Characteristics, formation periods and genetic mechanisms of tectonic fractures in the tight gas sandstones reservoir: A case study of Xujiahe Formation in YB area, Sichuan Basin, China

Li, Hu; Tang, Hongming; Qin, Qirong; Jiling, Zhou; Qin, Zhangjin; Fan, Chun‐An; Su, Peidong; Wang, Qin; Zhong, Cheng

doi:10.1016/j.petrol.2019.04.007

Cited by 136 publications

(75 citation statements)

References 53 publications

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“…Moreover, clay minerals are mostly schistose, and the pores between the clay flakes are mostly crescent-shaped and flocculent, with a large number and good connectivity (Figure 5H). Additionally, a large number of granular edge fractures are developed at the contacts between organic matter and shale minerals (Figure 5I); these fractures are mesh-like and show good connectivity under the microscope (Fan et al, 2018;Li et al, 2019b;Xie et al, 2019;Shan et al, 2021;Zhu et al, 2022).…”

Section: Development and Distribution Of Inorganic Pores And Fracturesmentioning

confidence: 99%

Geological Characteristics of Deep Shale Gas in the Silurian Longmaxi Formation in the Southern Sichuan Basin, China

Qin

et al. 2022

Front. Earth Sci.

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To investigate the geological characteristics and exploration potential of shale gas in the southern Sichuan Basin, we analyze the coupling relationship between the hydrocarbon generation and storage conditions of the Longmaxi Formation and discuss the preservation conditions from the lateral and vertical migration mechanisms of shale gas. According to the results, the organic-rich shale at the bottom was formed in a strongly euxinic and anoxic reducing environment, the oxygen content increased in the upper water body in which the Longmaxi Formation was deposited, and the water body became oxidized. The organic matter type in the shale is dominantly type I kerogen and a small amount of type II1 kerogen. The organic matter content is more than 3.0% and is in the high-to postmature stage. The enrichment of siliceous organisms increases the organic matter and enhances the brittleness of shale, resulting in “superior hydrocarbons and a favorable reservoir”. Pyrolysis of organic matter promotes the formation of organic matter pores and dissolution pores, resulting in a coupled “source-reservoir” accumulation control system. The high vertical formation pressure guarantees the sealing of shale and restrains the lateral escape of shale gas. The high-angle intersection of the highly filled fractures and the current crustal stress can effectively enhance the fracture sealing and inhibit the vertical escape of shale gas, forming a three-dimensional effective closure. Hence, the area featuring a short tectonic uplift time, small amplitudes, large-scale underdeveloped fractures, and a high formation pressure coefficient is a favorable area for shale gas exploration, according to the analysis of three-dimensional preservation conditions.

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Section: Development and Distribution Of Inorganic Pores And Fracturesmentioning

confidence: 99%

Geological Characteristics of Deep Shale Gas in the Silurian Longmaxi Formation in the Southern Sichuan Basin, China

Qin

et al. 2022

Front. Earth Sci.

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“…In fact, the position of these features around the wellbore can be used to determine the azimuth of S Hmax . The azimuth of wellbore breakout indicates the azimuth of S Hmin , and the azimuth of drilling-induced tensile fractures indicates the direction of S Hmax [19,[21][22][23]. The full wellbore micro-resistivity imaging (FMI) and Caliper log data of W203 and W205, and the XRMI data of R202 were obtained to analyse the S Hmax direction.…”

Section: Orientation Of Horizontal Stressmentioning

confidence: 99%

Geomechanical Analysis for Deep Shale Gas Exploration Wells in the NDNR Blocks, Sichuan Basin, Southwest China

Zheng

Tang

et al. 2020

Energies

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The abundant reserve of shale gas in Sichuan Basin has become a significant natural gas component in China. To achieve efficient development of shale gas, it is necessary to analyze the stress state, pore pressure, and reservoir mechanical properties such that an accurate geomechanical model can be established. In this paper, Six wells of Neijiang-Dazu and North Rongchang (NDNR) Block were thoroughly investigated to establish the geomechanical model for the study area. The well log analysis was performed to derive the in-situ stresses and pore pressure while the stress polygon was applied to constrain the value of the maximum horizontal principal stress. Image and caliper data, mini-frac test and laboratory rock mechanics test results were used to calibrate the geomechanical model. The model was further validated by comparing the model prediction against the actual wellbore failure observed in the field. It was found that it is associated with the strike-slip (SS) stress regime; the orientation of SHmax was inferred to be 106–130° N. The pore pressure appears to be approximately hydrostatic from the surface to 1000 m true vertical depth (TVD), but then becomes over-pressured from the Xujiahe formation. The geomechanical model can provide guidance for the subsequent drilling and completion in this area and be used to effectively avoid complex drilling events such as collapse, kick, and lost circulation (mud losses) along the entire well. Also, the in-situ stress and pore pressure database can be used to analyze wellbore stability issues as well as help design hydraulic fracturing operations.

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“…The Sichuan Basin is located in the western Yangtze quasi-platform, with Dalou Mountain in the east, Longmen Mountain fold belt in the west, Daxiangling-Lou Mountain fold belt in the south and Micang Mountain uplift-Daba Mountain fold belt in the north (Figure 1a,b). With Huaying Mountain and Longquan Mountain anticlinal belts as the boundary of the Sichuan Basin, it is divided into three tectonic zones, the southeastern tectonic area (including the high-steep fold belt in the eastern Sichuan Basin and the low-steep fold belt in the southern Sichuan Basin), the northwestern tectonic area (including the low-flat fold belt in the northern Sichuan Basin and the low-steep fold belt in the western Sichuan Basin), and the central Sichuan tectonic area between Huaying Mountain and Longquan Mountain (Figure 1b) [32][33][34]. Organic-rich shales are deposited mainly in Yibin-Luzhou city in the southern Sichuan Basin, Fuling-Shizhu city in the southeastern margin and Lichuan city in western Hubei Province in the eastern margin.…”

Section: Geological Settingmentioning

confidence: 99%

Micropore Structural Heterogeneity of Siliceous Shale Reservoir of the Longmaxi Formation in the Southern Sichuan Basin, China

Tang

Zheng

2019

Minerals

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In recent years, the shale gas in the southern Sichuan Basin has achieved great commercial development, and the Silurian Longmaxi Formation is the main development stratum. In order to solve the problems of great difference production and inaccurate gas content of the Longmaxi Formation shale gas field in the southern Sichuan Basin, based on thin section identification, argon ion polishing-field emission scanning electron microscopy, high pressure mercury injection, low temperature nitrogen adsorption and the fractal method, the micropore structural heterogeneity of the siliceous shale reservoir of the Longmaxi Formation has been studied. The results show the following: The pores of siliceous shale are mainly intergranular pores and organic pores. Image analysis shows that there are obvious differences in size and distribution of shale pores among different types. The micropore structural heterogeneity is as follows: intragranular pore > intergranular pore > organic pore. In the paper, the combination of low temperature nitrogen adsorption method and high-pressure mercury injection method is proposed to characterize the micropore size distribution and fractal dimension, which ensures the credibility of pore heterogeneity. The shale pores are mainly composed of mesopores (2–20 nm), followed by macropores (100–300 nm). For different pore sizes, the fractal dimension from large to small is mesopore, micropore and macropore. Shale pore structure and fractal dimension are correlated with mineral composition and total organic carbon (TOC) content, but the correlation is significantly different in different areas, being mainly controlled by the sedimentary environment and diagenesis.

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Characteristics, formation periods and genetic mechanisms of tectonic fractures in the tight gas sandstones reservoir: A case study of Xujiahe Formation in YB area, Sichuan Basin, China

Cited by 136 publications

References 53 publications

Geological Characteristics of Deep Shale Gas in the Silurian Longmaxi Formation in the Southern Sichuan Basin, China

Geological Characteristics of Deep Shale Gas in the Silurian Longmaxi Formation in the Southern Sichuan Basin, China

Geomechanical Analysis for Deep Shale Gas Exploration Wells in the NDNR Blocks, Sichuan Basin, Southwest China

Micropore Structural Heterogeneity of Siliceous Shale Reservoir of the Longmaxi Formation in the Southern Sichuan Basin, China

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