Lacustrine mixed siliciclastic-carbonate sedimentary rocks in Paleogene Funing Formation of the Subei Basin, eastern China: characteristics and origin

2020 ◽  
pp. 1-50
Author(s):  
Wei Li ◽  
Xiaomin Zhu ◽  
Qidong Liu ◽  
Shifa Zhu ◽  
Heyong Li
Keyword(s):  
Eastern China ◽  
Petroleum Exploration ◽  
Gravity Flow ◽  
Geochemical Data ◽  
Small Scale ◽  
Carbonate Sediments ◽  
Sedimentary Characteristics ◽  
Section Data ◽  
Dominant Component ◽  
Mixed Sediments

The study of sedimentary characteristics and genetic mechanism of the mixed siliciclastic-carbonate sediments (MSCSs) is not only the focus of sedimentary geology, but also the important issue in petroleum exploration and development. We discover the lacustrine MSCSs, both the interstratified siliciclastic-carbonate sediments and the textural mixture of siliciclastic and carbonate materials (s-MSCSs) in the second member of Paleogene Funing Formation (E1f2) in Gaoyou and Jinhu sags, Subei Basin, eastern China. We use core, mud-log and thin section data to clarify the E1f2 s-MSCSs into 5 types, and we also use geochemical data of the E1f2 mudstone including XRD whole rock, XRD clay and trace elements to quantitatively analyze lake paleosalinity. The E1f2 s-MSCSs mainly consist of siliciclasts, ooids, intraclasts and mud, could be siliciclasts-dominated, allochems-dominated or without dominant component. We analyze that mixed sediments occur under either traction flow or gravity flow. The s-MSCSs of traction flow origin develop small-scale wavy cross-bedding and consist of siliciclasts and ooids of similar size; the s-MSCSs of gravity flow origin develop massive

Sedimentary characteristics and genetic mechanisms of high-quality reservoirs in a mixed siliciclastic-carbonate system in the Qinhuangdao area, Bohai Sea, China

2020 ◽  
Vol 8 (2) ◽  
pp. SF95-SF111
Author(s):  
Yongan Xue ◽  
Chengmin Niu ◽  
Wei Xu ◽  
Xiaojun Pang ◽  
Li Zhang
Keyword(s):  
Bohai Sea ◽  
Genetic Model ◽  
Thermal Evolution ◽  
Critical Factor ◽  
Carbonate Sediments ◽  
High Quality ◽  
Mixing Processes ◽  
Sedimentary Characteristics ◽  
Shahejie Formation ◽  
Mixed Sediments

Mixed siliciclastic-carbonate sediments occur broadly in modern and ancient systems. Studies on mixing processes began in shallow shelf environments; however, the genetic model of marine mixed sediments is difficult to apply to continental rift basins due to the complex palaeogeographic environment. We identified three mixing types in the first and second members of the Palaeogene Shahejie Formation (E2s1–2) in the Qinhuangdao area of the Bohai Sea: (1) mixed fan delta, (2) retrogradation mixed sheet, and (3) mixed sheet without siliciclastic influx. Tectonic stability, arid climate, and saline lakes are prerequisite conditions for the development of mixed sediments, whereas the palaeogeomorphologic unit should be the critical factor. We also concluded that the primary sedimentary material contains near-source coarse terrestrial debris, and the advantageous lithologic facies producing biological components are the foundation for high-quality mixed reservoirs, which are characterized by thick layers and favorable porosities and permeabilities. The micritic coatings and early dolomitization against the background of a saline lake environment favored the preservation of primary pores, whereas the leaching by atmospheric water and organic acid erosion during thermal evolution of the source rock created many secondary pores. In addition, hydrocarbon charging protected the reservoir space from carbonate cementation.

Dissolution and recrystallization in modern shelf carbonates: evidence from pore water and solid phase chemistry

1993 ◽  
Vol 344 (1670) ◽  
pp. 27-36 ◽  
Keyword(s):  
Organic Matter ◽  
Pore Water ◽  
Solid Phase ◽  
Chemical Exchange ◽  
Isotope Composition ◽  
Geochemical Data ◽  
Carbonate Sediments ◽  
Pore Waters ◽  
Carbonate Minerals ◽  
Carbonate Production

We present an overview of geochemical data from pore waters and solid phases that clarify earliest diagenetic processes affecting modern, shallow marine carbonate sediments. Acids produced by organic matter decomposition react rapidly with metastable carbonate minerals in pore waters to produce extensive syndepositional dissolution and recrystallization. Stoichiometric relations among pore water solutes suggest that dissolution is related to oxidation of H 2 S which can accumulate in these low-Fe sediments. Sulphide oxidation likely occurs by enhanced diffusion of O 2 mediated by sulphide-oxidizing bacteria which colonize oxic/anoxic interfaces invaginating these intensely bioturbated sediments. Buffering of pore water stable isotopic compositions towards values of bulk sediment and rapid 45 Ca exchange rates during sediment incubations demonstrate that carbonate recrystallization is a significant process. Comparison of average biogenic carbonate production rates with estimated rates of dissolution and recrystallization suggests that over half the gross production is dissolved and/or recrystallized. Thus isotopic and elemental composition of carbonate minerals can experience significant alteration during earliest burial driven by chemical exchange among carbonate minerals and decomposing organic matter. Temporal shifts in palaeo-ocean carbon isotope composition inferred from bulk-rocks may be seriously compromised by facies-dependent differences in dissolution and recrystallization rates.

Rhombic Calcite Microcrystals as a Textural Proxy for Meteoric Diagenesis

2021 ◽  
Author(s):  
Mohammed S. Hashim ◽  
Stephen E. Kaczmarek
Keyword(s):  
Trace Elements ◽  
Laboratory Experiments ◽  
Geochemical Data ◽  
Carbonate Sediments ◽  
Geochemical Evidence ◽  
Meteoric Diagenesis ◽  
Rock Record ◽  
High Supersaturation

Abstract Numerous Phanerozoic limestones are characterized by diagenetic calcite microcrystals formed during mineralogical stabilization of metastable carbonate sediments in various diagenetic environments. Laboratory experiments show that calcite precipitating under conditions similar to those that characterize meteoric settings (impurity-free, low supersaturation, high fluid:solid ratio) exhibits the rhombic form, whereas calcite precipitating under conditions similar to those that prevail in marine burial settings (impurity-rich, high supersaturation, low fluid:solid ratio) exhibits non-rhombic forms. This prediction is tested here using new and previously published textural and geochemical data from the rock record. These data show that the vast majority of Phanerozoic limestones characterized by rhombic microcrystals also exhibit petrographic and/or geochemical evidence (depleted 𝛿13C, 𝛿18O, and trace elements) indicative of meteoric diagenesis. In contrast, non-rhombic forms are associated with marine burial conditions, suggesting that rhombic calcite microcrystals may provide a valuable textural proxy for meteoric diagenesis in Phanerozoic limestones.

scholarly journals Rhombic calcite microcrystals as a textural proxy for meteoric diagenesis

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Mohammed S. Hashim ◽  
Stephen E. Kaczmarek
Keyword(s):  
Trace Elements ◽  
Laboratory Experiments ◽  
Crystal Form ◽  
Geochemical Data ◽  
Carbonate Sediments ◽  
Geochemical Evidence ◽  
Meteoric Diagenesis ◽  
Low Degree ◽  
Rock Record ◽  
High Degree

AbstractNumerous Phanerozoic limestones are comprised of diagenetic calcite microcrystals formed during mineralogical stabilization of metastable carbonate sediments. Previous laboratory experiments show that calcite microcrystals crystallizing under conditions similar to those that characterize meteoric diagenetic settings (impurity-free, low degree of supersaturation, high fluid:solid ratio) exhibit the rhombic form/morphology, whereas calcite microcrystals crystallizing under conditions similar to those that prevail in marine and marine burial diagenetic settings (impurity-rich, high degree of supersaturation, low fluid:solid ratio) exhibit non-rhombic forms. Based on these experimental observations, it is proposed here that rhombic calcite microcrystals form exclusively in meteoric environments. This hypothesis is tested using new and previously published textural and geochemical data from the rock record. These data show that the vast majority of Phanerozoic limestones characterized by rhombic microcrystals also exhibit petrographic and/or geochemical evidence (depleted δ13C, δ18O, and trace elements) indicative of meteoric diagenesis whereas non-rhombic forms are associated with marine burial conditions. By linking calcite microcrystal textures to specific diagenetic environments, our observations bring clarity to the conditions under which the various microcrystal textures form. Furthermore, the hypothesis that rhombic calcite microcrystals form exclusively in meteoric environments implies that this crystal form may be a useful textural proxy for meteoric diagenesis.

scholarly journals Reservoir Characteristics of Buried-hill Draping Zone in L Oilfield, Offshore China

2021 ◽  
Vol 10 (2) ◽  
pp. 33
Author(s):  
Yujuan Liu ◽  
Qianping Zhang ◽  
Bin Zheng ◽  
Jing Zhang ◽  
Zhaozhao Qu
Keyword(s):  
Seismic Data ◽  
Eastern China ◽  
Seismic Facies ◽  
Bohai Bay ◽  
Bohai Bay Basin ◽  
Sedimentary Characteristics ◽  
Reservoir Characteristics ◽  
Production Practices ◽  
Buried Hill ◽  
Different Parts

The reservoir in different parts of buried-hill draping zone is often quite different, so it is of great significance to clarify the reservoir characteristics for exploration and development. Based on core, well logging, seismic data and production data, reservoir characteristics of oil layer Ⅱ in the lower second member of Dongying Formation of L oilfield, Bohai Bay Basin, offshore eastern China are systematically studied. Analyses of seismic facies, well-seismic combination, paleogeomorphology, and sedimentary characteristics are carried out. Sediment source supply, lake level and buried hill basement geomorphology all contribute to reservoir quality. The research suggests that the different parts of buried-hill draping zone can be divided into four types. Reservoir thickness and physical properties vary. The area where the provenance direction is consistent with the ancient valley direction is a favorable location for the development of high-quality reservoirs. Under the guidance of the results, oilfield production practices in L oilfield offshore China are successful. Knowledge gained from study of L oilfield has application to the development of other similar fields.

The relationship between source supply and mixed deposition of siliciclastic and carbonate: First to second member of the Shahejie Formation, Paleogene, Bohai Sea area, China

2021 ◽  
pp. 1-28
Author(s):  
Wei Xu ◽  
Zhengyu Li ◽  
Huiyong Li ◽  
Can Zhang ◽  
Meng Zhao ◽  
...  
Keyword(s):  
Large Scale ◽  
Bohai Sea ◽  
Source Area ◽  
Carbonate Sediments ◽  
Fine Grained ◽  
Strong Source ◽  
Shahejie Formation ◽  
Mixed Sediments ◽  
Sea Area ◽  
Buried Hill

There are various types of mixed siliciclastic-carbonate sediments developed in the Bohai Sea area during the period of the first to second member of the Shahejie Formation (E2s1-2) of the Paleocene. We have concluded that the period of E2s1-2 was very suitable for the development of carbonate minerals and organisms because of the stable tectonic background, the weak siliciclastic influence of large source systems outside the basin, and the high salinity of the water. There were many local uplifts inside the basin during E2s1-2, and the source area, supply direction, and quantity of the local provenance varied greatly. We summarized that the mixed sediments generally developed in the intermittent and stagnant periods of the source supply, or on the flank or distal end of the source supply direction due to the absence of direct interference of terrigenous clasts. To a large extent, the formation of different types of mixed deposits is controlled by the different spatiotemporal relationship with siliciclastic supply. The background of strong source supply led to the formation of large-scale mixed deposits that were mainly composed of terrigenous clasts. Mixed deposits are mainly composed of organisms and carbonate with relatively large depositional thickness formed on the flank of source supply in the steep slope area. On the flank of source supply in the gentle slope belt, thinner mixed deposits with terrigenous clasts mainly formed and thin-layer carbonate clastic-dominated deposits formed on abandoned deltas. On the uplift of the buried hill far away from the provenance, thick mixed deposits mainly composed of bioclastic were formed whereas fine-grained mixed deposits formed under the low-energy argillaceous background.

scholarly journals Distinguishing between Deep-Water Sediment Facies: Turbidites, Contourites and Hemipelagites

Geosciences ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 68 ◽  
Author(s):  
Dorrik Stow ◽  
Zeinab Smillie
Keyword(s):  
Deep Water ◽  
Large Scale ◽  
Tectonic Setting ◽  
Regional Scale ◽  
Small Scale ◽  
Physical Parameters ◽  
Sedimentary Characteristics ◽  
Natural Systems ◽  
Facies Types ◽  
Water Facies

The distinction between turbidites, contourites and hemipelagites in modern and ancient deep-water systems has long been a matter of controversy. This is partly because the processes themselves show a degree of overlap as part of a continuum, so that the deposit characteristics also overlap. In addition, the three facies types commonly occur within interbedded sequences of continental margin deposits. The nature of these end-member processes and their physical parameters are becoming much better known and are summarised here briefly. Good progress has also been made over the past decade in recognising differences between end-member facies in terms of their sedimentary structures, facies sequences, ichnofacies, sediment textures, composition and microfabric. These characteristics are summarised here in terms of standard facies models and the variations from these models that are typically encountered in natural systems. Nevertheless, it must be acknowledged that clear distinction is not always possible on the basis of sedimentary characteristics alone, and that uncertainties should be highlighted in any interpretation. A three-scale approach to distinction for all deep-water facies types should be attempted wherever possible, including large-scale (oceanographic and tectonic setting), regional-scale (architecture and association) and small-scale (sediment facies) observations.

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