晚期泥底辟控制作用导致神狐海域SH5钻位未获水合物的分析

摘要/Abstract

摘要：

海底泥底辟构造与天然气水合物成藏关系密切，泥底辟既能为水合物提供充分的气源物质，同时又能促使地层温度场改变进而影响水合物成藏稳定性。南海北部神狐海域SH5站位虽然BSR明显，但钻探证实不存在天然气水合物。该钻位温度剖面异常高，温度场上移，同时在其下伏地层中发现泥底辟构造和裂隙通道。根据上述事实并结合泥底辟发育各个阶段中的特点，认为泥底辟构造对天然气水合物成藏具有控制作用。泥底辟发育早期和中期阶段，低热导率和低热量有机气体有利于天然气水合物生成；而在晚期阶段，高热量液体上侵稳定带底界，导致水合物分解迁移。SH5站位很可能由于受到处于晚期阶段的泥底辟上侵而未能获取天然气水合物。

关键词: 泥底辟, 天然气水合物, 神狐海域, 南海

Abstract:

There is a close relationship between mud diapirs and occurrences of gas hydrates in the marine sediments. While mud diapirs provide gas hydrates with abundant source material, they control gas hydrates occurrences by disturbing the thermal field. Borehole SH5 located in the Shenhu working area in the northern South China Sea shows a clear BSR in the seismic profile, but it turns out to be a sediment lack of gas hydrates by the evidence of borehole sampling. The thermal field moves upwards with higher equilibrium temperatures in the borehole SH5 below which a mud diapir and associated faults are approaching. Based on the facts above and the mud diapirs evolution in each stage, a model is proposed that the occurrence of gas hydrates is very likely to be under the control of mud diapirs in this site. During the early and intermediate stages of mud diapir growth, organic gases with low thermal conductivity and low thermal energy are converted into gas hydrates at the bottom of gas hydrate stability zone. In the late stage of mud diapir growth, fluid with high thermal energy invading the bottom of gas hydrate stability zone, makes the gas hydrate disintegrated. Then the librated free gases will move along the sediment strata and be condensed into gas hydrates again when temperature and pressure favor their formation. The borehole SH5, probably too close to a latestage mud diapir, captures no gas hydrate.

Key words: mud diapir, gas hydrate, Shenhu area, the South China Sea

中图分类号:

P744.4

王力峰, 沙志彬, 梁金强, 陆敬安. 晚期泥底辟控制作用导致神狐海域SH5钻位未获水合物的分析[J]. 现代地质, 2010, 24(3): 450-456.

WANG Li-Feng, SHA Zhi-Bin, LIANG Jin-qiang, LIU Jing-An. Analysis of Gas Hydrate Absence Induced by the Latestage Diapir Domination in the Borehole SH5 of Shenhu Area[J]. Geoscience, 2010, 24(3): 450-456.

参考文献

[1]Sloan E D. Clathrate Hydrates of Natural Gases. ［M］. Second edition. New York: Marcel Dekker Inc, 1998: 19-23.

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

[3]Boetius A, Suess E. Hydrate ridge: a natural laboratory for the study of microbial life fueled by methane from nearsurface gas hydrates ［J］. Chemical Geology, 2004, 205（3): 291-310.

[4]沙志彬, 王宏斌, 张光学，等. 底辟构造与天然气水合物的成矿关系［J］. 地学前缘, 2005, 12（3): 283-288.

[5]Kvenvolden K A. A primer on the geological occurrence of gas hydrate: Relevance to world margin stability and climate change ［J］. Geological Society Special Publication of London, 1998, 137: 39-80.

[6]Shyu C T, Hsu S K, Liu C S. Heat flows off southwest Taiwan: Measurements over mud diapirs and estimated from bottom simulating reflector ［J］. Terrestrial, Atmospheric and Oceanic Sciences, 1998, 9（4): 795-812.

[7]Dillon W P, Hutchinson D R, Drury R M. Seismic reflection profiles on the Black Ridge near sites 994, 995 and 997［M］// Paull C K, Matsumoto R, Wallace P J, et al. Proceedings of the Ocean Drilling Program,Initial Reports, 164. College Station, TX:Ocean Drilling Program,1996: 47-56.

[8]Shipley T H. Seismic reflection evidence for widespread occurrence of possible gas hydrate horizons on continental slopes and rises ［J］. AAPG Bulletin, 1979,63: 2204-2213.

[9]中国科学院南海海洋研究所海洋地质构造研究室. 南海地质构造与陆缘扩张［M］. 北京: 科学出版社, 1988:15-18.

[10]邓希光, 付少英, 黄永样,等. 南海北部东沙群岛HD196站位地球化学特征及其对水合物的指示［J］. 现代地质, 2006, 20（1): 92-102.

[11]Shipboard Scientific Party. Leg 184 summary: Exploring the Asian monsoon through drilling in the South China Sea［M］// Wang W L, Prell W L, Blum P, et al. Proceedings of the Ocean Drilling Program, Initial Reports, 184. College Station, TX:Ocean Drilling Program, 2000:1-77.

[12]Mountain G S, Tucholke B E. Mesozoic and Cenozoic geology of the US Atlantic continental slope and rise ［M］ // Poag C W. Geologic Evolution of the US Atlantic Margin. New York :Van Nostrand Reinhold, 1985: 293-341.

[13]何家雄, 徐瑞松, 刘全稳,等. 莺歌海盆地泥底辟发育演化与天然气及CO2运聚成藏规律［J］. 海洋地质与第四纪地质, 2008, 28（1): 91-98.

[14]龚再升, 李思田, 汪集旸，等. 南海北部大陆边缘盆地油气成藏动力学研究［M］. 北京: 科学出版社, 2004：69-71.

[15]Potter P E, Maynard J B, Depetris P J. Mud and Mudstones ［M］. Berlin: Springer Verlag, 2005: 128-129.

[16]Fetter C W. Applied Hydrogeology［M］.Third edition. New Jersey: Prentice Hall, 1994:213-220.

[17]Lynch F L, Lawrence E M, Lynton S L. Burial diagenesis of illite/smectite in shales and the origins of authigenic quartz and secondary porosity in sandstones［J］. Geochimica et Cosmochimica Acta, 1997, 61（10): 1995-2006.

[18]Ivanov V V, Guliev I S. Attempt at an explanation of physicochemical modeling of mud volcanism［J］. Bulletin Moscow Society of Naturalists, Geology Branch, 1986, 61（1): 72-79.

[19]Camerlenghi A, Cita M B, Vedova D, et al. Geophysical evidence of mud diapirism on the Mediterranean Ridge Accretionary Complex［J］. Marine Geophysics Research, 1995, 17: 115-141.

[20]Henrys P, Pichon X L, Lallemant S, et al. Mud volcano field seaward of the Barbados Accretionary Complex: A deeptowed side scan sonar survey［J］. Journal of Geophysical Research, 1990, 95(B6): 8917-8929.