New study examines the nanoscale properties of the Gulong shale oil reservoir

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a) and b): A large number of nanopores (red arrows) and nanofissures (yellow arrows) developed in the clay layers, which initially adsorbed organic matter and later became the site for hydrocarbon accumulation. c): A larger representation of visual b). Credit: Dr. He Wenyuan and Earth Science Boundaries

Shale oil, a type of crude oil similar to petroleum, is found between layers of organic-rich shale. It can be refined into gasoline, diesel and other products, making it a sought-after resource. The Qingshankou Formation in the Gulong Sag of the Songliao Basin in China is a large geological body of shale deposits formed at the bottom of an ancient lake. These deposits contain about 15.3 billion tons of pure shale oil. Of course, the Gulong-Qingshankou Formation is an important national reservoir for shale oil. Recent studies have revealed interesting features of this huge reservoir, in particular the presence of nanopores in the shale layers containing solid bitumen that has remained unmoved for centuries.

Studying the petrological characteristics of shale can reveal much about the formation, spatial and physical properties, oil content and developmental value of a reservoir. Therefore, a new study published in Earth Science Boundaries examines the petrological and microtissue properties of shale from the Gulong Sag to unearth evidence about the formation, reservoir space and in situ collection of shale oil.

The study was led by Dr. He Wenyuan of Daqing Oilfield Co. Ltd., who says: “Nanopores in shale are considered important sites for shale oil accumulation. Since the shale oil in the Gulong Sag is known to have a 90% reservoir ratio resource, examining the nanopores in this reservoir can help to discover valuable information.”

dr. He used electron microscopy, energy spectrum analysis and thermal simulation to analyze the Gulong shale samples. He found that the Gulong shale is mainly clay, with well-developed nanopores and nanofissures – about 10-50 nm in diameter/width. Over the years, organic matter such as decomposed algae waste and kerogen (fossilized organic matter) was deposited in these nanopores to form organic clay aggregates. The organic content of this clay was no less than 91.5% (average >53%). Subsequently, this organic clay became the main source material for the production of hydrocarbons, mainly liquid bitumen and shale oil.

From the analyzes of Dr. He found that nearly 87% of the original organic material was consumed during the generation of hydrocarbons. In addition, the empty nanopores left by the organic matter were occupied by the liquid hydrocarbons. Given the closed shape of the nanopores and the high capillary resistance, the hydrocarbons stuck in the rocks with little movement and eventually solidified into solid bitumen/asphalt. Thus, the Gulong shale deposits generated and stored the shale oil itself, which explains the region’s high resource-to-reservoir ratio.

New study examines the nanoscale properties of the Gulong Shale Oil Reservoir. Credit: Earth Science Boundaries (2022). DOI: 10.13745/j.esf.sf.2022.8.32-nl

Despite being a preliminary study, these results help provide a clearer picture of the Gulong-Qingshankou reservoir. dr. Discussing the potential implications of these findings, He says: “The results of this study could drive progress in shale oil exploration and development in the region and perhaps even China. But for now, future research should focus on further verification and exploring of these exploratory findings.”

Perhaps this is one of those rare occasions when “reaching rock bottom” could be a good thing.

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More information:
He Wenyuan, Preliminary Study on Nanopores, Nanofissures and In Situ Accumulation of Gulong Shale Oil, Earth Science Boundaries (2022). DOI: 10.13745/j.esf.sf.2022.8.32-nl

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Quote: Digging a little deeper: New study examines the nanoscale properties of the Gulong oil shale reservoir (2022, Sept. 8), retrieved Sept. 8, 2022 from -gulong.html

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