22 results on '"Lishui Sag"'
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2. Paleoclimatic and paleoenvironmental constraints on organic matter enrichment in the Paleocene strata in the Lishui Sag, East China Sea Shelf Basin.
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Shiyan Yin, Chuang Lei, Jiaren Ye, Jingfu Wu, Yu Wang, Ying Zhang, and Xiaoying Han
- Abstract
Using major and trace element analyses, this study investigated the impacts of paleoclimatic and paleoenvironmental variations on organic matter enrichment in the Paleocene Yueguifeng, Lingfeng, and Mingyuefeng formations in the Lishui Sag, East China Sea Shelf Basin. Multiple geochemical proxies suggest that during the deposition of the three formations, the paleoclimate evolved from a humid climate to an arid and then back to humid conditions, the paleosalinity conditions underwent brackish, saline, and fresh water sequentially, and the paleowater conditions shifted from relatively deep water to relatively shallow water and then to shallow water. Accordingly, the water column evolved from reducing to oxidizing and then to weakly oxidizing to oxidizing conditions. Organic matter productivity, as well as the preservation or degradation of organic matter, was controlled by covariation in the paleoclimatic and paleoenvironmental conditions. This can account for the difference in organic matter enrichment in the mudstones of the three formations. The mudstones in the Yueguifeng Formation were deposited in a semi-deep- to deep-water lacustrine environment with high primary productivity in a warm, humid climate. Numerous planktonic algae were efficiently preserved in stratified and dysoxic water columns, resulting in high organic matter enrichment in this formation. The mudstones in the Lingfeng Formation were formed in a shallow marine environment with low primary productivity in an arid climate. The combined effects of high salinity and oxygen-enriched conditions in the water bodies were unfavorable for the reproduction and preservation of planktonic algae, resulting in low organic matter enrichment. For the Mingyuefeng Formation, the slow tectonic subsidence and flat topography during the deposition of this formation led to the development of a swamp environment in a warm, humid climate. The swamp environment was characterized by an oxic water column, low aquatic organic matter input, and high terrigenous organic matter input. The Yueguifeng Formation has greater hydrocarbon-generating potential than the Lingfeng and Mingyuefeng formations. Constructing the developmental models of organic-rich mudstones based on the covariation in the paleoclimatic and paleoenvironmental conditions represents a valid method for understanding the hydrocarbon-generating potential of these source rocks. [ABSTRACT FROM AUTHOR] more...
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- 2025
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3. Tectono-stratigraphic evolution in the Paleocene Lishui Sag, East China Sea Shelf Basin.
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Zhu, Z., Qi, L., Chen, H., Li, J., Zhang, Y., Qin, J., Zhao, Y., and Ni, C.
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PALEOCENE Epoch , *SEQUENCE stratigraphy , *FAULT zones , *RIFTS (Geology) , *SPATIAL variation , *SEDIMENTARY basins - Abstract
The tectonic evolution of the Lishui Sag in the East China Sea Shelf Basin significantly influences its sequence stratigraphy. By integrating seismic reflections, well logs and core data, this study examines the quantitative activity of the Lingfeng fault, sequence framework and sequence architecture in the Lishui Sag. The Paleocene succession is divided into one second-order sequence (SSQ1), three third-order sequences (SQ1–SQ3) and nine system tracts, representing a complete syn-rift evolution consisting of initial syn-rift, rift climax and late syn-rift stages. The results indicate that the differential activity of the Lingfeng fault shapes the basin structure and controls the subsidence centre, leading to prominent variations in the spatial distribution and filling of the sequence stratigraphy during different tectonic stages. The initial syn-rift sequence (SQ1), characterised by a low activity of the segmented Lingfeng fault, is primarily found in isolated small sub-sags. The rift climax sequence (SQ2), with increasing displacement and longer segmented fault zones, exhibits a wedge-shaped filling pattern with substantial topographic elevation differences. The late syn-rift sequence (SQ3) shows a gradual decrease in tectonic activity and uniform filling, with all system tracts within the sequences fully developed. The sequence architecture of the hanging wall in the Lishui Sag can be classified into fault-scarp and fault-slope type, whereas the sequence architecture of the hanging wall dip-slope can be classified into sedimentary slope-break and faulted slope-break. The Lingfeng fault controlled the tectonic evolution, sedimentary subsidence centre and sequence filling and architecture in the Paleocene rifted Lishui Sag. The Paleocene succession is divided into one second-order sequence (SSQ1), three third-order sequences (SQ1–SQ3) and nine system tracts, representing a complete syn-rift evolution consisting of initial syn-rift, rift climax and late syn-rift stages. The sequence architecture of the hangingwall can be classified into fault-scarp and fault-slope type, and hanging wall dip-slope sequence architecture can be divided into sedimentary slope-break and faulted slope-break types. [ABSTRACT FROM AUTHOR] more...
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- 2024
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4. Early Cenozoic paleontological assemblages and provenance evolution of the Lishui Sag, East China Sea.
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Zhang, Yingzhao, Jiang, Yiming, Liu, Zhenghua, Li, Shuai, Li, Ning, Liu, Jinshui, Qiao, Peijun, Zhong, Kai, Chen, Shuhui, and Goh, Thian Lai
- Abstract
The East China Sea Shelf Basin generated a series of back-arc basins with thick successions of marine- and terrestrial-facies sediments during Cenozoic. It is enriched with abundant oil and gas resources and is of great significance to the petroleum exploration undertakings. Therein, the Lishui Sag formed fan delta, fluvial delta and littoral-to-neritic facies sediments during Paleocene—Eocene, and the research on its sedimentary environment and sediment source was controversial. This study analyzed the paleontological combination characteristics, and conducted a source-to-sink comparative analysis to restore the sedimentary environment and provenance evolution of the Lishui Sag during Paleocene—Eocene based on the integration of detrital zircon U-Pb age spectra patterns with paleontological assemblages. The results indicated that Lishui Sag was dominated by littoral and neritic-facies environment during time corroborated by large abundance of foraminifera, calcareous nannofossils and dinoflagellates. Chronological analysis of detrital zircon U-Pb revealed that there were significant differences in sediment sources between the east and west area of the Lishui Sag. The western area was featured by deeper water depths in the Paleocene—Eocene, and the sediment was characterized by a single Yanshanian peak of zircon U-Pb age spectra, and mainly influenced from Yanshanian magmatic rocks of South China Coast and the surrounding paleo-uplifts. However, its eastern area partly showed Indosinian populations. In particular, the upper Eocene Wenzhou sediments were featured by increasingly plentiful Precambrian zircons in addition to the large Indosinian-Yanshanian peaks, indicating a possible impact from the Yushan Low Uplift to the east. Therefore, it is likely that the eastern Lishui Sag generated large river systems as well as deltas during time. Due to the Yuquan Movement, the Lishui Sag experienced uplifting and exhumation in the late stage of the late Eocene and was not deposited with sediments until Miocene. Featured by transitional-facies depositions of Paleocene—Eocene, the Lishui Sag thus beared significant potential for source rock and oil-gas reservoir accumulation. [ABSTRACT FROM AUTHOR] more...
- Published
- 2023
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5. Impact of Terrigenous Organic Matter Input on Organic Matter Enrichment of Paleocene Source Rocks, Lishui Sag, East China Sea.
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Han, Xu, Hou, Dujie, Cheng, Xiong, and Li, Yan
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ORGANIC compounds , *PALEOCENE Epoch - Abstract
To clarify the organic matter (OM) enrichment of the Lishui Sag, the factors influencing the variable abundance of OM in the Lingfeng Formation are studied using organic geochemical data. The source rocks of the Lingfeng Formation have medium–high total organic carbon (TOC) values (0.53–3.56%). The main type of kerogen is II2-III. Compared to the shallow marine subfacies source rocks, the TOC of the delta front subfacies source rocks is higher. The distribution of biomarkers shows that the redox environment of the delta front subfacies source rock is the sub-oxidizing and oxic environment, and the source rock is mainly supplied by terrigenous higher plants; the redox environment of shallow marine subfacies source rocks is a sub-reducing and suboxic environment, and the OM mainly comes from algae. The link between OM input and OM abundance demonstrates that terrigenous OM (TOM) input has a considerable influence on OM abundance. However, there is no obvious relationship between preservation and OM abundance, which suggests that preservation is not the determining element in OM enrichment. The strong sediment flux decreases the amount of time that OM is exposed to oxygen. As a result, delta front subfacies with large TOM input have a huge number of excellent source rocks. This paper proposes a "delta front-OM input model" for excellent source rocks. [ABSTRACT FROM AUTHOR] more...
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- 2023
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6. Model-data-driven seismic inversion method based on small sample data.
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LIU, Jinshui, SUN, Yuhang, and LIU, Yang
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- 2022
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7. Geochemical Characteristics and Environmental Implications of Trace Elements of the Paleocene in the West Lishui Sag, East China Sea Basin.
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Yang, Shuai, Fu, Qiang, Liu, Jinshui, Ma, Wenrui, Yang, Bing, Zhu, Zhiwei, and Teng, Wen
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PALEOCENE Epoch , *OXYGEN isotopes , *CARBON isotopes , *SEDIMENTARY structures , *TRACE elements , *DRILL core analysis - Abstract
Analysis of the sedimentary environment during the clastic formation process is of great significance for reservoir evaluation and desert prediction. This paper focused on the Paleocene in the West Lishui Sag, East China Sea Basin. XRF fluorescence diffraction and carbon and oxygen isotope tests were carried out on core samples from four wells. Based on the geochemical characteristics of the samples and the changes in the elemental ratios, combined with the lithologic characteristics and sedimentary structure of the samples, the paleoclimate, paleosalinity, paleobathymetric, paleoredox, paleotemperature, and other paleoenvironmental characteristics were analyzed. The results show that the characteristics of major and trace elements were similar in the lower Mingyuefeng Formation (E1m2), Upper Lingfeng Formation (E1l1), Lower Lingfing Formation (E1l2), and Yueguifeng Formation (E1y). The Paleocene in the West Lishui Sag was mainly in the reducing environment of brackish-salt water with weak water stratification. The water depth showed a trend of becoming deeper, then shallower, and then deeper. The paleoclimate in the West Lishui Sag was warm on the whole. However, the content of Sr became smaller after later deposition, so the calculated paleowater temperature was higher. In addition, oxygen isotopes were affected by diagenesis, resulting in a negative oxygen isotope value. The paleoproductivity was low, and the hydrocarbon generation potential was poor. The content of nutrient elements mainly came from terrigenous input rather than biological origin, and terrigenous intrusion characteristics gradually increased from E1y to E1m2. The study also shows that paleoproductivity was affected by the paleoclimate and paleowater depth. Warm and humid climate and deep water body were conducive to the accumulation of paleoproductivity. [ABSTRACT FROM AUTHOR] more...
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- 2022
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8. Paleosalinity Reconstruction for the Paleocene Sequence of Lishui Sag in the East China Sea Shelf Basin.
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Sun, Long, Zhang, Jinliang, Zhang, Tianya, Yan, Xue, Chen, Tao, and Liu, Jinshui
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PALEOCENE Epoch , *BRACKISH waters , *PETROLEUM prospecting , *NATURAL gas prospecting , *FRESH water , *PROVENANCE (Geology) - Abstract
The Lishui Sag on the southwest margin of the East China Sea Shelf Basin (ECSSB) is a relatively new oil and gas exploration area, with the Paleocene being one of the most potential oil-bearing intervals in the sag. In this study, combined with the principles of element geochemistry and mineralogy, the salinity characteristics of the paleowater body are reconstructed and discussed using the Sr/Ba ratio, B/Ga ratio, equivalent boron content and Couch's method. The results show that (1) the highest salinity indicated by Sr/Ba and B/Ga ratios appears in the Upper Lingfeng Formation; (2) the equivalent boron content ranges from 62 to 254 ppm, with an average of 122 ppm, showing the existence of fresh water and brackish deposition settings; and (3) the paleosalinity calculated quantitatively by Couch's method is between 4.9 and 13.1‰. To ensure the reliability of the study, paleosalinity results from the different methods are cross-plotted, and the effects of provenance and diagenesis on the paleosalinity analysis are negligible. The comparison results show that Couch's method, equivalent boron content and B/Ga ratio are more reliable among all paleosalimeters. The identified paleosalinity type of paleowater body is mainly brackish water, which is exactly mesohaline water. The paleosalinity of the Paleocene stratigraphic interval in Lishui Sag is consistent with the sedimentary facies distribution. Our comprehensive comparison provides a basis for inferring the source of fresh water, the genesis of transitional water bodies and the evolution of sedimentary facies. [ABSTRACT FROM AUTHOR] more...
- Published
- 2022
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9. Comparison of the Pore Structure of Ultralow-Permeability Reservoirs Between the East and West Subsags of the Lishui Sag Using Constant-Rate Mercury Injection.
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Wang, Jinkai, Zhang, Jinliang, Shen, Wenlong, and Liu, Hengyi
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In this study, the differences in reservoir parameters, such as pore radius, throat radius, and pore-throat ratio, between the east and west subsags of the Lishui Sag are analyzed by using data obtained from a constant-rate mercury injection experiment. Furthermore, the quality of the reservoirs in the two subsags is systematically evaluated. Results show that the throat radius of the Lishui west subsag is larger than that of the east subsag, and this parameter has a positive correlation with reservoir quality. However, the pore-throat ratio of the east subsag is larger than that of the west subsag, which has an inverse relationship with reservoir quality. The main reasons for this reservoir difference can be attributed to sedimentation and diagenesis. The sedimentary facies types of the Lishui east subsag are the fan delta, shore lake, shallow lake, and shore shallow lake; their sandstone composition maturity is low; the clay mineral content is high; and the rock has undergone strong diagenesis. Therefore, the physical conditions of the reservoir are poor. However, the sandstones in the Lishui west subsag have weak cementation and compaction, mainly with an intergranular pore structure type, which leads to good connectivity between pores. Therefore, the storage performance and seepage capacity of the Lishui west subsag are better than those of the east subsag; the west subsag is the main area of oil and gas accumulation, as confirmed in the process of exploration and development. [ABSTRACT FROM AUTHOR] more...
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- 2021
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10. Base level changes based on Basin Filling Modelling: a case study from the Paleocene Lishui Sag, East China Sea Basin.
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Li, Jing-Zhe, Liu, Pi-Yang, Zhang, Jin-Liang, Sun, Shu-Yu, Sun, Zhi-Feng, Du, Dong-Xing, and Zhang, Ming
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BURGERS' equation , *CASE studies , *SEQUENCE stratigraphy , *SEAS , *GEOLOGISTS - Abstract
Estimation of base level changes in geological records is an important topic for petroleum geologists. Taking the Paleocene Upper Lingfeng Member of Lishui Sag as an example, this paper conducted a base level reconstruction based on Basin Filling Modelling (BFM). The reconstruction was processed on the ground of a previously interpreted seismic stratigraphic framework with several assumptions and simplification. The BFM is implemented with a nonlinear diffusion equation solver written in R coding that excels in shallow marine stratigraphic simulation. The modeled results fit the original stratigraphy very well. The BFM is a powerful tool for reconstructing the base level, and is an effective way to check the reasonableness of previous interpretations. Although simulation solutions may not be unique, the BFM still provides us a chance to gain some insights into the mechanism and dynamic details of the stratigraphy of sedimentary basins. [ABSTRACT FROM AUTHOR] more...
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- 2020
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11. Recovery of the Erosion Thickness and Characterization of the Paleogeomorphology in the Southern Lishui Sag, East China Sea Shelf Basin.
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Li, Na, Zhang, Jinliang, Shen, Wenlong, Liu, Yang, Liu, Huaishan, Wang, Jinkai, and Xie, Jun
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The restoration of the denudation thickness is the basis for quantitatively analyzing the basin burial history, thermal evolution history and hydrocarbon accumulation conditions. The well data is not sufficient to do this in the southern Lishui Sag with only 5 wells, so the new, high-quality three-dimensional (3D) seismic data is essential. The methods employed to determine the eroded thicknesses of key unconformities in the study area are the mudstone acoustic time difference (AC) method, vitrinite reflectance (Ro%) method and stratigraphic trend comparison method. On the basis of the structural evolution, the restoration of the paleogeomorphology is carried out. The results show that the Wenzhou formation (E
2 w) in the entire study area has been all denuded. The denudation thickness is in the range of 0-550 m, and decreases gradually from west, thicker than 200 m, to east. The erosion of the upper Lingfeng formation (E1 1) are mainly occurred in the N-P-1 structural trap (N-P-1), the N-P-2 structural trap (N-P-2) and the N-P-3 structural trap (N-P-3). Among them, the eroded area in N-P-1 (near well S-1) and N-P-2 is 200-230km2 , and the denudation thickness is 0-600m, which increases from south to north, even up to 200-400m in the region around well S-1. In N-P-3, the extent of denudation is 30-50 km2 , and the denudation thickness is 0-400m. In the early stage of the upper E1 1, one north-south strike slip fault began to develop in the southern study area. Affected by this fault, the southern Lingfeng bulge was offset, forming a gorge, and the eastern and western sides of the concave belt connected to each other. On the basis of the paleo-geomorphological characteristics, it is shown that the sedimentary center of the west subsag began to migrate to the south. [ABSTRACT FROM AUTHOR] more...- Published
- 2020
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12. Organic geochemistry, distribution and hydrocarbon potential of source rocks in the Paleocene, Lishui Sag, East China Sea Shelf Basin.
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Li, Yang, Zhang, Jinliang, Liu, Yang, Shen, Wenlong, Chang, Xiangchun, Sun, Zhongqiang, and Xu, Guangchen
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ORGANIC geochemistry , *ROCKS , *ARTIFICIAL neural networks , *LIQUID hydrocarbons , *NATURAL gas ,POTENTIAL distribution - Abstract
The Lishui Sag, one of the most promising hydrocarbon exploration areas in the East China Sea Shelf Basin, has had no major breakthroughs after its exploration and development. Therefore, it is crucial to carry out a comprehensive assessment of this basin to illustrate the potential and distribution of source rocks in the Lishui Sag. Based on organic petrographic examinations, Rock-Eval pyrolysis, gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS) analysis, the organic geochemical characteristics and paleoenvironment of the source rocks were investigated. The results imply that the kerogen type of the source rocks in the Lishui Sag is dominated by Type III, with a small amount of Type II kerogen. Biomarkers show that the source rocks are characterized by a mixed origin of organic matter in a transitional environment. The lower Mingyuefeng (E 1 m l), lower Lingfeng (E 1 l l) and Yueguifeng (E 1 y) Formations show higher inputs of aquatic organic matter. The base limits of the total organic carbon (TOC) values of effective source rocks were determined to be 0.9 wt % in the E 1 m Formation, 1.0 wt % in the E 1 l Formation and 0.7 wt % in the E 1 y Formation. Based on an artificial neural network (ANN) model and the Δ log R method, the distribution of effective source rocks in the Lishui Sag was illustrated. Source rocks in the E 1 m l and Lingfeng (E 1 l) Formations can be expected to generate mixed liquid hydrocarbons, while samples from E 1 y Formation are oil prone source rocks with normal oil and light oil potentials. Additionally, the post mature source rocks of the E 1 y Formation may be the origin of natural gas. Upon full consideration of the potential and distribution of source rocks, the North part of the Lingfeng Uplift is the most favorable exploration zone. • A comprehensive assessment of source rocks in Lishui Sag is provided. • The base limits of the TOC values of effective source rocks are determined. • The source rocks in the Lishui Sag are characterized by a mixed origin of organic matter in a transitional environment. • The North of the Lingfeng Uplift is the most favorable exploration zone. [ABSTRACT FROM AUTHOR] more...
- Published
- 2019
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13. Tectonic-sedimentary evolution in a Palaeocene rifted Lishui Sag, East China Sea Shelf Basin.
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Zhu, Zhenjun, Li, Qi, Chen, Hehe, Li, Jian, Zhang, Yingzhao, Zhang, Weiping, Qin, Jun, Geng, Hui, and Yang, Fengfan
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RIFTS (Geology) , *SEDIMENT transport , *HEAVY minerals , *RESEARCH personnel , *STATISTICS - Abstract
Influenced by episodic tectonic activity and multiple sediment sources, the source-to-sink systems in rifted basins are relatively complex. Based on seismic data, well logging, cores, thin sections, and heavy mineral data, the growth and linkage of the Lingfeng fault were reconstructed and its influence on the sedimentary responses of the Palaeocene-rifted Lishui Sag in the East China Sea Shelf Basin was examined. The researchers conducted a fault throw-distance analysis on the Lingfeng fault and found that it displayed an overall weak-strong-weak evolutionary process. During the early syn-rift stage, the Lingfeng fault exhibited a segmented geometry consisting of seven fault segments with low fault activity along its strike, and small-scale source-to-sink systems developed in both the hanging wall dip-slope and footwall. As the main syn-rift stage progressed, strong fault activity induced large-scale exposure of the source area, resulting in a high sediment-supply rate and large-scale source-to-sink systems. During the late syn-rift stage, the fault weakened and evolved into a connected basin-boundary fault, and proximal source-to-sink systems in the footwall gradually disappeared. Semi-quantitative measurements of the geomorphic parameters of these source-to-sink systems indicated wide and shallow sediment transport pathways in hanging wall dip-slope areas (average width and depth of approximately 6.34 kmand 0.13 km, respectively) and narrow and deep sediment transport pathways in the footwall (average width and depth of approximately 3.75 km and 0.15 km, respectively). The semi-quantitative statistical analysis implies that the cross-sectional area of the transport channels was positively correlated with the corresponding fan/delta complexes in a rift basin. • The Lingfeng fault controlled the source-to-sink systems in the Palaeocene rifted Lishui Sag. • Fault activity led to tilting the hanging wall dip-slope in the syn-rift basin, which controlled the transport pathway and sediment supply. • The dimension of the sedimentary transport pathways were positive to sediment flux, providing a good approximation of source dimensions. [ABSTRACT FROM AUTHOR] more...
- Published
- 2024
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14. Petrographic and stable isotopic evidences of CO2-induced alterations in sandstones in the Lishui sag, East China Sea Basin, China.
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Zhao, Shuang, Liu, Li, and Liu, Na
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SANDSTONE , *PETROLOGY , *STABLE isotopes , *PLAGIOCLASE - Abstract
Dawsonite-bearing sandstones in the Lishui sag, East China Sea Basin, China, have been investigated as a natural occurrence for CO 2 -induced diagenesis using petrography, X-ray diffraction and stable isotopes. The sandstones are predominantly litharenite, with the order of cements growth comprising clay coatings and pyriteⅠ, siderite, pyriteⅡ, quartz overgrowths, ankerite, kaolinite and microcrystalline quartz, dawsonite and late calcite. Dawsonite, which has recently been considered as trapping mineral after massive CO 2 charging, constituted up to 7% of the whole rock volume, occurring as pore-filling clusters or replacement of detrital grains. Stable isotopic data suggest that the CO 2 in equilibrium with dawsonite and calcite display a mantle-magmatic origin and is in close proximity to those of the CO 2 gas now present in the reservoir, indicating the same origin for both. The elevated CO 2 concentrations induced by a mass influx of magmatic CO 2 into host rock was favourable for dawsonite cementation. Plagioclase was then considered as the precursor of dawsonite. K-feldspar could also serve as the aluminum source of dawsonite with an external supply of Na + in a geochemically open system. [ABSTRACT FROM AUTHOR] more...
- Published
- 2018
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15. 3D-Basin Modelling of the Lishui Sag: Research of Hydrocarbon Potential, Petroleum Generation and Migration
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Jinliang Zhang, Jiaqi Guo, Jinshui Liu, Wenlong Shen, Na Li, and Guangchen Xu
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Lishui Sag ,3D basin modelling ,model calibration ,hydrocarbon generation and migration ,Technology - Abstract
The Lishui Sag is located in the southeastern part of the Taibei Depression, in the East China Sea basin, where the sag is the major hydrocarbon accumulation zone. A three dimensional modelling approach was used to estimate the mass of petroleum generation and accumulated during the evolution of the basin. Calibration of the model, based on measured maturity (vitrinite reflectance) and borehole temperatures, took into consideration two main periods of erosion events: a late Cretaceous to early Paleocene event, and an Oligocene erosion event. The maturation histories of the main source rock formations were reconstructed and show that the peak maturities have been reached in the west central part of the basin. Our study included source rock analysis, measurement of fluid inclusion homogenization temperatures, and basin history modelling to define the source rock properties, the thermal evolution and hydrocarbon generation history, and possible hydrocarbon accumulation processes in the Lishui Sag. The study found that the main hydrocarbon source for the Lishui Sag are argillaceous source rocks in the Yueguifeng Formation. The hydrocarbon generation period lasted from 58 Ma to 32 Ma. The first period of hydrocarbon accumulation lasted from 51.8 Ma to 32 Ma, and the second period lasted from 23 Ma to the present. The accumulation zones mainly located in the structural high and lithologic-fault screened reservoir filling with the hydrocarbon migrated from the deep sag in the south west direction. more...
- Published
- 2019
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16. Geochemistry of the Paleocene Clastic Rocks in Lishui Sag, East China Sea Shelf Basin: Implications for Tectonic Background and Provenance.
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Deyong, LI, Xiaodian, JIANG, Fa, XU, Jinshui, LIU, and Guowei, HOU
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GEOCHEMISTRY , *CLASTIC rocks , *PALEOCENE Epoch , *GEOLOGICAL basins , *STRUCTURAL geology , *PETROLOGY - Abstract
The Lishui Sag, in the East China Sea Shelf Basin, is rich in hydrocarbons, with the major hydrocarbon-bearing layers being the Paleocene Mingyuefeng clastic rocks. Analysis of the implicit geologic background information of these Paleocene clastic rocks using petrological and geochemical methods has significant practical importance. These Paleocene sandstones are mainly lithic arenite, lithic arkose and greywacke, composed of K-feldspar, plagioclase, authigenic clays, silica and carbonates. As continental deposits, Yueguifeng clastic rocks have high aluminosilicate and mafic detritus contents, while the Lingfeng and Mingyuefeng Formations are rich in silica due to an oscillating coastal marine depositional environment The major element contents of these Paleocene sandstones are low and have a concentrated distribution, indicating that the geochemical composition is non-epigenetic, transformed by sedimentary processes and diagenesis. The Yueguifeng detritus comprises recycled sediments, controlled by moderate weathering and erosion, while the Lingfeng and Mingyuefeng detritus is interpreted as primarily first-cycle materials due to low chemical weathering. In the Late Cretaceous to Early Paleocene, the Pacific Plate began subducting under the Eurasian Plate, causing an orogeny by plate collision and magma eruption due to the melting of subducted oceanic crust This resulted in the dual tectonic settings of 'active margin' and 'continental island arc' in the East China Sea Shelf Basin. During the Late Paleocene, the Pacific Plate margin migrated eastward along with development of the Philippine Ocean Plate, and the tectonic setting of the Lishui Sag gradually turned into a passive continental margin. Detrital sources included both orogenic continental blocks and continental island arcs, and the parent rocks are primarily felsic volcanic rocks and granites. [ABSTRACT FROM AUTHOR] more...
- Published
- 2016
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17. Paleocene sequence stratigraphy and depositional systems in the Lishui Sag, East China Sea Shelf Basin.
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Zhang, Ming, Zhang, Jinliang, Xu, Fa, Li, Jingzhe, Liu, Jinshui, Hou, Guowei, and Zhang, Penghui
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SEQUENCE stratigraphy , *PALEOCENE Epoch , *SEDIMENTATION & deposition , *GEOLOGICAL basins - Abstract
The East China Sea Shelf Basin (ECSSB) is a typical back-arc rift basin and is divided further by a series of sags and basement ridges. The Lishui Sag on the southwest margin of the ECSSB, is underlain by a productive, gas-prone, marine Paleocene section. In combination with sequence stratigraphy and seismic geomorphology, an integrated approach was applied to map the high-frequency sequences and systems tracts of the Lower E1m (57.2–56.5 Ma) and Upper E1l strata (60–57.2 Ma) by using well, two-dimensional and three-dimensional seismic data. Our approach involves documentation of seismic stratal geometries, seismic facies and core lithofacies. Seismic truncation, offlap, onlap and downlap geometries were used for identifying two depositional sequences with four systems tracts in the Upper E1l and Lower E1m strata. Two sedimentary facies were recognized from core and log data and identified as tidal sand ridges and delta mouth bar deposits. The depositional facies were imaged from a series of strata slices obtained by 3D survey. Five types of depositional systems were recognized based on the geometry change expressed on strata slices. In stratigraphic order these are (a) incised channels on the inner shelf and subaqueous fans on the middle shelf, (b) diffuse, elongated linear tidal sand ridges on the continental shelf and turbidity flows on the slope, (c) incised valley, prograding shelf edge delta on the continental shelf and shelf edge and delta front turbidites on the slope, (d) incised valley fills, fluvial aggradation and fluvial dominated mouth bar on the continental shelf, and (e) shoreface barrier bar and sand ridges that are parallel to the shoreline. This integrated analysis provides us an opportunity to evaluate the exploration significance in the stratigraphic framework and improve the accuracy of petroleum plays prediction. [ABSTRACT FROM AUTHOR] more...
- Published
- 2015
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18. The Cenozoic structural evolution and its influences on gas accumulation in the Lishui Sag, East China Sea Shelf Basin.
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Jiang, Zhenglong, Li, Yajun, Du, Hailing, and Zhang, Yunfei
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CENOZOIC Era ,GAS wells ,GEOLOGICAL research ,HYDROCARBON analysis - Abstract
Given the natural gas pools that have been discovered at the Lishui Sag, this region has great potential as a favorable prospecting area in the East China Sea Shelf Basin, which is a gas-rich basin in China. Well and seismic data, special geological techniques, including erosion history reconstruction, balanced cross-section restoration and basin modeling, were used to reconstruct the paleostructure. The major conclusions of the Cenozoic paleostructure reconstruction in Lishui Sag included the following: The Lishui Sag experienced a multi-period burial history, including rapid subsidence in the Paleocene, a transition during the Eocene and slow subsidence in the Neogene, and uplifting and erosion in the Paleogene Oujiang and Yuquan movements. The burial history can be summarized into four evolution stages, namely, rifting, post-rifting, uplift-inversion and regional subsidence. The rapid subsidence facilitated the hydrocarbon generation, and the uplift-inversion created a lot of traps in the central uplift area and facilitated the hydrocarbon migration, and regional subsidence facilitated the preservation of accumulated hydrocarbons. [ABSTRACT FROM AUTHOR] more...
- Published
- 2015
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19. Classification and origin of natural gases from Lishui Sag, the East China Sea Basin.
- Author
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Chen, JianPing, Ge, HePing, Chen, XiaoDong, Deng, ChunPing, and Liang, DiGang
- Abstract
Natural gases discovered up to now in Lishui Sag, the East China Sea Basin, differ greatly in gaseous compositions, of which hydrocarbon gases amount to 2%–94% while non-hydrocarbon gases are dominated by CO
2 . Their hydrocarbon gases, without exception, contain less than 90% of methane and over 10% of C2 + heavier hydrocarbons, indicating a wet gas. Carbon isotopic analyses on these hydrocarbon gases showed that δ13 C1 , δ13 C2 and δ13 C3 are basically lighter than −44‰, −29‰ and −26‰, respectively. The difference in carbon isotopic values between methane and ethane is great, suggesting a biogenic oil-type gas produced by the mixed organic matter at peak generation. δ13 $$ C_{CO_2 } $$ values of nonhydrocarbon gases are all heavier than −10‰, indicating a typical abiogenic gas. The simulation experiment on hydrocarbon generation of organic matter in a closed gold-tube system showed that the proportion of methane in natural gases produced by terrigenous organic matter in the Lingfeng Formation marine deposit is obviously higher than that in natural gases derived from the aquatic and terrigenous mixed organic matter in the Yueguifeng Formation lacustrine deposit, consequently the proportion of heavier hydrocarbons of the former is remarkably lower than that of the latter. Moreover, δ13 C1 values of natural gases produced by terrigenous organic matter in the Lingfeng Formation marine deposit are about 5‰ heavier than those of natural gases derived from the aquatic and terrigenous mixed organic matter in the Yueguifeng Formation lacustrine deposit while δ13 C2 and δ13 values of the former are over 9‰ heavier than those of the latter. Currently the LS36-1 oil-gas pool is the only commercial oil-gas reservoir in Lishui Sag, where carbon isotopic compositions of various hydrocarbon components differ greatly from those of natural gases produced by the Lingfeng Formation organic matter but are very similar to those of natural gases derived from the Yueguifeng Formation organic matter, therefore, natural gases in the LS36-1 oil-gas pool are mainly derived from the Yueguifeng Formation lacustrine source rock rather than the Lingfeng Formation marine or Mingyuefeng Formation coal-measures source rocks. [ABSTRACT FROM AUTHOR]3 values of the former are over 9‰ heavier than those of the latter. Currently the LS36-1 oil-gas pool is the only commercial oil-gas reservoir in Lishui Sag, where carbon isotopic compositions of various hydrocarbon components differ greatly from those of natural gases produced by the Lingfeng Formation organic matter but are very similar to those of natural gases derived from the Yueguifeng Formation organic matter, therefore, natural gases in the LS36-1 oil-gas pool are mainly derived from the Yueguifeng Formation lacustrine source rock rather than the Lingfeng Formation marine or Mingyuefeng Formation coal-measures source rocks. [ABSTRACT FROM AUTHOR] more...- Published
- 2008
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20. Characteristics and deposition models of the paleocene source rocks in the Lishui Sag, east China sea shelf basin: Evidences from organic and inorganic geochemistry.
- Author
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Lei, Chuang, Yin, Shiyan, Ye, Jiaren, Wu, Jingfu, Wang, Zhaosheng, and Gao, Bin
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ORGANIC geochemistry , *PALEOCENE Epoch , *PETROLEUM prospecting , *CLIMATE change , *NATURAL gas prospecting , *PROSPECTING , *HYDROCARBON reservoirs - Abstract
The Lishui Sag, situated at the East China Sea Shelf Basin, is regarded as one of the most prospecting oil exploration zones. Low exploration in this region requires detailed identification of source rocks to enhance further oil and gas exploration. Three potential source rocks, including the Paleocene Yueguifeng (E 1 y), Lingfeng (E 1 l) and Mingyuefeng (E 1 m) Formations, were investigated by integrating organic and inorganic geochemistry to estimate hydrocarbon generation potential, and to document original organic matter input and deposition environments. Two deposition models for source rocks were established considering tectonic subsidence and climate variation. The result shows that the E 1 y mudstones are dominated by high TOC content, oil/gas-prone kerogen at moderate maturity stage with relatively high hydrocarbon generation potential, whereas E 1 l and E 1 m mudstones are dominated by low TOC content, gas-prone kerogen at low to moderate maturity stage with low hydrocarbon generation potential, and coals with high hydrocarbon generation potential. The original organic matter input and deposition environment are obviously different among these three potential source rocks and are controlled by the coupling of tectonic subsidence and climate variation. Insufficient material supply lead mudstone deposition in a hemi-deep/deep lake during the E 1 y period, resulting in inefficient water mixing and stable water column stratification (high Gammacerane Indexs). The weak water inflow supplied minor oxygen and terrigenous organic matter to the lake due to arid-hot climate, as indicated by low Pr/Ph, C 19 T/C 23 T, C 20 T/C 23 T and C 24 Tet/C 26 T ratios, low Oleanane Indexs, and high C 35 Homohopane Indexs and V/Ni ratios. Water algae, including pediastrums and chlorellas, which contributed to the development of high-quality source rocks, could be efficiently preserved in dysoxic condition. High subsidence rate together with sufficient sediment supply during the transgression in the E 1 l and E 1 m periods developed a coastal marine or paralic environment. The alternated climate brought unstable water inflow against stable water column stratification (low Gammacerane Indexs). Strong water inflow due to warm-humid climate provides abundant terrigenous organic matter and oxygen to the lake as indicated by high Pr/Ph, C 19 T/C 23 T, C 20 T/C 23 T and C 24 Tet/C 26 T ratios, high Oleanane Indexs, low C 35 Homohopane Indexs and V/Ni ratios, and rich C 29 steranes. Algal might be preferentially oxidized and degraded in aerobic conditions. Thus, mudstone is regarded as general-quality source rocks but coal is regarded as high-quality source rocks. Weak water inflow under arid-hot climate provided subtle aquatic and terrigenous organic matter to the lake, resulting in poor-quality source rocks. • Based on Rock-Eval pyrolysis, hydrocarbon generation potential of the E 1 y, E 1 l, E 1 m source rocks were investigated. • Organic and inorganic geochemistry were integrated to document the original organic matter input and deposition environment. • Two source rock deposition models are established considering the tectonic subsidence and climate variation. [ABSTRACT FROM AUTHOR] more...
- Published
- 2021
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21. Diagenesis and reservoir quality of Paleocene tight sandstones, Lishui Sag, East China Sea Shelf Basin.
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Liu, Longlong, Li, Yang, Dong, Hongzhi, and Sun, Zhongqiang
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- *
PARAGENESIS , *DIAGENESIS , *RESERVOIRS , *SANDSTONE , *SAND bars , *PETROLEUM reservoirs - Abstract
The Lishui Sag in the East China Sea Shelf Basin (ECSSB) has significant potential hydrocarbon resources, with Paleocene sandstones as its main oil and gas-bearing reservoir. The sandstones in the Paleocene formations are mainly composed of medium-grained, moderately sorted litharenite. In this study, distributions of the porosity and permeability reveal that the Paleocene sandstones have the characteristics of medium porosity and low permeability. The sedimentary microfacies, primary texture, diagenesis, and bioturbation jointly control the reservoir quality. Sandstones with distributary channel and sand bar sedimentary microfacies as well as better sorting tend to exhibit a higher quality. Compaction and carbonate cementation are the major determinants to reductions in porosity and permeability. Grain-coating chlorites within a certain content range may play a positive role in the preservation of porosity in eodiagenesis. Early dissolution has a constructive effect on the reservoir quality. In contrast, the dissolution products such as kaolinite and dawsonite cannot move over a long distance and precipitate nearby to block the intergranular pores when reservoir closure increases. Therefore, dissolution in a relatively closed geochemical reservoir system may contribute little to porosity. Contrastingly, the permeability of the Paleocene reservoir may be reduced by the conversion of the pore network. In the Lishui Sag, the bioturbation plays a role in the deterioration of reservoir quality in a limited scale by decreasing reservoir sorting and increasing compaction. • The main diagenetic processes of the Paleocene sandstones were determined. • Pore structure and pore throat distribution were studied using rate-controlled porosimetry (RCP). • Bioturbation may responsible for the formation of reservoir with extremely low permeability in limited depth. • Dissolution may play a constructive or destructive role for reservoir quality in different zone. [ABSTRACT FROM AUTHOR] more...
- Published
- 2020
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22. 3D-Basin Modelling of the Lishui Sag: Research of Hydrocarbon Potential, Petroleum Generation and Migration.
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Zhang, Jinliang, Guo, Jiaqi, Liu, Jinshui, Shen, Wenlong, Li, Na, and Xu, Guangchen
- Subjects
HYDROCARBONS ,SANDSTONE ,OIL shales ,HEAT transfer ,STRATIGRAPHIC geology ,KEROGEN ,VITRINITE - Abstract
The Lishui Sag is located in the southeastern part of the Taibei Depression, in the East China Sea basin, where the sag is the major hydrocarbon accumulation zone. A three dimensional modelling approach was used to estimate the mass of petroleum generation and accumulated during the evolution of the basin. Calibration of the model, based on measured maturity (vitrinite reflectance) and borehole temperatures, took into consideration two main periods of erosion events: a late Cretaceous to early Paleocene event, and an Oligocene erosion event. The maturation histories of the main source rock formations were reconstructed and show that the peak maturities have been reached in the west central part of the basin. Our study included source rock analysis, measurement of fluid inclusion homogenization temperatures, and basin history modelling to define the source rock properties, the thermal evolution and hydrocarbon generation history, and possible hydrocarbon accumulation processes in the Lishui Sag. The study found that the main hydrocarbon source for the Lishui Sag are argillaceous source rocks in the Yueguifeng Formation. The hydrocarbon generation period lasted from 58 Ma to 32 Ma. The first period of hydrocarbon accumulation lasted from 51.8 Ma to 32 Ma, and the second period lasted from 23 Ma to the present. The accumulation zones mainly located in the structural high and lithologic-fault screened reservoir filling with the hydrocarbon migrated from the deep sag in the south west direction. [ABSTRACT FROM AUTHOR] more...
- Published
- 2019
- Full Text
- View/download PDF
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