Study on the pore structure, fluid mobility, and oiliness of the lacustrine organic-rich shale affected by volcanic ash from the Permian Lucaogou Formation in the Santanghu Basin, Northwest China

Pan, Yongshuai; Huang, Zhilong; Guo, Xingwei; Liu, Baichuan; Wang, Guangqiu; Xu, Xiongfei

doi:10.1016/j.petrol.2021.109351

Cited by 17 publications

(9 citation statements)

References 45 publications

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“…Because of the high resistance, the fluid is easily blocked in the pore throat, with some micropores becoming dead pores; moreover, the fluid in pore cannot flow, reducing the movable fluid saturation. The macropore significantly influences the movable fluid saturation, and the large throat is suitable for fluid migration and seepage. , The large radius of the pore throat effectively increases the saturation of movable fluid …”

Section: Discussionmentioning

confidence: 99%

Oil Mobility Evaluation of Fine-Grained Sedimentary Rocks with High Heterogeneity: A Case Study of the Lucaogou Formation in the Jimusar Sag, Junggar Basin, NW China

et al. 2023

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The oil mobility in unconventional tight/shale oil reservoirs is complex because of the high heterogeneity in the matrix pore structure and connectivity. Thus, it is difficult to evaluate hydrocarbon exploration potential precisely. In this study, multistep temperature pyrolysis (MTP) Rock-Eval and 1D (dimensional) as well as 2D nuclear magnetic resonance (NMR) techniques were employed to systematically characterize the oil mobility in lacustrine fine-grained sedimentary rocks from the Lucaogou Formation in the Jimusar Sag, Junggar Basin, NW China. The results show that the Lucaogou Formation fine-grained sedimentary rocks can be subdivided into six types of lithofacies. With the increase of organic matter richness, the content of adsorbed oil increases, whereas the content of movable oil increases first and tends to stabilize (when total organic carbon (TOC) > 4%). This is because when TOC is low, the fine-grained sedimentary rocks need to self-adsorb before oil production; when TOC increases further, the generated oil will break through the absorption limit and charge into the adjacent reservoirs; therefore, the movable oil ceases to increase. Permeability is found to have a greater impact on movable fluid saturation than porosity. Meanwhile, good throat radius and pore connectivity are conducive to oil flow as movable oil is more sensitive to throats rather than pores. Furthermore, a higher content of brittle minerals is not necessarily favorable for oil flow; alternatively, more clay minerals are easy to from cements causing pore blockage, which will essentially hinder oil mobility. Overall, the organic matter content, reservoir pore structure, and rock mineral composition are the main factors affecting tight/shale oil mobility. On the basis of the above research, a conceptual model of oil mobility in different lithofacies’ reservoirs is established. These results have a reference significance for evaluating oil recoverability in fine-grained sedimentary rocks.

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Section: Discussionmentioning

confidence: 99%

Oil Mobility Evaluation of Fine-Grained Sedimentary Rocks with High Heterogeneity: A Case Study of the Lucaogou Formation in the Jimusar Sag, Junggar Basin, NW China

et al. 2023

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“…26,27,43 In general terms, however, the N 2 adsorption techniques are best suited for the investigation of pores in a range of about 2−300 nm. 16 Especially, the lower limit of the pore size, e.g., 10 nm, 37 12.1 nm, 58 30 nm, 59 and 40 nm, 60 for medium and light oil components occurrence have been widely reported. On the basis of the penetration tests, meanwhile, Zou et al 13 noticed that oil easily penetrated the pores with a size >200 nm regardless of the chemical or physical conditions.…”

Section: Classification Of a Shalementioning

confidence: 99%

Novel Method for the Classification of Shale Oil Reservoirs Associated with Mobility: Inspiration from Gas Adsorption and Multiple Isothermal Stage Pyrolysis

Gou

Chen

et al. 2023

Energy Fuels

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The characterization and description of pores in shale oil reservoirs have long been based on the classification of micropores (<2 nm), mesopores (2–50 nm), and macropores (>50 nm) in shale gas reservoirs. However, the great difference between oil and gas molecules leads to its poor applicability, which further results in the relationship between oil properties and pores being rarely understood. To establish an individual pore division method for shale oil reservoirs, N2 adsorption, Soxhlet extraction, and programmed pyrolysis were performed on the Paleogene Xin’gouzui lacustrine shale in the Jianghan Basin. With the results, a new classification method, i.e., adsorption pores (pore diameter <20 nm), restricted pores (20–100 nm), and movable pores (>100 nm), was proposed. A fractal theory and scanning electron microscopy (SEM) images confirm the rationality of this method. Hydrocarbons in movable pores determine the initial productivity of a shale oil well, while those in restricted pores are closely related to the production time of a well to some extent. Compared to the previous division methods, this novel method reveals the correlation between shale oil attributes as well as movability and pore spaces for the first time. Our work can provide more accurate evaluation results for shale oil recoverable resource potential and is of great significance for optimizing favorable areas and reducing exploration risks.

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“…Movable fluid saturation, bound water saturation, and porosity were measured in 20 samples of Longmaxi Formation shale using a low magnetic field NMR core analyzer (RecCore03). Fluid relaxation time in rock pores depends on the strength of the action of the solid surface on the fluid molecules [31]. If the action of the water molecules on the solid surface is strong, then the fluid is bound, and the bound fluid has a small T2 value; otherwise, the fluid would be movable.…”

Section: Nmr Experimentmentioning

confidence: 99%

Influencing Factors of Shale Permeability in the Longmaxi Formation, Southern Sichuan Basin and Northern Yunnan-Guizhou Depression

Han

Liu

et al. 2022

Geofluids

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The current paper studies the influencing factors of permeability in shales of the Longmaxi Formation, located in the southern Sichuan Basin, China. The methodologies used in the present study include overburden pore permeability experiments, whole rock analysis and geochemical tests, NMR measurements of fluid saturation, pore size distribution and specific surface area distribution, SEM and extraction of pore structure parameters, and core analysis. The results show the following: (1) high TOC and high maturity generate a large number of organic pores, which may improve the permeability of shale. (2) Mineral composition and rock relative permeability also have influence on permeability to a certain degree, since different minerals have different effects on shale permeability. Clay in the study area has an adverse effect on permeability. The results show that the organic-rich siliceous clay mixed shale facies in this area has the best permeability. (3) A large specific surface area and total pore volume are associated with good shale permeability, while average pore size does not correlate with permeability. A small fractal dimension of pore morphology and simple pore structure result in good permeability, and bedding is the key controlling factor for the anisotropy of shale permeability. (4) Water in shales can influence the permeability of microfractures by binding to clay minerals. Low permeability in shales with high bound water saturation suggests that water and clay mineral absorption may block flow channels, resulting in poor permeability. The purpose of this study is to clarify the influencing factors on shale permeability of the Longmaxi Formation in the study area and to provide a reference for the exploration and development of shale gas in this area of the Sichuan Basin.

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Study on the pore structure, fluid mobility, and oiliness of the lacustrine organic-rich shale affected by volcanic ash from the Permian Lucaogou Formation in the Santanghu Basin, Northwest China

Cited by 17 publications

References 45 publications

Oil Mobility Evaluation of Fine-Grained Sedimentary Rocks with High Heterogeneity: A Case Study of the Lucaogou Formation in the Jimusar Sag, Junggar Basin, NW China

Oil Mobility Evaluation of Fine-Grained Sedimentary Rocks with High Heterogeneity: A Case Study of the Lucaogou Formation in the Jimusar Sag, Junggar Basin, NW China

Novel Method for the Classification of Shale Oil Reservoirs Associated with Mobility: Inspiration from Gas Adsorption and Multiple Isothermal Stage Pyrolysis

Influencing Factors of Shale Permeability in the Longmaxi Formation, Southern Sichuan Basin and Northern Yunnan-Guizhou Depression

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