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Discovery of the Lower Cambrian high-quality source rocks and deep oil and gas exploration potential in the Tarim Basin, China

Zhu Guangyou, Chen Feiran, Wang Meng, Zhang Zhiyao, Ren Rong and Wu Lin
Discovery of the Lower Cambrian high-quality source rocks and deep oil and gas exploration potential in the Tarim Basin, China
AAPG Bulletin (October 2018) 102 (10): 2123-2151

Abstract

The global Precambrian-Cambrian system includes an important series of hydrocarbon-bearing strata. However, because rocks of this age are typically deeply buried, few petroleum exploration breakthroughs have been made, and the presence of source rocks remains somewhat controversial. Recently, commercial condensate and gas were discovered from the deep ( approximately 6900 m [ approximately 22,600 ft]) Zhongshen 1C (ZS1C) exploratory well drilled in the Tazhong uplift of the Tarim Basin, China, leading to renewed interest in the development of Cambrian source rocks in the basin. On the basis of outcrop reconnaissance and sample testing from around the Tarim Basin, we show that a set of high-quality source rocks were developed within the lower Cambrian Yuertusi Formation (Je1y), at the base of the lower Cambrian. These rocks are black shales and typically have a total organic carbon content between 2% and 6% but extending as high as 17% in selected regions. This marine sequence is 10-15 m (33-49 ft) thick in some outcrops along the margins of the basin. Seismic data indicate that these high-quality source rocks may cover an area as large as 260,000 km (super 2) (100,000 mi (super 2) ). Their main organic parent material was benthic multicellular algae. On the basis of high-temperature thermal simulations conducted on these source rocks, we show that the gas composition and carbon isotopes from the ZS1C well are similar to the products generated at a thermal evolution stage corresponding to a vitrinite reflectance of between 2.2% and 2.5%. Late-stage natural gas accumulated within these rocks over time. The delta (super 34) S correlation of organic sulfur compounds in the condensate with Cambrian sulfates provides further evidence for a Je1y source rock origin of the ZS1C condensate and gas. The Cambrian dolomites in association with a salt seal exhibit favorable geological conditions for large-scale hydrocarbon accumulation. A new set of deep exploration strata can, therefore, be developed, guiding future deep Cambrian hydrocarbon exploration in the Tarim Basin.


ISSN: 0149-1423
EISSN: 1558-9153
Coden: AABUD2
Serial Title: AAPG Bulletin
Serial Volume: 102
Serial Issue: 10
Title: Discovery of the Lower Cambrian high-quality source rocks and deep oil and gas exploration potential in the Tarim Basin, China
Affiliation: PetroChina, Research Institute of Petroleum Exploration and Development, Beijing, China
Pages: 2123-2151
Published: 201810
Text Language: English
Publisher: American Association of Petroleum Geologists, Tulsa, OK, United States
References: 32
Accession Number: 2018-086915
Categories: Economic geology, geology of energy sourcesIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., strat. cols., 2 tables, sketch maps
N40°40'00" - N41°10'00", E79°00'00" - E80°10'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by American Association of Petroleum Geologists, Tulsa, OK, United States
Update Code: 201848
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