Reservoir heterogeneity of the Longmaxi Formation and its significance for shale gas enrichment

Zhang, Qin; Liang, Feng; Pang, Zhenglian; Liang, Pingping; Zhou, Shangwen; Guo, Wei; Lü, Bin

doi:10.1002/ese3.807

Cited by 7 publications

(7 citation statements)

References 38 publications

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“…As shown in Table , the deep Longmaxi shales analyzed herein are mainly constituted by quartz, clay, and carbonates (with the average values of 39.6%, 30.5%, and 17.6%, respectively); feldspars and pyrite are the minor constituents with the average values of 6.5% and 5.2%, respectively. The main mineral types are the same as those of shallow shales of the Longmaxi Formation in the Sichuan Basin. , The TOC content is between 1.83% and 7.08%, with an average of 3.20%. The mineral compositions of these deep shales show obvious discrepancies in the contents of clay minerals and carbonates.…”

Section: Resultsmentioning

confidence: 96%

Controlling Factor Analysis of Microstructural Property and Storage Capacity of Deep Longmaxi Formation Shale in Sichuan Basin

et al. 2021

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As the commercial development of shallow shale gas reservoirs has been successfully achieved in Sichuan Basin, the deep shale gas reservoirs become the key development target in the next step. The accurate quantitative characterization of the fluid storage and structural properties of deep shale is of great significance in resource evaluation and gas exploitation. In this study, fifteen deep Longmaxi Formation shale samples belonging to three sublayers are collected from the L208 well area, Luzhou Block, southern Sichuan Basin. Nuclear magnetic resonance and nitrogen adsorption are conducted on these samples to obtain the fluid storage capacity and microstructural information. Pore fractal dimension and surface fractal dimension are interpreted from these experimental data for quantitative evaluation of the pore distribution complexity and pore surface irregularity, respectively. The controlling factors of storage and microstructural properties of these deep shales are analyzed. From the perspective of stratigraphic division, the shales belonging to the lower sublayers possess a larger transverse relaxation time of the main peak, a weaker nitrogen adsorption amount, a lower pore volume, a lower specific surface area, and a higher surface fractal dimension as compared to those of the shales from the upper sublayer. From the perspective of shale composition, clay mineral content and total organic carbon content are the main and minor controlling factors of the storage capacity, pore fractal dimension, and surface fractal dimension of deep Longmaxi shale, respectively. Moreover, the pore surface irregularity is relevant to the average pore diameter and specific surface area.

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Section: Resultsmentioning

confidence: 96%

Controlling Factor Analysis of Microstructural Property and Storage Capacity of Deep Longmaxi Formation Shale in Sichuan Basin

et al. 2021

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“…We have collected 82 fresh samples from the upper Ordovician Wufeng Lower Silurian Longmaxi Formation in the southern Sichuan Basin. This shale formation is famous for its large reserves and commercial development of shale gas in southern China [40,41]. The shale samples were selected from 10 wells in the Zhaotong shale gas demonstration zone shown in Figure 1, covering different sublayers of the Longmaxi Formation, their depth ranging from 1014.50 m to 3039.78 m [7].…”

Section: Samplesmentioning

confidence: 99%

“…The shale samples were selected from 10 wells in the Zhaotong shale gas demonstration zone shown in Figure 1, covering different sublayers of the Longmaxi Formation, their depth ranging from 1014.50 m to 3039.78 m [7]. The lower part of the Longmaxi Formation is dominated by black siliceous shale and carbonaceous shale, which is a high-quality shale gas reservoir with a thickness of more than 40 m [41]. The middle and upper parts of the Longmaxi Formation comprise mainly gray silty shale with a total thickness of more than 100 m [41].…”

Section: Samplesmentioning

confidence: 99%

“…The lower part of the Longmaxi Formation is dominated by black siliceous shale and carbonaceous shale, which is a high-quality shale gas reservoir with a thickness of more than 40 m [41]. The middle and upper parts of the Longmaxi Formation comprise mainly gray silty shale with a total thickness of more than 100 m [41]. All these Longmaxi shales are overmatured, with Ro ranging from 2.45% to 2.86%.…”

Section: Samplesmentioning

confidence: 99%

“…The TOC is one of the most important parameters to evaluate shale gas reservoirs, which are closely related to the development of nanopores and gas adsorption capacity of shales. The bottom of the Longmaxi Formation has the highest TOC, so this sublayer is selected for the shale gas development in China [41].…”

Section: Toc and Clay Mineral Compositionmentioning

confidence: 99%

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Clarifying the Effect of Clay Minerals on Methane Adsorption Capacity of Marine Shales in Sichuan Basin, China

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et al. 2021

Energies

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The effect of clay minerals on the methane adsorption capacity of shales is a basic issue that needs to be clarified and is of great significance for understanding the adsorption characteristics and mechanisms of shale gas. In this study, a variety of experimental methods, including XRD, LTNA, HPMA experiments, were conducted on 82 marine shale samples from the Wufeng–Longmaxi Formation of 10 evaluation wells in the southern Sichuan Basin of China. The controlling factors of adsorption capacities were determined through a correlation analysis with pore characteristics and mineral composition. In terms of mineral composition, organic matter (OM) is the most key methane adsorbent in marine shale, and clay minerals have little effect on methane adsorption. The ultra-low adsorption capacity of illite and chlorite and the hydrophilicity and water absorption ability of clay minerals are the main reasons for their limited effect on gas adsorption in marine shales. From the perspective of the pore structure, the micropore and mesopore specific surface areas (SSAs) control the methane adsorption capacity of marine shales, which are mainly provided by OM. Clay minerals have no relationship with SSAs, regardless of mesopores or micropores. In the competitive adsorption process of OM and clay minerals, OM has an absolute advantage. Clay minerals become carriers for water absorption, due to their interlayer polarity and water wettability. Based on the analysis of a large number of experimental datasets, this study clarified the key problem of whether clay minerals in marine shales control methane adsorption.

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Pore-scale characterization and fractal analysis for gas migration mechanisms in shale gas reservoirs

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Tian

Wood

2022

Sustainable Geoscience for Natural Gas Subsurface Systems

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Reservoir heterogeneity of the Longmaxi Formation and its significance for shale gas enrichment

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 7 publications

References 38 publications

Controlling Factor Analysis of Microstructural Property and Storage Capacity of Deep Longmaxi Formation Shale in Sichuan Basin

Controlling Factor Analysis of Microstructural Property and Storage Capacity of Deep Longmaxi Formation Shale in Sichuan Basin

Clarifying the Effect of Clay Minerals on Methane Adsorption Capacity of Marine Shales in Sichuan Basin, China

Pore-scale characterization and fractal analysis for gas migration mechanisms in shale gas reservoirs

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