Characterization and interpretation of organic matter, clay minerals, and gas shale rocks with low-field NMR

Zhou, Gongfu; Gu, Zhaobin; Hu, Zhiming; Chang, Jin; Duan, Xianggang; Liu, Xiangui; Li, Yanran; Zhan, Hongming

doi:10.1016/j.petrol.2020.107926

Cited by 17 publications

(7 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As one of the essential mineral compositions of shale, clay mineral is usually an aggregation of multiple minerals, output in the shale in schistose. Hence, various pore types can be witnessed among clay mineral particles, clay mineral schistose, and inside particles, including pores between clay schistose, layered slip-bedding fractures, etc. , Microscopic pores have been developed in various types since significant variations are observed in the composition and content of clay minerals of the Longmaxi Formation in the Dingshan area. When the content of clay minerals is low, it is distributed in dots with large amounts of intergranular pores.…”

Section: Discussionmentioning

confidence: 99%

Influence of Mineral Compositions on Shale Pore Development of Longmaxi Formation in the Dingshan Area, Southeastern Sichuan Basin, China

Qin

et al. 2021

Energy Fuels

View full text Add to dashboard Cite

Influences of the characteristics of organic matters and mineral compositions on the development of shale microscopic pores were discussed through performing low-temperature nitrogen adsorption, whole-rock "X" diffraction, and field emission scanning electron microscope on black organic-rich shale samples of Longmaxi Formation in the Dingshan area, southeastern Sichuan Basin, in combination with the characteristics of shale organic matters. The shale in the Dingshan area has complex mineral composition, which is mainly quartz and clay minerals. Both contents range from 23% to 72% and 36% to 70%, respectively. The vertical variation is obvious, and there are few feldspar and carbonate rocks; the pyrite content is more than 2%. The bottom shale has high brittleness and gradually decreases in the vertical direction. The brittleness index is between 0.481 and 0.627 and is concentrated above 0.5. It shows strong compressibility and is easy to form a complex network system in hydraulic fracturing. Quartz and feldspar mainly provide secondary dissolved pores, intercrystalline mineral pores, and nanoedge gaps in contact with organic matter. They have no obvious correlation with the specific surface area of shale but have a weak correlation with pore volume. They mainly control the development of macropores. Organic matter develops many hydrocarbon-generating pores, which strongly correlate with the specific surface area and a weak correlation with pore volume. It mainly controls the development of micromesopores. Clay minerals mainly provide a large number of interlaminar pores and interlayer fractures in the clay. The intergranular pores of clay and clay have a weak correlation with pore volume and specific surfaces. They contribute to the development of shale micropores, mesopores, and macropores. Pyrite mainly provides intercrystalline pores and mold pores. By restricting the interaction with organic matter, the development of shale pores is promoted within a certain content range. When the content exceeds this range, the development of micropores is inhibited. The conversion threshold in the Dingshan area is 5.0%.

show abstract

Section: Discussionmentioning

confidence: 99%

Influence of Mineral Compositions on Shale Pore Development of Longmaxi Formation in the Dingshan Area, Southeastern Sichuan Basin, China

Qin

et al. 2021

Energy Fuels

View full text Add to dashboard Cite

show abstract

“…It is well-known that shale deposits in an oxygen-deficient reducing environment and reserves reductive components, such as organic matter (OM), pyrite, and chlorite . As an essential component of calcareous shale, OM is mainly composed of kerogen, where organic pores with good connectivity develop in abundance, having strong methane adsorption capacity. , Therefore, the oxidation of OM in shale may reduce methane adsorption and promote adsorbed gas desorption. Under oxidation, OM may convert into organic acids, which may dissolve acid-soluble minerals, further promoting dissolved pores generation …”

Section: Resultsmentioning

confidence: 99%

Investigation of Oxidative Dissolution and Mineral Swelling Effects on Seepage Channels and Permeability of Calcareous Shale Reservoirs: An Experimental Study

et al. 2022

View full text Add to dashboard Cite

Multistaged hydraulic fracturing of a horizontal well may significantly improve the permeability of the calcareous shale reservoir, but hard to improve the transport capacity of gas in nanopores, resulting in insufficient gas supply from the shale matrix to fractures and rapid production decline after the stimulation. Nevertheless, the seepage capacity and production will increase due to the water-rock interaction during the soaking process after fracturing. Our research proposes to utilize the reaction between persulfate and calcareous shale to strengthen the water-rock interaction, achieving oxidative dissolution and swelling. Ammonium persulfate was selected as the fracturing fluid additive to analyze the effect of oxidative dissolution and swelling on the macroscopic and microscopic seepage capacity of calcareous shale through technical means such as stress sensitivity test, NMR, and SEM. We conclude that persulfate’s oxidative dissolution and swelling will greatly promote fractures and increase permeability in calcareous shale reservoirs to reconstruct the seepage channels. The findings of this study have implications for determining and optimizing the fracturing fluid’s performance and the postfracturing production management system to develop calcareous shale reservoirs in a green and efficient manner.

show abstract

“…Previous studies have made great progress in understanding the geological characteristics of shale reservoirs; defined the geochemical characteristics, mineralogical characteristics, and reservoir space characteristics of the reservoirs; found that the sedimentary environment, organic matter (OM), clay minerals, brittle minerals, and fractures are the main controlling factors of shale reservoir yields; and formed a comprehensive research system for shale reservoirs (Chen et al, 2016;Li et al, 2019c;Chen S. L. et al, 2020;Li et al, 2020;Liu et al, 2020;Chen et al, 2021a;Chen et al, 2021b;Liu J. et al, 2021;Sun, 2021). However, these research results and conclusions apply mainly to shallow shale gas with a burial depth of less than 3,500 m. Due to the influence of sedimentation, diagenesis, and tectonism, deep shale gas reservoirs have higher contents of brittle minerals, more developed natural fractures, and more complex pore evolution, resulting in different shale geological characteristics and controlling factors for shale gas enrichment and yield (Yin et al, 2019;Chen F. et al, 2020;Chai et al, 2020;Xu and Gao, 2020;Yin and Wu, 2020;Zhou et al, 2020;Song et al, 2021;Tabatabaei 2021). Therefore, clarifying the geological characteristics of deep shale is needed to explore and extract deep shale gas.…”

Section: Introductionmentioning

confidence: 99%

Geological Characteristics and Controlling Factors of Enrichment of Deep Shale Gas in the East Weiyuan–North Rongchang Area, Sichuan Basin, China

Tang

Li³

et al. 2022

Front. Earth Sci.

View full text Add to dashboard Cite

The southern Sichuan Basin is the core area of China’s efficient development of deep shale gas (burial depth greater than 3,500 m). Reservoir geological characteristics determine whether shale gas can be preserved, enriched, and produced. Taking the Long 11 sub-member of the Wufeng Formation of the Upper Ordovician and the Longmaxi Formation of the Lower Silurian in the East Weiyuan–North Rongchang area as an example, we used the core, logging, production test, and other data, combining X-ray diffraction analysis, LECO Total Organic Carbon (TOC)-S analysis, optical microscopy, and argon ion polishing field-emission scanning electron microscopy, to study the shale mineral composition, geochemistry, reservoir space, pore structure characteristics, and reservoir physical properties. The following results were obtained: 1) The brittle mineral content, organic matter maturity, and TOC content are high, gradually increase from top to bottom, and reach their maxima at small layer 1 of Long 11. 2) Organic pores, inorganic pores, and fractures are important reservoir spaces, among which organic pores and fractures are important seepage channels for shale gas. 3) The shale pore structure revealed by electron microscopy shows that the pore structure in target layers can be divided into four types: unimodal type (mainly organic pores), bimodal type (both organic and inorganic pores), monoclinic type I (mainly organic pores), and monoclinic type II (mainly inorganic pores). The pore morphology is complex, and circular and oval shapes predominate. 4) Sedimentary facies are the main factor controlling the enrichment of shale gas, and the development of fractures is the key to obtaining high yields of shale gas. 5) The class I favorable target area is mainly distributed in wells W206, W206H1, R234H, and R233H and areas to its south, and some areas in the east of the study area.

show abstract

Characterization and interpretation of organic matter, clay minerals, and gas shale rocks with low-field NMR

Cited by 17 publications

References 46 publications

Influence of Mineral Compositions on Shale Pore Development of Longmaxi Formation in the Dingshan Area, Southeastern Sichuan Basin, China

Influence of Mineral Compositions on Shale Pore Development of Longmaxi Formation in the Dingshan Area, Southeastern Sichuan Basin, China

Investigation of Oxidative Dissolution and Mineral Swelling Effects on Seepage Channels and Permeability of Calcareous Shale Reservoirs: An Experimental Study

Geological Characteristics and Controlling Factors of Enrichment of Deep Shale Gas in the East Weiyuan–North Rongchang Area, Sichuan Basin, China

Contact Info

Product

Resources

About