Comparison of Three Key Marine Shale Reservoirs in the Southeastern Margin of the Sichuan Basin, SW China

Liu, Jun; Yao, Yanbin; Liu, Dameng; Pan, Zhejun; Cai, Yidong

doi:10.3390/min7100179

Cited by 21 publications

(37 citation statements)

References 33 publications

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“…For this purpose, low-pressure N 2 adsorption analysis was employed because it has been proven as an effective method to investigate pore structures and fractal characteristics of shale reservoirs. 18,[27][28][29][30] In addition, for both the marine and continental shales, the relationships between fractal dimensions and conventional reservoir parameters (mineral constituents, content of total organic carbon (TOC), porosity, permeability and methane adsorption capability) were also discussed. These investigations are helpful for understanding the controlling factors of pore development, as well as the gas accumulation mechanisms in marine and continental shales.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Pore Fractal Characteristics Between Marine and Continental Shales

Yao

Liu

et al. 2018

Fractals

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Fractal characterization offers a quantitative evaluation on the heterogeneity of pore structure which greatly affects gas adsorption and transportation in shales. To compare the fractal characteristics between marine and continental shales, nine samples from the Lower Silurian Longmaxi formation in the Sichuan basin and nine from the Middle Jurassic Dameigou formation in the Qaidam basin were collected. Reservoir properties and fractal dimensions were characterized for all the collected samples. In this study, fractal dimensions were originated ¶ Corresponding author. This is an Open Access article published by World Scientific Publishing Company. It is distributed under the terms of the Creative Commons Attribution 4.0 (CC-BY) License. Further distribution of this work is permitted, provided the original work is properly cited. 1840016-1Fractals 2018.26. Downloaded from www.worldscientific.com by 13.66.222.141 on 06/19/19. Re-use and distribution is strictly not permitted, except for Open Access articles. J. Liu et al.from the Frenkel-Halsey-Hill (FHH) model with N 2 adsorption data. Compared to continental shale, marine shale has greater values of quartz content, porosity, specific surface area and total pore volume but lower level of clay minerals content, permeability, average pore diameter and methane adsorption capacity. The quartz in marine shale is mostly associated with biogenic origin, while that in continental shale is mainly due to terrigenous debris. The N 2 adsorption-desorption isotherms exhibit that marine shale has fewer inkbottle-shaped pores but more plate-like and slit-shaped pores than continental shale. Two fractal dimensions (D 1 and D 2 ) were obtained at P/P o of 0-0.5 and 0.5-1. The dimension D 2 is commonly greater than D 1 , suggesting that larger pores (diameter >∼ 4 nm) have more complex structures than small pores (diameter <∼ 4 nm). The fractal dimensions (both D 1 and D 2 ) positively correlate to clay minerals content, specific surface area and methane adsorption capacity, but have negative relationships with porosity, permeability and average pore diameter. The fractal dimensions increase proportionally with the increasing quartz content in marine shale but have no obvious correlation with that in continental shale. The dimension D 1 is correlative to the TOC content and permeability of marine shale at a similar degree with dimension D 2 , while the dimension D 1 is more sensitive to those of continental shale than dimension D 2 . Compared with dimension D 2 , for two shales, dimension D 1 is better associated with the content of clay minerals but has worse correlations with the specific surface area and average pore diameter.

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Section: Introductionmentioning

confidence: 99%

Comparison of Pore Fractal Characteristics Between Marine and Continental Shales

Yao

Liu

et al. 2018

Fractals

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“…where GH is hydrostatic pressure gradient, g/cm 3 ; ECD is the circulating equivalent density of drilling fluid, g/cm 3 .…”

Section: Overpressure Characterizationmentioning

confidence: 99%

“…where GH is hydrostatic pressure gradient, g/cm 3 ; ECD is the circulating equivalent density of drilling fluid, g/cm 3 . Drilling engineering data show that dc is mainly controlled by reservoir pressure changes [26,27].…”

Section: Overpressure Characterizationmentioning

confidence: 99%

“…The black shales from the Wufeng Group (O 3 w) and the Longmaxi Group (S 1 l) are considered to be the most developed shale strata in China [1][2][3][4][5]. It has been proven by reservoir exploration and development that reservoir overpressure is an important indicator dominating the shale gas enrichment and production in southern China [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

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The Genetic Mechanism and Evolution Process of Overpressure in the Upper Ordovician–Lower Silurian Black Shale Formation in the Southern Sichuan Basin

Wang

Zhu

2020

Minerals

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The overpressure phenomenon is a widespread occurrence in unconventional shale gas reservoirs. Multiple overpressure shale gas fields were discovered in southern China, and there is no doubt that the gas production per well increases with increasing pressure coefficient (the ratio of the reservoir fluid pressure to the corresponding normal hydrostatic pressure). Thus, successful evaluation and production strategies of organic-rich shale deposits require an understanding of the evolution of the pressure coefficient and its controlling factors in these deposits. In this paper, drilling engineering data of a typical well were collected, and clay mineral tests and overburden diffusion coefficient experiments were conducted. Based on multiphysics simulations, this paper analyzes the overpressure characteristics and formation mechanisms of overpressure in the Longmaxi Formation shale, as well as its geological evolution and controlling factors. The results show that the large amount of shale gas is the cause of overpressure formation rather than disequilibrium compaction. The simulation results show that pressure coefficients of the typical well range from 0.84 to 1.49. The current pressure coefficient increases with increasing pressure coefficient after the last hydrocarbon generation. A large initial pressure coefficient (>1.9), short lifting time (<100 Ma) and small lifting amplitude (<4000 m) are favorable for the preservation of shale gas.

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“…In particular, Zhu et al [25] show the development of abundant macropores in the Longmaxi Shale and suggest, similar to the findings of Liang et al [26], that the proportions of different pore types were significantly changed by structural deformation, and that strongly deformed shales have the least organic pores and the lowest adsorption capacity. The microstructures of tectonically deformed coal (TDC) have also been analyzed in detail by coal geologists [54][55][56][57][58][59][60][61][62]. These studies have mainly focused on three different aspects: (1) development of TDCs by brittle and ductile deformation of coal seams, (2) macro-and micro-deformation behavior of TDCs, and (3) impact of tectonism and coal rank on the characteristics of pore structures.…”

Section: Influence Of Combined Thermal Evolution and Tectonic Deformamentioning

confidence: 99%

Tectonic and Thermal Controls on the Nano-Micro Structural Characteristic in a Cambrian Organic-Rich Shale

Zhu

Huang

et al. 2019

Minerals

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Until recently, the characteristics of nano-microscale structures in the naturally deformed, overmature, marine shales were poorly known. Thermally overmature Lujiaping shales in the complex tectonic area of the northeast part of the upper Yangtze area, China have experienced strong tectonic deformation and are considered as potentially important strata for shale gas exploration. Naturally deformed samples from the main source rocks are selected from the Lower Cambrian Lujiaping Formation in the Dabashan Thrust-fold Belt to investigate nanometer- to micrometer-sized structures. A combination of scanning electron microscope (SEM), low-pressure nitrogen adsorption (LPNA), and low-field nuclear magnetic resonance (NMR) suggests that the pore types are dominantly fracture-related pores with a lesser abundance of mineral-hosted pores. These two pore types account for the 90% of total pore space. Organic matter (OM)-hosted pores are rare and make up a small part of the pore systems (less than 10%) due to high thermal maturity and intensive tectonic compression. Overall, the Lujiaping deformed, overmature samples have abundant nanometer- to micrometer-sized inorganic pores. High-resolution SEM images provide direct evidence of the formation of nano- and microsized structures such as OM–clay aggregates and silica nanograins. OM–clay aggregates are commonly observed in samples, which also exhibit abundant open microfractures and interparticle pores. Quartz can occur as silica nanograins and botryoids typically 20–100 nm in size, which may influence porosity through the creation or occupying interparticle pore space.

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Comparison of Three Key Marine Shale Reservoirs in the Southeastern Margin of the Sichuan Basin, SW China

Cited by 21 publications

References 33 publications

Comparison of Pore Fractal Characteristics Between Marine and Continental Shales

Comparison of Pore Fractal Characteristics Between Marine and Continental Shales

The Genetic Mechanism and Evolution Process of Overpressure in the Upper Ordovician–Lower Silurian Black Shale Formation in the Southern Sichuan Basin

Tectonic and Thermal Controls on the Nano-Micro Structural Characteristic in a Cambrian Organic-Rich Shale

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