Author:
Liu Bei,Teng Juan,Mastalerz Maria
Abstract
Organic matter (OM) type critically controls the hydrocarbon generation potential and organic pore development in black shales. However, maceral variation in lacustrine shales and its control on hydrocarbon generation potential and organic pore development are not yet well understood. In this study, 15 Chang 7 Member shale samples of the Yanchang Formation, Ordos Basin, were investigated with organic petrography, Rock-Eval pyrolysis, and a scanning electron microscope to study the maceral composition, hydrocarbon generation potential, and organic pores in this black shale succession. The results show that the studied shales are in the oil window (Ro~0.70%). OM belongs to Type I and Type III kerogen, as demonstrated by Rock-Eval pyrolysis. Macerals in the Chang 7 Member shales are composed of amorphous OM, alginite, sporinite, liptodetrinite, vitrinite, inertinite, and solid bitumen. Amorphous OM and alginite are major hydrocarbon-generating macerals, and their content determines the hydrocarbon potential of shales. Secondary organic pores were not observed in the studied Chang 7 Member shales due to either a low thermal maturity or a dominance of terrigenous OM. Maceral variation can affect the reliability of using Rock-Eval Tmax as a thermal maturity indicator. This study provides important insights into maceral control on hydrocarbon generation and organic pore development in black shales, calling for a critical evaluation of OM in black shale successions with organic petrography.
Funder
State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development
National Science Foundation of China
Subject
Energy (miscellaneous),Energy Engineering and Power Technology,Renewable Energy, Sustainability and the Environment,Electrical and Electronic Engineering,Control and Optimization,Engineering (miscellaneous),Building and Construction
Reference69 articles.
1. Tissot, B.P., and Welte, D.H. (1984). Petroleum Formation and Occurrence, Springer. [2nd ed.].
2. Application of organic petrography in North American shale petroleum systems: A review;Hackley;Int. J. Coal Geol.,2016
3. Controlling factors on the formation and distribution of “sweet-spot areas” of marine gas shales in South China and a preliminary discussion on unconventional petroleum sedimentology;Qiu;J. Asian Earth Sci.,2020
4. Potter, J., Stasiuk, L.D., and Cameron, A.R. (1998). A Petrographic Atlas of Canadian Coal Macerals and Dispersed Organic Matter, Canadian Society for Coal Science and Organic Petrology—Geological Survey of Canada (Calgary)—Canmet Energy Technology Centre.
5. Status report on TSOP-ICCP dispersed organic matter classification working group;Stasiuk;Soc. Org. Petrol. Newsl.,2002