Sequence stratigraphy and its application in marine shale gas exploration: A case study of the Lower Silurian Longmaxi Formation in the Jiaoshiba shale gas field and its adjacent area in southeast Sichuan Basin, SW China

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

doi:10.1016/j.jngse.2015.09.016

Cited by 89 publications

(70 citation statements)

References 26 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%

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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%

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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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“…Geographically, it covers Fuling, Pengshui, Youyang, and Xiushan counties. This area has undergone multiple stages of tectonic activity, including the Caledonian orogeny (542-386 Ma), Hercynian orogeny (386-257 Ma), Indo-China movement (257-205 Ma), Yanshan movement (205-65 Ma) and Himalayan orogeny (beginning 65 Ma) [20,21]. This multistage tectonism was responsible for the complexities of the geological setting, such as numerous faults (some now active), universally steep dips and high tectonic stress [20].…”

Section: Geological Settingmentioning

confidence: 99%

“…Regarding the litho-stratigraphy of the study area, there are three typical marine shale formations, which from the top to the bottom consist of the LSL, UOW and LCN ( Figure 2). The topmost shale is the LSL, with a thickness ranging from 35 m to 200 m and a maximum burial depth of 4900 m [21]. The UOW lies beneath the LSL and forms a conformable contact with the overlying LSL ( Figure 2).…”

Section: Geological Settingmentioning

confidence: 99%

Comparison of Three Key Marine Shale Reservoirs in the Southeastern Margin of the Sichuan Basin, SW China

et al. 2017

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This study performs a comprehensive comparison of three key marine shale reservoirs in the southeastern margin of the Sichuan Basin, and explains why commercial gas production was only achieved in the Lower Silurian Longmaxi (LSL) and Upper Ordovician Wufeng (UOW) formations, but not in the Lower Cambrian Niutitang (LCN) formation. The experimental methods included in situ gas content and gas composition tests, methane adsorption analysis, low-pressure N 2 adsorption, field emission scanning electron microscopy (FE-SEM), and total organic carbon (TOC) and vitrinite reflectance (R o ) analyses to evaluate the lithology, mineralogy, physical properties of the reservoir, organic geochemistry, in situ gas content and methane adsorption capacity characteristics of the three shales. The LCN shale has lower quartz and clay mineral contents and a low brittleness index, but higher contents of feldspar, pyrite and carbonate minerals than the LSL and UOW shales. The porosity and permeability of the LSL and UOW shales are higher than those of the LCN shale. The primary contributions to the high permeability in the LSL shale are its well-developed fractures and organic matter pores. In contrast, the over-mature LCN shale is unfavorable for the development of organic pores and fractures. Although the LCN shale has a higher methane sorption capacity than the LSL and UOW shales, the gas content and methane saturation of the LCN shale are distinctly lower than those of the LSL and UOW shales. This is primarily due to gas migration from the LCN shale, resulting from the activities of tectonic uplift and the unconformable contact between the LCN shale and the Dengying formation. When compared with gas shale in North America, the LSL shale is the most favorable shale reservoir out of the three Sichuan shales, while the combination of the LSL and UOW shales is also potentially productive. However, the individual single layer production of the UOW or LCN shales is still limited due to poor resource potential and/or reservoir physical characteristics in the study area.

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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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Sequence stratigraphy and its application in marine shale gas exploration: A case study of the Lower Silurian Longmaxi Formation in the Jiaoshiba shale gas field and its adjacent area in southeast Sichuan Basin, SW China

Cited by 89 publications

References 26 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

Comparison of Three Key Marine Shale Reservoirs in the Southeastern Margin of the Sichuan Basin, SW China

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

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