Pore characteristics of different organic matter in black shale: A case study of the Wufeng-Longmaxi Formation in the Southeast Sichuan Basin, China

Zhang, Wentao; Hu, Wenxuan; Borjigin, Tenger; Zhu, Feng

doi:10.1016/j.marpetgeo.2019.08.010

Cited by 49 publications

(55 citation statements)

References 26 publications

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“…Though clay minerals are usually treated as "soft" minerals in shale, recent AFM and nanoindentation studies have proved that OM grains are the softest component in shale [22,23], and thus OM grains may be the first components to be squeezed and out of shape during the sedimentation. 16 Geofluids…”

Section: Factors Affecting the Directionality Of The Om Grainsmentioning

confidence: 99%

“…However, the development of organic pores varies among different OM types. Bitumen usually gets well-developed pores, and algal fragments may have angular pores, while graptolites are relatively tight and usually have few or no pores [22]. Sample YY gets the lowest thermal maturity, and organic pores are less developed among most OM grains.…”

Section: Factors Affecting the Directionality Of The Om Grainsmentioning

confidence: 99%

“…Besides organic pores, studies have also shown that microfractures in shale are closely related to the elongated OM particles [22]. Recent nanoindentation and AFM (atomic force microscope) studies have proved that Young's modulus of the OM grains in shale is much lower than clay or other inorganic minerals and OM is the softest part in shale [23][24][25], and the development of organic pores may further lower their Young's modulus [26].…”

Section: Introductionmentioning

confidence: 99%

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Experimental Investigation on Organic Matter Orientation Characteristics of Terrestrial and Marine Shale in China

Liu

Shen

et al. 2021

Geofluids

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As an essential component in shale, OM (organic matter) grains and their arrangements may play essential roles in affecting the anisotropy of the reservoir. However, OM grains are commonly treated as an evenly distributed isotropic medium in current studies, and few works have been done to investigate their detailed arrangement characteristics. In this study, terrestrial and marine shale samples were collected from three different shale plays in China, and the arrangement characteristics of OM grains in each sample were investigated by SEM (scanning electron microscope) image analysis. The results indicate that OM grains in shale are not evenly distributed in isotropic medium, and their directional alignment is pervasive in both marine and terrestrial shale. OM grains in shale tend to subparallel to the bedding section, and their orientation degree and controlling factors differ among different shales. OM grains in samples from terrestrial C-7(Chang-7 Formation) exhibit the strongest directionality in their arrangement, and OM grains in samples from marine LMX (Longmaxi Formation) shale in the Fuling area also exhibit strong directional alignment. While in samples from marine LMX shale in the Baojing area, their directional alignment is much weaker. Shales with high clay content, high TOC (total organic carbon), low thermal maturity, and flat reservoir structure get more OM grains parallel to the bedding section. The biogenetic texture of graptolite in marine LMX shale is the dominating factor leading to the strong directional alignment of the OM grains. However, syncline structure may disorganize the preformed directional alignment and weaken the directionality of the OM grains, which results in the OM arrangement difference between LMX samples from Fuling and Baojing. While the compaction of the layered clay particles is the dominating mechanism leading to the strong directional alignment of the OM grains in terrestrial shale samples from C-7.

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Section: Factors Affecting the Directionality Of The Om Grainsmentioning

confidence: 99%

Section: Factors Affecting the Directionality Of The Om Grainsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental Investigation on Organic Matter Orientation Characteristics of Terrestrial and Marine Shale in China

Liu

Shen

et al. 2021

Geofluids

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“…In recent years, investigations on the pore type, pore size, and pore structure characteristic parameters of mud shale have been conducted providing significant achievements under an increasing interest in unconventional hydrocarbons [1][2][3]. Previous studies on organic-rich shales, such as Barnett, Woodford, Marcellus, and Wufeng-Longmaxi shales, have found that porosity in organic matter represents a significant fraction of the reservoir space [4][5][6]. The formation and evolution of organic matter pores play an important role in the storage and migration of oil and gas in shale reservoirs, increasing the specific surface area and pore volume of shale providing storage space for shale gas [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

“…Previous studies on organic-rich shales, such as Barnett, Woodford, Marcellus, and Wufeng-Longmaxi shales, have found that porosity in organic matter represents a significant fraction of the reservoir space [4][5][6]. The formation and evolution of organic matter pores play an important role in the storage and migration of oil and gas in shale reservoirs, increasing the specific surface area and pore volume of shale providing storage space for shale gas [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Organic Matter Pores and the Relationship with Current Pressure System of Lower Silurian Longmaxi Shales in Dingshan Field, Southern Sichuan, China

et al. 2021

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Organic matter pores (OMP) provide significant storage space for hydrocarbons in lower Silurian Longmaxi shales in the Dingshan field of southern Sichuan, China. The distributions of organic matter and the different OMP structure parameters were characterized through Ar-ion polishing, scanning electron microscopy (SEM), and image analysis software for shale samples of different wells. The research results indicated that organic matter has been divided into two categories based on its occurrence, location, and its relationship with authigenic minerals: organic matter in situ and migrated organic matter. OMP for organic matter in situ are mainly micropores mostly arranged isolatedly, while in migrated organic matter pores show larger sizes and higher roundness. The development of OMP in samples is predominantly controlled by the formation pressure. The existence of overpressure alleviated the stress on the rock skeleton, causing the compaction of some migrated organic matters to lag or decrease. This played a positive role in protecting the development of pores in the interior and edge of the rock skeleton, and it can also induce the development of microfractures in shale. The protective effect of formation pressure on organic pores was provided for understanding the exploration and exploitation of Longmaxi shales in the study area.

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Study on the distribution and connectivity of organic matter pores in Longmaxi shale based on 2D and 3D FIB‐SEM

Hui

Zhang²,

Hu³

et al. 2022

Energy Science & Engineering

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Knowledge of shale pore structure characteristics is crucial to understand gas storage and seepage mechanisms. Organic matter (OM) pores are considered the most important pore type in shale, and one of the currently significant research questions focuses on the spatial distribution and connectivity of OM pores. To answer this question, typical OM‐rich siliceous shale samples from the Lower Silurian Longmaxi Formation were comprehensively investigated using focused ion beam scanning electron microscopy. A three‐dimensional model of the OM‐rich region of interest was segmented and reconstructed based on numerous two‐dimensional slices. The types of OM were found to control the development of organic pores, and OM pores including honeycomb‐shaped pores, spongy‐shaped pores, and slit‐like irregular pores are mainly formed in the pyrobitumen. The pore structure parameters of the OM‐rich ROI revealed that the pore size distribution of honeycomb‐shaped OM pores formed in the pyrobitumen was mainly distributed in the range of 10–50 and 80–100 nm, while the throat equivalent diameter distribution demonstrated a unimodal curve with the main peak located at approximately 30 nm. Pore connectivity analysis further indicated that pyrobitumen also contained several isolated nano‐pores, and pores with diameters smaller than 40 nm were poorly connected. Furthermore, permeability simulation revealed clear discrepancies in different directions owing to the heterogeneity of the OM pores. These findings provide experimental evidence for the assessment of shale gas resources and their development potential.

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Pore characteristics of different organic matter in black shale: A case study of the Wufeng-Longmaxi Formation in the Southeast Sichuan Basin, China

Cited by 49 publications

References 26 publications

Experimental Investigation on Organic Matter Orientation Characteristics of Terrestrial and Marine Shale in China

Experimental Investigation on Organic Matter Orientation Characteristics of Terrestrial and Marine Shale in China

Characteristics of Organic Matter Pores and the Relationship with Current Pressure System of Lower Silurian Longmaxi Shales in Dingshan Field, Southern Sichuan, China

Study on the distribution and connectivity of organic matter pores in Longmaxi shale based on 2D and 3D FIB‐SEM

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