Variations of lacustrine shale reservoirs in different deformation zones of Mohe Basin, northeastern China: Insights into the impact of thrust nappe structure on shale gas preservation

Hou, Yuguang; Gao, Junfeng; Ren, Kexiong; Liu, Yukun; He, Sheng; Tang, Daqing; Guo, Xiaowen; Yang, Rui

doi:10.1016/j.marpetgeo.2021.105272

Cited by 4 publications

(3 citation statements)

References 44 publications

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“…Meanwhile, industrial drilling cores of the Wufeng-Longmaxi shale collected from compression anticlines (scale of tens of kilometers) of the Fuling (Liu et al, 2020a;Gou et al, 2021) and Changning (Liu et al, 2020b) areas indicated that the deformation of a shale pore system, particularly organic pores, accounted for abnormally low porosity and high TOC content in some particular structural domains; shale porosity was decreased to a greater extent in the core and forelimb areas of thin-skinned and basement-involved anticlines, respectively, than others. A similar variation in pore structural damage in the structural domains was identified in lacustrine shale reservoirs (Emuerhe and Ershierzhan Formations) of the Mohe Basin (Hou et al, 2021).…”

Section: Introductionsupporting

confidence: 68%

Structural deformation of shale pores in the fold-thrust belt: The Wufeng-Longmaxi shale in the Anchang Syncline of Central Yangtze Block

Guo¹,

Li²,

Xu³

et al. 2022

Adv. Geo-Energy Res.

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The gas-rich Wufeng-Longmaxi shale has been intensely deformed within the fold-thrust belt of the Yangtze Block. To better understand the impact of structural deformation on the shale pore system, this paper systematically investigated the matrix components, porosity and pore structures in core samples from the Wufeng-Longmaxi shale, newly collected from various structural domains in the first commercial shale gas field of the Central Yangtze Block, the Anchang Syncline. The shale porosity generally showed a positive relationship with total organic carbon content. Nevertheless, even at a constant total organic carbon content, the shale porosity decreased from the syncline limb to the syncline hinge zone and with a decreasing interlimb angle in the syncline hinge zone, which aligned with the structural deformation strain during folding. The artificial axial compression of shale samples also confirmed that the decrease in shale porosity was stronger at an elevated axial compression stress and was relatively higher in samples with higher total organic carbon content. The organic pore size decreased with higher structural deformation strain, but the aspect ratio of the pore shape increased. Even quartz failed to resist the effective stress under the intensive structural deformation, changing the correlation between porosity and quartz from positive to negative. In contrast, pore spaces generated by the slipping between clay flakes under intensive deformation accounted for a positive relationship between clay content and bulk porosity. Considering the shale porosity reduction caused by the intensive structural deformation of shale pores, the Wufeng-Longmaxi shale, that is rich in fracture networks between roof and floor layers, may still be an excellent exploration target in the fold-thrust belt of the Yangtze Block.

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Section: Introductionsupporting

confidence: 68%

Structural deformation of shale pores in the fold-thrust belt: The Wufeng-Longmaxi shale in the Anchang Syncline of Central Yangtze Block

Guo¹,

Li²,

Xu³

et al. 2022

Adv. Geo-Energy Res.

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“…However, due to the difference in shale gas exploration degree and the lack of three-dimensional seismic resources, the evaluation of preservation conditions is often concentrated in the same block (Li et al, 2021b;Wang H. et al, 2021;Hadded et al, 2021;Hou et al, 2021). The differences in gas-rich structural types and preservation conditions in different structural areas outside the basin, at the edge of the basin, and in the basin still need to be further analyzed, which is the basis for the optimization of favorable areas for shale gas.…”

Section: Introductionmentioning

confidence: 99%

Deformation Differences in Complex Structural Areas in the Southern Sichuan Basin and Its Influence on Shale Gas Preservation: A Case Study of Changning and Luzhou Areas

Qin

et al. 2022

Front. Earth Sci.

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Preservation conditions are the key factors that determine the effective accumulation of shale gas. The damage of faults formed by differential structures to the roof and floor and the shielding of lateral edges are the direct reasons for the difference in preservation conditions. Taking the organic-rich shale of the Wufeng–Longmaxi Formation in the south of the Sichuan Basin as an example, this paper reveals different types of shale gas-rich structures by using typical seismic profiles and puts forward the main controlling factors of different gas-rich structures and their influence on preservation. The results show that three kinds of gas-rich structures are developed in the Wufeng–Longmaxi Formation in southern Sichuan: positive type, negative type, and fault transformed slope type. The basin is dominated by a wide and gentle syncline, fault spreading fold, and low scope concealed anticlines. Wide and gentle anticline, arc anticline, and fault transformation slope are developed at the basin edge. Fault sealing is the main controlling factor for the preservation of shale gas in wide and gentle anticlines. The main controlling factors for the preservation of circular arc anticlines and hidden anticlines are anticline curvature and the distance between faults. The preservation of shale gas in a syncline is mainly controlled because it includes formation buried depth, foliation development degree, and formation dip angle. The preservation of fault transformed syncline is mainly affected by formation buried depth, dip angle, and fault sealing. Foliation and faults form a three-dimensional migration system, which jointly controls the intensity of gas escape. Positive structures such as wide and gentle anticline and circular arc anticline at the basin edge, and deep buried gentle syncline and low scope concealed anticline in the basin are favorable shale gas-rich structures.

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“…These differences also hinder the exploration and efficient development of SG. Various methods for assessing the preservation of SG are currently available. − Earlier research has identified two key factors that affect SG preservation: the temporal and spatial match between tectonic movements and the hydrocarbon (HC) generation stage after the formation of a shale bed, as well as the damage caused by the faults that form from intense tectonic movements to the roof and floor of the shale bed. − Assessment of the preservation conditions in a formation has been primarily centered on factors such as fault development and sealing capacity, the time and extent of uplifts, , and the integrity of the roof and floor. In addition, according to the degree of influence of different factors, the corresponding preservation assessment systems have been established. , Tang evaluated the preservation conditions of the Longmaxi Formation marine shale in the southeastern Sichuan Basin by assigning values to factors such as roof and floor conditions, structural locations, fracture development, fracture spacing, and stratum thickness.…”

Section: Introductionmentioning

confidence: 99%

Composition of Formation Water and Natural Gas as an Indicator of Shale Gas Preservation Conditions: A Case Study of the Marine Shale of the Niutitang Formation in the Cengong Block in Northern Guizhou, China

Wang

et al. 2022

ACS Omega

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Shale gas (SG) wells in the Wufeng–Longmaxi Formation in northern Guizhou differ considerably in their production capacities. Preservation conditions are a crucial factor affecting the formation of SG reservoirs. In this study, the formation water (FW) in four wells in northern Guizhou was analyzed to determine the type; the Cl/Mg, Ca/Mg, and Na/Cl coefficients (C Cl/Mg, C Ca/Mg, and C Na/Cl, respectively), and the coefficient of desulfurization (C d); the SG in these wells was tested to identify its composition and the sources of its components. The results show the following: wells TX1 and CY1 contain two types (CaCl2 and NaHCO3) of FW, each with low C Na/Cl, low C d, high C Ca/Mg, and high C Cl/Mg, suggesting a high level of FW retention. The FW in wells TM1 and CD1 is of NaHCO3 type and is characterized by high C Na/Cl, high C d, low C Ca/Mg, and low C Cl/Mg, indicating a high level of connectivity between the FW and surface water. Nonhydrocarbon gases account for a high proportion of SG in composition; with a 15N value between −8.7 and −4.2‰, N2 accounts for approximately 20% of SG in wells TX1 and CY1, respectively. This result indicates the ammonification of organic matter (OM) during pyrolysis and hydrocarbon generation as sources of N2. In contrast, with a 15N value between −3.6 and 0‰, N2 accounts for over 70% of SG in wells TM1 and CD1, respectively, indicating the atmosphere, the ammonification of OM, and the presence of poor preservation conditions due to a high level of connectivity between the shale bed and the atmosphere acted as the sources of N2. The metamorphism coefficients of FW in conjunction with the SG composition and the sources of nonhydrocarbon gases can serve as auxiliary indicators of the quality of SG preservation conditions.

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Variations of lacustrine shale reservoirs in different deformation zones of Mohe Basin, northeastern China: Insights into the impact of thrust nappe structure on shale gas preservation

Cited by 4 publications

References 44 publications

Structural deformation of shale pores in the fold-thrust belt: The Wufeng-Longmaxi shale in the Anchang Syncline of Central Yangtze Block

Structural deformation of shale pores in the fold-thrust belt: The Wufeng-Longmaxi shale in the Anchang Syncline of Central Yangtze Block

Deformation Differences in Complex Structural Areas in the Southern Sichuan Basin and Its Influence on Shale Gas Preservation: A Case Study of Changning and Luzhou Areas

Composition of Formation Water and Natural Gas as an Indicator of Shale Gas Preservation Conditions: A Case Study of the Marine Shale of the Niutitang Formation in the Cengong Block in Northern Guizhou, China

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