Origin of different chlorite occurrences and their effects on tight clastic reservoir porosity

Cao, Zhe; Liu, Guangdi; Meng, Wei; Wang, Peng; Yang, Chengyu

doi:10.1016/j.petrol.2017.10.080

Cited by 43 publications

(28 citation statements)

References 28 publications

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“…The chlorite primarily formed in the eodiagenetic stage because the primary contact types between the particles covered by grain-coating chlorite cement were point and line contacts (Worden & Morad, 2003) (Figure 10a). There are multiple conditions for the formation of authigenic chlorites, including the presence of a precursor clay mineral as the material base and the presence of Fe 2+ and Mg 2+ from pore water (Cao et al, 2018;Yu et al, 2019;Zhu et al, 2017). The chlorites that transformed from precursor clay minerals retain their original structural properties (Marfil, La Iglesia, Herrero, Scherer, & Delgado, 2014;Worden & Morad, 2003).…”

Section: Formation Of Clay Mineralsmentioning

confidence: 99%

“…However, when the acidic pore fluid is suitable for the formation of silica cement, the fluid exerts a dissolution effect on the chlorite cement, which was initially formed under alkaline conditions. Consequently, the concentration of silica in the fluid is decreased, preventing the formation of silica cement and protecting the pore space from being filled (Cao et al, 2018;Zhang, Shi, An, Zeng, & Zhang, 2010). Mineral alteration during chlorite formation changes the pore structure of the reservoir and consumes a large amount of pore water, which reduces pressure generation; water is replaced by gas, which fills the pores, forming oil and gas enrichment (Zhang et al, 2010).…”

Section: Impact Of Diagenesis On Reservoir Qualitymentioning

confidence: 99%

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Diagenesis and reservoir quality of the second member of the Upper Triassic Xujiahe Formation tight gas sandstones in the Western Sichuan Depression, southwest China

et al. 2021

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The tight sandstones reservoir of the second member of the Xujiahe Formation (Xu2 member) is gradually becoming the main reservoir for natural gas exploration and exploitation in the Western Sichuan Basin. The tight sandstone is normally deeply buried, where it is controlled by complex diagenetic processes. To gain insights into reservoir exploration of the Xu2 member, the diagenetic history and the impacts of diagenesis on reservoir quality were established using several experimental methods.The sandstones were found to be mainly litharenite, sublitharenite, and feldspathic litharenite. The reservoir quality was characterized by low porosity (3.4% on average), low permeability (0.17 mD on average), low pore throat radius, and high displacement pressure. The tight sandstones experienced a series of significant diagenetic processes, including mechanical compaction, early dissolution, and precipitation of carbonate and siliceous cements during eodiagenesis. They also underwent chemical compaction, late dissolution, and transformation of clay minerals during mesodiagenesis. The silica cementation mainly resulted from chemical compaction, feldspar dissolution, and the transformation of clay minerals. A higher degree of compaction has a vital role in destroying most of the primary pores. Cementation had a significant impact on reducing the porosity and permeability, although chlorite preserved primary pores by slowing the compaction. This study aimed to provide a comprehensive insight into diagenesis and its impact on the reservoir quality of deeply buried sandstone, and provide insights into reservoir exploration and development in deeply buried tight sandstones.

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Section: Formation Of Clay Mineralsmentioning

confidence: 99%

Section: Impact Of Diagenesis On Reservoir Qualitymentioning

confidence: 99%

Diagenesis and reservoir quality of the second member of the Upper Triassic Xujiahe Formation tight gas sandstones in the Western Sichuan Depression, southwest China

et al. 2021

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“…The chlorite is generally produced as coatings of detrital grains, which has been widely proven to be able to retain more interparticle pores by preventing the overgrowth of quartz (Fig. 16c) (Zhu et al, 2017;Cao et al, 2018). The porosity and permeability of sandstones increase with the increase of chlorite content (Figs.…”

Section: Cementationmentioning

confidence: 99%

Characteristics of Tight Sandstone Reservoirs and Controls of Reservoir Quality: A Case Study of He 8 Sandstones in the Linxing Area, Eastern Ordos Basin, China

Gao

Wang

et al. 2019

Acta Geologica Sinica (Eng)

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Determining the process of densification and tectonic evolution of tight sandstone can help to understand the distribution of reservoirs and find relatively high‐permeability areas. Based on integrated approaches of thin section, scanning electron microscopy (SEM), cathode luminescence (CL), nuclear magnetic resonance (NMR), X‐ray diffraction (XRD), N2 porosity and permeability, micro‐resistivity imaging log (MIL) and three‐dimensional seismic data analysis, this work discussed the reservoir characteristics of the member 8 of the Permian Xiashihezi Formation (He 8 sandstones) in the Linxing area of eastern Ordos Basin, determined the factors affecting reservoir quality, and revealed the formation mechanism of relatively high‐permeability areas. The results show that the He 8 sandstones in the Linxing area are mainly composed of feldspathic litharenites, and are typical tight sandstones (with porosity <10% and permeability <1 mD accounting for 80.3% of the total samples). Rapid burial is the main reason for reservoir densification, which resulted in 61% loss of the primary porosity. In this process, quartz protected the original porosity by resisting compaction. The cementation (including carbonate, clay mineral and siliceous cementation) further densified the sandstone reservoirs, reducing the primary porosity with an average value of 28%. The calcite formed in the eodiagenesis occupied intergranular pores and affected the formation of the secondary pores by preventing the later fluid intrusion, and the Fe‐calcite formed in the mesodiagenetic stage densified the sandstones further by filling the residual intergranular pores. The clay minerals show negative effects on reservoir quality, however, the chlorite coatings protected the original porosity by preventing the overgrowth of quartz. The dissolution of feldspars provides extensive intergranular pores which constitute the main pore type, and improves the reservoir quality. The tectonic movements play an important role in improving the reservoir quality. The current tectonic traces of the study area are mainly controlled by the Himalayan movement, and the high‐permeability reservoirs are mainly distributed in the anticline areas. Additionally, the improvement degree (by tectonic movements) of reservoir quality is partly controlled by the original composition of the sandstones. Thus, the selection of potential tight gas well locations in the study area should be focused on the anticline areas with relatively good original reservoir quality. And the phenomena can be referenced for other fluvial tight sandstone basins worldwide.

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“…Formation and evolution of diagenetic products could result in preservation or destruction of primary pores as well as formation and transformation of secondary pores, which could significantly influence the formation and occurrence of effective reservoirs in the deep part of petroliferous basins [4][5][6][7][8][9][10][11][12][13][14][15][16]. Previous studies mainly highlighted evolution of physical properties of clastic rocks and primarily investigated diagenetic facies and sequences based on sedimentological and petrological analyses [11,[17][18][19][20][21][22][23][24][25][26]. However, insufficient attention was paid to the nature of diagenesis, namely, the exchange and migration of basin materials loaded by pore fluids.…”

Section: Introductionmentioning

confidence: 99%

Material Exchange and Migration between Pore Fluids and Sandstones during Diagenetic Processes in Rift Basins: A Case Study Based on Analysis of Diagenetic Products in Dongying Sag, Bohai Bay Basin, East China

et al. 2018

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The exchange and migration of basin materials that are carried by pore fluids are the essence of diagenesis, which can alter physical properties of clastic rocks as well as control formation and distribution of favorable reservoirs of petroliferous basins. Diagenetic products and pore fluids, resulting from migration and exchange of basin materials, can be used to deduce those processes. In this study, 300 core samples from 46 wells were collected for preparation of casting thin sections, SEM, BSE, EDS, inclusion analysis, and isotope analysis in Dongying Sag, Bohai Bay Basin, East China. Combined with geochemical characteristics of pore fluids and geological background of the study area, the source and exchange mechanisms of materials in the pore fluids of rift basins were discussed. It was revealed that the material exchange of pore fluids could be divided into five stages. The first stage was the evaporation concentration stage during which mainly Ca 2+ , Mg 2+ , and CO 3 2− precipitated as high-Mg calcites. Then came the shale compaction stage, when mainly Ca 2+ and CO 3 2− from shale compaction water precipitated as calcites. The third stage was the carboxylic acid dissolution stage featured by predominant dissolution of plagioclases, during which Ca 2+ and Na + entered pore fluids, and Si and Al also entered pore fluids and then migrated as clathrates, ultimately precipitating as kaolinites. The fourth stage was the organic CO 2 stage, mainly characterized by the kaolinization of K-feldspar as well as dissolution of metamorphic lithic fragments and carbon cements. During this stage, K + , Fe 2+ , Mg 2+ , Ca 2+ , HCO 3 − , and CO 3 2− entered pore fluids. The fifth stage was the alkaline fluid stage, during which the cementation of ferro-carbonates and ankerites as well as illitization or chloritization of kaolinites prevailed, leading to the precipitation of K + , Fe 2+ , Mg 2+ , Ca 2+ , and CO 3 2− from pore fluids.

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Origin of different chlorite occurrences and their effects on tight clastic reservoir porosity

Cited by 43 publications

References 28 publications

Diagenesis and reservoir quality of the second member of the Upper Triassic Xujiahe Formation tight gas sandstones in the Western Sichuan Depression, southwest China

Diagenesis and reservoir quality of the second member of the Upper Triassic Xujiahe Formation tight gas sandstones in the Western Sichuan Depression, southwest China

Characteristics of Tight Sandstone Reservoirs and Controls of Reservoir Quality: A Case Study of He 8 Sandstones in the Linxing Area, Eastern Ordos Basin, China

Material Exchange and Migration between Pore Fluids and Sandstones during Diagenetic Processes in Rift Basins: A Case Study Based on Analysis of Diagenetic Products in Dongying Sag, Bohai Bay Basin, East China

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