Impacts of Pore Structure on the Occurrence of Free Oil in Lacustrine Shale Pore Networks

Fuliang You (), Guangdi Liu (), Mingliang Sun, Cheng An, Chaozheng Li and Yishu Li
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Fuliang You: College of Geosciences, China University of Petroleum, Beijing 102249, China
Guangdi Liu: College of Geosciences, China University of Petroleum, Beijing 102249, China
Mingliang Sun: College of Geosciences, China University of Petroleum, Beijing 102249, China
Cheng An: College of Geosciences, China University of Petroleum, Beijing 102249, China
Chaozheng Li: Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
Yishu Li: College of Geosciences, China University of Petroleum, Beijing 102249, China

Energies, 2023, vol. 16, issue 20, 1-22

Abstract: The ultimate recovery of shale oil is mostly dependent upon the occurrence and content of free oil within the nano-scaled pore network of shale reservoirs. Due to the nanoporous nature of shale, quantitatively characterizing the occurrence and content of free oil in shale is a formidable undertaking. To tackle this challenge, 12 lacustrine shale samples with diverse organic matter content from the Chang7 Member in the southern Ordos Basin were selected, and the characteristics of free oil occurrence were indirectly characterized by comparing changes in pore structure before and after organic solvent extraction. The free oil enrichment in shale was assessed using the oil saturation index (OSI), corrected oil saturation index (OSI corr ), and percentage of saturated hydrocarbons. The results revealed that slit-like interparticle pores with diameters less than 30 nm are dominant in the Chang7 shale. Conceptual models for the pore structures containing free oil were established for shale with total organic carbon (TOC) content less than 9% and greater than 9%, respectively. Shale samples with TOC content less than 9% exhibit a well-developed pore network characterized by relatively larger pore volume, surface area, and heterogeneity. Conversely, shale samples with TOC content exceeding 9% display a less developed pore network characterized by relatively smaller pore volume, surface area, and heterogeneity. Larger pore volume and lower organic matter abundance favor the enrichment of free oil within the lacustrine shale pore network. This study may have significant implications for understanding oil transport in shales.

Keywords: shale oil; pore structure; Chang7 member; Ordos Basin (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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