26 Apr 2022
26 Apr 2022
Status: this preprint is currently under review for the journal MR.

Magnetic locking in kerogen: impact on fluid transport

Benjamin Nicot1, Jean-Pierre Korb2, Isabelle Jolivet1, Hervé Vezin3, Didier Gourier4, and Anne-Laure Rollet2 Benjamin Nicot et al.
  • 1TotalEnergies, Avenue Larribau, 64000 Pau, France
  • 2Sorbonne-Université, CNRS, PHENIX, 75005 Paris, France
  • 3Univ. Lille, CNRS, UMR8516 – LASIRe, F-59000, Lille, France
  • 4Chimie ParisTech, PSL University, CNRS, Institut de Recherche de Chimie de Paris (IRCP), F-75005 Paris, France

Abstract. How the transport of fluids in a confined and complex mixed organic/inorganic matrix can be far below the expected value from topological aspect? A good example of this situation is oil shales. Oil and gas shales are source rocks in which organic matter has matured to form hydrocarbons. They exhibit a dual porous network formed by the intertwining of mineral and organic pores that leads to very low permeability. Still, the exact origin of this extremely low permeability remains somehow unclear. The present communication addresses this important question and provides novel insights on the mechanisms that strongly hinder fluid diffusion in such materials. By combining nuclear and electronic magnetic resonance techniques combined with SEM imaging, we evidence that magnetic locking occurs in kerogen. This locking results from a magnetic coupling between vanadyl present in porphyrins and the organic matrix. We demonstrate that such coupling retards fluid diffusion and is reversible. This key dynamical feature explains the extremely low mobility of oil in shale rocks. This phenomenon may be a more general feature occurring in several systems where fluids are confined in a complex hierarchical matrix that embeds both organic and inorganic radicals resulting from ageing process.

Benjamin Nicot et al.

Status: open (until 24 May 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on mr-2022-7', Anonymous Referee #1, 10 May 2022 reply
  • RC2: 'Comment on mr-2022-7', Anonymous Referee #2, 13 May 2022 reply
    • EC1: 'Reply on RC2', Geoffrey Bodenhausen, 14 May 2022 reply
      • CC1: 'Reply on EC1', Hervé Vezin, 14 May 2022 reply
  • CC2: 'Comment on mr-2022-7', Nino Wili, 15 May 2022 reply

Benjamin Nicot et al.

Benjamin Nicot et al.


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Short summary
We report in this article a multiscale approach for explaining why the transport of fluids in oil shales is so hindered. Thanks to nuclear and electronic magnetic resonances, we first demonstrate that the kerogen within the shale is capable of swelling in the presence of oil, second we show that this swelling is reversible and reveals the presence of vanadyl porphyrin by breaking magnetic interaction. The magnetic locking evidenced here helps understanding the very low mobility of hydrocarbons.