Vertical sealing mechanism of shale and its roof and floor and effect on shale gas accumulation, a case study of marine shale in Sichuan basin, the Upper Yangtze area

Zhang, Kun; Song, Yan; Jia, Chengzao; Jiang, Zhenxue; Jiang, Shu; Huang, Yizhou; Wen, Ming; Liu, Xiaoxue; Liu, Weiwei; Chen, Zhi-yuan; Xie, Xuelian; Liu, Tianlin; Wang, Xin; Wang, Pengfei; Li, Xin; Shan, Chang’an

doi:10.1016/j.petrol.2019.01.009

Cited by 36 publications

(27 citation statements)

References 28 publications

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“…The third member contained a large scale of shale gas, but the major component was nitrogen, which is the similar component as the gas in the Lower Cambrian shale of Xiuwu Basin in the Lower Yangtze [7]. It was obvious that the third member of the Carboniferous Dawuba Formation shale in the southern Guizhou depression was not sealed well as the Wufeng-Longmaxi Formation shale in Sichuan Basin [12]. The second member of the Dawuba Formation had a thin thickness, generally less than 20 m. The obvious feature is mudstone interbedded with limestone and was formed under the oxidation environment of semideep water.…”

Section: Comparative Evaluation Of the Dawuba Formation Shalementioning

confidence: 99%

“…In recent years, the success of shale oil and gas exploration and development in North America, such as the Barnett shale with tremendous cumulative gas production, has driven and promoted the development of shale oil and gas industry in China [1][2][3][4][5][6][7][8]. The industrial breakthroughs of shale gas exploration and development in China were achieved mainly in the Ordovician Wufeng and Silurian Longmaxi Formation marine shale reservoirs in Weiyuan, Zhaotong, and Jiaoshiba areas in the southern Sichuan Basin, where the shale gas output reached 10 billion cubic meters in 2019 [9][10][11][12][13][14]. Although the strata, pattern, mechanism, and geological factors for shale gas source and accumulation were different for different areas, such as in the Weiyuan block and Xiuwu basin [7,8], the high-quality shale section is generally located at the top of Wufeng Formation and the bottom of Longmaxi Formation, in which the biogenic silica caused by frequent volcanic activities hugely developed [13,15,16].…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Favorable Shale Gas Intervals in Dawuba Formation of Ziyun Area, South Qian Depression

et al. 2021

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A series of qualitative descriptions and quantitative analyses was used to determine the lithofacies characteristics and recognize the favorable shale intervals of Dawuba Formation in the Ziyun area of South Qian Depression. The qualitative descriptions include core description and scanning electron microscope (SEM) observation. The quantitative analyses include X-ray diffraction, total organic content analysis, vitrinite reflectance, maceral composition, porosity, and permeability, as well as gas and element composition. The Dawuba Formation could be divided into four members. In general, the shale in the first and third members showed similarly high organic matter content with most samples in range of 2–2.5% and higher brittle mineral content with a content of quartz 40.53% and 33.21%, respectively, compared with the other two members, as well as high gas content. However, the first member shale samples exhibited much higher porosity and permeability than the third member shale samples. Furthermore, the shale gas in the first member was chiefly composed of methane (average: 83.63%), while that in the third member mainly consisted of nitrogen (average: 79.92%). Hence, the first member should be regarded as the most favorable target.

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Section: Comparative Evaluation Of the Dawuba Formation Shalementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evaluation of Favorable Shale Gas Intervals in Dawuba Formation of Ziyun Area, South Qian Depression

et al. 2021

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“…As shown in Figure 2, the P/Al in the middle part of the Lower Figure 1 for the well location. 4 Geofluids…”

Section: Biological Productivitymentioning

confidence: 99%

“…As targets of geological explorations of oil and gas change from conventional reservoirs to unconventional reservoirs, the exploration and development of unconventional oil and gas (including shale gas, shale oil, and tight gas) have achieved great success in North America, and this makes the United States essentially self-sufficient in oil and gas, thus achieving "energy independence" [1][2][3][4][5][6]. There are also unconventional oil and gas resources with great potential in South China, among which are two sets of marine shales, the Upper Ordovician-Lower Silurian shales and the Lower Cambrian shales, which are the main exploration target series.…”

Section: Introductionmentioning

confidence: 99%

Study on the Mechanism of Organic Matter Enrichment in Early Cambrian Marine Shales in the Lower Yangtze Area, South China: An Example Using Well JXY1

Cheng

Zhang

et al. 2020

Geofluids

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The abundance of organic matter in shales, which has a direct effect on the hydrocarbon generation potential of shales, is an important organic geochemical parameter for evaluating shale gas reservoirs. The total organic carbon content (TOC content) in shale is controlled by the abundance of original sedimentary organic matter. Therefore, it is very important to study the mechanism of organic matter enrichment in shale. In this paper, the Lower Cambrian marine shales from the Lower Yangtze region are selected as the research subject, most of which originate from a typical area well called Well JXY1. The degree of pyritization (DOP) is used to characterize the redox environment of the water body, while the P/Al ratio is used to analyze the biological productivity of paleoseawater. The paleosalinity of seawater is calculated via carbon and oxygen isotope analysis. In addition, the early Cambrian hydrothermal activities were studied by using core description; Si, Al, Fe, and Mn elemental analysis; and oxygen isotope calculations. The results show that during the early Cambrian Wangyinpu sedimentary period, the seawater was an anaerobic water body with H2S, and the oxygen concentration was approximately 0 mL/L. In the middle stages of the Wangyinpu sedimentary period, the water body had the strongest reducibility and the highest biological productivity. Moreover, the paleoocean in this period between the Yangtze plate and the Cathaysian plate was greatly affected by hydrothermal activities, with temperatures ranging from 90°C to 120°C. Active hydrothermal activities promoted high biological productivity and an anaerobic environment, both of which were conducive to the preservation and enrichment of organic matter, resulting in extremely high TOC content in the Wangyinpu shales (from 6.5% to approximately 16%).

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“…After the oil companies, such as PetroChina and Sinopec, explored the marine shale gas in this stratum, shale gas fields such as Weiyuan, Changning, Zhaotong, Fushun-Yongchuan, Dingshan, and Jiaoshiba have been built since 2010, and good industrial production capacity has been obtained [7][8][9][10]. Predecessors did researches on shale reservoir characteristics [11][12][13][14][15][16][17], shale gas accumulation mechanism [18][19][20][21][22], and shale gas preservation conditions [23][24][25][26][27][28] and have yielded a series of scientific research results. Organic matter is the material basis for hydrocarbon generation in shale and is also the main reservoir space and seepage channel for shale gas.…”

Section: Introductionmentioning

confidence: 99%

Mechanism Analysis of Organic Matter Enrichment of Upper Ordovician-Lower Silurian Shale in the Upper Yangtze Area: Taking Jiaoye-1 Well in the Jiaoshiba Block as an Example

et al. 2019

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Organic matter is the material basis of shale hydrocarbon generation. The current organic matter content in shale is controlled by the original sedimentary organic matter abundance. Therefore, the study of the enrichment mechanism of sedimentary organic matter in shale has become an important issue to be solved. The Upper Yangtze area is the important exploration and exploitation area of marine shale gas in China. The shale of the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in the Yangtze area is the research object. Choosing redox indicator and biological productivity indicator, the study explores the enrichment mechanism of sedimentary organic matter from two aspects, sealing of water and volcanic activity. The results show that excess siliceous mineral in the shale of the Wufeng Formation-Longmaxi Formation in the Upper Yangtze area is bioorigin. Excess siliceous mineral can be used as one of the indicators of biological productivity. On the one hand, layer phenomenon occurred since the strong water sealing during the sedimentary period of Wufeng and the lower section of the Longmaxi Formation, which results in the high content of oxygen in surface water. On the other hand, the active volcanic activity brought volcanic ash which was beneficial to biological reproduction. Both of these factors led to higher biological productivity during this period. At the same time, the strong sealing of water made the lower layer of the water more reductive, and the active volcanic activity caused climate change, enhancing the reduction of the lower layer of the water, which made the rich organic matter deposited from the surface water well preserved. In the sedimentary period of the upper section of the Longmaxi Formation 1st member in the Upper Yangtze area, on the one hand, due to the weakened sealing of water, the oxygen content of the upper water decreased. On the other hand, the volcanic activity weakened until it stopped, and the source of volcanic ash rich in nutrient elements decreased. These two aspects led to lower biological productivity during this period. At the same time, the weaker water sealing could lead to a decrease in the reduction of the lower layer of the water, and the gradual cessation of volcanic activity no longer affected the climate, causing the destruction of sedimentary organic matter by oxidation.

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Vertical sealing mechanism of shale and its roof and floor and effect on shale gas accumulation, a case study of marine shale in Sichuan basin, the Upper Yangtze area

Cited by 36 publications

References 28 publications

Evaluation of Favorable Shale Gas Intervals in Dawuba Formation of Ziyun Area, South Qian Depression

Evaluation of Favorable Shale Gas Intervals in Dawuba Formation of Ziyun Area, South Qian Depression

Study on the Mechanism of Organic Matter Enrichment in Early Cambrian Marine Shales in the Lower Yangtze Area, South China: An Example Using Well JXY1

Mechanism Analysis of Organic Matter Enrichment of Upper Ordovician-Lower Silurian Shale in the Upper Yangtze Area: Taking Jiaoye-1 Well in the Jiaoshiba Block as an Example

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