Noble gas geochemical characteristics of shallow hydrate in the deep water of the Qiongdongnan Basin and their significance

doi:10.13745/j.esf.sf.2022.2.59

Abstract

Abstract:

The deep water area of the Qiongdongnan Basin possesses favorable geological condition for gas hydrate accumulation and is one of the leading demonstration areas for marine gas hydrate exploration and development. Based on geochemical analyses of natural gas and noble gases, this paper selects the shallow surface hydrate of the deep water area to carry out a comparative study relating to deep conventional natural gas reservoirs. The results show that shallow surface gas in the study area shares similar carbon isotope characteristics with deep conventional natural gas. The gas source is mainly deep thermogenic gas, with no obvious contribution from biogas, and genetically relates to coal-type gas. It is speculated that the gas source is the coal measure strata of the Yacheng Formation. The Ar isotopic compositions of light noble gases show that the gas source rock is related to the Tertiary formation, whilst the high ³He/⁴He ratios in samples indicate certain contributions from mantle derived gas. Therefore, under the background of gas-rich depression, it is of great significance to discuss the deep thermogenic gas for hydrate accumulation. The deep thermogenic gas reservoir and shallow hydrate reservoir can form a vertical three-dimensional gas reservoir, which lends theoretical support in future “multi-gas exploitation” for improving economic benefits of gas hydrate reservoir development in deep water areas.

Key words: Qiongdongnan Basin, gas hydrate, gas source, coal-type gas, noble gases

CLC Number:

SUN Tao, WU Tao, GE Yang, FAN Qi, LI Lixia, LÜ Xin. Noble gas geochemical characteristics of shallow hydrate in the deep water of the Qiongdongnan Basin and their significance[J]. Earth Science Frontiers, 2022, 29(5): 476-482.

Figures/Tables 7

References 41

[1]	何家雄, 苏丕波, 卢振权, 等. 南海北部琼东南盆地天然气水合物气源及运聚成藏模式预测[J]. 天然气工业, 2015, 35(8): 19-29.
[2]	ZHANG G X, YANG S X, ZHANG M. GMGS2 2 expedition investigates rich and complex gas hydrate environment in the South China Sea[J]. Fire in the Ice, 2014, 14(1): 1-5.
[3]	YANG S X, ZHANG M, LIANG J Q, et al. Preliminary results of China's third gas hydrate drilling expedition: a critical step from discovery to development in the South China Sea[J]. Fire in the Ice, 2015, 15(2): 1-5.
[4]	陈多福, 李绪宣, 夏斌. 南海琼东南盆地天然气水合物稳定域分布特征及资源预测[J]. 地球物理学报, 2004, 47(3): 483-489.
[5]	孙春岩, 吴能有, 牛滨华, 等. 南海琼东南盆地气态烃地球化学特征及天然气水合物资源远景预测[J]. 现代地质, 2007, 21(1): 95-100.
[6]	王秀娟, 吴时国, 董冬冬, 等. 琼东南盆地气烟囱构造特点及其与天然气水合物的关系[J]. 海洋地质与第四纪地质, 2008, 28(3): 103-108.
[7]	王静丽, 梁金强, 沙志彬, 等. 南海北部琼东南海域气烟囱发育特征及其对水合物形成与分布的影响[J]. 海洋地质前沿, 2017, 33(3): 1-6.
[8]	杨力, 刘斌, 徐梦婕, 等. 南海北部琼东南海域活动冷泉特征及形成模式[J]. 地球物理学报, 2018, 61(7): 2905-2914.
[9]	满晓, 朱继田, 姚哲, 等. 琼东南盆地深水区泥-流体底辟发育特征与天然气成藏[J]. 地质找矿论丛, 2018, 33(2): 257-263.
[10]	于兴河, 王建忠, 梁金强, 等. 南海北部陆坡天然气水合物沉积成藏特征[J]. 石油学报, 2014, 35(2): 253-264. DOI
[11]	梁金强, 王宏斌, 苏新, 等. 南海北部陆坡天然气水合物成藏条件及其控制因素[J]. 天然气工业, 2014, 34(7): 128-135.
[12]	冯俊熙, 杨胜雄, 孙晓明, 等. 琼东南盆地甲烷微渗漏活动地球化学示踪研究[J]. 西南石油大学学报(自然科学版), 2018, 40(3): 63-75.
[13]	孙运宝, 蔡峰, 李清, 等. 海洋浅表层天然气水合物资源评价[J]. 海洋地质前沿, 2020, 36(9): 87-93.
[14]	LIANG J Q, ZHANG W, LU J A, et al. Geological occurrence and accumulation mechanism of natural gas hydrates in the eastern Qiongdongnan Basin of the South China Sea: insights from site GMGS5-W9-2018[J]. Marine Geology, 2019, 418: 106042. DOI URL
[15]	刘玉山, 祝有海, 吴必豪. 更具开发前景的浅成天然气水合物[J]. 海洋地质前沿, 2016, 32(4): 24-30.
[16]	傅宁, 林青, 刘英丽. 从南海北部浅层气的成因看水合物潜在的气源[J]. 现代地质, 2011, 25(2): 332-339.
[17]	张伟, 何家雄, 卢振权, 等. 琼东南盆地疑似泥底辟与天然气水合物成矿成藏关系初探[J]. 天然气地球科学, 2015, 26(11): 2185-2197.
[18]	梁刚, 甘军, 游君君, 等. 琼东南盆地低熟煤型气地球化学特征及勘探前景[J]. 天然气地球科学, 2020, 31(7): 895-903.
[19]	HUANG B J, TIAN H, LI X S, et al. Geochemistry, origin and accumulation of natural gases in the deepwater area of the Qiongdongnan Basin, South China Sea[J]. Marine and Petroleum Geology, 2016, 72: 254-267. DOI URL
[20]	孙瑞, 韩银学, 曾清波, 等. 琼东南盆地深水区东段崖城组沉积特征及对海相烃源岩的控制[J]. 石油学报, 2019, 40(增刊2): 57-66.
[21]	周杰, 杨希冰, 杨金海, 等. 琼东南盆地松南低凸起古近系构造-沉积演化特征与天然气成藏[J]. 地球科学, 2019, 44(8): 2704-2716.
[22]	谢文彦, 张一伟, 孙珍, 等. 琼东南盆地断裂构造与成因机制[J]. 海洋地质与第四纪地质, 2007, 27(1): 71-78.
[23]	张迎朝, 徐新德, 甘军, 等. 琼东南盆地深水大气田地质特征、成藏模式及勘探方向研究[J]. 地质学报, 2017, 91(7): 1620-1633.
[24]	于鹏, 王家林, 钟慧智, 等. 琼东南盆地基底结构综合地球物理研究[J]. 中国海上油气(地质), 1999, 11(6): 443-450.
[25]	ZHU W L, HUANG B J, MI L J, et al. Geochemistry, origin, and deep-water exploration potential of natural gases in the Pearl River Mouth and Qiongdongnan basins, South China Sea[J]. AAPG Bulletin, 2009, 93(6): 741-761. DOI URL
[26]	甘军, 张迎朝, 梁刚, 等. 琼东南盆地深水区烃源岩沉积模式及差异热演化[J]. 地球科学, 2019, 44(8): 2627-2635.
[27]	董伟良, 黄保家. 南海莺-琼盆地煤型气的鉴别标志及气源判识[J]. 天然气工业, 2000, 20(1): 23-27.
[28]	李友川, 邓运华, 张功成. 中国近海海域烃源岩和油气的分带性[J]. 中国海上油气, 2012, 24(1): 6-12.
[29]	付少英. 海底沉积物中不同形式烃类气体的地球化学意义[J]. 地学前缘, 2005, 12(3):253-257.
[30]	刘文汇, 张殿伟, 王晓锋, 等. 天然气气-源对比的地球化学研究[J]. 沉积学报, 2004, 22(增刊1): 27-32.
[31]	戴金星, 戚厚发, 宋岩. 鉴别煤成气和油型气若干指标的初步探讨[J]. 石油学报, 1985, 6(2): 31-38. DOI
[32]	沈平, 申歧祥, 王先彬, 等. 气态烃同位素组成特征及煤型气判识[J]. 中国科学: B辑, 1987, 17(6): 647-656.
[33]	STAHL W J, CAREY B D Jr. Source rock identification by isotope analyses of natural gases from fields in the Val Verde and Delaware basins, West Texas[J]. Chemical Geology, 1975, 16(4): 257-267. DOI URL
[34]	戴金星, 戚厚发. 我国煤成烃气的δ¹³C-R_o关系[J]. 科学通报, 1989, 34(9): 690-692.
[35]	沈平, 徐永昌. 中国陆相成因天然气同位素组成特征[J]. 地球化学, 1991, 20(2): 144-152.
[36]	戴金星. 各类天然气的成因鉴别[J]. 中国海上油气(地质), 1992, 6(1): 11-19.
[37]	戴金星, 戚厚发, 郝石生. 天然气地质学概论[M]. 北京: 石油工业出版社, 1978: 41-42.
[38]	XU Y C, LIU W H, SHEN P, et al. Geochemistry of noble gases in natural gases[M]. Beijing: Science Press, 1996: 1-275.
[39]	刘文汇, 孙明良, 徐永昌. 鄂尔多斯盆地天然气稀有气体同位素特征及气源示踪[J]. 科学通报, 2001, 46(22): 1902-1905.
[40]	徐永昌, 刘文汇, 沈平, 等. 天然气地球化学的重要分支: 稀有气体地球化学[J]. 天然气地球科学, 2003, 14(3): 157-166.
[41]	陶明信, 徐永昌, 沈平, 等. 中国东部幔源气藏聚集带的大地构造与地球化学特征及成藏条件[J], 中国科学: D辑, 1996, 26(6): 531-536.

样品号	深度/m	烃类气含量/%
样品号	深度/m	C₁	C₂	C₃	nC₄	iC₄	nC₅		iC₅		CO₂		N₂	O₂
LS25-1-1W01	37.00	10.22	0.46	0.15	0.02	0.03	0.00	0.01		0.02		70.63		17.65
LS25-1-1W02	42.00	3.55	0.18	0.07	0.01	0.01	0.00	0.00		0.04		76.67		18.63
LS25-1-1W03	47.00	8.12	0.16	0.02	0	0	0.00	0.00		0.05		72.26		18.54
LS25-1-1W04	52.00	2.64	0.12	0.04	0.01	0.01	0.00	0.00		0.06		76.44		19.80

样品号	深度/m	烃类气含量/%
样品号	深度/m	C₁	C₂	C₃	nC₄	iC₄	nC₅		iC₅		CO₂		N₂	O₂
LS25-1-1W01	37.00	10.22	0.46	0.15	0.02	0.03	0.00	0.01		0.02		70.63		17.65
LS25-1-1W02	42.00	3.55	0.18	0.07	0.01	0.01	0.00	0.00		0.04		76.67		18.63
LS25-1-1W03	47.00	8.12	0.16	0.02	0	0	0.00	0.00		0.05		72.26		18.54
LS25-1-1W04	52.00	2.64	0.12	0.04	0.01	0.01	0.00	0.00		0.06		76.44		19.80

样品号	深度/m	δ¹³C/‰							δD/‰
样品号	深度/m	CO₂	C₁	C₂	C₃		nC₄		C₁		C₂	C₃
LS25-1-1W01	37.00	-15.7	-46.2	-27.6	-25.1	-24.5		-195.7		-166.3		-141.2
LS25-1-1W02	42.00	-17.7	-45.9	-26.3	-24.2	—		-188		-150		-124.2
LS25-1-1W03	47.00	-20.2	-46.5	-25.5	-22.7	—		-195.9		-156.2		-117.6
LS25-1-1W04	52.00	-16.6	-46.7	-26.9	-24.5	-24		-192.9		-172.3		-130.7

样品号	深度/m	δ¹³C/‰							δD/‰
样品号	深度/m	CO₂	C₁	C₂	C₃		nC₄		C₁		C₂	C₃
LS25-1-1W01	37.00	-15.7	-46.2	-27.6	-25.1	-24.5		-195.7		-166.3		-141.2
LS25-1-1W02	42.00	-17.7	-45.9	-26.3	-24.2	—		-188		-150		-124.2
LS25-1-1W03	47.00	-20.2	-46.5	-25.5	-22.7	—		-195.9		-156.2		-117.6
LS25-1-1W04	52.00	-16.6	-46.7	-26.9	-24.5	-24		-192.9		-172.3		-130.7

样品号	He浓度/10^-6	R/R_a	(³He/⁴He)/10^-6	⁴He/²⁰Ne	Ne浓度/10^-6	²⁰Ne/²²Ne	²¹Ne/²²Ne	Ar浓度/%	⁴⁰Ar/³⁶Ar	³⁸Ar/³⁶Ar
LS25-1-1W01	7.2	1.7	2.4	0.672	10.8	10.9	0.029	0.0086	305.0	0.188
LS25-1-1W02	7.7	1.4	2.0	0.625	12.2	9.9	0.027	0.0080	302.8	0.186
LS25-1-1W03	8.0	1.9	2.6	0.719	11.2	9.9	0.028	0.0077	308.0	0.180
LS25-1-1W04	8.2	1.6	2.3	0.758	10.8	9.8	0.028	0.0078	307.5	0.182