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 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.

Spatiotemporal variations in seismic attenuation during hydraulic fracturing: A case study in a tight oil reservoir in the Ordos Basin, China

Geophysics ◽  
2021 ◽  
pp. 1-56
Author(s):  
Han Li ◽  
Xu Chang ◽  
Xiao-Bi Xie ◽  
Yibo Wang
Keyword(s):  
Hydraulic Fracturing ◽  
Ordos Basin ◽  
Seismic Attenuation ◽  
Tight Oil ◽  
Oil Reservoir ◽  
Spatiotemporal Variations ◽  
Waveform Data ◽  
Log Data ◽  
The Ordos Basin ◽  
Tight Oil Reservoir

During hydraulic fracturing (HF) stimulation for unconventional reservoir development, seismic attenuation has a significant influence on high-frequency microseismic data. Attenuation also provides important information for characterizing reservoir structure and changes to it due to HF injections. However, the attenuation effect is typically not considered in microseismic analysis. We have adopted the spectral ratio and centroid-frequency shift methods to estimate the subsurface attenuation (the factor Q−1) in a tight oil reservoir in the Ordos Basin, China. The P- and S-wave attenuations are calculated using the 3C waveform data recorded by a single-well downhole geophone array during a 12-stage HF stimulation. Both methods provide similar results (with differences in Q−1 of absolute values less than 0.010 for P- and S-waves). For individual events, their median Q−1 values calculated from different geophones are selected to represent the average attenuation. Spatiotemporal variations in attenuation are obtained by investigating Q−1 values along propagating rays linking different source-receiver pairs. The Q−1 values derived at different HF stages reveal significant attenuation in the targeted tight sandstone layer (0.030–0.062 for Q−1P and 0.026−0.058 for Q−1S), and the attenuation is apparently increased by fluid injection activities. We explain the sudden decrease in attenuation near the geophone array as a result of high shale content using log data from a horizontal treatment well. The consistency between the Q−1 values and horizontal well-log data, as well as the HF process, indicates the reliability and robustness of the attenuation results. By studying spatiotemporal variations in attenuation, the changes in subsurface structures may be quantitatively characterized, thereby creating a reliable basis for microseismic modeling and data processing and providing additional information on monitoring the HF process.

Characteristics and Origin of Tight Oil Accumulations in the Upper Triassic Yanchang Formation of the Ordos Basin, North-Central China

2016 ◽  
Vol 90 (5) ◽  
pp. 1821-1837 ◽  
Author(s):  
Songtao WU ◽  
Caineng ZOU ◽  
Rukai ZHU ◽  
Jingli YAO ◽  
Shizhen TAO ◽  
...  
Keyword(s):  
Ordos Basin ◽  
Upper Triassic ◽  
Central China ◽  
Tight Oil ◽  
North Central ◽  
Yanchang Formation ◽  
The Ordos Basin
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