Insights into the pore structure and oil mobility in fine-grained sedimentary rocks: The Lucaogou Formation in Jimusar Sag, Junggar Basin, China

Pang, Xiaojiao; Wang, Guiwen; Kuang, Lichun; Li, Hongbin; Zhao, Yidi; Dong, Li; Zhao, Xianzheng; Wu, Souheng; Zhou, Feng; Lai, Jin

doi:10.1016/j.marpetgeo.2021.105492

Cited by 27 publications

(8 citation statements)

References 64 publications

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“…74 The adsorbed oil content has a stronger correlation with the micropore content, while the occurrence space for the free oil is primarily related to large intra-and intergranular pores and fractures in the micron scale. 67,75 In this study, the average micropore (<10 nm) volume of the Lucaogou source rock is 0.00187 cm 3 /g, accounting for about 11.14% of the total pore volume and 62.45% of the total specific surface area of the source rocks. However, the average micron-scale macropore (Figure 12a,b) and fracture (>1000 nm) (Figure 12c) volume is 0.00698cm 3 /g, accounting for about 56.47% of pore volume and 1.63% of the total specific surface area of source rocks, indicating great potential for free oil accumulation.…”

Section: Full-scalementioning

confidence: 71%

Role of Organic Matter, Mineral, and Rock Fabric in the Full-Scale Pore and Fracture Network Development in the Mixed Lacustrine Source Rock System

et al. 2022

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The mixed deposition constitutes the external clastic, intrabasinal, and pyroclastic components in both marine and lacustrine environments. The finegrained mixed lacustrine source rocks are rich in organic matter and present good unconventional energy resources. However, the mixed lacustrine source rock systems have extremely low permeabilities and need hydraulic fracturing to stimulate oil from the complex nanoscale matrix. The role of rock fabric, organic matter, and mineral compositions in full-scale pore structures is still unclear, especially for the source rock from a mixed sedimentary environment. This restricts sweet spot identification. Here, we use three groups of Permian Lucaogou source rock samples with fine laminated, thick laminated, and massive rock fabric to investigate the relationship between rock fabric, organic matter, and pore structure using a combination of mineralogy, organic geochemistry, low-pressure nitrogen adsorption, micro-CT, and mercury injection capillary pressure data. The results indicate that the Lucaogou source rocks mainly contain type I and type II kerogen and show good to excellent hydrocarbon generation potential. The source rock was deposited in a mixed environment with high contents of carbonate and less siliceous minerals, showing good frackability. The mineralogy-based ternary classification shows that the source rock mainly belongs to high total organic carbon (TOC > 4%) mixed carbonate mudstone and high TOC mixed mudstone. For mixed lacustrine source rock, the full-scale pore-fracture distribution shows that the average percentage values of pore volume for micropores (<10 nm), transitional pores (10−100 nm), mesopores (100−1000 nm), and macropores (fracture) (>1000 nm) are 11.14, 21.62, 10.77, and 56.47%, respectively. However, the average percentage values of pore surface area for the abovementioned pores are 62.45, 30.45, 5.47, and 1.63%, respectively. Both quartz and terrigenous clast present a weak-medium unimodal correlation with the TOC content. Both terrigenous clast and clay minerals control the source rock hydrocarbon generation potential. The carbonate and terrigenous clast mineral content play a significant role in micropores and transitional pores, while the clay mineral presents a negative impact on macropore development. The effect of rock fabric on shale oil potential is negligible compared with organic matter abundance. Shales with thick parallel laminae and medium TOC (2% < TOC < 4%) possess favorable shale oil potential.

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Section: Full-scalementioning

confidence: 71%

Role of Organic Matter, Mineral, and Rock Fabric in the Full-Scale Pore and Fracture Network Development in the Mixed Lacustrine Source Rock System

et al. 2022

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“…The pore structure is crucial for controlling the storage and seepage capacity of fluids in the reservoir [10][11][12]. In addition, various techniques have been used by several groups, such as low-pressure nitrogen adsorption-desorption, nuclear magnetic resonance, scanning electron microscopy, mercury compression, and thin-section identification, to explore the reservoir spatial types and pore structure characteristics of fine-grained sedimentary rocks [13,14]. High total organic carbon (TOC) fine-grained sedimentary rocks have relatively high micropore and mesopore proportions and a complex pore structure, which increases both reservoir porosity and permeability and is conducive to oil and gas transport and storage [15].…”

Section: Introductionmentioning

confidence: 99%

Comprehensive Comparison of Lacustrine Fine-Grained Sedimentary Rock Reservoirs, Organic Matter, and Palaeoenvironment: A Case Study of the Jurassic Ziliujing Formation and Xintiangou Formation in the Sichuan Basin

Li,

Wu,

et al. 2024

Minerals

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Lacustrine sedimentary formations potentially contain hydrocarbons. The lacustrine sedimentary rocks of the Ziliujung and Xintiangou Formations have been investigated for their hydrocarbon potential using low-pressure nitrogen adsorption (LP-N2A), low-field nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), total organic carbon (TOC), rock-eval pyrolysis (Rock-Eval), gas chromatography (GC), gas chromatography–mass spectrometry (GC–MS), X-ray fluorescence spectrometry (XRF), and inductively coupled plasma mass spectrometry (ICP-MS). The results show that the normalized difference of the pore parameters between the two formations is less than 10%, and the pores are mainly slit-like mesopores with high porosity. Macropores and micropores are often developed in the quartz skeleton, while mesopores often occur among organic matter, clay minerals, carbonate minerals, and pyrite particles. The organic matter abundance of the Ziliujing Formation is relatively high. Additionally, the organic matter types of the two formations are mainly type II and type III, and the sources of the organic matter are plankton and bacteria which have reached the mature gas production stage. The palaeoenvironmental differences between the depositional periods of the two formations lie within 10% of each other. The warm and humid climate promotes the development of quartz minerals to further enhance the proportion of both micropores and macropores, and the clay minerals, carbonate minerals, and pyrite carried in the terrigenous detritus are closely associated with the total organic carbon (TOC), which promotes the development of mesopores to enhance the porosity. The reservoir, organic matter, and palaeoenvironmental characteristics of fine-grained sedimentary rocks in the two formations are similar, and both of them have good potential for development. The above results provide a basic geological theoretical basis for unconventional oil and gas exploration in the northeastern margin of the Sichuan Basin.

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“…Centrifugation experiment can simulate the displacement process because the liquid cannot be moved out of the pore structure until the capillary force is lower than the centrifugation force, which has been widely used to distinguish the movable and irreducible water. − Combining NMR, centrifugation experiments, and heat-treating methods, water can be subdivided into different fluid types in tight sand, and a nine-grid model provided a method for this analysis . The movable liquid content changes with displacement pressure, and the higher the centrifugal speed is, the higher the movable liquid. − By changing the centrifugal speeds, the displacement efficiency can be obtained in reservoirs with different initial oil/gas pressures. At present, there is still less work related to the different irreducible water and its influencing factors in the tight gas reservoirs from the eastern Ordos Basin.…”

Section: Introductionmentioning

confidence: 99%

Rock Fabric of Tight Sandstone and Its Influence on Irreducible Water Saturation in Eastern Ordos Basin

Meng

Shen

et al. 2023

Energy Fuels

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After flowback, the residual fracturing fluid will reduce the gas seepage space and influence natural gas production, which attracts widespread attention. In this study, the irreducible water saturation was investigated, and its controlling factors were clarified. We target the Upper Paleozoic Taiyuan and Shihezi Formations, which belong to a tight gas reservoir in the eastern Ordos Basin. The main experiments include porosity, permeability, mineral composition, nitrogen adsorption, mercury intrusion porosimetry, nuclear magnetic resonance, and high-speed centrifugation. The specific surface area is very low and varies from 0.95 to 4.03 m 2 /g, and the median pore-throat diameter ranges from 28.6 to 698.6 nm. Through the T 2 cutoff value, the water saturation can be divided into movable water saturation (S mov ) and irreducible water saturation (S irr ). Furthermore, the S irr can be divided into water saturation in large pores controlled by the small throat (S irrl ) and water saturation controlled by the capillary force (S irrc ). In both formations, the S irr has a negative relationship with porosity, permeability, and average pore diameter and exhibits a positive relationship with the specific surface area. The S irrl has a positive relationship with the median pore-throat diameter in Taiyuan Formation, but the S irrl has a weak relationship with the median pore-throat diameter in Shihezi Formation. The S irrc has a negative relationship with porosity, permeability, and average pore diameter and displays a positive relationship with the specific surface area in Taiyuan Formation, but the S irrc has a weak relationship with these parameters in Shihezi Formation. The relationship difference between Taiyuan and Shihezi Formations was mainly caused by the pore structure, demonstrated by the amplitude ratio in three peaks. Based on the above analysis, this study is conducive to understanding the mechanism of water occurrence and its controlling factors.

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Insights into the pore structure and oil mobility in fine-grained sedimentary rocks: The Lucaogou Formation in Jimusar Sag, Junggar Basin, China

Cited by 27 publications

References 64 publications

Role of Organic Matter, Mineral, and Rock Fabric in the Full-Scale Pore and Fracture Network Development in the Mixed Lacustrine Source Rock System

Role of Organic Matter, Mineral, and Rock Fabric in the Full-Scale Pore and Fracture Network Development in the Mixed Lacustrine Source Rock System

Comprehensive Comparison of Lacustrine Fine-Grained Sedimentary Rock Reservoirs, Organic Matter, and Palaeoenvironment: A Case Study of the Jurassic Ziliujing Formation and Xintiangou Formation in the Sichuan Basin

Rock Fabric of Tight Sandstone and Its Influence on Irreducible Water Saturation in Eastern Ordos Basin

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