scholarly journals Mineral Composition of Prospective Section of Wufeng-Longmaxi Shale in Luzhou Shale Play, Sichuan Basin

Minerals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 20
Author(s):  
Hongzhi Yang ◽  
Xuewen Shi ◽  
Chao Luo ◽  
Wei Wu ◽  
Yi Li ◽  
...  
Keyword(s):  
Mineral Composition ◽  
Shale Gas ◽  
Sichuan Basin ◽  
Focal Point ◽  
Quartz Content ◽  
Biological Origin ◽  
Longmaxi Formation ◽  
Longmaxi Shale ◽  
The Sichuan Basin ◽  
Identification And Characterization

Currently, Luzhou in the Sichuan Basin is a focal point for shale-gas exploration and development in China. However, a lack of detailed research on the mineral composition of the Wufeng Formation-Longmaxi Formation (WF-LF) shale is hindering the extraction of deep-buried shale gas in the Luzhou shale play. Herein, a field emission scanning electron microscope (FESEM) equipped with the Advanced Mineral Identification and Characterization System (AMICS) software was employed to analyze the mineral composition of the WF-LF shale from six wells in Luzhou. Quartz was the dominant mineral type, (16.9–87.21%, average 51.33%), followed by illite, calcite, dolomite, and pyrite. Our study revealed that (1) quartz content showed a moderate positive correlation with the total organic carbon (TOC) content, indicating that the quartz found in the shale is mostly of biological origin; and (2) the sum content of siliceous minerals and carbonaceous minerals was moderately positively correlated with the brittleness index (BRIT) in well SS1H2-7 and in the well group of RS8 and RS5, indicating that the siliceous minerals and carbonaceous minerals had an active effect on reservoir compressibility. Finally, according to the mineralogical features of each sublayer, we identified four types of reservoirs to determine their scope for exploration.

scholarly journals Factors Affecting Shale Gas Chemistry and Stable Isotope and Noble Gas Isotope Composition and Distribution: A Case Study of Lower Silurian Longmaxi Shale Gas, Sichuan Basin

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5981
Author(s):  
Chunhui Cao ◽  
Liwu Li ◽  
Yuhu Liu ◽  
Li Du ◽  
Zhongping Li ◽  
...  
Keyword(s):  
Natural Gas ◽  
Isotopic Composition ◽  
Shale Gas ◽  
Sichuan Basin ◽  
Noble Gas ◽  
Longmaxi Formation ◽  
Lower Silurian ◽  
The Sichuan Basin ◽  
Gas Fields ◽  
Cracking Gas

The Weiyuan (WY) and Changning (CN) fields are the largest shale gas fields in the Sichuan Basin. Though the shale gases in both fields are sourced from the Longmaxi Formation, this study found notable differences between them in molecular composition, carbon isotopic composition, and noble gas abundance and isotopic composition. CO2 (av. 0.52%) and N2 (av. 0.94%) were higher in Weiyuan than in Changning by an average of 0.45% and 0.70%, respectively. The δ13C1 (−26.9% to −29.7%) and δ13C2 (−32.0% to −34.9%) ratios in the Changning shale gases were about 8% and 6% heavier than those in Weiyuan, respectively. Both shale gases had similar 3He/4He ratios but different 40Ar/36Ar ratios. These geochemical differences indicated complex geological conditions and shed light on the evolution of the Lonmaxi shale gas in the Sichuan Basin. In this study, we highlight the possible impacts on the geochemical characteristics of gas due to tectonic activity, thermal evolution, and migration. By combining previous gas geochemical data and the geological background of these natural gas fields, we concluded that four factors account for the differences in the Longmaxi Formation shale gas in the Sichuan Basin: a) A different ratio of oil cracking gas and kerogen cracking gas mixed in the closed system at the high over-mature stage. b) The Longmaxi shales in WY and CN have had differential geothermal histories, especially in terms of the effects from the Emeishan Large Igneous Province (LIP), which have led to the discrepancy in evolution of the shales in the two areas. c) The heterogeneity of the Lower Silurian Longmaxi shales is another important factor, according to the noble gas data. d) Although shale gas is generated in closed systems, natural gas loss throughout geological history cannot be avoided, which also accounts for gas geochemical differences. This research offers some useful information regarding the theory of shale gas generation and evolution.

Evolution and migration of shale facies and their control on shale gas: A case study from the Wufeng-Longmaxi Formations in the Sichuan Basin and its surroundings

2018 ◽  
Vol 6 (4) ◽  
pp. SN57-SN70 ◽  
Author(s):  
Zongquan Hu ◽  
Wei Du ◽  
Chuanxiang Sun ◽  
Jing Wu ◽  
Tong Zhu ◽  
...  
Keyword(s):  
Shale Gas ◽  
Sichuan Basin ◽  
Early Stage ◽  
Carbonate Content ◽  
Thin Sections ◽  
Longmaxi Formation ◽  
Material Basis ◽  
The Sichuan Basin ◽  
Siliceous Shale ◽  
Sweet Spots

The Fuling gas field, the largest commercial discovery of shale gas in China, has been producing from the organic-rich shale in the Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation in the Sichuan Basin, China. A refined shale gas E&P and sweet spots identification require studies to be carried out not only at the sedimentary facies scale but also at the petrographic scale. This paper focuses on the characteristics of organic-rich shales. Based on data from outcrops, drilling cores, X-ray diffraction, thin sections, and scanning electric microscope, a systematic analysis of wells and well-correlation sections indicates that shales in the study area underwent two progressive and regressive cycles. In addition, differences in lithofacies and their organic or inorganic components are significant either in the vertical or in the horizontal direction, which generally controls the material basis of shale gas. The early-stage siliceous shale distributes in the east, whereas the late-stage carbonate-bearing shale extends to the west. In the southeastern Sichuan Basin, the siliceous composition decreases, whereas the clay minerals increase upward. In the central Sichuan uplift, there is a higher carbonate content. And with our new lithofacies maps, distribution of the sweet spots was identified. The northeastern Sichuan Basin has the siliceous shale in the Wufeng Formation and the silicon-bearing shale in the Longmaxi Formation, making it a play area with the greatest gas potential. The southern Sichuan Basin occurs as a favorable lithofacies area with the stacked siliceous shale in the Wufeng Formation and the calcareous shale in the Longmaxi Formation. The relatively favorable lithofacies area covers the regions extending from the periphery of southern Sichuan Basin toward the central Sichuan uplift and the northern Guizhou uplift, featuring stacked carbonate-bearing shale and clay mineral-bearing shale in the Longmaxi Formation. The shallow-marine areas close to the uplifts are dominated by mudstone and silty mudstone, thereby possessing poor material basis.

In Situ Sequestration of a Hydraulic Fracturing Fluid in Longmaxi Shale Gas Formation in the Sichuan Basin

2019 ◽  
Vol 33 (8) ◽  
pp. 6983-6994 ◽  
Author(s):  
Bin Yang ◽  
Hao Zhang ◽  
Yili Kang ◽  
Lijun You ◽  
Jiping She ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Shale Gas ◽  
Sichuan Basin ◽  
Fracturing Fluid ◽  
Gas Formation ◽  
Longmaxi Shale ◽  
The Sichuan Basin ◽  
Hydraulic Fracturing Fluid

scholarly journals Origin and Accumulation Mechanisms of Wufeng-Longmaxi Shale Gas in the Sichuan Basin, China

2020 ◽  
Author(s):  
Jamie Robert Beagle ◽  
Chunhui Cao ◽  
Yunpeng Wang ◽  
Greg Holland ◽  
Zheng Zhou
Keyword(s):  
Shale Gas ◽  
Sichuan Basin ◽  
Longmaxi Shale ◽  
The Sichuan Basin
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