Division of diagenesis and pore evolution of a Permian Shanxi shale in the Ordos Basin, China

Guo, Shaohui; Mao, Wenjing

doi:10.1016/j.petrol.2019.106351

Cited by 32 publications

(24 citation statements)

References 39 publications

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“…Furthermore, the liquid hydrocarbon expulsion of OM and kerogen at a maturity of approximately 0.4–0.7% could also result in an increase in the PV owing to the appearance of organic bubble pores [ 22 ]. Additionally, the earlier dissolution and transformation of unstable minerals can contribute to the PV increases at different diameter scales [ 50 , 51 ].…”

Section: Discussionmentioning

confidence: 99%

Full-Scale Pore Structure Characteristics and the Main Controlling Factors of Mesoproterozoic Xiamaling Shale in Zhangjiakou, Hebei, China

Yang

Wei

et al. 2021

Nanomaterials

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Nanoscale pore structure characteristics and their main controlling factors are key elements affecting the gas storage capacity, permeability, and the accumulation mechanism of shale. A multidisciplinary analytical program was applied to quantify the pore structure of all sizes of Xiamaling shale from Zhangjiakou, Hebei. The result implies that Mercury injection porosimetry (MIP) and low-pressure N2 curves of the samples can be divided into three and four types, respectively, reflecting different connectivity performances. The maximum CO2 adsorbing capacity increases with increasing total organic carbon (TOC) content, pore volume (PV), and surface area (SA) of the micropores are distributed in a three-peak type. The full-scale pore structure distribution characteristics reveal the coexistence of multiple peaks with multiple dominant scales and bi-peak forms with mesopores and micropores. The porosity positively correlates with the TOC and quartz content, but negatively correlates with clay mineral content. Organic matter (OM) is the main contributor to micropore and mesopore development. Smectite and illite/smectite (I/S) assist the development of the PV and SA of pores with different size. Illite promotes the development of the nanoscale PV, but is detrimental to the development of the SA. Thermal maturity controls the evolution of pores with different size, and the evolution model for the TOC-normalized PVs of different diameter scales is established. Residual hydrocarbon is mainly accumulated in micropores sized 0.3 to 1.0 nm and mesopores sized 40 nm, 2 nm and less than 10 nm. Since the samples were extracted, the pore space occupied by residual hydrocarbon was released, resulting in a remarkable increase in PV and SA.

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Section: Discussionmentioning

confidence: 99%

Full-Scale Pore Structure Characteristics and the Main Controlling Factors of Mesoproterozoic Xiamaling Shale in Zhangjiakou, Hebei, China

Yang

Wei

et al. 2021

Nanomaterials

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“…(a) During the early diagenetic stage, corresponding to the immature stage of OM evolution ( R o < 0.8%, T max < 400°C), the OM was not in the “oil window” and only a small amount of biogenic methane was produced through biological action. At this time, the sediment was still muddy (not completely consolidated) 36 and the shale pore system was mainly composed of mesopores and macropores. With the development of diagenesis, compaction inhibited pore development, reducing PV and SSA.…”

Section: Discussionmentioning

confidence: 99%

“…Characteristics of pore type, pore structure, PSD, and clay mineral content have obvious changes during diagenesis. For example, macropores in montmorillonite decrease rapidly with increasing pressure, while micropores in OM gradually increase during the generation of hydrocarbon 36 . In the past few years, pore evolution has been studied mainly by comparing shale samples with different maturities from different regions, and discussing their porosities, pore structure characteristics, 6,8,17,37‐39 .…”

Section: Introductionmentioning

confidence: 99%

Study on pore evolution and diagenesis division of a Permian Longtan transitional shale in Southwest Guizhou, China

Guo

2020

Energy Science & Engineering

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Organic‐rich shales, deposited in marine‐continental transitional environments, are widely distributed in southern China. The pore evolution of the Late Permian Longtan Formation shale (Guizhou Province) during its diagenesis and organic matter (OM) evolution was quantitatively and qualitatively investigated through thermal simulation, mercury intrusion capillary pressure, gas adsorption, fractal dimension, and field emission‐scanning electron microscopy observation. Diagenesis and OM evolution stage were subdivided on the basis of X‐ray diffraction, rock pyrolysis, and vitrinite reflectance test; moreover, the main controlling factors of pore structure during evolution were also discussed. Shales were heated to different temperatures with their vitrinite reflectance ranged between 1.23% and 3.12%, indicating that organic matter had evolved from a low‐ to a post‐mature stage. According to the changes in clay mineral composition, hydrocarbon generation, and Tmax, we subdivided diagenesis into four parts, each of which has a good correspondence with OM evolution. Pore volume (PV) varied between 0.012162 and 0.033482 cm3/g, while the specific surface area (SSA) varied between 13.3693 and 23.0094 m2/g. Mesopores were the main contributors to the total pore volume, while mesopores and micropores were the main contributors to the total specific surface area. In this study, the evolution of pore structure was not monotonous, but intermittent: The PV and SSA of shale samples first decreased and then increased. Maturity was the most important factor affecting the evolution of pore structure. The abundance of pores in OM, associated with hydrocarbon generation, resulted in large micro‐PV and micro‐SSA; moreover, the composition of clay minerals also influenced the pore structure evolution. The transformation of kaolinite into illite increased the content of illite and illite/smectite mixed layer, hence affecting the overall meso‐PV and meso‐SSA.

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“…For example, the average porosity of high-mature shale with a burial depth of more than 2500 m is 3.02% in Sichuan Basin (Zou et al 2010) and 2.8% in Southern North China Basin (Yang and Guo 2020). However, the shale porosity in the thermal simulation experiment is always not less than 4% (Chen and Xiao 2014;Xie et al 2014;Guo and Mao 2019). Therefore, thermal simulation experiments alone cannot truly reflect the evolution of shale reservoirs.…”

Section: Edited By Jie Haomentioning

confidence: 98%

“…Regardless of the type of oil and gas research being conducted, the evolution process is an important and difficult topic. Thermal simulation experiments are often used to simulate thermal evolution in the laboratory to discuss hydrocarbon generation and diagenesis of shales (Xie et al 2014;Akande et al 2015;Guo and Mao 2019). The thermal maturation process undoubtedly has an important influence on the pore evolution of shale.…”

Section: Edited By Jie Haomentioning

confidence: 99%

Porosity model and pore evolution of transitional shales: an example from the Southern North China Basin

Yang

Guo

2020

Pet. Sci.

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The evolution of shale reservoirs is mainly related to two functions: mechanical compaction controlled by ground stress and chemical compaction controlled by thermal effect. Thermal simulation experiments were conducted to simulate the chemical compaction of marine-continental transitional shale, and X-ray diffraction (XRD), CO 2 adsorption, N 2 adsorption and high-pressure mercury injection (MIP) were then used to characterize shale diagenesis and porosity. Moreover, simulations of mechanical compaction adhering to mathematical models were performed, and a shale compaction model was proposed considering clay content and kaolinite proportions. The advantage of this model is that the change in shale compressibility, which is caused by the transformation of clay minerals during thermal evolution, may be considered. The combination of the thermal simulation and compaction model may depict the interactions between chemical and mechanical compaction. Such interactions may then express the pore evolution of shale in actual conditions of formation. Accordingly, the obtained results demonstrated that shales having low kaolinite possess higher porosity at the same burial depth and clay mineral content, proving that other clay minerals such as illite-smectite mixed layers (I/S) and illite are conducive to the development of pores. Shales possessing a high clay mineral content have a higher porosity in shallow layers (< 3500 m) and a lower porosity in deep layers (> 3500 m). Both the amount and location of the increase in porosity differ at different geothermal gradients. High geothermal gradients favor the preservation of high porosity in shale at an appropriate R o. The pore evolution of the marine-continental transitional shale is divided into five stages. Stage 2 possesses an R o of 1.0%-1.6% and has high porosity along with a high specific surface area. Stage 3 has an R o of 1.6%-2.0% and contains a higher porosity with a low specific surface area. Finally, Stage 4 has an R o of 2.0%-2.9% with a low porosity and high specific surface area.

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Division of diagenesis and pore evolution of a Permian Shanxi shale in the Ordos Basin, China

Cited by 32 publications

References 39 publications

Full-Scale Pore Structure Characteristics and the Main Controlling Factors of Mesoproterozoic Xiamaling Shale in Zhangjiakou, Hebei, China

Full-Scale Pore Structure Characteristics and the Main Controlling Factors of Mesoproterozoic Xiamaling Shale in Zhangjiakou, Hebei, China

Study on pore evolution and diagenesis division of a Permian Longtan transitional shale in Southwest Guizhou, China

Porosity model and pore evolution of transitional shales: an example from the Southern North China Basin

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