The hydrocarbon generation potential and migration in an alkaline evaporite basin: The Early Permian Fengcheng Formation in the Junggar Basin, northwestern China

Previous studies on Chepaizi Uplift mainly focused on its reservoirs, and the potential source rocks natively occurred was ignored. During the exploration process, dark mudstones and tuffaceous mudstones were found in the Carboniferous interval. These possible source rocks have caused great concern about whether they have hydrocarbon generation potential and can contribute to the reservoirs of the Chepaizi Uplift. In this paper, the potential source rocks are not only evaluated by the organic richness, type, maturity, and depositional environment, but also divided into different kinetics groups. The Carboniferous mudstones dominated by Type III kerogen were evolved into the stage of mature. Biomarkers indicate that the source rocks were deposited in a marine environment under weakly reducing conditions and received mixed aquatic and terrigenous organic matter, with the latter being predominant. The effective source rocks are characterized by the total organic carbon values >0.5 wt.% and the buried depth >1500 m. The tuffaceous mudstone shows a greater potential for its lower active energy and longer hydrocarbon generation time. Considering the hydrocarbon generation potential, base limits of the total organic carbon and positive correlation of oil–source rock together, the native Carboniferous mudstones and tuffaceous mudstones might contribute to the Chepaizi Uplift reservoirs of the northwestern region of the Junggar Basin, especially the deeper effective source rocks should be paid enough attention to.

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CHARACTERISTICS OF SODIUM CARBONATE- BEARING RHYTHMS AND PALEOCLIMATES VARIATIONS IN CLOSED EVAPORATE BASIN: THE CASE OF THE EARLY PERMIAN FENGCHENG FORMATION IN THE MAHU SAG, JUNGGAR BASIN IN NORTHWESTERN CHINA

10.1130/abs/2017am-298094 ◽

2017 ◽

Author(s):

Kuanhong Yu ◽

◽

Yingchang Cao ◽

Longwei Qiu

Keyword(s):

Sodium Carbonate ◽

Junggar Basin ◽

Northwestern China ◽

Early Permian

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Hydrocarbon generation potential of Triassic mudstones in the Junggar Basin, northwest China

AAPG Bulletin ◽

10.1306/03111413022 ◽

2014 ◽

Vol 98 (9) ◽

pp. 1885-1906 ◽

Cited By ~ 18

Author(s):

Ming Wu ◽

Jian Cao ◽

Xulong Wang ◽

Yong Tang ◽

Bin Wang ◽

...

Keyword(s):

Junggar Basin ◽

Northwest China ◽

Hydrocarbon Generation ◽

Hydrocarbon Generation Potential

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Source Rock Evaluation and Hydrocarbon Generation Model of a Permian Alkaline Lakes—A Case Study of the Fengcheng Formation in the Mahu Sag, Junggar Basin

Minerals ◽

10.3390/min11060644 ◽

2021 ◽

Vol 11 (6) ◽

pp. 644

Author(s):

Yong Tang ◽

Wenjun He ◽

Yubin Bai ◽

Xiang Zhang ◽

Jingzhou Zhao ◽

...

Keyword(s):

Organic Matter ◽

Evaluation Criteria ◽

Junggar Basin ◽

Source Rocks ◽

Geochemical Data ◽

Generation Model ◽

Hydrocarbon Generation ◽

High Hydrocarbon ◽

Hydrocarbon Generation Potential ◽

Alkaline Lake

The alkaline lake source rocks of the Fengcheng Formation are developed in the Mahu Sag of the Junggar Basin. Different from traditional continental fresh water and saltwater lake source rocks, alkaline lake source rocks lack targeted evaluation criteria, and it is unknown whether their hydrocarbon generation models are consistent with traditional models. Therefore, in the present study, evaluation standards and hydrocarbon generation models of alkaline lake source rocks are discussed based on geological and organic geochemical data and a systematic summary of the geochemical characteristics of the Fengcheng Formation source rocks. The Fengcheng Formation source rocks are mainly diamictite with mixed argillaceous rock and dolomite; most total organic carbon (TOC) values range from 0.2–1.4%; and the kerogen is primarily oil-prone type II, reaching low- to high-maturity stages. Based on the types of organic matter in source rocks and the relationships between organic matter abundance parameters, the evaluation standard of alkaline lake source rocks is proposed. The Fengcheng Formation is mainly composed of good to excellent source rocks (55.5%) with high hydrocarbon generation potential. The single-peak hydrocarbon generation model of the Fengcheng Formation is similar to that of traditional freshwater or saltwater lakes, with a high hydrocarbon generation rate, two to five times that of the traditional model; its main particularity is in the formation of naphthenic crude oil from the kerogen of bacteria and algae. A new understanding of the hydrocarbon generation potential and model of alkaline lake source rocks in the Fengcheng Formation can provide support for tight oil and shale oil exploration in the Mahu Sag.

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Revisiting Controls on Shale Oil Accumulation in Saline Lacustrine Basins: The Permian Lucaogou Formation Mixed Rocks, Junggar Basin

Geofluids ◽

10.1155/2021/5206381 ◽

2021 ◽

Vol 2021 ◽

pp. 1-25

Author(s):

Chenjia Zhang ◽

Jian Cao ◽

Erting Li ◽

Yuce Wang ◽

Wenyao Xiao ◽

...

Keyword(s):

Carbonate Rocks ◽

Junggar Basin ◽

Type I ◽

Hydrocarbon Generation ◽

Shale Oil ◽

Oil Accumulation ◽

Hydrocarbon Generation Potential ◽

Lucaogou Formation ◽

Saline Lacustrine ◽

Lacustrine Basins

Fine-grained mixed rocks in saline lacustrine basins are important targets for shale oil exploration. However, the controls on shale oil accumulation are complex due to the multi-source mixed deposition. This is a challenging issue in the study of shale oil. Here, we present a case study in the Middle Permian Lucaogou Formation in the Jimusar Sag, Junggar Basin, northwestern China. Results show that the Lucaogou Formation consists mainly of carbonate rocks, dolomitic or calcareous mudstones, tuffaceous or silty mudstones, and siltstones. The dolomitic/calcareous mudstones ( TO C average = 6.44 wt . % ) and tuffaceous/silty mudstones ( TO C average = 4.83 wt . % ) have the best hydrocarbon generation potential and contain type I–II1 kerogens that are in the peak oil generation stage. However, the shale oil potential is highest for the carbonate rocks and siltstones with average oil saturation index (OSI) values of 315.03 mg HC/g TOC and 343.27 mg HC/g TOC, respectively. This indicates that hydrocarbon generation potential is not the main factor controlling shale oil potential. Micro-nanoscale pores are the main control. Abundant dissolution pores provide excellent reservoir space for near-source migration and accumulation of shale oil. Different mixing processes between lithofacies control the accumulation of shale oil, and shale oil productivity is the best when multi-facies deposition in transitional zones formed the mixed rocks (facies mixing). In addition, local accumulations of calcareous organisms and adjacent carbonate components on terrigenous sediments (in situ mixing) are also conducive to shale oil enrichment. This is an unusual and special feature of saline lacustrine shale oils, which is different from freshwater lacustrine and marine shale oils. Comprehensive assessment of source rock and reservoir is needed to robustly establish a widely applicable method to determine the shale oil potential in such basins.

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