Occurrence State of Soluble Organic Matter in Shale Oil Reservoirs from the Upper Triassic Yanchang Formation in the Ordos Basin, China: Insights from Multipolarity Sequential Extraction

2021 ◽  
Author(s):  
Shutong Li ◽  
Shixiang Li ◽  
Ruiliang Guo ◽  
Xinping Zhou ◽  
Yang Wang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Ordos Basin ◽  
Upper Triassic ◽  
Oil Reservoirs ◽  
Shale Oil ◽  
Soluble Organic Matter ◽  
Yanchang Formation ◽  
Occurrence State ◽  
The Ordos Basin ◽  
Shale Oil Reservoirs

scholarly journals The Influence of Lamina Density and Occurrence on the Permeability of Lamellar Shale after Hydration

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1524
Author(s):  
Pengfei Zhao ◽  
Xingxing Wang ◽  
Xiangyu Fan ◽  
Xingzhi Wang ◽  
Feitao Zeng ◽  
...  
Keyword(s):  
Significant Influence ◽  
Ordos Basin ◽  
Oil Reservoirs ◽  
Shale Oil ◽  
Direction Parallel ◽  
Yanchang Formation ◽  
Research Results ◽  
Micropore Structure ◽  
Permeability Anisotropy ◽  
Shale Oil Reservoirs

The characteristics of laminae in lamellar shale oil reservoirs have important influences on reservoir parameters, especially permeability. In order to explore the influence of lamina density and occurrence on the permeability of lamellar shale after hydration, we studied the lamellar shale in the Chang 7 member of the Yanchang Formation of Triassic in Ordos Basin. By comparing the permeability of bedding shale and lamellar shale with different densities of laminae, it was found that the permeability anisotropy of lamellar shale was stronger. In the direction parallel to the lamina, the permeability increased approximately linearly with an increase in lamina density. The effect of hydration on rock micropore structure and permeability was studied by soaking shale in different fluids. Most of the microfracture in the lamellar shale was parallel to the lamina direction, and hydration led to a widening of the microfracture, which led to the most obvious increase in permeability parallel to the lamina. Collectively, the research results proved that lamina density, occurrence, and hydration have a significant influence on the permeability anisotropy of lamellar shale.

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

Fractures in continental shale reservoirs: a case study of the Upper Triassic strata in the SE Ordos Basin, Central China

2015 ◽  
Vol 153 (4) ◽  
pp. 663-680 ◽  
Author(s):  
WENLONG DING ◽  
PENG DAI ◽  
DINGWEI ZHU ◽  
YEQIAN ZHANG ◽  
JIANHUA HE ◽  
...  
Keyword(s):  
Organic Matter ◽  
Shale Gas ◽  
Mineral Content ◽  
Ordos Basin ◽  
Total Content ◽  
Upper Triassic ◽  
Thin Sections ◽  
Yanchang Formation ◽  
Fracture Development ◽  
Shale Reservoirs

AbstractFractures are important for shale-gas reservoirs with low matrix porosity because they increase the effective reservoir space and migration pathways for shale gas, thus favouring an increased volume of free gas and the adsorption of gases in shale reservoirs, and they increase the specific surface area of gas-bearing shales which improves the adsorption capacity. We discuss the characteristics and dominant factors of fracture development in a continental organic matter-rich shale reservoir bed in the Yanchang Formation based on observations and descriptions of fracture systems in outcrops, drilling cores, cast-thin sections and polished sections of black shale from the Upper Triassic Yanchang Formation in the SE Ordos Basin; detailed characteristics and parameters of fractures; analyses and tests of corresponding fracture segment samples; and the identification of fracture segments with normal logging. The results indicate that the mineral composition of the continental organic-matter-rich shale in the Yanchang Formation is clearly characterized by a low brittle mineral content and high clay mineral content relative to marine shale in the United States and China and Mesozoic continental shale in other basins. The total content of brittle minerals, such as quartz and feldspar, is c. 41%, with quartz and feldspar accounting for 22% and 19% respectively, and mainly occurring as plagioclase with small amounts of carbonate rocks. The total content of clay minerals is high at up to 52%, and mainly occurs as a mixed layer of illite-smectite (I/S) which accounts for more than 58% of the total clay mineral content. The Upper Triassic Yanchang Formation developed two groups of fracture (joint) systems: a NW–SE-trending system and near-E–W-trending system. Multiple types of fractures are observed, and they are mainly horizontal bedding seams and low-dip-angle structural fractures. Micro-fractures are primarily observed in or along organic matter bands. Shale fractures were mainly formed during Late Jurassic – late Early Cretaceous time under superimposed stress caused by regional WNW–ESE-trending horizontal compressive stress and deep burial effects. The extent of fracture development was mainly influenced by multiple factors (tectonic factors and non-tectonic factors) such as the lithology, rock mechanical properties, organic matter abundance and brittle mineral composition and content. Specifically, higher sand content has been observed to correspond to more rapid lithological changes and more extensive fracture development. In addition, higher organic matter content has been observed to correspond to greater fracture development, and higher quartz, feldspar and mixed-layer I/S contents have been observed to correspond to more extensive micro-fracture development. These results are consistent with the measured mechanical properties of the shale and silty shale, the observations of fractures in cores and thin-sections from more than 20 shale-gas drilling wells, and the registered anomalies from gas logging.

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