Diagenetic patterns and pore systems of the Lower Ordovician Majiagou Formation reservoirs of the central Changqing gas fields.

	Diagenetic patterns and pore systems of the Lower Ordovician Majiagou Formation reservoirs of the central Changqing gas fields.
	Wu, Y. S.; He, S. L.; Lu, T.; Da, S. P.; Li, Y. G.; Dai, Y. D.
刊名	ACTA PETROLOGICA SINICA
	2006-08-01
卷号	22 期号:8 页码:2171-2181
关键词	Ordos basin Majiagou Formation central Changqing gas fields diagenesis porosity system
ISSN号	1000-0569
文献子类	Article
英文摘要	The main Ordovician reservoirs of the central Changqing gas fields include the eight beds of the M5 Member of the Early Ordovician Majiagou Formation: M5(1)(1), M5(2)(2), M5(3)(1), M5(4)(1), M5(2)(1), M5(2)(2), M5(3)(3), and M5(4)(1), in descending order. Beds M5(1)(1), M5(1)(2) and M5(1)(3) are mainly finely-crystalling penecontemporaneous dolomites with abundant anhydrite nodules (generally 1 similar to 5mm wide) indicating upper supratidal environments. Beds M5(1)(4), M5(2)(1), M5(2)(2) are mainly laminated dolostones of upper intertidal environments. Beds M5(3)(3) and M5(4)(1) are mainly anhydrite rock with chicken-wire structure indicating continental sabkha environments and finely-crystalline dolomites with abundant anhydrite nodules (1 similar to 5 mm wide) indicating upper supratidal environments. The most important diagenetic processes undergone by the M5 Member include: (1) precipitation of gypsum nodules in interstitial pores in the tidal-flat deposits due to evaporation and the penecontemporaneous dolomitization of the original calcium carbonate deposits; (II) partial or total replacement of the gypsum/anhydrite nodules by dolomites caused by mixing of seawater and freshwater; (III) dissolution of the gypsum in nodules by meteoric water and formation of nodule-moldie pores; (IV) partial or total filling of the nodule-moldic pores by fine, early calcites; (V) partial or total filling of the remaining pores by coarse, late calcites; and (VI) filling of the remaining pores by sylvite. Processes (I), (II) and (III) improved the reservoir quality, while (IV), (V) and (VI) reduced the reservoir quality. Seven main diagenetic patterns were recognized from the M5 Member: dolomitization interstitial dissolution; dolomitization-interstitial dissolution -calcite filling; dolomitization -gypsum dissolution; dolomitization -dolomite replacement -gypsum dissolution; dolomitization-dolomite replacement-gypsum dissolution -early calcite filling; dolomitization -dolomite replacement-gypsum dissolution-early calcite filling-late calcite filling; and dolomitization-dolomite replacement-gypsum dissolution -early calcite filling -late calcite filling-sylvite filling. Dolomitization-gypsum dissolution, dolomitization -dolomite replacement-gypsum dissolution, and dolomitization interstitial dissolution accounted for formation of the main reservoirs. The main pore systems in the M5 Member include: (a) nodule-derived pores; (b) nodule- derived pores and nodule-swell fissures; (c) nodule-derived pores and intercrystalline pores; (d) gypsum crystal moldic pores; and (e) intercrystalline pores. Pore systems (a), (b) and (c) are the main types in this Member. Gypsum nodules are abundant in beds M5(1)(1), M5(1)(2), M5(1)(3), and M5(3)(3), especially M5(4)(1).
WOS关键词	ORDOS BASIN ; CHINA ; ORIGIN
WOS研究方向	Geology
语种	英语
出版者	SCIENCE CHINA PRESS
WOS记录号	WOS:000245957400007
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/66762]
专题	中国科学院地质与地球物理研究所
通讯作者	Wu, Y. S.
作者单位	1.Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China 2.China Univ Petroleum, Beijing 102249, Peoples R China 3.Changqing Oilfield Co, Res Inst Petr Explorat & Dev, Xian 710021, Peoples R China
推荐引用方式 GB/T 7714	Wu, Y. S.,He, S. L.,Lu, T.,et al. Diagenetic patterns and pore systems of the Lower Ordovician Majiagou Formation reservoirs of the central Changqing gas fields.[J]. ACTA PETROLOGICA SINICA,2006,22(8):2171-2181.
APA	Wu, Y. S.,He, S. L.,Lu, T.,Da, S. P.,Li, Y. G.,&Dai, Y. D..(2006).Diagenetic patterns and pore systems of the Lower Ordovician Majiagou Formation reservoirs of the central Changqing gas fields..ACTA PETROLOGICA SINICA,22(8),2171-2181.
MLA	Wu, Y. S.,et al."Diagenetic patterns and pore systems of the Lower Ordovician Majiagou Formation reservoirs of the central Changqing gas fields.".ACTA PETROLOGICA SINICA 22.8(2006):2171-2181.