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

Li, Hu; Tang, Hongming; Zheng, Majia

doi:10.3390/min9090548

Cited by 44 publications

(39 citation statements)

References 69 publications

(75 reference statements)

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“…Large numbers of intergranular pores with unregular shapes and sizes of 50 nm-1.5 µm form via the mutual support of mineral particles. In addition, as pyrite is characterized by a high elastic modulus, pyrite in shale mostly exists in the form of framboids with different crystal sizes, thereby forming a certain number of intercrystalline pores (Li et al, 2019a). The pores in a single pyrite framboid crystal have good connectivity and are often filled with organic matter.…”

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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“…The marine shale gas resources in China are abundant. Reservoir geological characteristics have always been a hot topic in shale gas exploration and development in China and abroad since they play an important role in controlling the enrichment and production of shale gas (Fan et al, 2018;Li et al, 2019;Fan et al, 2020a;Fan et al, 2020b;He et al, 2021a). The favorable areas for marine shale gas are mainly located in Sichuan Basin, China.…”

Section: Introductionmentioning

confidence: 99%

Geological Characteristics and Controlling Factors of Enrichment of Deep Shale Gas in the East Weiyuan–North Rongchang Area, Sichuan Basin, China

Tang

Li³

et al. 2022

Front. Earth Sci.

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The southern Sichuan Basin is the core area of China’s efficient development of deep shale gas (burial depth greater than 3,500 m). Reservoir geological characteristics determine whether shale gas can be preserved, enriched, and produced. Taking the Long 11 sub-member of the Wufeng Formation of the Upper Ordovician and the Longmaxi Formation of the Lower Silurian in the East Weiyuan–North Rongchang area as an example, we used the core, logging, production test, and other data, combining X-ray diffraction analysis, LECO Total Organic Carbon (TOC)-S analysis, optical microscopy, and argon ion polishing field-emission scanning electron microscopy, to study the shale mineral composition, geochemistry, reservoir space, pore structure characteristics, and reservoir physical properties. The following results were obtained: 1) The brittle mineral content, organic matter maturity, and TOC content are high, gradually increase from top to bottom, and reach their maxima at small layer 1 of Long 11. 2) Organic pores, inorganic pores, and fractures are important reservoir spaces, among which organic pores and fractures are important seepage channels for shale gas. 3) The shale pore structure revealed by electron microscopy shows that the pore structure in target layers can be divided into four types: unimodal type (mainly organic pores), bimodal type (both organic and inorganic pores), monoclinic type I (mainly organic pores), and monoclinic type II (mainly inorganic pores). The pore morphology is complex, and circular and oval shapes predominate. 4) Sedimentary facies are the main factor controlling the enrichment of shale gas, and the development of fractures is the key to obtaining high yields of shale gas. 5) The class I favorable target area is mainly distributed in wells W206, W206H1, R234H, and R233H and areas to its south, and some areas in the east of the study area.

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“…Shale gas resource is the fastest growing natural gas resources in exploration and development of unconventional oil and gas resource over the world. The recoverable shale gas resource of China is estimated to be 12.85 × 10 12 m 3 , of which Sichuan Basin is the area with the largest reserve of natural gas and the greatest cumulative production of natural gas in China [1][2][3]. Shale gas is an important energy component that changes China's natural gas development and even the entire energy development pattern.…”

Section: Introductionmentioning

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

Cited by 44 publications

References 69 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

Geological Characteristics and Controlling Factors of Enrichment of Deep Shale Gas in the East Weiyuan–North Rongchang Area, Sichuan Basin, China

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

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