Prediction of diagenetic facies using well logs – A case study from the upper Triassic Yanchang Formation, Ordos Basin, China

Cui, Yufeng; Wang, Guiwen; Jones, Stuart J.; Zhou, Zhong‐Zhen; Ye, Ran; Lai, Jin; Li, Ruijie; Deng, Li

doi:10.1016/j.marpetgeo.2017.01.001

Cited by 74 publications

(50 citation statements)

References 40 publications

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“…Understanding diagenetic heterogeneity is vital for hydrocarbon exploration in tight sandstone reservoirs [8]. Carbonate cementation is an important diagenetic alteration that has profound impact on sandstone reservoir quality and heterogeneity [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Origin and Distribution of Carbonate Cement in Tight Sandstones: The Upper Triassic Yanchang Formation Chang 8 Oil Layer in West Ordos Basin, China

et al. 2017

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Two generations of carbonate cement as Type I (microcrystalline calcite and dolomite) and Type II (mainly Fe-calcite and Fedolomite) are recognized in Chang 8 sandstones, Ordos basin. Carbonate cement in Chang 8 sandstones is closely related to the dissolved carbon from thermal maturation of organic matters. Carbonate cement in the loosely packed framework grains precipitated shortly after deposition, and late-stage ferroan calcite and ferroan dolomite formed with progressive burial. The early diagenetic carbonate cement is partially to completely replaced by late-stage ferroan calcite and ferroan dolomite. Carbonate cement is much more commonly observed in sand bodies adjacent to Chang 7 source rocks. With increasing distance from the Chang 7 oil layers, the carbonate cement content gradually decreases. However, some tight carbonate cemented zones also occur at the sandstone-mudstone interfaces. Dissolution of Ca-feldspars by organic acids-rich fluids, together with clay mineral transformations such as illitization of smectite, would provide Ca 2+ and Mg 2+ ions for carbonate cementation. Organic acids and CO 2 rich fluids would charge into the reservoirs with the hydrocarbons, and when the CO 2 and acids were buffered by the framework grain dissolution, carbonate cement would precipitate with a decrease in CO 2 concentration.

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Section: Introductionmentioning

confidence: 99%

Origin and Distribution of Carbonate Cement in Tight Sandstones: The Upper Triassic Yanchang Formation Chang 8 Oil Layer in West Ordos Basin, China

et al. 2017

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“…Diagenetic facies is the comprehensive description of diagenesis type and degree and diagenetic minerals (Cui et al, ; Lai, Wang, Cai, et al, ; Lai, Wang, Ran, et al, ; Liu et al, ; Ozkan, Cumella, Milliken, & Laubach, ; Rushing, Newsham, & Blasingame, ; Zhang, Bai, Wang, et al, ). Diagenetic facies may be called lithofacies or sedimentary‐diagenetic facies in some cases when taking the depositional attributes into consideration (Lai, Wang, Chai, et al, ; Lai, Wang, Wang, et al, ; Wang, Cao, et al, ).…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, understanding the impact of diagenesis on reservoir quality is critical to hydrocarbon exploration and production (Khalifa & Morada, ). In addition, diagenetic facies, which is the integration of diagenesis, diagenetic minerals, and pore systems (Cui et al, ; Lai, Wang, Wang, et al, ; Liu, Zhao, Luo, Chen, & He, ; Wang, Cao, Liu, Liu, & Kashif, ; Zeng, Zhu, Zhu, & Zhang, ; Zou et al, ), can be defined by studies of thin sections, cathodoluminescence, X‐ray diffraction, SEM, and conventional well logs (Liu et al, ; Wang, Cao, et al, ) and are widely used for predicting “sweet spots” in low‐permeability sandstones (Cui et al, ; Lai et al, ; Zeng et al, ; Zou et al, ).…”

Section: Introductionmentioning

confidence: 99%

Diagenesis and reservoir quality of sandstones in the Eocene Shahejie Formation, Raoyang Sag (Jizhong Depression), Bohai Bay Basin, China

et al. 2019

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Deeply buried (3.5–4.5 km) fan deltaic and braided deltaic sandstones of the Eocene Shahejie Formation are important hydrocarbon reservoirs in the Raoyang Sag of the Bohai Bay Basin (North China). An integrated approach incorporating petrophysics, thin‐section petrography, scanning electron microscope (SEM), cathodoluminescence (CL), and well log analysis was applied to investigate diagenesis, diagenetic minerals, and their impacts on reservoir quality. The sandstones of the Sha‐3 (the third Member of the Shahejie Formation) are dominated by lithic arkoses and arkoses with a low‐moderate compositional maturity and a moderate textural maturity. The pore systems are dominated by secondary pores resulting from dissolution of framework grains, micropores among authigenic clays, and minor amounts of primary intergranular pores. Chemically unstable framework grains such as feldspar and lithic fragments experienced alteration and resulted in formation of authigenic kaolinite. Dissolution and alteration of feldspars and rock fragments and pressure solution of detrital quartz grains were the main sources for quartz cements. Mechanical compaction and cementation by calcite, dolomite, quartz, kaolinite, and mixed‐layer illite/smectite destroyed primary pores, whereas dissolution of framework grains generated secondary pores. Five types of diagenetic facies are identified based on framework mineralogy, texture, diagenetic minerals, and pore systems. These comprise the following: (a) quartz‐cemented sandstone, (b) tightly compacted sandstone, (c) carbonate‐cemented sandstone, (d) clay‐mineral‐cemented sandstone, and (e) clean dissolved sandstone. Diagenetic processes and evolution sequences for the five diagenetic facies were reconstructed based on textural relationships from thin section, SEM, and CL studies. The reservoir quality evolution of various diagenetic facies is predicted by considering variations in grain size, sorting, shape, and matrix content of sandstones. This work, which investigates the diagenetic sequence of sandstones, will provide insights into reservoir quality prediction for low‐permeability sandstones with similar tectono‐depositional settings.

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“…During the Late Triassic, the Yanchang Formation is dominated by fluvial, lacustrine, and deltaic sedimentation with a thickness of 1,000–1,300 m throughout most of the Ordos Basin (Figure ; Cui et al, ; Qiu, Liu, Wang, Deng, & Mao, ; Zou, Wang, Li, Tao, & Hou, ). Recent hydrocarbon exploration and outcrop studies have demonstrated that shallow‐lacustrine sand‐rich deltas developed extensively along the gentle slopes and central part of the basin, forming the main reservoir rocks of the Triassic oilfields (Zhou et al, ).…”

Section: Geological Backgroundmentioning

confidence: 99%

Tight oil sandstones in Upper Triassic Yanchang Formation, Ordos Basin, N. China: Reservoir quality destruction in a closed diagenetic system

et al. 2018

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An investigation of the Triassic Yanchang Formation, Ordos Basin, N. China, revealed that the diagenesis and quality of tight oil sandstone reservoirs (with an average porosity of 9.83% and an average permeability of 0.96 mD) were controlled by a closed diagenetic system. The carbonate cements observed in the sandstone were derived from decarboxylation of organic matter that occurred in the adjacent mudstones. These reactions supplied CO32−, which reacted with cations derived from grain dissolution in the sandstones. The average size of the diagenetic geochemical system with respect to carbonate cements was small (<6 × 10−2 m3), comprising sandstone and its adjacent mudstone(s). The carbonate cements tend to concentrate in the marginal sandstone, which is taken to indicate that the flux of CO32− into the sandstones limited the quantity of carbonate precipitated. In addition, the mass is near balance between the amount of feldspar dissolution and its by‐products in the central sandstone (distance to the sandstone/mudstone interface is mainly more than 1 m), where the permeability of sandstone will present a decreasing trend with the increase of feldspar dissolution pores. The pore space of central sandstone will be just redistributed, with primary intergranular pores converting to feldspar dissolution pores and clay mineral micropores. Thus, the best part of the sandstone reservoirs tends to be the central part of sandstone. In particular, sandstones that are more than 2 m thick could be the potential hydrocarbon reservoirs because they retain the best porosity (average of 13.6%) and permeability (average of 1.8 mD). The results of our study provide an important guide for the exploration of tight oil sandstones in other petroliferous basins over the world.

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Prediction of diagenetic facies using well logs – A case study from the upper Triassic Yanchang Formation, Ordos Basin, China

Cited by 74 publications

References 40 publications

Origin and Distribution of Carbonate Cement in Tight Sandstones: The Upper Triassic Yanchang Formation Chang 8 Oil Layer in West Ordos Basin, China

Origin and Distribution of Carbonate Cement in Tight Sandstones: The Upper Triassic Yanchang Formation Chang 8 Oil Layer in West Ordos Basin, China

Diagenesis and reservoir quality of sandstones in the Eocene Shahejie Formation, Raoyang Sag (Jizhong Depression), Bohai Bay Basin, China

Tight oil sandstones in Upper Triassic Yanchang Formation, Ordos Basin, N. China: Reservoir quality destruction in a closed diagenetic system

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