Effects of dissolved organic matter on shale pore structure of low-mature lacustrine facies organic-rich shale

ABSTRACT

Soluble organic matter greatly affects shale pore structure and gas storage capacity. Based on elucidating the organic type, maturity, and content of shale of Qingshankou formation in Songliao Basin, this paper uses the mixed reagent of dichloromethane/methanol for cable extraction of shale and the change of shale pore structure before and after extraction of dissolved organic matter (DOM) was determined by low-temperature nitrogen adsorption method. The results show that DOM occupies a certain pore space and reduces pore connectivity. After extraction, the shale pore volume and specific surface area were increased, the specific surface area increased by 28.38%-221%, the total pore volume increased by 25.4%-73.2%, and the micropore grew by 48.89%. The effects of DOM on micropores are mainly occlusion and blocking, and mesoporous and macropores are mainly adsorbed and filled. The analysis of the effects of DOM on micropores provides a theoretical basis to examine shale pore structure with low maturity in the future.

KEYWORDS:

• Pore structure
• organic extraction
• low-temperature nitrogen adsorption
• DOM
• lacustrine shale

Nomenclature list

DOM- dissolved organic matter; Tmax-the maximum pyrolysis temperature; HI- hydrogen index; OI- oxygen index; Ro- thermal evolution of organic matter; TOC-total organic carbon; P- actual pressure of test samples; Po- saturated steam pressure; P/Po- relative pressure.

Acknowledgments

This study was financially supported by the Open fund of Sinopec Key Laboratory of Shale Oil/Gas Exploration and Production Technology (No. G5800-20-ZS-KFZY002).

Additional information

Funding

This work was supported by the Open fund of Sinopec Key Laboratory of Shale Oil/Gas Exploration and Production Technology [G5800-20-ZS-KFZY002].

Notes on contributors

Shun He

Shun He, male, born in 1993, student pursuing a Ph.D. degree, majored in geological resources and geological engineering.

Hu Li

Hu Li, male, born in 1986, Ph.D., postdoctor, instructor, majored in structural geology, rock mechanics.

Qirong Qin

Qirong Qin, male, born in 1964, Ph.D., professor and ddoctoral supervisor, majored in geological resources and geological engineering.

Shengxiang Long

Shengxiang Long, male, born in 1959, Ph.D., professor of engineering, majored in oil-gas exploration and production.