Hydrocarbon generation potential of the C-P continental source rocks in the Qinshui Basin

Sediments with organic matter content (total organic carbon) TOC ≤ 0.5% which can act as effective source rocks are critical and challenging in the field of petroleum geology. A new method is proposed through a case study to identify and evaluate the effective source rocks, which is applied to study the changing characteristic of hydrocarbon-generation potential index with depth. The burial depth corresponding to the beginning of hydrocarbon-generation potential index reduction represents the hydrocarbon expulsion threshold in source rocks. Then, new identification standards are established for discrimination of effective source rocks of Middle–Upper Ordovician in Tarim Basin. The critical value of TOC for effective source rocks change with their burial depth: the TOC > 0.5% with source rock depth > 4000 m, TOC > 0.4% with depth >4500 m, TOC > 0.3% with depth > 5000 m, TOC > 0.2% with depth >5500 m. Based on the new criteria, effective source rocks in the Middle–Upper Ordovician are identified and their total potential hydrocarbon resources is evaluated, reaches 0.68 × 109 t in the Tazhong area, which is 65.4% higher than that of previous studies and consistent with the exploration result. Thus, this new method is of significance to resource evaluation and can be applied in the carbonate source rocks and mudstone source rocks with high degree of exploration.

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Geochemical characterization and possible hydrocarbon contribution of the Carboniferous interval natively developed in the Chepaizi Uplift of Junggar Basin, northwestern China

Energy Exploration & Exploitation ◽

10.1177/0144598719892901 ◽

2019 ◽

Vol 38 (3) ◽

pp. 654-681 ◽

Cited By ~ 2

Author(s):

Lixin Mao ◽

Xiangchun Chang ◽

Youde Xu ◽

Bingbing Shi ◽

Dengkuan Gao

Keyword(s):

Organic Carbon ◽

Total Organic Carbon ◽

Junggar Basin ◽

Source Rocks ◽

Hydrocarbon Generation ◽

Exploration Process ◽

Potential Source ◽

Hydrocarbon Generation Potential ◽

Northwestern Region ◽

Effective Source

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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