scholarly journals Genetic mechanisms of deep-water massive sandstones in continental lake basins and their significance in micro–nano reservoir storage systems: A case study of the Yanchang formation in the Ordos Basin

2020 ◽  
Vol 9 (1) ◽  
pp. 489-503
Author(s):  
Jianbo Liao ◽  
Aihua Xi ◽  
Sujuan Liang ◽  
Xinping Zhou ◽  
Zhiyong Li ◽  
...  
Keyword(s):  
Debris Flow ◽  
Deep Water ◽  
Pore Radius ◽  
Ordos Basin ◽  
Shear Resistance ◽  
Deep Lake ◽  
Yanchang Formation ◽  
Sedimentary Structures ◽  
The Ordos Basin ◽  
Sedimentary Layer

AbstractBased on field geological surveys of two deep-water sedimentary outcrops in the Yanchang formation of the Ordos Basin, X-ray diffraction analysis, elemental geochemical analysis, and polarizing microscope observations were conducted to investigate the causes of various sedimentary structures inside the massive sand bodies from deep-water debris flow. A genesis model of deep-water debris-flow sandstone is established: during the handling of the mass transport complexes in the basin slope, the soft sandy sedimentary layer with relatively strong shear resistance tears the soft muddy sedimentary layer with weak shear resistance and pulls various clumps inside the muddy layer. Finally, debris-flow massive sandstones with rich sedimentary structures are formed. Through argon ion polishing and field emission scanning electron microscopy, the debris-flow sandstones mainly develop micron-scale pores, and the pore radius is mainly distributed in the range of 1–8 µm. The sedimentary rocks from the semi-deep lake to deep lake facies only have a small number of nano-scale pores, and the pore radius is distributed between 20 and 120 nm.

Depocenter migration of the Ordos Basin in the late Triassic and its controls on shale distribution

2017 ◽  
Vol 5 (2) ◽  
pp. SF81-SF98
Author(s):  
Jing Wang ◽  
Xiangbo Li ◽  
Huaqing Liu ◽  
Xiuqin Deng ◽  
Rong Wanyan
Keyword(s):  
Oil Shale ◽  
Ordos Basin ◽  
Source Rocks ◽  
Late Triassic ◽  
The South ◽  
Deep Lake ◽  
The West ◽  
Resource Potential ◽  
Yanchang Formation ◽  
The Ordos Basin

The Ordos Basin has abundant conventional and unconventional oil and gas resources. Focusing on shale oil in the Ordos Basin, we studied the distribution, depositional features, and resource potential of shales in the upper Triassic Yanchang Formation based on the Ordos Basin development and depocenter migration. During the late Triassic, the Ordos Basin was a large cratonic sedimentary basin that bordered to the Hexi Corridor to the west, the southern North China block to the east, the Qilian and western Qinling orogenic zone to the south, and the foot of the Yin Mountains to the north. During deposition of the Yanchang Formation, its depocenter was not fixed. It migrated to the west before deposition of the Chang 7 oil layer and to the south after deposition of the Chang 7 oil layer. Controlled by the depocenter migration and relevant deep-lake facies, the Yanchang Formation mainly developed two sets of source rocks. The dark mudstone and shale in the Chang 9 oil layer is chiefly distributed in the south-central region of the basin, with thicknesses of 4–16 m and covers an area of approximately [Formula: see text]. The shales in the Chang 7 oil layer can be divided into two types, black oil shale and dark mudstone, and they are much thicker and more widespread than the dark mudstone in the Chang 9 oil layer. The black shale alone can be up to 60 m thick, and covers an area of more than [Formula: see text]. The shales in the Chang 7 and 9 oil layers were mainly formed in a deep-lake environment that produced high concentrations of organic matter and large hydrocarbon generation potential. According to preliminary estimates, the Chang 7 oil shale may contain [Formula: see text] of oil, thereby representing a huge resource potential with broad exploration prospectivity.

scholarly journals Soft-sediment Deformation Structures and Sand Body Architecture in the Chang 6 Oil Member of the Upper Triassic Yanchang Formation, Southwestern Ordos Basin, China

2019 ◽  
Vol 23 (2) ◽  
pp. 119-126 ◽  
Author(s):  
Qingshao Liang ◽  
Jingchun Tian ◽  
Feng Wang ◽  
Xiang Zhang
Keyword(s):  
Ordos Basin ◽  
Upper Triassic ◽  
Seismic Events ◽  
Soft Sediment ◽  
Delta Front ◽  
Yanchang Formation ◽  
Sand Body ◽  
Sediment Deformation ◽  
The Ordos Basin ◽  
Sand Bodies

Soft-sediment deformation (SSD) structures of the Upper Triassic Yanchang Formation are laterally widespread in the Ordos Basin. In the Huachi-Qingyang (H-Q) area of the Ordos Basin, the Chang6 oil member of the Upper Triassic Yanchang Formation is among the most significant Mesozoic oil-bearing strata. It is characterized by the development of reservoir sand bodies. During the depositional evolution of the Chang6 oil member, SSD structures induced by paleo-seismic events developed in the H-Q area in the middle of the basin. The SSD structures developed in the sand bodies of the Chang6 oil member are mainly ball-and-pillow structures, fold structures, sand dikes, irregular convolute stratifications and synsedimentary faults. The architecture of the sand bodies resulted from paleo-seismic events and gravity slumping and mainly include two types of structures: 1) SSD structures driven by paleo-seismic events with normal sedimentation (delta front sand body) (SN-SSD) and 2) SSD structures driven by paleo-seismic events with turbidites (formed by delta-front slumping and re-distribution due to seismic action) (ST-SSD). As a consequence, genetic models of the sand bodies formed by different sedimentation processes are established.

scholarly journals Seismic sedimentary characteristics and filling structure of the Upper Triassic Yanchang Formation, Ordos Basin, China

2020 ◽  
Vol 8 (2) ◽  
pp. T259-T274
Author(s):  
Congjun Feng ◽  
Mengsi Sun ◽  
Chiyang Liu ◽  
Xili Deng ◽  
Yuze Xue ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Ordos Basin ◽  
Yanchang Formation ◽  
Sedimentary Characteristics ◽  
Study Results ◽  
History Of ◽  
The Ordos Basin ◽  
Initial Depression ◽  
Depositional Age ◽  
Seismic Sections

Following the analysis of cores, outcrops, well log, and seismic sections, we have studied the seismic reflection configuration and depositional history of the hydrocarbon-rich Yanchang Formation in the Ordos Basin. We divided the seismic reflection configurations into five types: subparallel reflection, parallel reflection, tangential progradational reflection, shingled progradational reflection, and chaotic reflection. Based on our study results, we concluded that the slopes exhibit differences in the different regions of the Ordos Basin during the sedimentary period of the Yanchang Formation: The slope with the largest gradient of approximately 10°–20° occurred in the southwestern basin, followed by the northwestern basin (with a slope of approximately 1.6°–3.3°), but the slope was relatively gentle in the northeastern basin (approximately 0.8°–1.2°). We also found that the paleocurrent direction of the basin mainly includes two directions: The paleocurrent direction of the southwest region is 186°–259°, which indicates the provenance came from the southwestern region, whereas the paleocurrent direction of the northeast region is 10°–79°, which indicates that the provenance came from the northeastern region. In addition, the Ordos Basin was under isostatic subsidence as a whole during this period, and its sedimentary infilling evolution underwent five stages: the initial depression, intense depression, progradational filling, uplifting and denudation, as well as shrinking and extinction stages, just corresponding with the Chang 10-Chang 9, the Chang 8-Chang 7, the Chang 6-Chang 4+5, the Chang 3-Chang 2, and the Chang 1 depositional age, respectively.

scholarly journals Imaging‐Based Characterization of Perthite in the Upper Triassic Yanchang Formation Tight Sandstone of the Ordos Basin, China

2019 ◽  
Vol 93 (2) ◽  
pp. 373-385 ◽  
Author(s):  
Shuheng DU ◽  
Guoxin SHI ◽  
Xinjian YUE ◽  
Gen KOU ◽  
Bo ZHOU ◽  
...  
Keyword(s):  
Ordos Basin ◽  
Upper Triassic ◽  
Tight Sandstone ◽  
Yanchang Formation ◽  
The Ordos Basin
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