Geochemical Characteristics and Shale Oil Potential of Shale in the Yan’an Area

doi:10.19657/j.geoscience.1000-8527.2021.001

Abstract

Abstract:

Industrial oil flow has been obtained in Chang 7 shale Formation in Ansai area, which turns this area into a shale oil target. Based on this, systematic quality evaluation of source rocks and shale oil potential analysis are carried out to provide reference for future shale oil exploration. The results show high organic matter abundance in the shale (average TOC=4.05%), with the main organic matter types being type I, type II₁ and type II₂. The Chang 7 shale has entered the oil-generating window and is in the oil-generating thermal stage. The shale has both terrestrial and lacustrine source inputs, and the depositional environment was weakly reducing or oxidizing. Among the three organic matter types (higher organic matter would lead to higher hydrocarbon generating capacity), type I has higher hydrocarbon generating capacity than type II₁, and type II₂ has the lowest hydrocarbon generating capacity. The shale oil content of types I, II₁,and II₂ organic matter are 10.30 mg/g, 8.99 mg/g, and 8.14 mg/g, respectively. In terms of availability, the available shale oil resources are concentrated in type I organic matter. Type II₁ organic matter is lowly available and type II₂ organic matter is poorly available. In terms of comprehensive exploration potential, the most suitable target is type I organic matter, followed by type II₁ and then by type II₂ organic matter.

Key words: Ordos Basin, Chang 7 shale, geochemical characteristics, shale oil

CLC Number:

TE135.6

SHI Liang, ZHAO Tongtong, ZHA Hui, WANG Yanyan, HUO Pingping, FAN Bojiang. Geochemical Characteristics and Shale Oil Potential of Shale in the Yan’an Area[J]. Geoscience, 2021, 35(04): 1043-1053.

Figures/Tables 12

Fig.1 Development features of interlayer fractures of shale in the study area

Fig.2 Chromatogram comparison of typical organic matter in the study area

Fig.3 Distribution of organic matter types in the study area

Fig. 4 Tmax distribution of organic natter in the study area

Fig.5 Thermal maturity of organic matter based on biomarker parametric discrimination

Fig.6 Sedimentary environment discrimination diagram of shale in the study area

Fig.7 Organic matter source of shale in the study area

Fig.8 Relations between organic matter content and pyrolysis parameters

Fig.9 Relations between pyrolysis parameters and burial depth

Fig.10 Hydrocarbon expulsion characteristics of the shale

Fig.11 Classification of shale oil resource in the study area

Fig. 12 Seepage features of shale oil

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