scholarly journals Porosity Development Controlled by Deep-Burial Diagenetic Process in Lacustrine Sandstones Deposited in a Back-Arc Basin (Makó Trough, Pannonian Basin, Hungary)

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-26
Author(s):  
Emese Laczkó-Dobos ◽  
Susanne Gier ◽  
Orsolya Sztanó ◽  
Rastislav Milovský ◽  
Kinga Hips
Keyword(s):  
Organic Matter ◽  
Late Stage ◽  
Pannonian Basin ◽  
Depth Interval ◽  
Quartz Content ◽  
Secondary Porosity ◽  
Rock Fragments ◽  
Deep Burial ◽  
Back Arc ◽  
Porosity Development

Deeply buried Pannonian (Upper Miocene) siliciclastic deposits show evidence of secondary porosity development via dissolution processes at a late stage of diagenesis. This is demonstrated by detailed petrographic (optical, cathodoluminescence, fluorescence, and scanning electron microscopy) as well as elemental and stable isotope geochemical investigations of lacustrine deposits from the Makó Trough, the deepest depression within the extensional Pannonian back-arc basin. The analyses were carried out on core samples from six wells located in various positions from centre to margins of the trough. The paragenetic sequence of three formations was reconstructed with special emphasis on sandstone beds in a depth interval between ca 2700 and 5500 m. The three formations consist, from bottom to top, of (1) open-water marls of the Endrőd Formation, which is a hydrocarbon source rock with locally derived coarse clastics and (2) a confined and (3) an unconfined turbidite system (respectively, the Szolnok and the Algyő Formation). In the sandstones, detrital grains consist of quartz, feldspar, and mica, as well as sedimentary and metamorphic rock fragments. The quartz content is high in the upper, unconfined turbidite formation (Algyő), whereas feldspars and rock fragments are more widespread in the lower formations (Szolnok and Endrőd). Eogenetic minerals are framboidal pyrite, calcite, and clay minerals. Mesogenetic minerals are ankerite, ferroan calcite, albite, quartz, illite, chlorite, and solid bituminous organic matter. Eogenetic finely crystalline calcite yielded δ13 C V − PDB values from 1.4 to 0.7‰ and δ18 O V − PDB values from –6.0 to –7.4‰, respectively. Mesogenetic ferroan calcite yielded δ13 C V − PDB values from 2.6 to –1.2‰ and δ18 O V − PDB values from –8.3 to –14.0‰, respectively. In the upper part of the turbidite systems, remnants of the migrated organic matter are preserved along pressure dissolution surfaces. All these features indicate that compaction and mineral precipitations resulted in tightly cemented sandstones prior to hydrocarbon migration. Interconnected, secondary, open porosity is associated with pyrite, kaolinite/dickite, and postdates of the late-stage calcite cement. This indicates that dissolution processes took place in the deep burial realm in an extraformational fluid-dominated diagenetic system. The findings of this study add a unique insight to the previously proposed hydrological model of the Pannonian Basin and describe the complex interactions between the basinal deposits and the basement blocks.

Diagenetic carbonate and evaporite minerals in Rotliegend aeolian sandstones of the Southern North Sea: their nature and relationship to secondary porosity development

Clay Minerals ◽  
1986 ◽  
Vol 21 (4) ◽  
pp. 443-457 ◽  
Author(s):  
K. Pye ◽  
D. H. Krinsley
Keyword(s):  
North Sea ◽  
Secondary Porosity ◽  
Southern North Sea ◽  
Carbonate Cements ◽  
Deep Burial ◽  
Reducing Conditions ◽  
Two Generations ◽  
Stage 1 ◽  
Evaporite Minerals ◽  
Porosity Development

AbstractDeeply buried (> 3·5 km) Rotliegend aeolian sandstones in the Southern North Sea Basin display a number of interesting diagenetic features including (i) zoned iron-rich carbonate cements, (ii) anhydrite, halite and baryte cements, (iii) at least two generations of authigenic illite, and (iv) significant secondary porosity created by cement and framework-grain dissolution. The creation and destruction of secondary porosity is the result of changes in porewater chemistry during burial and subsequent uplift. Three pore-fluid regimes can be identified: (1) alkaline, oxidizing conditions during shallow to intermediate burial; (2) acid, reducing conditions during intermediate to deep burial; (3) alkaline, reducing conditions during deep burial and uplift. The transition from stage 1 to stage 2 was probably caused by expulsion of waters from the underlying Carboniferous shales. The transition to stage 3 probably began when faulting associated with uplift allowed invasion by alkaline fluids derived from Zechstein sediments.

scholarly journals Adsorption Characteristics and Controlling Factors of CH4 on Coal-Measure Shale, Hedong Coalfield

Minerals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 63
Author(s):  
Weidong Xie ◽  
Meng Wang ◽  
Hongyue Duan
Keyword(s):  
Organic Matter ◽  
Adsorption Capacity ◽  
Mineral Composition ◽  
Shale Gas ◽  
Total Content ◽  
Coal Measure ◽  
Gas Reservoirs ◽  
Quartz Content ◽  
Adsorption Characteristics ◽  
Adsorbed Gas

Adsorbed gas is one of the crucial occurrences in shale gas reservoirs; thus, it is of great significance to ascertain the adsorption capacity of shale and the adsorption characteristics of CH4. In this investigation, the Taiyuan–Shanxi Formations’ coal-measure shale gas reservoir of the Carboniferous–Permian era in the Hedong Coalfield was treated as the research target. Our results exhibit that the shale samples were characterized by a high total organic carbon (TOC) and over to high-over maturity, with an average TOC of 2.45% and average Ro of 2.59%. The mineral composition was dominated by clay (62% on average) and quartz (22.45% on average), and clay was mainly composed of kaolinite and illite. The Langmuir model showed a perfect fitting degree to the experimental data: VL was in the range of 0.01 cm3/g to 0.77 cm3/g and PL was in the range of 0.23–8.58 MPa. In addition, the fitting degree depicted a linear negative correlation versus TOC, while mineral composition did not exhibit a significant effect on the fitting degree, which was caused by the complex pore structure of organic matter, and the applicability of the monolayer adsorption theory was lower than that of CH4 adsorption on the mineral’s pore surface. An apparent linear positive correlation of VL versus the TOC value was recorded; furthermore, the normalized VL increased with the growth of the total content of clay mineral (TCCM), decreased with the growth of the total content of brittle mineral (TCBM), while there was no obvious correlation of normalized VL versus kaolinite, illite and quartz content. The huge amount of micropores and complex internal structure led to organic matter possessing a strong adsorption capacity for CH4, and clay minerals also promoted adsorption due to the development of interlayer pores and intergranular pores.

scholarly journals Foraminiferal biostratigraphy and palaeoenviron- mental analysis of the basal part of Kalamavka formation (Late Miocene, Ierapetra Basin, Eastern Crete)

2016 ◽  
Vol 47 (1) ◽  
pp. 102
Author(s):  
H. Drinia ◽  
A. Antonarakou ◽  
M. A. Louvari
Keyword(s):  
Organic Matter ◽  
Quantitative Assessment ◽  
Bottom Water ◽  
Depositional Environment ◽  
Depth Interval ◽  
Foraminiferal Record ◽  
Water Depths ◽  
Foraminiferal Biostratigraphy ◽  
Planktonic Species

This work involves a preliminary quantitative analysis of benthic foraminifera for the purpose of the determination of palaeoenvironmental parameters (oxygenation, palaeobathymetry) of the depositional environment of the lower part of the typical section of Kalamavka Formation, in Ierapetra Basin, eastern Crete. The sediments of the studied section contain a rich foraminiferal fauna, mainly dominated by planktonic species. High resolution planktonic foraminiferal record reveals the presence of N. atlantica praeatlantica, N. acostaensis, P. siakensis suggesting an early Tortonian chronostratigraphic age. The quantitative assessment of palaeodepth, suggests deposition at middle shelf to bathyal water depths with moderate organic matter fluxes and elevated oxygen contents of the bottom water, typical for this water depth interval.

scholarly journals Evaluation of fine aggregates from the Budhi Gandaki-Narayani River, central Nepal for mortar and concrete

2019 ◽  
Vol 58 ◽  
pp. 69-81
Author(s):  
Ajay Babu Nayaju ◽  
Naresh Kazi Tamrakar
Keyword(s):  
Organic Matter ◽  
Construction Materials ◽  
Compositional Analysis ◽  
Dry Density ◽  
Fine Aggregate ◽  
Hydro Power ◽  
Fine Sediments ◽  
Rock Fragments ◽  
Fine Aggregates ◽  
Lesser Himalayas

Huge amounts of construction materials are required to fulfill construction works, which are being undertaken by local and Government levels. In this regard, searching for good quality construction materials is a tough job. The Budhi Gandaki-Narayani River is rich in carrying natural fine aggregates from the Higher and the Lesser Himalayas, which are extensively exposed along its bank. Currently ongoing and future hydro power projects, will require a tremendous amount of fine aggregates. In light of this, the present study was made to evaluate fine aggregates of the Budhi Gandaki-Narayani River. The gradation curves of fine aggregates from this river varied from well graded to uniform graded. Compositional analysis shows that quartz is dominant over other minerals. Rock fragments are composed of gneiss, schist, quartzite, metasandstone, phyllite, shale, granite, etc. Deleterious materials excluding organic matter range from 0.3 % to 1.5 % and organic matter present in range from 0.57 % to 1.11 %. The trend of presence of inorganic deleterious material and organic matter is increasing towards southern segments of the river, but they remain below 2%. Mean roundness of particles ranges from 1.88 to 2.54. Bulk dry density of fine aggregate is below 2 gm/cm³. Similarly, the specific gravity ranges between 1.49 and 1.79. Fineness modulus ranges between 1.36 and 3.50 showing that, coarse, medium, fine and very fine sediments are distributed along the stretch of river. Water absorption value of fine aggregate ranges from 0.48 % to 2.87 %. When using fine aggregates from southern segments of the Budhi Gandaki-Narayani River, reduction of mica and beneficiation process will enhance and provide better result for smooth plastering, rendering and screeding.

Depositional and geotectonic history of the Gala area, eastern Southern Uplands, Scotland

1993 ◽  
Vol 84 (2) ◽  
pp. 161-173 ◽  
Author(s):  
A. M. Kassi ◽  
J. A. Weir
Keyword(s):  
Late Stage ◽  
Large Scale ◽  
Strike Slip ◽  
Upper Ordovician ◽  
Volcanic Arc ◽  
History Of ◽  
Back Arc

AbstractThe Ordovician and Silurian successions between Falahill and Galashiels encompass six flysch-dominated formations: the Upper Ordovician Portpatrick and Shinnel Formations representing the Leadhills Group, the Llandovery Mindork, Garheugh, and Buckholm Formations together comprising the Gala Group, and a formation indeterminate of age within the Hawick Group. Southward ensialic andesitic volcanic arc and northward low- to medium-grade sialic sources contributed sediment, whilst ophiolitic and subduction-related sources made minor contributions. Deposition took place firstly, in a SE-migrating back-arc basin bordering the northerly source, the Laurentian continent. Subsequent NW-directed underthrusting led to formation out of the back-arc basin of an imbricate thrust stack which migrated southeastwards. Ultimately a foreland successor basin formed ahead of the rising thrust stack.Flysch units are typically associated with linear outcrops of Moffat Shales which are the loci of major steep SE-translating reverse faults, two of which participate in a late-stage sinistral strike–slip duplex with large-scale imbrication. The faults divide the succession into a sequence of tectonostratigraphic blocks, successively younger to the SE. At least six of the ten blocks customarily recognised in the Southern Uplands, Blocks 3–8, are represented, some of which coincide with single or complete formations.

Grain-size trends and provenance of southwestern Gulf of Mexico beach sands

1995 ◽  
Vol 32 (12) ◽  
pp. 2009-2014 ◽  
Author(s):  
Arturo Carranza-Edwards ◽  
Leticia Rosales-Hoz
Keyword(s):  
Gulf Of Mexico ◽  
Source Region ◽  
Volcanic Rocks ◽  
Breaking Waves ◽  
High Energy ◽  
Rock Fragment ◽  
Triangular Diagram ◽  
Quartz Content ◽  
Rock Fragments ◽  
Beach Sands

Sand samples from 30 beach locations of the southwestern Gulf of Mexico littoral zone were texturally and mineralogically investigated. Based on their source lithology and fluvial network, they were subdivided into two groups: (1) sands with volcanic rocks in the source region and (2) sands with a nonvolcanic source. Sands from foreshore and backshore areas exhibit similar textural characteristics, with less rock fragments than those from the inshore zone, where the high energy of breaking waves and littoral currents is present. A quartz–feldspar–rock fragment triangular diagram indicates that the proximity of volcanic sources is responsible for the enrichment of rock fragment content in the beach sands. Beach sands associated with Tampico and Veracruz embayments have greater quartz content, caused by a greater transport distance. Mineralogical maturity and provenance indexes used in a binary diagram are helpful in discriminating sand samples from volcanic and nonvolcanic domains.

scholarly journals Relationship between Organic Geochemistry and Reservoir Characteristics of the Wufeng-Longmaxi Formation Shale in Southeastern Chongqing, SW China

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6716
Author(s):  
Shengxiu Wang ◽  
Jia Wang ◽  
Yuelei Zhang ◽  
Dahua Li ◽  
Weiwei Jiao ◽  
...  
Keyword(s):  
Organic Matter ◽  
Specific Surface ◽  
Adsorption Capacity ◽  
Surface Area ◽  
Clay Mineral ◽  
Shale Gas ◽  
Mineral Content ◽  
Organic Geochemistry ◽  
Quartz Content ◽  
Longmaxi Formation

Shale gas accumulates in reservoirs that have favorable characteristics and associated organic geochemistry. The Wufeng-Longmaxi formation of Well Yucan-6 in Southeast Chongqing, SW China was used as a representative example to analyze the organic geochemical and reservoir characteristics of various shale intervals. Total organic carbon (TOC), vitrinite reflectance (Ro), rock pyrolysis, scanning electron microscopy (SEM), and nitrogen adsorption analyses were conducted, and a vertical coupling variation law was established. Results showed the following: the Wufeng-Longmaxi formation shale contains kerogen types I and II2; the average TOC value at the bottom of the formation is 3.04% (and the average value overall is 0.78%); the average Ro value is 1.94%; the organic matter is in a post mature thermal evolutionary stage; the shale minerals are mainly quartz and clay; and the pores are mainly intergranular, intragranular dissolved pores, organic matter pores and micro fractures. In addition, the average specific surface area (BET) of the shale is 5.171 m2/g; micropores account for 4.46% of the total volume; the specific surface area reaches 14.6%; and mesopores and macropores are the main pore spaces. There is a positive correlation between TOC and the quartz content of Wufeng-Longmaxi shale, and porosity is positively correlated with the clay mineral content. It is known that organic pores and the specific area develop more favorably when the clay mineral content is higher because the adsorption capacity is enhanced. In addition, as shale with a high clay mineral content and high TOC content promotes the formation of a large number of nanopores, it has a strong adsorption capacity. Therefore, the most favorable interval for shale gas exploration and development in this well is the shale that has a high TOC content, high clay mineral content, and a suitable quartz content. The findings of this study can help to better identify shale reservoirs and predict the sweet point in shale gas exploration and development.

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