Multistage dolomitization of deeply buried dolomite in the Lower Cambrian Canglangpu Formation, central and northern Sichuan Basin

Huang, Huiwen; Wen, Huaguo; Wen, L.; Zhang, Benjian; Zhou, Gang; He, Yumei; Wen, Longbin; Yan, Zhao; Jiang, Huachuan

doi:10.1016/j.marpetgeo.2023.106261

Cited by 3 publications

(3 citation statements)

References 70 publications

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“…The rounded, inclusion-rich nuclei of dolomite and calcite crystals (Figure 7C) covered by euhedral overgrowths may represent a recrystallization/stabilization process of less stable phases. Proto-dolomite or HMC commonly display extremely defective forms [107], which are replaced during diagenesis to more stable dolomite or LMC calcite with euhedral or subhedral forms via a dissolution-reprecipitation mechanism, potentially resulting in the precipitation of both carbonate phases as per Equation ( 6) [108][109][110][111].…”

Section: Eodiagenetic Interactionsmentioning

confidence: 99%

“…An initial metastable phase is not required, however, to form the inclusion-rich "turbid" cores in blocky dolomites. These cores could represent an initial phase of matrix-replacive dolomite followed by clear overgrowths [111,113] (Figure 7D,F), suggesting at least two eodiagenetic dolomitization events for the Pre-salt. The recrystallization of earlier phases could also occur together with the overgrowths, possibly using the less stable core as an ion source for further dolomite precipitation [114][115][116][117][118][119][120][121].…”

Section: Eodiagenetic Interactionsmentioning

confidence: 99%

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Interactions between Clays and Carbonates in the Aptian Pre-Salt Reservoirs of Santos Basin, Eastern Brazilian Margin

Schrank,

Dos Santos,

Altenhofen

et al. 2024

Minerals

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The giant Pre-salt reservoirs represent most of the oil production in Brazil. The main Aptian sag reservoirs were deposited in a unique and highly complex hyper-alkaline lacustrine setting. These deposits are essentially constituted by fascicular and spherulitic calcite precipitated in a magnesian clay matrix (stevensite, kerolite, and saponite/hectorite). Although vital for understanding the origin and main reservoir quality control, the genesis and interactions of clays and carbonates are still poorly constrained. The detailed petrographic description was focused on 812 thin sections from five wells drilled in the Santos Basin Aptian Barra Velha Formation, combined with cathodoluminescence, UV epifluorescence, and X-ray diffraction analyses. The main syngenetic processes were the deposition of finely laminated peloidal and ooidal Mg-clays, the formation of fascicular calcite crusts on the sediment–water interface, and the redeposition of these materials as intraclasts. Abundant clay peloids engulfed in syngenetic shrubs indicate that calcite and clay precipitation was concomitant, though with highly variable rates. Eodiagenetic phases include matrix-replacive and -displacive spherulites and fascicular shrubs; matrix-replacive blocky calcite and dolomite; lamellar carbonates filling matrix shrinkage pores; and microcrystalline calcite, dolomite, and silica replacing the Mg-clay matrix. The preferential dolomitization and calcitization of peloidal layers were most likely due to their higher permeability and larger specific surface. Matrix-replacive saddle dolomite, macrocrystalline calcite, and dawsonite are interpreted as mesodiagenetic or hydrothermal phases after significant matrix dissolution. Unraveling the processes of the formation and alteration of the carbonates and clays and their interactions in the Pre-salt deposits is essential for constraining the depositional and diagenetic conditions in their unique environments and their diagenetic overprinting and for decreasing the exploration risks and increasing the production of those extraordinary reservoirs.

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Section: Eodiagenetic Interactionsmentioning

confidence: 99%

Section: Eodiagenetic Interactionsmentioning

confidence: 99%

Interactions between Clays and Carbonates in the Aptian Pre-Salt Reservoirs of Santos Basin, Eastern Brazilian Margin

Schrank,

Dos Santos,

Altenhofen

et al. 2024

Minerals

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“…According to whether the original fabric is retained, the reservoir can be divided into fabric-retentive dolostone and fabric-destructive dolostone [42]. Fabric-retentive dolostone can be divided again according to crystal size.…”

Section: Petrographic Characteristicsmentioning

confidence: 99%

Characteristics and Controlling Factors of Crystalline Dolostone Reservoirs of the Sanshanzi Formation, Central-Eastern Ordos Basin, Northwestern China

Wu,

Liu,

Wei

et al. 2023

Minerals

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In recent years, Ordos Basin has been the largest petroleum field in China and represents significant potential for gas exploration in the Lower Paleozoic carbonate reservoirs. Taking the central-eastern Ordos Basin as an example, this work studies the reservoir characteristics, origin, and controlling factors of the crystalline dolomites of the Sanshanzi Formation by means of petrological and geochemical studies. The Sanshanzi Formation dolostones comprise three kinds: crystalline dolostone with grain-shadow (Rd1), very fine–fine crystalline dolostone (Rd2), and medium-coarse crystalline dolostone (Rd3). The pore spaces include intercrystalline pores and intercrystalline solution pores, residual intergranular pores, vugs, and fractures. The medium-coarse crystalline dolostone is the best reservoir. The average porosity is 4.61%, and the average permeability is 0.91 mD. The sedimentary environment in the upper Cambrian was a large area of tidal flats. Under the influence of penecontemporaneous meteoric water leaching, dissolution developed at the top of the dolomite flat–lagoon depositional cycle, with vugs developing in the very fine–fine crystalline dolostone. Penecontemporaneous dolomitization enhanced the compaction resistance and effectively preserved the pore space of the reservoir. In addition, recrystallization improved the crystalline texture, turning the intergranular pores into residual intergranular pores and intercrystalline micropores into intercrystalline pores. In this case, the very fine–fine crystalline dolostone was transformed into medium-coarse crystalline dolostone. The results of this study provide a case for the in-depth understanding of the development and preservation mechanism of ancient dolomite reservoirs and also point to the research pathways for oil and gas exploration in the Cambrian in the Ordos Basin in the future.

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Carbon-isotope stratigraphy of the Lower Cambrian (Cambrian explosion) in northwestern Yangtze Platform, China: Implications for global correlation

Zhang,

Liang,

Azmy

et al. 2024

Marine and Petroleum Geology

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Multistage dolomitization of deeply buried dolomite in the Lower Cambrian Canglangpu Formation, central and northern Sichuan Basin

Cited by 3 publications

References 70 publications

Interactions between Clays and Carbonates in the Aptian Pre-Salt Reservoirs of Santos Basin, Eastern Brazilian Margin

Interactions between Clays and Carbonates in the Aptian Pre-Salt Reservoirs of Santos Basin, Eastern Brazilian Margin

Characteristics and Controlling Factors of Crystalline Dolostone Reservoirs of the Sanshanzi Formation, Central-Eastern Ordos Basin, Northwestern China

Carbon-isotope stratigraphy of the Lower Cambrian (Cambrian explosion) in northwestern Yangtze Platform, China: Implications for global correlation

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