Key factors controlling oil contents in different lithofacies shales from the Funing Formation, Subei Basin: Evidence from scanning electron microscopy

Zhang, Pengfei; Yin, Yajie; Lu, Shuangfang; Wang, Junjie; Zhang, Junjian; Zhi, Qi; Huang, Hongsheng

doi:10.1016/j.geoen.2023.212115

Cited by 4 publications

(12 citation statements)

References 33 publications

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“…Pore fluids exist in shale pore networks, and the occurrence and distribution of fluids are directly affected by pore types, sizes, morphologies, etc . Pores can be well analyzed by high-resolution SEM images after argon-ion polishing . The pyrite can be first identified due to the largest gray values, and it appears as strawberry-shaped aggregates with developed intercrystalline pores (Figure a,i).…”

Section: Resultsmentioning

confidence: 99%

“…Compared with shales from the Qingshankou Formation, the studied shales have much 23 Pores can be well analyzed by high-resolution SEM images after argon-ion polishing. 58 The pyrite can be first identified due to the largest gray values, and it appears as strawberry-shaped aggregates with developed intercrystalline pores (Figure 9a,i). The dolomite is commonly characterized by the regular rhombohedra with large gray values, mainly related to the interparticle pores (Figure 9a−d).…”

Section: Pore Fluid Contents At Ar and Wor Statesmentioning

confidence: 99%

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Insight into Fluid Occurrence and Pore Structure of Lacustrine Shale from the Cretaceous Tengger Formation, A’nan Sag, Erlian Basin, China

Xiang,

Dan,

et al. 2024

Energy Fuels

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Fluid occurrence and pore structure are prerequisites for exploring the enrichment pattern of shale oil. The Cretaceous Tengger Formation in the A'nan Sag, Erlian Basin, China, contains abundant shale oil resources. In this study, a series of NMR T 2 and T 1 −T 2 , combined with Rock-Eval, scanning electron microscopy (SEM), and low-temperature nitrogen adsorption−desorption (LTNA/D), were conducted to clarify the fluid occurrence and pore structure characteristics of the shale oil reservoirs. Meanwhile, the influences of the pore structure on fluid occurrence were discussed. Results suggest that the in situ occurrences and distributions of pore water and oil can be well analyzed by the NMR T 1 −T 2 technique combined with water and oil restorations. The selected shales are characterized by high contents of capillary-bound water and bound oil, and bound oil mainly contributes to shale oil, followed by adsorbed and movable oil. The shales at the as-received state have lost half of the capillary-bound water, as well as most of the bound and movable oil, while adsorbed oil is less affected. The pore spaces primarily consist of interparticle pores related to brittle granules, followed by intraparticle pores in clay mineral aggregates. The T 2 spectra are characterized by the dominant peak p2 ranging from 0.7 to 20 ms, corresponding to the developed mesopores (100−1000 nm). Fluid occurrence is closely related to pore structures. Capillary-bound water primarily occurs in micropores (<25 nm) and minipores (25−100 nm) and coexists with adsorbed oil. Mesopores and macropores (>1000 nm) are mainly saturated with bound and movable oil, respectively. The developed large pores generally correspond to less capillary-bound water but more shale oil, especially bound and movable oil. These findings may improve the understanding of enrichment mechanisms of shale oil and provide the references for sweet spot exploitation in the A'nan Sag, Erlian Basin.

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Section: Resultsmentioning

confidence: 99%

Section: Pore Fluid Contents At Ar and Wor Statesmentioning

confidence: 99%

Insight into Fluid Occurrence and Pore Structure of Lacustrine Shale from the Cretaceous Tengger Formation, A’nan Sag, Erlian Basin, China

Xiang,

Dan,

et al. 2024

Energy Fuels

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“…The comprehensive analysis of logging cuttings, RT curve values, GR log curve signatures, and seismic facies showed that delta front and littoral-shallow lacustrine subfacies were deposited in the central part of the Qintong Sag (Figure 13) [24,69].…”

Section: Sedimentary Facies Analysis Using Well Logs and Seismic Faciesmentioning

confidence: 99%

“…The Qintong Sag is one of the most hydrocarbon-rich regions in China, contributing approximately 30% of the oil and gas reserves in the Subei Basin [23,24]. The common lack of potential provenance and sedimentary facies analysis has seriously hindered oil exploration.…”

Section: Introductionmentioning

confidence: 99%

A Multi-Faceted Approach to Determining the Provenance of the Lacustrine Rift Basin in the Initial Rifting Stage: A Case Study of the Paleocene Qintong Sag, Subei Basin, East China

Jiang,

Liu,

Xia

et al. 2024

Minerals

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Research on the provenance of sedimentary systems is key to better understanding the sedimentary framework and improving exploration-associated decision-making and deployment. With regard to the provenance of sedimentary systems, there is still poor understanding in the initial rifting stage due to imbalanced and insufficient exploration and a common lack of seismic data, which have seriously hindered oil exploration in the Qintong Sag, Subei Basin. This study aimed at investigating the provenance in the direction of the fault-terrace zone in the southeast part of the Qintong Sag and aimed to examine whether large-scale sedimentary systems are formed by these sediment sources. Integrated analysis of heavy minerals, sandstone petrologic maturity, drilling cutting dates, 3D seismic data, and well logs was employed to identify the provenance. This study is the first time that large-scale provenance from the direction of the fault-terrace zone has been discovered in the third member of the Paleocene Funing Formation (referred to as the third Mbr of the Funing Fm in this paper) in the Subei Basin, east China. The documentation shows that sediments from the northwest Wubao Low Uplift and the southeast Taizhou Uplift can be distinguished in the Qintong Sag, with the large-scale delta system in the central and eastern part of the Qintong Sag comprising sediments from the Taizhou Uplift, improving upon previous understanding of the sedimentary framework. The deposition formed by the Taizhou Uplift provenance system was characterized by gradual weakening of the hydrodynamic forces, a decreasing sediment supply, and shrinking of the retrogradational delta depositional systems with good reservoir qualities, which are characterized by high-quality source–reservoir–cap combinations and are likely to develop into a hydrocarbon-rich belt. The discovery of the Taizhou Uplift provenance proves that there may be major provenance and large-scale sedimentary systems from the fault-terrace zone of the rift basins in the initial rifting stage. The experience of rapid retrogradation showed that these large-scale delta systems are likely to only flourish in the initial rifting stage. This study is helpful for improving the understanding of sediment provenance and the sedimentary framework of lacustrine rift basins in the initial rifting stage.

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“…19,25,26 However, studies focusing solely on reservoir characteristics or the hydrocarbon generation potential have limitations. Zhang et al ( 2023) 12 combined these aspects to investigate different lithofacies shales in the second member (second Mbr) of the Funing Formation in the Subei Basin. Their research indicates that the abundance of OM and the development of pores control the enrichment of shale oil.…”

Section: Introductionmentioning

confidence: 99%

Geological Controls on Reservoir Characteristics Influencing Shale Oil Occurrence in Lacustrine Mixed Fine-Grained Sediments of the Paleogene Funing Formation, Subei Basin

Deng,

Lu,

et al. 2024

Energy Fuels

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Unconventional lacustrine shale formations exhibit significant heterogeneity, with substantial variations in vertical shale oil content vertically. However, most research focuses on the reservoir characteristics of shales, analyzing the impact of organic matter and pore structure on shale storage while overlooking the material foundation of shale hydrocarbon generation capacity. This study adopts petrophysical and geochemical experiments to systematically analyze the total organic content (TOC), free hydrocarbon (S1), thermal maturity (Ro), OM type, mineral content, and overall pore system of the second member of the Funing Formation in Qintong Sag, the Subei Basin. Additionally, statistical methods were employed to analyze the data correlations. The results indicate that the TOC content, thermal maturity, mineral composition, and pore network structure significantly influence the enrichment of lacustrine shale oil. Fluorescence observations reveal that shale oil primarily occurs within the interparticle pores, and its migration is influenced by microfractures. The maturity level is low (within the oil window), with organic matter significantly reducing the pore volume and specific surface area while enhancing the pore throat size. As the TOC content increases, the concentration of free hydrocarbons (S1) also rises. Oil occurrence is influenced by both the mineral composition and pore network structure. Clay minerals positively impact the pore volume and specific surface area but negatively affect the pore throat size. The critical threshold for clay minerals is 28%. Free oil initially increases with the clay mineral content but decreases when the clay mineral content surpasses the critical threshold. Carbonate minerals undergo alteration due to organic acids formed during hydrocarbon generation. The critical threshold for carbonate minerals is 30%. Furthermore, the predominant mineral combination was identified. Free oil increases with increasing carbonate mineral content and then gradually declines. When the ratio of clay minerals to siliceous minerals to carbonate minerals ranged from 1:1:1 to 1:2:1, free oil increased with a higher siliceous mineral content. Additionally, based on qualitative and quantitative pore analysis, a microscopic pore network structure model of reservoirs was developed. It was elucidated that a network structure comprising brittle minerals and mixed pore types facilitates the storage and migration of shale oil.

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Key factors controlling oil contents in different lithofacies shales from the Funing Formation, Subei Basin: Evidence from scanning electron microscopy

Cited by 4 publications

References 33 publications

Insight into Fluid Occurrence and Pore Structure of Lacustrine Shale from the Cretaceous Tengger Formation, A’nan Sag, Erlian Basin, China

Insight into Fluid Occurrence and Pore Structure of Lacustrine Shale from the Cretaceous Tengger Formation, A’nan Sag, Erlian Basin, China

A Multi-Faceted Approach to Determining the Provenance of the Lacustrine Rift Basin in the Initial Rifting Stage: A Case Study of the Paleocene Qintong Sag, Subei Basin, East China

Geological Controls on Reservoir Characteristics Influencing Shale Oil Occurrence in Lacustrine Mixed Fine-Grained Sediments of the Paleogene Funing Formation, Subei Basin

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