Heterogeneity of the Lower Silurian Longmaxi marine shale in the southeast Sichuan Basin of China

Chen, Lei; Lu, Yongchao; Jiang, Shu; Li, Jianqing; Guo, Tonglou; Luo, Chan

doi:10.1016/j.marpetgeo.2015.04.003

Cited by 166 publications

(67 citation statements)

References 35 publications

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“…The sequence division for LSL formation is consistent with Xiong et al [8], Wang et al [9], and Chen et al [7,30]. SQ1 and SQ2 are both composed of a transgressive system tract (TST) and a high-stand system tract (HST) according to the vertical variation in GR logging.…”

Section: Vertical Variation Of Lithofaciessupporting

confidence: 85%

“…Based on research in the southern and southeastern Sichuan Basin by Xiong et al [8], Wang et al [9], and Chen et al [7,30], detailed core observations, and well logging analyses in the study area, we identified a sequence boundary in the LSL formation and established the sequence stratigraphic framework of Well-WQ2 in the LSL formation ( Figure 3).…”

Section: Vertical Variation Of Lithofaciesmentioning

confidence: 99%

“…Although limited research has been conducted on stratigraphic sequences in the LSL formation of the northeastern Sichuan Basin, some investigations related to the LSL formation in the southern and southeastern Sichuan Basin have been performed (Xiong et al [8], Wang et al [9], and Chen et al [7,30]). Based on research in the southern and southeastern Sichuan Basin by Xiong et al [8], Wang et al [9], and Chen et al [7,30], detailed core observations, and well logging analyses in the study area, we identified a sequence boundary in the LSL formation and established the sequence stratigraphic framework of Well-WQ2 in the LSL formation ( Figure 3).…”

Section: Vertical Variation Of Lithofaciesmentioning

confidence: 99%

“…As a clean and efficient energy source, shale gas has become an increasingly significant resource worldwide [2][3][4][5][6]. The exploration and exploitation of shale gas has accelerated in recent years, with significant progress made in the Sichuan Basin of Southern China [7,8].…”

Section: Introductionmentioning

confidence: 99%

“…Among these, the Lower Silurian Longmaxi Formation (abbreviated as LSL) marine shale is a significant shale gas reserve with prolific production potential. LSL shale produced approximately 1.8 × 10 8 m 3 (6.3 Bcf) of gas in 2013 in the southeastern Sichuan Basin, with an overall estimated recoverable resource of 8.1 × 10 12 m 3 (286.5 Tcf) [7]. LSL shale has become the most favored target stratum for shale gas recovery in China.…”

Section: Introductionmentioning

confidence: 99%

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Vertical Heterogeneity of the Shale Reservoir in the Lower Silurian Longmaxi Formation: Analogy between the Southeastern and Northeastern Sichuan Basin, SW China

et al. 2017

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Lower Silurian Longmaxi formation (LSL) shale is widely and continuously distributed in the northeastern Sichuan Basin and, based on structural analogies with the gas producing LSL formation in the southeastern Sichuan Basin, has significant potential for shale gas exploration. However, limited research has been performed to evaluate the shale gas potential in this region. Samples from a recently completed exploratory well (Well-WQ2) in the northeastern Sichuan Basin indicate that the LSL shale has a vertical property sequence that closely resembles the vertical property sequences in wells in the gas-producing sections of the southeastern Sichuan Basin. The continuous sampling and analyses of Well-WQ2 have allowed a detailed investigation of the vertical variations in lithofacies, mineral characteristics, pore structures, and organic geochemical characteristics. The Longmaxi formation was divided into two third-order sequences (SQ1 and SQ2) based on systematic core observations and well logging analyses. Both SQ1 and SQ2 include a transgressive system tract (TST) and a high-stand system tract (HST). The lithofacies exhibit an upward decrease in the organic content. From SQ1 to SQ2, the quartz content, in situ graptolite content, total organic carbon (TOC) content, and brittleness index decrease, but the clay mineral content increases. The LSL shale sections from depths of 1204 to 1214 m and from 1271 to 1282 m possess well-developed fractures and high permeability. Additionally, the average porosity and permeability in SQ1 are higher than those in SQ2. In addition, the positive correlation between the TOC and quartz contents of the assayed samples suggests that much of the quartz is of biogenic origin. Changes in the sedimentary and diagenetic environments during deposition are two key factors that contribute to the observed vertical heterogeneity of the Longmaxi formation. In conclusion, the shale sections of the lower part of the SQ1, like their analogs in the southeastern Sichuan Basin, are the most favorable targets for shale gas production in the northeastern Sichuan Basin.

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Section: Vertical Variation Of Lithofaciessupporting

confidence: 85%

Section: Vertical Variation Of Lithofaciesmentioning

confidence: 99%

Section: Vertical Variation Of Lithofaciesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Vertical Heterogeneity of the Shale Reservoir in the Lower Silurian Longmaxi Formation: Analogy between the Southeastern and Northeastern Sichuan Basin, SW China

et al. 2017

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Characterization of the Lower Silurian Longmaxi marine shale in Changning area in the south Sichuan Basin, China

Jiang

Chen

et al. 2017

Geological Journal

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On the basis of the core description, thin sections, and geochemistry data, we characterized the Lower Silurian Longmaxi marine shale in the Changning area in the south Sichuan Basin. Ten lithofacies were identified in the Lower Silurian Longmaxi marine shale: (a) massive silty shale (Lithofacies A); (b) laminated siliceous calcareous shale (Lithofacies B); (c) calcareous shale (Lithofacies C); (d) silty dolomitic shale (Lithofacies D); (e) argillaceous siltstone (Lithofacies E); (f) siltstone (Lithofacies F); (g) laminated silty shale (Lithofacies G); (h) silty calcareous shale (Lithofacies H); (i) argillaceous lime shale (marl) (Lithofacies I); and (j) bentonite (Lithofacies J). Obvious heterogeneity occurred in different lithofacies in terms of mineralogy, total organic carbon (TOC) content, porosity, permeability, pore surface area, total pore volume, and total gas content. Among these lithofacies, Lithofacies B has the highest porosity (5.4%), pore surface area (12.79 m2/g), total pore volume (0.015 cc/g), TOC content (4.37%), total gas content (3.4 m3/ton), and relatively high brittle minerals, suggesting great shale gas potential. Lithofacies A, C, and D have a relatively high brittle minerals, porosity, pore surface area, total pore volume, TOC content, and total gas content, which means that these 3 lithofacies show relatively good potential for shale gas. The rest of the lithofacies have low brittle minerals content, porosity, pore surface area, total pore volume, TOC content, and total gas content, representing poor shale gas potential.

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Comparative study of nanoscale pore structure of Lower Palaeozoic marine shales in the Middle‐Upper Yangtze area, China: Implications for gas production potential

et al. 2017

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The Lower Cambrian Niutitang and Lower Silurian Longmaxi shales in the Middle‐Upper Yangtze area are considered the primary shale gas units targeted for development in China. To shed some light on the difference in nanopore structures between Niutitang and Longmaxi shales, systematic comparative investigations were conducted using various techniques, including geochemical analyses, field emission scanning electron microscopy (FE‐SEM), high‐pressure mercury intrusion porosimetry (MIP), and low‐pressure N2/CO2 adsorption techniques. The results show that both Niutitang and Longmaxi shales have high total organic carbon (TOC) content and complex mineral compositions. The porosity of Longmaxi shales is higher than that of Niutitang shales, with an average value of 3.26% and 2.04%, respectively. Interestingly, for both shale formations, the mesopores (2–50 nm) are the major contributors to pore volumes, whereas the specific surface area is dominated by micropores (<2 nm). For the mesopore size distributions (PSDs) calculated from the N2 adsorption, the Longmaxi shales have a dominant pore size ranging from 10 to 60 nm. In contrast, there are more fine mesopores (2–8 nm) in the Niutitang shales. Furthermore, we found that numerous nanoscale pores are well‐developed within graptolite‐derived organic matter (OM) in the Longmaxi shales. These interconnected graptolite periderm pore systems may not only provide a storage space for both adsorbed and free gas but also serve as pathways for gas transport. The Niutitang shales developed relatively fewer OM pores with smaller diameters, lower OM surface porosity, and lower connectivity compared to the Longmaxi shales. The differences in OM pore structure partly explain why there is a large production difference between these two formations.

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Heterogeneity of the Lower Silurian Longmaxi marine shale in the southeast Sichuan Basin of China

Cited by 166 publications

References 35 publications

Vertical Heterogeneity of the Shale Reservoir in the Lower Silurian Longmaxi Formation: Analogy between the Southeastern and Northeastern Sichuan Basin, SW China

Vertical Heterogeneity of the Shale Reservoir in the Lower Silurian Longmaxi Formation: Analogy between the Southeastern and Northeastern Sichuan Basin, SW China

Characterization of the Lower Silurian Longmaxi marine shale in Changning area in the south Sichuan Basin, China

Comparative study of nanoscale pore structure of Lower Palaeozoic marine shales in the Middle‐Upper Yangtze area, China: Implications for gas production potential

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