Kaolinite-to-dickite reaction in sandstone reservoirs
Abstract:The SEM, XRD, FTIR and DTA analyses of different size-fractions of clay material from sandstone reservoirs which have experienced a large range of burial conditions have been used to examine the different steps of the depth-related kaolinite-dickite reaction. Dickite progressively replaced kaolinite within a range of burial depths estimated between about 2500 m and 5000 m. The kaolinite-to-dickite reaction proceeds by gradual structural changes concomitant to crystal coarsening and change from booklet to blocky morphology. The crystallization of dickite proceeds by two distinct paths: (1) Accretion of new material from either dissolution of smaller unstable kaolinite crystals and/or detrital minerals (chiefly feldspars), on early-formed coarser metastable kaolinite crystals which exert extended morphological control on the growing crystals. (2) Neoformation of ordered dickite which will continue to grow by a dissolution-crystallization process. The kaolinite-todickite reaction is kinetically controlled and anomalies in the kaolinite/dickite ratio observed in certain sandstone reservoirs may be used to assess the timing of invasion by hydrocarbons.
Document Type: Research Article
Affiliations: 1: CNRSUMR 6532, Université de Poitiers 40Av. du Recteur Pineau 86022 Poitiers Cedex 2: LGITIRIGM, Universite J. Fourier, CNRS- BP53, 38041 Grenoble Cedex 9 3: Laboratoire de Géochimie, UMR 5563 CNRS Université 4: Laboratoire de Géochimie, UMR 5563 CNRS Université
Publication date: June 1, 1998