1D and 2D Nuclear magnetic resonance (NMR) relaxation behaviors of protons in clay, kerogen and oil-bearing shale rocks

Zhang, Pengfei; Lu, Shuangfang; Li, Junqian; Chang, Xiangchun

doi:10.1016/j.marpetgeo.2019.104210

Cited by 118 publications

(84 citation statements)

References 22 publications

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“…In contrast, 2D NMR, especially high-frequency 2D NMR, can improve the detection ability of trace signals and can more efficiently distinguish light oil, heavy components, kerogen, bound water and other fluids in shales. Specifically, kerogen (with high T 1 ) and structural water have shorter T 2 and wider T 1 , oil generally has a higher T 1 /T 2 ratio than water (with low T 1 ), and the T 2 value of adsorbed oil is lower than that of movable oil Khatibi et al, 2019;Song and Kausik, 2019;Zhang P. F. et al, 2020) (Figure 9A). Based on the principle that 2D NMR can effectively distinguish hydrogen nuclei of fluids in different occurrence states, researchers have combined 2D NMR with geochemical experiments, such as rock pyrolysis, solvent extraction, and quantitative grain fluorescence on extract, to comprehensively analyze the content of movable shale oil (Bai et al, 2019;Liu B. et al, 2019;Li J.…”

Section: Nmr Methodsmentioning

confidence: 99%

Oil Retention in Shales: A Review of the Mechanism, Controls and Assessment

et al. 2021

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Shale oil is a vital alternative energy source for oil and gas and has recently received an extensive attention. Characterization of the shale oil content provides an important guiding significance for resource potential evaluation, sweet spot prediction, and development of shale oil. In this paper, the mechanism, evaluation and influencing factors of oil retention in shales are reviewed. Oil is retained in shales through adsorption and swelling of kerogen, adsorption onto minerals and storage in shale pores. Quite a few methods are developed for oil content evaluation, such as three-dimensional fluorescence quantitation, two-dimensional nuclear magnetic resonance (2D NMR), solvent extraction, pyrolysis, multiple extraction-multiple pyrolysis-multiple chromatography, logging calculation, statistical regression, pyrolysis simulation experiment, and mass balance calculation. However, the limitations of these methods represent a challenge in practical applications. On this basis, the influencing factors of the oil retention are summarized from the microscale to the macroscale. The oil retention capacity is comprehensively controlled by organic matter abundance, type and maturity, mineral composition and diagenesis, oil storage space, shale thickness, and preservation conditions. Finally, oil mobility evaluation methods are introduced, mainly including the multitemperature pyrolysis, 2D NMR, and adsorption-swelling experiment, and the influencing factors of movable shale oil are briefly discussed. The aim of this paper is to deepen the understanding of shale oil evaluation and provide a basis for further research.

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Section: Nmr Methodsmentioning

confidence: 99%

Oil Retention in Shales: A Review of the Mechanism, Controls and Assessment

et al. 2021

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“…Area. For the unconventional reservoirs, the hydraulic fracturing treatment concurrent with the horizontal well technology provide more surface area for hydrocarbon flow and thus lead to the rapid oil production from shale reservoirs indirectly [70][71][72]. From this perspective, the surface area of the organic and inorganic pores may relate to more fractures and greater pore volume; therefore, this pore structure parameter is considered a vital indicator of shale oil [73][74][75].…”

Section: The Relationships Between Pore Types and Pore Surfacementioning

confidence: 99%

Geochemical Properties and Pore Structure Control on Oil Extraction of Shale

Liu

et al. 2021

Lithosphere

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Despite geochemical properties and pore structures for shale oil extraction, the interplay among shale chemistry, pore network, and hydrocarbon movability still is an open question. Here, by using hybrid experimental methods, including backscatter scanning electron microscopy, X-ray diffraction, adsorption/desorption isotherm, and nuclear magnetic resonance, we provide a general characteristic of geochemistry and pore structures of Chang 7 (C7) shale in Ordos basin and figure out how these properties impact the shale oil extraction. Our results confirmed that the C7 shale in Ordos basin could be divided into three types based on the mineral components with various pore structures, and the proportion of the pores that radius below 4.8 nm (from adsorption branch) or 3.8 nm (from desorption branch) play a dominant role in the determination of pore size distributions. The kerogen index that is derived from maceral types was the most significant geochemical indicator; high kerogen index was corresponding to large pore volumes and surface areas, but low pore diameters. We identify the pore structure mechanism—mesopores predominantly or micropores abundantly (increase free fluid index) and absence of inorganic or organic pores (decrease free fluid index)—responsible for the oil extraction capability and show that the unmovable fluid stained in the voids would lead to the slow rate decay of the curves, which caused the nonsignal disturbance. Our results demonstrate the powerful control of maceral components and pore diameters on shale oil extraction and show the markedly different flow behavior of various types of shale.

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“…Both casting the thin section and SEM can directly observe the pore characteristics in two dimensions, but SEM has a higher resolution [29][30][31][32]. The methods of NA and NMR are indirect ways to reflect the pore size distribution, while the MIP method can reflect the pore throat size distribution [33,34]. For researching the mineral distribution in a large area, the quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) is regarded as an effective way [35].…”

Section: Pore Throat Size Distribution Sem and Qemscan Analysismentioning

confidence: 99%

The Effect of Fracturing Fluid Saturation on Natural Gas Flow Behavior in Tight Reservoirs

Meng

Shen

et al. 2020

Energies

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Hydraulic fracturing becomes an essential method to develop tight gas. Under high injection pressure, fracturing fluid entering into the formation will reduce the flow channel. To investigate the influence of water saturation on gas flow behavior, this study conducted the gas relative permeability with water saturation and the flow rate with the pressure gradient at different water saturations. As the two dominant tight gas-bearing intervals, the Upper Paleozoic Taiyuan and Shihezi Formations deposited in Ordos Basin were selected because they are the target layers for holding vast tight gas. Median pore radius in the Taiyuan Formation is higher than the one in the Shihezi Formation, while the most probable seepage pore radius in the Taiyuan Formation is lower than the one in the Shihezi Formation. The average irreducible water saturation is 54.4% in the Taiyuan Formation and 61.6% in the Shihezi Formation, which indicates that the Taiyuan Formation has more movable water. The average critical gas saturation is 80.4% and 69.9% in these two formations, respectively, which indicates that the Shihezi Formation has more movable gas. Both critical gas saturation and irreducible water saturation have a negative relationship with porosity as well as permeability. At the same water saturation, the threshold gradient pressure of the Taiyuan Formation is higher than the one in the Shihezi Formation, which means that water saturation has a great influence on the Taiyuan Formation. Overall, compared with the Shihezi Formation, the Taiyuan Formation has a higher median pore size and movable water saturation, but water saturation has more influence on its gas flow capacity. Our research is conducive to understanding the effect of fracturing fluid filtration on the production of natural gas from tight reservoirs.

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1D and 2D Nuclear magnetic resonance (NMR) relaxation behaviors of protons in clay, kerogen and oil-bearing shale rocks

Cited by 118 publications

References 22 publications

Oil Retention in Shales: A Review of the Mechanism, Controls and Assessment

Oil Retention in Shales: A Review of the Mechanism, Controls and Assessment

Geochemical Properties and Pore Structure Control on Oil Extraction of Shale

The Effect of Fracturing Fluid Saturation on Natural Gas Flow Behavior in Tight Reservoirs

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