Secondary Alteration and Preservation of Ultra-Deep Ordovician Oil Reservoirs of North Shuntuoguole Area of Tarim Basin, NW China

被引：10

作者：

Ma A. ^{[1
,2
]}

Jin Z. ^{[1
]}

Li H. ^{[1
]}

Gu Y. ^{[1
]}

Qiu N. ^{[3
]}

Zhu X. ^{[4
]}

Wu X. ^{[4
]}

Yang X. ^{[1
]}

Wang S. ^{[1
]}

机构：

[1] Petroleum Exploration & Production Research Institute, SINOPEC, Beijing

[2] State Key Laboratory of Organic Geochemistry, Guangzhou

[3] College of Geosciences, China University of Petroleum, Beijing

[4] SINOPEC Northwest Oilfield Company, Urumqi

来源：

Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | 2020年 / 45卷 / 05期

关键词：

Gas invasion; North Shuntuoguole area; Oil cracking; Ordovician; Petroleum geology; Secondary alteration; Tarim basin; Thermochemical sulfate reduction (TSR); Ultra-deep;

D O I：

10.3799/dqkx.2019.157

中图分类号：

学科分类号：

摘要：

Volatile reservoir and light reservoir have been discovered in the ultra-deep Ordovician Yijianfang to Yingshan Formations with vertical depths ranging from 7 200 to 7 863.60 m from North Shuntuoguole area in the Tarim basin. The limit depth of oil phase occurring has been continuously challenging the traditional theory. This study focuses on geochemical characteristics and secondary alterations of reservoirs from different faults in North Shuntuoguole area. Most oils of different faults from North Shuntuoguole area are characterized by light carbon isotope, C23TT/C21TT>1, lower C28 sterane content, relatively high abundance of dibenzothiophene, suggesting that the source rock of oil in the North Shuntuoguole area is similar to that of Tahe oilfield. Using (C21+C22) sterane/(C27~C29) sterane, C27 diasterane/C27 regular steane, MPI index, dibenthiophene series maturity, the oil maturity trend in the North Shuntuoguole area is No.1 fault (including splay fault) ≈No.3 fault>secondary fault>No.5 fault >No.7 fault. The oil maturity is controlled by the reservoir initial static temperature. The natural gas in North Shuntuoguole area is wet gas and has light methane carbon isotope, ranging from -50.7‰ to -44.7‰. The gas maturity trend in different faults is similar to that of the oil. The abundance of (4-+3-) methyldiamantane in the oils from different faults is in the range of 9.25-36.44 μg/g, indicating low degree of oil cracking. The lower thiadiamondoids can be detected in the oils, with content ranging from 0.76 to 18.88 μg/g, showing low degree of thermochemical sulfate reduction (TSR). The Ordovician reservoir has suffered little gas invasion from the natural gas characteristics. The formation temperature indicates the geothermal gradient in the North Shuntuoguole area is low, only about 2.12 ℃/100 m. The formation temperature of strata buried at 8 000 m depth at present is in the range of 160-170 ℃. The maximum paleo-geotemperature of Ordovician has never been higher than 170 ℃, without reaching the temperature threshold of great scale oil cracking. The long term of low geothermal environment combined with low degree secondary alteration is the key to the preservation of ultra-deep Ordovician volatile reservoir in the North Shuntuogule area. © 2020, Editorial Department of Earth Science. All right reserved.

引用

页码：1737 / 1753

页数：16

共 40 条

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