The role of detrital anhydrite in diagenesis of aeolian sandstones (Upper Rotliegend, The Netherlands): Implications for reservoir-quality prediction
article
The Rotliegend (Upper Permian) reservoir interval in the Southern Permian Basin (SPB) contains low-permeability
streaks corresponding to anhydrite-cemented intervals. An integrated study was conducted using core, cuttings,
thin sections and well-log data from a gas exploration well and two geothermal wells that target the
zone of interest. This study aims at understanding the origin and nature of these low-permeability streaks, as
well as their impact on reservoir properties, and to establish a predictive model of their spatial distribution.
High-resolution XRF core-scanning analysis allowed to extrapolate spot observations in thin sections to the entire
core. Diagenetic history includes grain rearrangement and anhydrite, haematitic clay coatings, dolomite rims,
quartz overgrowths, kaolinite and second-generation carbonates as cementing phases. Coupling of all data reveals
the detrital origin of the anhydrite/gypsum grains which were deposited together with the coarse-grained
sand fraction in an aeolian sandflat environment. Such partially or completely dissolved grains acted as local
sources of anhydrite cement and as nuclei for precipitation, explaining its preferential occurrence in coarsegrained
laminae. Thick gypscretes in the vicinity likely supplied the anhydrite/gypsum grains. A conceptual
model is proposed, including the location of nearby gypscretes and the prevailing west-southwest aeolian transport
direction on the southern rim of the SPB
streaks corresponding to anhydrite-cemented intervals. An integrated study was conducted using core, cuttings,
thin sections and well-log data from a gas exploration well and two geothermal wells that target the
zone of interest. This study aims at understanding the origin and nature of these low-permeability streaks, as
well as their impact on reservoir properties, and to establish a predictive model of their spatial distribution.
High-resolution XRF core-scanning analysis allowed to extrapolate spot observations in thin sections to the entire
core. Diagenetic history includes grain rearrangement and anhydrite, haematitic clay coatings, dolomite rims,
quartz overgrowths, kaolinite and second-generation carbonates as cementing phases. Coupling of all data reveals
the detrital origin of the anhydrite/gypsum grains which were deposited together with the coarse-grained
sand fraction in an aeolian sandflat environment. Such partially or completely dissolved grains acted as local
sources of anhydrite cement and as nuclei for precipitation, explaining its preferential occurrence in coarsegrained
laminae. Thick gypscretes in the vicinity likely supplied the anhydrite/gypsum grains. A conceptual
model is proposed, including the location of nearby gypscretes and the prevailing west-southwest aeolian transport
direction on the southern rim of the SPB
TNO Identifier
519725
Source
Sedimentary Geology, 314, pp. 60-74.
Pages
60-74
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