Reconstruction of Depositional Environment and Source-Reservoir Configuration Relationship of Ordovician Majiagou Formation in Ordos Basin

被引：3

作者：

Wu D. ^{[1
,2
]}

Zhou J. ^{[1
,2
]}

Ren J. ^{[3
]}

Li W. ^{[1
,2
]}

Wei L. ^{[3
]}

Yu Z. ^{[1
,2
]}

Zhang C. ^{[3
]}

Wang S. ^{[1
,2
]}

机构：

[1] Petrochina Hangzhou Research Institute of Geology, Hangzhou

[2] Key Laboratory of Carbonate Reservoir, CNPC, Hangzhou

[3] Exploration and Development Research Institute of PetroChina Changqing Oilfield Company, Xi’an

来源：

Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | 2023年 / 48卷 / 02期

关键词：

carbonate evaporite sedimentary system; depositional environment; Ordos Basin; Ordovician; petroleum geology; source-reservoir configuration; sulfide section;

D O I：

10.3799/dqkx.2022.346

中图分类号：

学科分类号：

摘要：

The carbonate gypsum salt rock combination contains 46% of the global carbonate oil and gas reserves and is an important oil and gas enrichment horizon. The Majiagou Formation of Ordovician in Ordos basin develops a large set of thick carbonate gypsum salt rock mixed deposits. At present, nearly trillion cubic meters of proved reserves have been found on salt. Is there exploration potential under salt and between salt? The restoration of the Paleoenvironment of the sedimentary system is the key. Based on the description of 400 m systematic coring of well T112 in the basin, combined with thin section identification, supporting analysis of trace elements, rare earth elements, carbon, oxygen, strontium isotopes and rock components, this paper restores the depositional environment of carbonate gypsum salt rock sedimentary system of Majiagou formation. According to the rise and fall of sea level and the change of water oxidation degree, the system can be divided into four sub environments: anoxic section, secondary oxidation section, oxidation section and sulfide section. With the aggravation of oxidation degree, the contents of trace elements such as U and Mo decrease, and the carbon oxygen strontium isotope is gradually positive. However, the oxygen content decreases sharply due to the sulfide section, and the isotopes of U, Mo and carbon oxygen strontium rise sharply, showing a frequent oscillation distribution with sea level. Based on the comparative analysis of paleoenvironment, TOC and porosity, the sulfide section and anoxic section are the most favorable hydrocarbon source rock development sections. Strong evaporation leads to water stratification and vulcanization, so that organic matter can be effectively preserved. Oxidation section and secondary oxidation section are favorable sections for reservoir development. The mound and beach bodies deposited by local uplift in the platform were frequently exposed, encountered quasi syngenetic dissolution and developed a large number of dissolution pores, which were effectively preserved after dolomitization. The source rock in the sulfide section and the dolomite reservoir in the oxidation section are interbedded in the longitudinal direction, and finger crossing in the plane, forming a good source-reservoir matching relationship. The three-dimensional reservoir network developed on Wushenqi uplift belt is a favorable area for Ordovician subsalt exploration in Ordos Basin. © 2023 China University of Geosciences. All rights reserved.

引用

页码：553 / 567

页数：14

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