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 Palaeostructure, evolution and tight oil distribution of the Ordos Basin, China

2019 ◽  
Vol 74 ◽  
pp. 35
Author(s):  
Shengli Gao ◽  
Jinxia Yang
Keyword(s):  
Ordos Basin ◽  
Tight Oil ◽  
Oil Reservoir ◽  
Hydrocarbon Generation ◽  
Structural Factors ◽  
Yanchang Formation ◽  
Target Layer ◽  
History Of ◽  
The Ordos Basin ◽  
Generation Period

Whether or not the tight oil in the Triassic Yanchang Formation of the Ordos Basin is controlled by structural factors is a controversial issue, the relationship between the structural factors of the strata and the distribution of tight oil is limited to the study of current structures. The traditional view is that structural factors have no obvious control over the formation and distribution of the oil reservoir. Taking the Chang 8 member of the Triassic Yanchang Formation in the Ordos Basin as an example, this paper studies respectively the burial of strata-hydrocarbon generation history of the individual well and the structural evolution history of strata in the basin by using software tools of the Genex burial-hydrocarbon generation history restoration and TemisFlow evolution of stratigraphic structures. It is considered that the hydrocarbon generation period of the source rock of the Triassic Yanchang Formation in the Ordos Basin is from early Middle Jurassic to end of Early Cretaceous. By reconstructing the evolution and structure of the Chang 8 member during the hydrocarbon accumulation period, combined with a comprehensive analysis on the distributional characteristics of the Chang 8 oil reservoir, we found the palaeoslopes and palaeohighs of the Chang 8 reservoir to represent areas in which tight oils were distributed. Palaeo-structural characteristics of the target layer exhibit control over the Chang 8 reservoir. The new theory underlying tight oil exploration, which is based on the recovery of the palaeogeomorphology of the target layer during the hydrocarbon generation period, incorporates the vital roles of key controlling factors over tight oil accumulation, so that the mind-set on tight oil exploration in the Ordos Basin has evolved.

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 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

Paleogeographic framework and Paleo-sedimentary environmental restoration in the Lower Part of Yanchang formation in Triassic of Ordos Basin, China

2020 ◽  
Author(s):  
Yanhua Xu ◽  
Dengfa He
Keyword(s):  
Ordos Basin ◽  
Sedimentary Facies ◽  
Seismic Profile ◽  
Environmental Restoration ◽  
Yanchang Formation ◽  
North East ◽  
The North ◽  
Trace Elements Analysis ◽  
Oil And Natural Gas ◽  
The Ordos Basin

<p><strong>Title: Paleogeographic framework and Paleo-sedimentary environmental restoration in the Lower Part of Yanchang formation in Triassic of Ordos Basin, Chin</strong><strong>a</strong></p><p>Ordos basin is a craton basin, rich in coal, oil and natural gas resources. The Yanchang formation includes the lower part (Chang 10- Chang 8 oil bearing intervals) and the upper part (Chang 7- Chang 1 oil bearing intervals) in which we found many hydrocarbon-rich depressions. The sedimentary period of Chang 10-Chang 8 formation is the transition stage from the North China Craton depression basin to  Ordos basin due to the influence of the Indosinian movement. Previous studies mainly focused on the the interior of the present residual basin rather than the peripheral of the basin.</p><p>Twenty five outcrops out of Ordos basin and one hundred drilling cores in the basin are used and multiple methods including microscope, SEM observation , the major-trace elements analysis ; zircon U-Pb geochronological studies and seismic profile interpretation are applied to study the paleoredox, paleosalinity , paleoclimate and provenance of the the lower part of the Yanchang formation in the Ordos basin.</p><p>It is concluded that: (1)the main charateristics of the sedimentary facies about Chang 10 is rivers-deltas- shore-shallow lacustrine. The sedimentary facies of Chang 9 has the features of “multi-deltas surrounding the lake” with a transitory lake transgression. The main charateristics of Chang 8 is that the rivers became more powerful and the area of lake increased.(2) based on the zircon U-Pb age structure comparision beween the lower part the Yanchang formation and its periphery old land, the results indicate that it has consistent source, which are mainly northern and southern margin of Huabei block. However, the north-east Alashan old land and south Qinlin-Qilian tectonic belts may just supply few detrital sediments.(3) according to the seismic interpretation, we have found a large number of synsedimentary fault. Seismites developed in Chang9 and Chang8 and turbidite developed in Chang9. The distribution of the synsedimentary fault, seismites and turbidite can cetify that the structure activity was more active in the sedimentary period of the Yanchang formation.</p>

Sedimentary characteristics and sand body distributions in the Lower Permian He 8 member, Ordos Basin, China

2021 ◽  
pp. 1-50
Author(s):  
Zhiyuan Lu ◽  
Zhiliang He ◽  
Shizhong Ma ◽  
Yu He
Keyword(s):  
Ordos Basin ◽  
Lower Permian ◽  
Braided River ◽  
River Sand ◽  
Meandering River ◽  
Sedimentary Characteristics ◽  
Fluvial Deposits ◽  
Sand Body ◽  
The Ordos Basin ◽  
Sand Bodies

The Lower Permian He 8 Member (P1h8) in the Ordos Basin is a typical producing zone of tight lithologic gas reservoirs. Analyses of sedimentary characteristics, electrofacies, and sand-body distributions of P1h8, conducted on modern fluvial deposits, outcrops, cores, and well logs, revealed that braided rivers that developed in the Lower P1h8 and Upper P1h8 are characterized by meandering river. Within these fluvial deposits, the procedure consists of analyzing high-resolution sequence stratigraphy and sedimentary dynamics defined from calibrated logging curve signatures and depositional studies. According to modern and ancient fluvial deposits, we have developed a process-based sedimentary conceptual model for interpreting and predicting the distribution and geometries of sand bodies in braided and meandering deposits. The main sand body of the braided river system was bars and channel fill deposits. The braided river sand bodies are distributed over multiple vertical superimpositions and overlapping horizontal connections. The meandering river sand bodies are mainly point-bar deposits, which are bead-shaped and exhibit scattered development in the vertical direction. This comparison indicates that there were significant differences between braided and meandering deposystems. The sand bodies in the Lower P1h8 were multidirectionally connected and primarily distributed in a stacked pattern. In contrast, the sand bodies in the Upper P1h8 were distributed in an isolated manner, and fine grains (mud and silt) were deposited between the sand bodies with poor connectivity. We interpreted the fluvial deposits that control the distributions of the sand body of the He8 Member in the eastern Sulige gas field and constructed a corresponding prediction model of a braided-meandering reservoir. This model will promote understanding of the extent of fluvial deposits and sand-body distribution of P1h8, thus elucidating hydrocarbon-bearing sand units of the Ordos Basin for future exploration.

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