhang L, Yang L, Behaviors of CO₂ hydrate formation in the presence of acid-dissolvable organic matters. Environmental Science & Technology, 2021, 55(9): 6206–6213

30 Zhao J, Liu Y, Yang L, Organics-coated nanoclays further promote hydrate formation kinetics. Journal of Physical Chemistry Letters, 2021, 12(13): 3464–3467

31 Lu S, McMechan G A. Estimation of gas hydrate and free gas saturation, concentration, and distribution from seismic data. Geophysics, 2002, 67(2): 582–593

32 Waite W F, Santamarina J C, Cortes D D, Physical properties of hydrate-bearing sediments. Reviews of Geophysics, 2009, 47(4): RG4003

33 Gustafsson S E, Karawacki E, Khan M N. Transient hot-strip method for simultaneously measuring thermal conductivity and thermal diffusivity of solids and fluids. Journal of Physics D, Applied Physics, 1979, 12(9): 1411–1421

34 Kim Y G, Lee S M, Matsubayashi O. New heat flow measurements in the Ulleung Basin, East Sea (Sea of Japan): relationship to local BSR depth, and implications for regional heat flow distribution. Geo-Marine Letters, 2010, 30(6): 595–603

35 Yang L, Ai L, Xue K, Analyzing the effects of inhomogeneity on the permeability of porous media containing methane hydrates through pore network models combined with CT observation. Energy, 2018, 163: 27–37

36 Gao Q, Zhao J, Yin Z, Experimental study on methane hydrate formation in quartz sand under tri-axial condition. Journal of Natural Gas Science and Engineering, 2021, 85: 103707

37 Gao Q, Zhao J, Yin Z, Experimental study on fluid production from methane hydrate sediments under the marine triaxial condition. Energy & Fuels, 2021, 35(5): 3915–3924

38 Lyu X, Li Q, Ge Y, Fundamental characteristics of gas hydrate-bearing sediments in the Shenhu area, South China Sea. Frontiers in Energy, 2021, 15(2): 367–373