Sequence stratigraphic architecture of the Quaternary Ledong Formation in the deep-water area of the Qiongdongnan Basin and its significance to gas hydrate exploration
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摘要:
琼东南盆地深水区第四系乐东组是南海北部已证实的天然气水合物主要勘探层系。近年来,其层序地层格架、构成特征以及对天然气水合物稳定域及运聚成藏的控制影响作用等科学问题引发了广泛关注。为了厘清乐东组层序地层格架、构成特征及其展布规律,基于层序地层学理论,结合研究区高分辨率地震资料,建立了乐东组精细层序地层格架及层序样式。依据典型的地震接触关系识别了乐东组复合层序界面T20、T14和T0,同时划分确定了乐东组下段6套三级层序(LDSQ1-6)和上段8套三级层序(LDSQ7-14)。在三级层序内部还进一步识别出初始海泛面、最大海泛面以及最大海退面,在三级层序中进一步划分出低位体系域(LST)、海侵体系域(TST)、高位体系域(HST)和下降体系域(FFST)。研究表明,1.8 Ma以来,红河物源体系沉积物供给充足,乐东组下段陆架边缘体系进积和加积组分厚度大,层序样式主要为H型层序;0.9~0.8 Ma至今,地层以进积叠置样式为主,且峡谷发育频次增大,低位体系域组分占比增大,主要发育L-H型层序。笔者结合国内外相似区域的沉积相模式,明确了层序格架约束下的沉积相发育类型及时空演化特征,为该区域天然气水合物储层预测提供了地质依据。
Abstract:The Quaternary Ledong Formation in the deep-water area of the Qiongdongnan Basin is a proven gas hydrate enriched zone in the northern South China Sea. The sequence stratigraphic architecture, depositional patterns, and their influences on the gas hydrate stability, migration and accumulation have become hot topics internationally and attracted great attention from the geological society of the region. Based on the theory of sequence stratigraphy, and combined with the high-resolution seismic surveys in the working area, a detailed sequence stratigraphic framework of the Quaternary Ledong Formation is established in this paper, which includes 4 second-order sequence boundaries and 13 third-order sequence boundaries. In addition, the maximum flooding surface (MFS), first flooding surface (FTS) and maximum regression surface (MRS) are also identified. The third level of sequence is further divided into system tracts. Since 1.8 Ma, the Red River provenance system has supplied sufficient sediments to the basin, which led to the progradation of deltaic deposits of Lower Ledong Formation, and a sequence of H-type was formed. In the upper part of Ledong Formation, however, the stratigraphic sequence is dominated by an accretionary architecture, and the sequence style was mainly of L-H type. Finally, this paper established the depositional model under the constraints of the sequence framework, and discussed the deltaic-gravity flow related deposits in the study area. This study has provided an important clue for prediction and exploration of natural gas hydrate in the future.
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Key words:
- Qiongdongnan Basin /
- Ledong Formation /
- sequence stratigraphy /
- system tract /
- sequence architecture
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图 2 层序界面和最大海泛面识别标志及示意图[5]
Figure 2.
图 5 基于四分体系域模型的层序地层学模式[10]
Figure 5.
表 1 琼东南盆地乐东组层序地层格架
Table 1. Sequence stratigraphic framework of Ledong Formation in the Qiongdongnan Basin
表 2 体系域构成样式类型
Table 2. System tract composition types
构成样式 LST TST HST 样式特征 层序样式类型 L型 非常发育 厚度较薄或不发育 厚度较薄或不发育 hLST>hTST+HST-FSST T-H型 相对不发育 较为发育 较为发育 hTST≈hHST-FSST H型 相对较薄或不发育 相对较薄或不发育 非常发育 hHST-FSST>hLST+TST -
[1] 程世秀,李三忠,索艳慧,等. 南海北部新生代盆地群构造特征及其成因[J]. 海洋地质与第四纪地质,2012,32(6):79-93.
[2] 杨俊,赵彦彦,吴佳庆,等. 南海中部全新世以来海山深潜区有孔虫的地球化学记录及反映的气候变化[J]. 海洋地质与第四纪地质,2020,40(2):100-110.
[3] 刘莹,刘海燕,杨海长,等. 琼东南盆地古近纪成煤沉积体系类型及特征[J]. 石油与天然气地质,2019,40(1):142-151. doi: 10.11743/ogg20190114
[4] MITCHUM R M. Seismic stratigraphy and global changes of sea level,part II:glossary of terms used in seismic stratigraphy[J]. AAPG Memoir,1977,26(1):205-212.
[5] CATUNEANU O,GALLOWAY W E,KENDALL C G,et al. Sequence stratigraphy:methodology and nomenclature[J]. Newsletters on Stratigraphy,2011,44(3):173-245. doi: 10.1127/0078-0421/2011/0011
[6] 杜同军. 琼东南盆地层序地层和深水区沉积充填特征[D]. 青岛: 中国海洋大学, 2013.
[7] 谢金有,祝幼华,李绪深,等. 南海北部大陆架莺琼盆地新生代海平面变化[J]. 海相油气地质,2012,17(1):49-58. doi: 10.3969/j.issn.1672-9854.2012.01.008
[8] 孙辉. 南海西北部深水区重力流沉积体系特征及其控制因素分析[D]. 武汉: 中国地质大学(武汉), 2015.
[9] 刘招君, 董清水, 郭巍, 等. 陆相层序地层学导论与应用[M]. 北京: 石油工业出版社, 2002.
[10] CATUNEANU O. Principles of sequence stratigraphy[M].Amsterdam: Elsevier, 2006: 50-72.
[11] 张伟,梁金强,陆敬安,等. 琼东南盆地典型渗漏型天然气水合物成藏系统的特征与控藏机制[J]. 天然气工业,2020,40(8):90-99. doi: 10.3787/j.issn.1000-0976.2020.08.007
[12] 江定川,刘睿,赵晓明,等. 琼东南盆地深水区上新世以来天然气水合物稳定域时空迁移及其分布特征[J]. 海洋地质前沿,2021,37(7):43-51.
[13] 姚哲,张金锋,朱继田,等. 琼东南盆地深水区天然气水合物运聚成藏模式[J]. 海洋地质前沿,2021,37(7):22-32.
[14] YE J L,WEI J G,LIANG J Q,et al. Complex gas hydrate system in a gas chimney,South China Sea[J]. Marine and Petroleum Geology,2019,104:29-39. doi: 10.1016/j.marpetgeo.2019.03.023
[15] 朱继田,邓勇,郭明刚,等. 琼东南盆地盆底平原区天然气水合物成矿条件及成藏模式[J]. 中国海上油气,2020,32(3):1-10.
[16] 王秀娟,靳佳澎,郭依群,等. 南海北部天然气水合物富集特征及定量评价[J]. 地球科学,2020,46(3):10-15.
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