Fracture development in Paleozoic shale of Chongqing area (South China). Part one: Fracture characteristics and comparative analysis of main controlling factors

Zeng, Weite; Zhang, Jinchuan; Ding, Wenlong; Song, Zhao; Zhang, Yeqian; Liu, Zhujiang; Jiu, Kai

doi:10.1016/j.jseaes.2013.07.014

Cited by 133 publications

(42 citation statements)

References 12 publications

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“…The structure has undergone continuous multi-phase deformations during the Caledonian, Hercynian, Indosinian, and Himalayan orogeneses, and the NE, NW, and NS-treading faults and fold systems are well developed. The general structure is a NE-SW-trending nose-like anticline (Guo et al, 2013;Zeng et al, 2013;Hu et al, 2014;Wei et al, 2017). Devonian, Carboniferous, and Mesozoic strata are generally absent in the region.…”

Section: Geological Settingmentioning

confidence: 99%

Geological Factors Controlling the Accumulation and High Yield of Marine‐Facies Shale Gas: Case Study of the Wufeng‐Longmaxi Formation in the Dingshan Area of Southeast Sichuan, China

Fan

Zhong

Zhang

et al. 2019

Acta Geologica Sinica (Eng)

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The main geological factors controlling the accumulation and yield of marine‐facies shale gas reservoirs are the focus of the current shale gas exploration and development research. In this study, the Wufeng‐Longmaxi Formation in the Dingshan area of southeast Sichuan was investigated. Shale cores underwent laboratory testing, which included the evaluation of total organic carbon (TOC), vitrinite reflectance (Ro), whole‐rock X‐ray diffraction (XRD), pore permeability, and imaging through field emission scanning electron microscopy (FE‐SEM). Based on the results of natural gamma ray spectrum logging, conventional logging, imaging logging, and seismic coherence properties, the exploration and development potential of shale gas in the Dingshan area have been discussed comprehensively. The results showed that (1) layer No. 4 (WF2‐LM4) of the Wufeng‐Longmaxi Formation has a Th/U ratio <2 and a Th/K ratio of 3.5‐12. Graptolites and pyrite are relatively abundant in the shale core, indicating sub‐high‐energy and low‐energy marine‐facies anoxic reducing environments. (2) The organic matter is mainly I‐type kerogen with a small amount of II1‐type kerogen. There is a good correlation among TOC, Ro, gas content, and brittle minerals; the fracturing property (brittleness) is 57.3%. Organic and inorganic pores are moderately developed. A higher pressure coefficient is correlated with the increase in porosity and the decrease in permeability. (3) The DY1 well of the shale gas reservoir was affected by natural defects and important late‐stage double destructive effects, and it is poorly preserved. The DY2 well is located far from the Qiyueshan Fault. Large faults are absent, and upward fractures in the Longmaxi Formation are poorly developed. The well is affected by low tectonic deformation intensity, and it is well preserved. (4) The Dingshan area is located at the junction of the two sedimentary centers of Jiaoshiba and Changning. The thickness of the high‐quality shale interval (WF2‐LM4) is relatively small, which may be an important reason for the unstable production of shale gas thus far. Based on the systematic analysis of the geological factors controlling high‐yield shale gas enrichment in the Dingshan area, and the comparative analysis with the surrounding typical exploration areas, the geological understanding of marine shale gas enrichment in southern China has been improved. Therefore, this study can provide a useful reference for shale gas exploration and further development.

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Section: Geological Settingmentioning

confidence: 99%

Geological Factors Controlling the Accumulation and High Yield of Marine‐Facies Shale Gas: Case Study of the Wufeng‐Longmaxi Formation in the Dingshan Area of Southeast Sichuan, China

Fan

Zhong

Zhang

et al. 2019

Acta Geologica Sinica (Eng)

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“…The tectonic setting of the study area is primarily extensional, with a strike‐slip component. Due to long‐term mutual interference and superposition of various periods of tectonism, the current complex tectonic landscape of the combination of folds and faults was formed (Zeng et al, ).…”

Section: Geological Settingmentioning

confidence: 99%

Shale reservoir characterization and control factors on gas accumulation of the Lower Cambrian Niutitang shale, Sichuan Basin, South China

Liang

Jiang

et al. 2018

Geological Journal

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The Lower Cambrian Niutitang shale is reported to be the oldest strata for large‐scale shale gas reserves. Based on outcrop observations and laboratory analyses, this study used a comprehensive approach that integrated sedimentology, mineralogy, petrology, organic geochemistry, and reservoir geology to estimate the prospects for exploring for shale gas in the Lower Cambrian Niutitang Formation, southern China. Whole rock and clay mineral X‐ray diffraction, scanning electron microscope (SEM) observations, and petro‐physical property measurements indicate that the Niutitang shale is dominated by quartz and clay minerals with minor amounts of plagioclase, potassium feldspar, calcite, dolomite, and pyrite. The organic matter in the Niutitang shale is dominated by type‐1 kerogen, with TOC levels ranging from 1.35% to 14.3% (average 4.46%) and Ro values ranging from 1.86% to 4.18% (average 2.79%). The three primary types of pores in the shale are organic pores, microfractures, and micropores. The micropores are primarily found in the clay mineral crystals and pyrite, and the microfractures are found along the boundaries of quartz grains. Most of the pore diameters are less than 20 nm, mainly concentrate at about 10 nm, which is consistent with that the organic pores act as the main storage space. The pore volume and gas content are strongly controlled by the mineral composition and lithofacies, and TOC content. The factors favouring shale gas accumulation of the Niutitang shale in the study area include (1) an effective thickness and widespread distribution, (2) a high organic carbon content and appropriate organic matter maturity, and (3) a favourable depositional environment.

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“…Because the preexisting natural macrofractures have a significant influence on both seepage flow and fracturing process, current research studies focus on this type of natural fracture. However, referring to fractures at the microscale, some studies have indicated that shale reservoirs contain many natural microcracks that are randomly distributed . These microscale natural cracks are typically sealed and cannot contribute to reservoir storage or enhance permeability.…”

Section: Introductionmentioning

confidence: 99%

“…However, referring to fractures at the microscale, some studies have indicated that shale reservoirs contain many natural microcracks that are randomly distributed. [14][15][16] These microscale natural cracks are typically sealed and cannot contribute to reservoir storage or enhance permeability. Our literature review yielded no evidence of widespread open natural microcracks.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of the effect of natural microcracks on the supercritical CO₂ fracturing crack network of shale rock based on bonded particle models

Peng

Wang

et al. 2017

Num Anal Meth Geomechanics

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Summary The problem of predicting the geometric structure of induced fractures is highly complex and significant in the fracturing stimulation of rock reservoirs. In the traditional continuous fracturing models, the mechanical properties of reservoir rock are input as macroscopic quantities. These models neglect the microcracks and discontinuous characteristics of rock, which are important factors influencing the geometric structure of the induced fractures. In this paper, we simulate supercritical CO2 fracturing based on the bonded particle model to investigate the effect of original natural microcracks on the induced‐fracture network distribution. The microcracks are simulated explicitly as broken bonds that form and coalesce into macroscopic fractures in the supercritical CO2 fracturing process. A calculation method for the distribution uniformity index (DUI) is proposed. The influence of the total number and DUI of initial microcracks on the mechanical properties of the rock sample is studied. The DUI of the induced fractures of supercritical CO2 fracturing and hydraulic fracturing for different DUIs of initial microcracks are compared, holding other conditions constant. The sensitivity of the DUI of the induced fractures to that of initial natural microcracks under different horizontal stress ratios is also probed. The numerical results indicate that the distribution of induced fractures of supercritical CO2 fracturing is more uniform than that of common hydraulic fracturing when the horizontal stress ratio is small.

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Fracture development in Paleozoic shale of Chongqing area (South China). Part one: Fracture characteristics and comparative analysis of main controlling factors

Cited by 133 publications

References 12 publications

Geological Factors Controlling the Accumulation and High Yield of Marine‐Facies Shale Gas: Case Study of the Wufeng‐Longmaxi Formation in the Dingshan Area of Southeast Sichuan, China

Geological Factors Controlling the Accumulation and High Yield of Marine‐Facies Shale Gas: Case Study of the Wufeng‐Longmaxi Formation in the Dingshan Area of Southeast Sichuan, China

Shale reservoir characterization and control factors on gas accumulation of the Lower Cambrian Niutitang shale, Sichuan Basin, South China

Numerical analysis of the effect of natural microcracks on the supercritical CO₂ fracturing crack network of shale rock based on bonded particle models

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Fracture development in Paleozoic shale of Chongqing area (South China). Part one: Fracture characteristics and comparative analysis of main controlling factors

Cited by 133 publications

References 12 publications

Geological Factors Controlling the Accumulation and High Yield of Marine‐Facies Shale Gas: Case Study of the Wufeng‐Longmaxi Formation in the Dingshan Area of Southeast Sichuan, China

Geological Factors Controlling the Accumulation and High Yield of Marine‐Facies Shale Gas: Case Study of the Wufeng‐Longmaxi Formation in the Dingshan Area of Southeast Sichuan, China

Shale reservoir characterization and control factors on gas accumulation of the Lower Cambrian Niutitang shale, Sichuan Basin, South China

Numerical analysis of the effect of natural microcracks on the supercritical CO2 fracturing crack network of shale rock based on bonded particle models

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Numerical analysis of the effect of natural microcracks on the supercritical CO₂ fracturing crack network of shale rock based on bonded particle models