Reservoir quality, natural fractures, and gas productivity of upper Triassic Xujiahe tight gas sandstones in western Sichuan Basin, China

Yue, Dali; Wu, Shenghe; Xu, Zhangyou; Xiong, Lihua; Chen, Dongxia; Ji, Youliang; Zhou, Yong

doi:10.1016/j.marpetgeo.2017.10.007

Cited by 78 publications

(43 citation statements)

References 35 publications

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“…Sedimentary environments can significantly control the primary physical properties of reservoirs such as the grain size and sorting coefficient and diagenetic alteration (Lai, Wang, Fan, et al, 2018;Morad et al, 2000;Yue et al, 2018;Zhou et al, 2016). As mentioned before, sediments in a high-energy sedimentary environment, including distributary channels and mouth bars, are generally better able to resist compaction compared with the sediments in low-energy sedimentary environments (interdistributary bay).…”

Section: Sedimentary Environment and Composition And Texture Of Sedmentioning

confidence: 99%

“…The Es1 is the top member of the Paleogene Shahejie Formation and is a deeply buried sandstone reservoir characterized by low porosity but medium to high permeability with strong heterogeneity, thus limiting further hydrocarbon exploration in the Nanpu Sag. Diagenetic processes have a strong influence on the reservoir quality and heterogeneity (Higgs, Zwingmann, Reyes, & Funnell, ; Lai et al, ; Lai, Wang, Ran, Zhou, & Cui, ; Morad, AI‐Ramadan, Ketzer, & DeRos, ; Yue et al, ; Zhou, Ji, Zhang, & Wan, ). An in‐depth understanding of the effects of diagenetic alteration on the reservoir quality would help reduce exploration risks and achieve more efficient exploration (Lai et al, ; Taylor et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Characteristics, diagenetic evolution, and controlling factors of the Es1 deep burial high‐quality sandstone reservoirs in the PG2 oilfield, Nanpu Sag, Bohai Bay Basin, China

et al. 2019

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Significant achievements have been reported for deep oil and gas exploration in the Bohai Bay Basin. Among them, the Nanpu Sag has achieved good deep (greater than 3.5 km) hydrocarbon exploration results. However, the hydrocarbon formation mechanisms and the diagenetic evolution of these high‐quality sandstone reservoirs remain unclear. Mineralogical, petrographic, and fluid inclusion data were selected to investigate the deeply buried sandstone reservoir physical properties, pore systems, and diagenetic features and the main formation mechanisms of the deep high‐quality reservoirs of the Es1 (the top member of the Paleogene Shahejie Formation) sandstones in the Nanpu Sag, eastern China. The results show that the Es1 sandstone reservoirs are dominated by lithic arkoses and have low porosities (average porosity 13.4%) but medium to high permeability (average permeability 188 mD). The pore systems consist of primary intergranular pores, secondary dissolution pores, and microfractures. Loss of porosity is greater due to compaction (average 20.89%) than due to cementation (average 4.82%), and dissolution contributes an improvement in porosity of approximately 5.85%. Two peaks in the inclusion homogenization temperatures were observed: The first fluid inclusion homogenization temperature term ranges from 130°C to 145°C and exhibits yellow fluorescence; the other peak occurs from 155°C to 165°C, showing green fluorescence. Eodiagenesis is due to mechanical compaction, precipitation of early calcite cements and quartz overgrowths, and dissolution of feldspar and carbonate cements. Mesodiagenesis occurs due to mechanical compaction, framework grain (mainly feldspar) dissolution, and precipitation of quartz and late carbonate cements. The main factors controlling the formation of the deep high‐quality reservoirs are the presence of a high hydrodynamic depositional environment (subaqueous distributary channel), the type of provenance (Archean granites), and the creation of secondary porosity by feldspar dissolution.

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Section: Sedimentary Environment and Composition And Texture Of Sedmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characteristics, diagenetic evolution, and controlling factors of the Es1 deep burial high‐quality sandstone reservoirs in the PG2 oilfield, Nanpu Sag, Bohai Bay Basin, China

et al. 2019

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“…2. Put the core plug into the HPHT carbon fiber core holder and set the confining pressure at 15 MPa, then use the X-ray microscope to scan the core samples at 0 MPa pore pressure. 3.…”

Section: Pressure Experiments On Fractured Core Samplesmentioning

confidence: 99%

“…Tectonic deformations and abnormal high fluid pressure control the fracture density: near faults or anticlines (folds), fracture density increases, and fluid pressure of 15 MPa increases the aperture by 50%, and induces new fractures. The fracture networks with high linear density significantly improves tight reservoir quality and seepage performance: it enhances the reservoir permeability by 1-4 orders of magnitude, and the relative gas permeability by 2-10 magnitude; by enhancing permeability, the fracture networks reduce the initial flowing gradient from as high as 0.41 MPa/cm to 0 Mpa/cm, and make the gas flowing possible.Energies 2018, 11, 2808 2 of 22 basins like the Ordos Basin in China [13,14], Sichuan Basin in China [15], Western Canadian Basin in Canada [16], the reduction of tight gas reservoirs in KTB is several times higher. Studies have been carried out on the tectonic evolution [17][18][19][20][21][22][23][24], structural characteristics [25,26], stratigraphy [27,28], reservoirs [29][30][31][32], and hydrocarbon migration histories [33,34] in KTB, to explain why tight gas reservoirs in KTB have such high gas reserves and production at such great depths.…”

mentioning

confidence: 99%

Fracture Characteristics and Their Influence on Gas Seepage in Tight Gas Reservoirs in the Kelasu Thrust Belt (Kuqa Depression, NW China)

Yang

Fan

et al. 2018

Energies

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Natural fractures were generally accepted as a key factor influencing the gas seepage performance in tight gas reservoirs in Kelasu Thrust Belt (KTB). However, the mechanism was not fully clarified, especially from a microscopic perspective. Based on observation of core samples and cast thin sections and gas charging experiment on core plugs, the parameters of fractures and seepage performance in fractured tight reservoirs are studied; further, the controlling effect of fractures on gas seepage was discussed. The results show that in KTB fractures could be categorized by the size of their apertures as macro-fractures (aperture width ranges from 0.1 to 2 mm) and micro-fractures (aperture width ranges from 5 to 100 µm), which appear in the form of fractures networks. Tectonic deformations and abnormal high fluid pressure control the fracture density: near faults or anticlines (folds), fracture density increases, and fluid pressure of 15 MPa increases the aperture by 50%, and induces new fractures. The fracture networks with high linear density significantly improves tight reservoir quality and seepage performance: it enhances the reservoir permeability by 1-4 orders of magnitude, and the relative gas permeability by 2-10 magnitude; by enhancing permeability, the fracture networks reduce the initial flowing gradient from as high as 0.41 MPa/cm to 0 Mpa/cm, and make the gas flowing possible.Energies 2018, 11, 2808 2 of 22 basins like the Ordos Basin in China [13,14], Sichuan Basin in China [15], Western Canadian Basin in Canada [16], the reduction of tight gas reservoirs in KTB is several times higher. Studies have been carried out on the tectonic evolution [17][18][19][20][21][22][23][24], structural characteristics [25,26], stratigraphy [27,28], reservoirs [29][30][31][32], and hydrocarbon migration histories [33,34] in KTB, to explain why tight gas reservoirs in KTB have such high gas reserves and production at such great depths. It is generally agreed that tectonic faults and fractures played an important role in enhancing gas migration and production efficiency. Tao [35] fully described the characteristics of the natural fractures in KTB using FMI images and cores, and explain the relationship between fracture formation and in-situ stress. Sun [36] further studied the fracture-pore systems using cast thin sections, and identified a fracture zone in KTB. On this basis, Shen [24] determined gas source faults as key elements in natural gas migration and accumulation, and evaluated their effectiveness combining geochemistry and fluid potential analysis method. However, these studies explained the high reserve of KTB tight reservoirs in a macro view, and had not clarified the microscopic mechanism of gas seepage in gas charging or production process, including but not limited to pathways, characteristics, and controlling factors; whereas, a deep understanding of above could help explain and predict gas saturation and distribution, which is of great value to further explorations.The effects of fractures in improving p...

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“…The post-deposition actions, which are closely related to the reservoir quality of sandstones, mainly refer to diagenesis (including compaction, cementation, replacement, dissolution, etc. ) and tectonism (Zhu et al, 2009b;Yue et al, 2018). Tectonism has significant effects on reservoir quality.…”

mentioning

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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Reservoir quality, natural fractures, and gas productivity of upper Triassic Xujiahe tight gas sandstones in western Sichuan Basin, China

Cited by 78 publications

References 35 publications

Characteristics, diagenetic evolution, and controlling factors of the Es1 deep burial high‐quality sandstone reservoirs in the PG2 oilfield, Nanpu Sag, Bohai Bay Basin, China

Characteristics, diagenetic evolution, and controlling factors of the Es1 deep burial high‐quality sandstone reservoirs in the PG2 oilfield, Nanpu Sag, Bohai Bay Basin, China

Fracture Characteristics and Their Influence on Gas Seepage in Tight Gas Reservoirs in the Kelasu Thrust Belt (Kuqa Depression, NW 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

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