Calculation of oil saturation in clay-rich shale reservoirs: A case study of Qing 1 Member of Cretaceous Qingshankou Formation in Gulong Sag, Songliao Basin, NE China

LI, Chaoliu; Yan, Weilin; Wu, Hongliang; Han, Tao; ZHENG, Jiandong; Yu, Jun; Zhou, Feng; Xu, Huaimin

doi:10.1016/s1876-3804(23)60354-4

Cited by 13 publications

(3 citation statements)

References 5 publications

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“…Resistivity and polarizability are crucial physical parameters in geophysical exploration, extensively employed in shale gas exploration. On one hand, resistivity is commonly used as a parameter in logging interpretation models for determining reservoir properties such as shale gas water saturation, total organic carbon (TOC), thermal maturity, and fractures (Hinds and Berg, 1990; Passey et al, 2010;Zhao et al, 2019;Zhang et al, 2021;Li et al, 2022). On the other hand, in contrast to regions like North America, the shale gas reservoirs in Southern China exhibit complex geological structures and substantial burial depths, presenting signi cant challenges for seismic exploration due to intricate terrain conditions (Zhang et al, 2013;He et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Controlling mechanism of shale palaeoenvironment on its resistivity and polarizability: A case study of the Longmaxi Formation in Southern Sichuan

Yang,

Zhang,

Wang

et al. 2024

Preprint

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The mineral composition, content, and organic matter enrichment in shale are significantly influenced by the sedimentary environment. However, there is a limited understanding of how the sedimentary environment impacts the electrical resistivity and polarization properties of shale. This study conducts experimental tests on shale from the Longmaxi Formation in the extensively explored Sichuan Basin of China, employing techniques such as complex resistivity, X-ray diffraction, organic geochemistry, porosity analysis, elemental geochemistry, and argon-ion polishing scanning electron microscopy. The experimental findings reveal the following key points: 1) The core resistivity of the Longmaxi Formation shale ranges from 14.56 Ω·m to 115.96 Ω·m, with an average value of 64.08 Ω·m. The polarization rate ranges from 0.07 to 0.32, with an average of 0.15. 2) Redox conditions and paleoproductivity primarily influence TOC content and the formation of biogenic quartz. The content of pyrite is influenced by redox environments, while clay minerals and terrigenous quartz content are affected by paleoclimate and terrigenous input. 3) The interconnected network of organic matter pores with other types of pores and the content of pyrite are the main controlling factors affecting resistivity. The pyrite content also influences the polarization effect of shale. 4) Redox conditions and paleoproductivity positively influence conductivity and polarization, whereas terrigenous input and paleoclimate have inhibitory effects on both. This study provides essential theoretical insights for logging interpretation, electromagnetic exploration of shale gas and subsequent monitoring of hydraulic fracturing.

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Section: Introductionmentioning

confidence: 99%

Controlling mechanism of shale palaeoenvironment on its resistivity and polarizability: A case study of the Longmaxi Formation in Southern Sichuan

Yang,

Zhang,

Wang

et al. 2024

Preprint

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“…Gulong shale oil is located in the Songliao Basin in Daqing, China, and is situated in sedimentary deposits of freshwater to slightly brackish water lake basins. Its main body is a pure shale geological structure [4][5][6]. Gulong shale exhibits significant differences from other shale reservoirs around the world in terms of its rock composition, physical properties, oil content, and shale oil mobility [7,8].…”

Section: Introductionmentioning

confidence: 99%

NMR-Based Analysis of Fluid Occurrence Space and Imbibition Oil Recovery in Gulong Shale

Xu,

Jiang,

Liu

et al. 2023

Processes

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The Gulong shale oil reservoir is situated in freshwater to slightly saline lacustrine basins mainly consisting of a pure shale geological structure, which is quite different from other shale reservoirs around the world. Currently, the development of Gulong shale oil mainly relies on hydraulic fracturing, while the subsequent shut-in period for imbibition has been proven to be an effective method for enhancing shale oil recovery. To clarify the characteristics of the fluid occurrence space and the variation in the fluid occurrence during saltwater imbibition in Gulong shale, this paper carried out porosity and permeability tests on Gulong shale cores and analyzed the fluid occurrence space characteristics and imbibition oil recovery based on nuclear magnetic resonance (NMR). In the porosity and permeability tests, T2 distributions were used to correct the porosity measured by the saturation method to obtain the NMR porosity. Combined with the identification of fractures in shale cores using micro-CT and the analysis of porosity and permeability parameters, it was found that the permeability of the shale cores was related to the development of fractures in the shale cores. Through the testing and analysis of T1-T2 maps of the shale cores before and after saturation with oil, it was found that the shale mainly contained heavy oil, light oil, and clay-bound water, and they were distributed in different regions in the T1-T2 maps. Finally, the T1-T2 maps of the shale cores at different imbibition stages were analyzed, and it was found that saltwater mainly entered the minuscule inorganic pores of clay minerals during the imbibition process and squeezed the larger-sized inorganic pores containing light oil through the hydration expansion effect, thus expelling the light oil from the shale core and achieving the purpose of enhanced oil recovery.

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“…With the continuous exploration, development, and consumption of conventional oil and gas resources, it is necessary for people to broaden their horizons and focus on more diverse energy supplies. Unconventional energy sources have gradually become an important source of global energy supply [1][2][3][4][5][6][7][8][9][10][11][12][13]. Unconventional reservoirs are defined by the USA Gas Policy Act of 1978 as those that exhibit a matrix permeability lower than 0.1 mD [14].…”

Section: Introductionmentioning

confidence: 99%

A New Method for Mobility Logging Evaluation Based on Flowing Porosity in Shale Oil Reservoirs

Shen

Yan

Wang³

et al. 2023

Processes

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Shale oil reservoirs differ from conventional reservoirs in several aspects, including the sedimentary model, accumulation mechanism, and reservoir characteristics, which pose significant challenges to their exploration and development. Therefore, identifying the location of optimal spots is crucial for the successful exploration and development of shale oil reservoirs. Mobility, particularly in low-permeability shale oil reservoirs with nano-scale pores, is a crucial petrophysical property that determines the development plan. However, two-dimensional nuclear magnetic resonance (2D-NMR) is expensive and has limited applicability, although it can estimate shale oil mobility. Hence, it is of great significance to find a precise method for evaluating shale oil mobility using conventional logging. In this paper, we propose a new method for assessing shale oil mobility based on free oil porosity derived from the difference in flowing porosity detected at different ranges of logging, utilizing the Maxwell conductivity model and conductivity efficiency theory. Our study shows that longitudinal-T2 (T1-T2) NMR logging can accurately evaluate the mobility of shale oil. This is demonstrated by comparing the processing results obtained from our proposed method with those from 2D-NMR and laboratory NMR experiments. The predicted results based on conventional well logs also show good agreement with experimental results, confirming the effectiveness and reliability of our new method. Our proposed method carries reference significance for evaluating shale oil reservoir quality.

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Calculation of oil saturation in clay-rich shale reservoirs: A case study of Qing 1 Member of Cretaceous Qingshankou Formation in Gulong Sag, Songliao Basin, NE China

Cited by 13 publications

References 5 publications

Controlling mechanism of shale palaeoenvironment on its resistivity and polarizability: A case study of the Longmaxi Formation in Southern Sichuan

Controlling mechanism of shale palaeoenvironment on its resistivity and polarizability: A case study of the Longmaxi Formation in Southern Sichuan

NMR-Based Analysis of Fluid Occurrence Space and Imbibition Oil Recovery in Gulong Shale

A New Method for Mobility Logging Evaluation Based on Flowing Porosity in Shale Oil Reservoirs

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