Geochemistry of the extremely high thermal maturity Longmaxi shale gas, southern Sichuan Basin

Dai, Jianhua; Zou, Caineng; Liao, Shimeng; Dong, Dazhong; Ni, Yunyan; Huang, Jinliang; Wu, Wei; Gong, Daoyi; Huang, Shipeng; Hu, Guoyi

doi:10.1016/j.orggeochem.2014.01.018

Cited by 402 publications

(244 citation statements)

References 14 publications

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“…The permeability of the studied shales rank as LSL shale (average of 0.0016 mD) > UOW shale (average of 0.0014 mD) > LCN shale (average of 0.0012 mD) ( Table 1). The distinction of the porosity and permeability between different shales in this study is consistent with these previous studies [11,13,17], which indirectly confirms the veracity of the comparison regarding the porosity and permeability of different shales.…”

Section: Porosity and Permeabilitysupporting

confidence: 92%

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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Section: Porosity and Permeabilitysupporting

confidence: 92%

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

et al. 2017

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“…The main hydrocarbon source rocks in the Sichuan Basin include the Lower Cambrian, Upper Ordovician, Lower Silurian, Lower Permian, and Upper Permian formations [9,10]. Among these, the Lower Silurian Longmaxi Formation (abbreviated as LSL) marine shale is a significant shale gas reserve with prolific production potential.…”

Section: Introductionmentioning

confidence: 99%

“…LSL shale has become the most favored target stratum for shale gas recovery in China. Recent investigations of the LSL shale in the southeastern and eastern Sichuan Basin area have probed the geochemical characteristics [10], pore development characteristics [11], and methane adsorption capacity [12]. However, few investigations have evaluated the shale gas potential in the northeastern Sichuan Basin.…”

Section: Introductionmentioning

confidence: 99%

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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“…However, the geological settings of organic-rich, marine shale formations in China are distinct from those in North America. In China, shale gas formations are characterized by old strata, deep burial, high thermal maturity, and multi-stage tectonism (Dai et al, 2014;Zou et al, 2015). Therefore, more targeted criteria are needed to evaluate shale gas generation potential in China.…”

Section: Introductionmentioning

confidence: 99%

The origin and evolution of thermogenic gases in organic-rich marine shales

Xiong

Zhang

Chen

et al. 2016

Journal of Petroleum Science and Engineering

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Geochemistry of the extremely high thermal maturity Longmaxi shale gas, southern Sichuan Basin

Cited by 402 publications

References 14 publications

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

Comparison of Three Key Marine Shale Reservoirs in the Southeastern Margin of the 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

The origin and evolution of thermogenic gases in organic-rich marine shales

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