Authigenic berthierine and incipient chloritization in shallowly buried sandstone reservoirs: Key role of the source-to-sink context - CNRS - Centre national de la recherche scientifique Accéder directement au contenu
Article Dans Une Revue Geological Society of America Bulletin Année : 2022

Authigenic berthierine and incipient chloritization in shallowly buried sandstone reservoirs: Key role of the source-to-sink context

Résumé

Chlorite is recognized worldwide as a key mineral that inhibits the development of quartz cement in deeply buried sandstone reservoirs. Iron-rich chlorite is mainly formed by the transformation of a precursor clay mineral; however, few studies have focused on the early stages before the crystallization of chlorite. This study analyzed shallowly buried (400−1000 m) coastal sandstones from within the Wealden Group of the Paris Basin. Berthierine, a 7 Å trioctahedral clay mineral belonging to the serpentine group, approximatively with same chemistry as chlorite but a different crystal structure, has been identified in a 900-m-deep well but not in a 400−600-m-deep well. Berthierine has mainly been observed as clay coatings around detrital grains with a typical honeycomb texture. Nanopetrographic observations suggest that the honeycomb textural organization of the clay particles found in deeper buried sandstone reservoirs (>1500 m) is acquired from a berthierine precursor at shallow depths. However, small amounts of quartz overgrowths are observed on the surface of detrital grains at shallow depths and low temperature (below 40 °C), and it is believed that precursor berthierine coatings are primarily responsible for the inhibition of quartz overgrowths before Fe-rich chlorite is formed. This suggests that the key mineral primarily controlling the reservoir quality of deeply buried sandstone reservoirs is berthierine rather than iron-rich chlorite, which challenges the commonly accepted assertion that chlorite coating is the main process that inhibits quartz overgrowths. The source-to-sink context of the Paris Basin during the Early Cretaceous was decisive with respect to the supply of sands and berthierine clay precursors (in particular kaolinite and iron-rich, hydroxy-interlayered clay minerals) to the center of the basin.
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Dates et versions

hal-03341574 , version 1 (05-08-2023)

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Maxime Virolle, Benjamin Brigaud, Daniel Beaufort, Patricia Patrier, Eid Abdelrahman, et al.. Authigenic berthierine and incipient chloritization in shallowly buried sandstone reservoirs: Key role of the source-to-sink context. Geological Society of America Bulletin, 2022, 134 (3-4), pp.739-761. ⟨10.1130/B35865.1⟩. ⟨hal-03341574⟩
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