Overview and prospect of fracture propagation and conductivity characteristics in deep shale gas wells

Jiang, Tingxue; Zhou, Jian; Xu, Zhichuan J.; Hou, Lingyun; Xiao, Bailu

doi:10.1360/sspma2016-00535

Cited by 7 publications

(5 citation statements)

References 10 publications

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“…The Middle Jurassic strata crop out in the core, and the Lower Jurassic and Triassic strata crop out at both wings of the Jianwu syncline (Figure A). , Owing to the Duyun tectonic movement, most of the Sichuan Basin was enclosed by the Central Sichuan Underwater Uplift, the Niushoushan-Central Guizhou Uplift, and the Jiangnan-Xuefeng Uplift to form a large deep-water shelf-dominated depression from the late Ordovician to the early Silurian . Rapid transgression in the depression gave rise to an extensive dysoxic/anoxic deep-water shelf environment, in which cemented fiberized or lumpy remains and excrement of prolific lower siliceous ancient organisms, e.g., graptolite, sponge spicules, and foraminifera, settled underwater. − As a result, a package of deep-water organic-rich black siliceous shales formed in the early Rhuddanian–Aeronian. From the middle and late Aeronian to the Telychian, when the dysoxic/anoxic environment was destroyed due to sea level drop, a package of black silty shales was deposited in the semi-deep to shallow-water shelf, which changed from the deep-water depression, with extraneous terrigenous clastic sediments.…”

Section: Geological Settingmentioning

confidence: 99%

“… 40 Rapid transgression in the depression gave rise to an extensive dysoxic/anoxic deep-water shelf environment, in which cemented fiberized or lumpy remains and excrement of prolific lower siliceous ancient organisms, e.g., graptolite, sponge spicules, and foraminifera, settled underwater. 41 − 43 As a result, a package of deep-water organic-rich black siliceous shales formed in the early Rhuddanian–Aeronian. From the middle and late Aeronian to the Telychian, when the dysoxic/anoxic environment was destroyed due to sea level drop, a package of black silty shales was deposited in the semi-deep to shallow-water shelf, which changed from the deep-water depression, with extraneous terrigenous clastic sediments.…”

Section: Geological Settingmentioning

confidence: 99%

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Multi-scale Fractures and Their Influence on Shale Gas Deliverability in the Longmaxi Formation of the Changning Block, Southern Sichuan Basin, China

Zhao

Zheng²,

Liu³

et al. 2023

ACS Omega

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The capacity and deliverability of shale gas are closely linked to the presence of multi-scale fractures, including fractures and faults, within organic-rich shales. This study aims to investigate the fracture system of the Longmaxi Formation shale in the Changning Block of the southern Sichuan Basin and quantify the influence of multi-scale fractures on shale gas capacity and deliverability. The fracture system was analyzed through outcrop, core observations, and 3D seismic interpretation. Criteria for fault classification were established based on the horizon, throw, azimuth (phase), extension, and dip angle. The Longmaxi Formation shale mainly comprises shear fractures that form under multi-phase tectonic stress, characterized by large dip angles, small extensions, small apertures, and high density. The high content of organic matter and brittle minerals in the Long 1-1 Member facilitates the occurrence of natural fractures, which somewhat enhance shale gas capacity. Reverse faults with a dip angle of 45−70°e xist vertically, while laterally, there are early-stage nearly E-W faults, middle-stage NE faults, and late-stage NW faults. Based on the established criteria, faults that cut upward through the strata in and above the Permian with a throw greater than 200 m and a dip angle greater than 60°have the greatest influence on shale gas preservation and deliverability. These results provide important guidance for shale gas exploration and development in the Changning Block and contribute to our understanding of the relationship between multi-scale fractures and shale gas capacity and deliverability.

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Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Multi-scale Fractures and Their Influence on Shale Gas Deliverability in the Longmaxi Formation of the Changning Block, Southern Sichuan Basin, China

Zhao

Zheng²,

Liu³

et al. 2023

ACS Omega

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“…The thinner the reservoir, the lower the output per well and the faster the production decline. In order to maximize the fracturing effect of horizontal Wells in shale oil and gas, only by increasing the complexity of fractures as much as possible can the maximum volume of fracturing be achieved within the affected range of fractures, and the effect of fracturing of horizontal Wells and the economy of subsequent development be improved [12] . However, it is very difficult to effectively transform deep shale reservoir under the conditions of high temperature, high pressure and high ground stress by volume fracturing to form network fractures similar to medium-shallow shale [13] .…”

Section: The Thin Thickness Of Reservoirmentioning

confidence: 99%

Analysis of the difference between the test and production in Well Z202-H1

Lei¹,

Mao

et al. 2020

E3S Web Conf.

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In recent years, shale gas in the Upper Ordovician Wufeng Formation and lower Silurian Longmaxi Formation is gradually developing into deep strata in Sichuan Basin. Well 202-H1 is a evaluation well deployed to evaluate the productivity of horizontal Wells in longmaxi Formation and Wufeng Formation in The West Chongqing block. The well type is horizontal well. The main reasons for the poor production effect of Well Z202-H1 are as follows: Reservoir pores are not developed; continuous thickness of thin reservoir; insufficient fracturing treatment; low flowback rate, large water production and wellbore fluid accumulation. This article not only obtained the reasons for the difference between the test and production of well Z202-H1, but also provided a new research idea for the test and production tracking analysis of deep shale gas static in The Western Chongqing block.

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“…Fractures are tectonic weak surfaces that naturally occur, 18 − 20 which are expanded first in the hydraulic fracturing treatment of reservoirs, affecting the formation of artificial fracture networks. 16 , 21 , 22 Also, more natural fractures are expected to drill in the drilling process of horizontal wells during drill design. This is because of more complex fracture network systems that are easily formed in the fracturing process, contributing to the improved effect of reservoir fracturing treatment.…”

Section: Introductionmentioning

confidence: 99%

“…For reservoirs, unfilled fractures can also provide channels for the migration of shale gas to increase the effectiveness of shale reservoirs apart from being effective reservoir spaces. ,− Regarding the preservation conditions, the self-closed property of shale might be destroyed by the excessively developed fractures, leading to vertical dissipation of shale gas. Fractures are tectonic weak surfaces that naturally occur, − which are expanded first in the hydraulic fracturing treatment of reservoirs, affecting the formation of artificial fracture networks. ,, Also, more natural fractures are expected to drill in the drilling process of horizontal wells during drill design. This is because of more complex fracture network systems that are easily formed in the fracturing process, contributing to the improved effect of reservoir fracturing treatment .…”

Section: Introductionmentioning

confidence: 99%

Natural Fracture Development Characteristics and Their Relationship with Gas Contents─A Case Study of Wufeng–Longmaxi Formation in Luzhou Area, Southern Sichuan Basin, China

Qin

Qin³

et al. 2022

ACS Omega

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Natural fractures are critical factors that should be considered in shale reservoir evaluation, storage condition analysis, horizontal well design, and fracturing stimulation, which also play a non-negligible role in the occurrence state of shale gas in the reservoir. This paper discussed the influence of fracture development on gas-bearing properties based on the analysis results of core observation, scanning electron microscopy, mineral composition, and gas-bearing properties after the development characteristics of fractures and their longitudinal variation law were clarified. In this way, the development characteristics of organic-rich marine shale fractures in the Longmaxi Formation in the 203 well area of the Luzhou member of the Sichuan Basin and their effects on the gas-bearing properties can be analyzed. The results show that the Longmaxi Formation shale develops shear fractures, extensional fractures of tectonic origin, bedding fractures, dissolution fractures, and abnormally high-pressure fractures of nonstructural origin. Specifically, interlayer fractures, intercrystalline fractures, organic matter contraction fractures, and fractures between clay layers are microfractures. Fracture development is characterized by short longitudinal extension, small opening, high degrees of composite filling, and large density changes, with calcite and pyrite as the filling materials. The fracture density has a “three-stage” variation pattern longitudinally, and the bottom is dominated by thin siliceous shale development, together with a small amount of shale mixed with calcareous and calcareous materials. Moreover, the fracture is dominated by “splitting” and “shearing” failure, crossing stratification with the fracture density. The highest fracture density was found in the 2 sub-layer, featuring the joint development of horizontal and vertical fractures, which form the mesh fracture system through mutual cutting and restriction. The lithofacies in the 4 sub-layer are dominated by clay siliceous shale with a small amount of mixed shale of calcareous and siliceous materials. The formation of fractures always expands along the lamellation direction, which has concentrated development members of top and bottom fractures, with the development of horizontal fractures dominated and vertical fractures less developed. Furthermore, a synergistic effect can be found among the total organic carbon (TOC) content, fracture density, and gas-bearing property of the shale in Longmaxi Formation. It is worth noting that a high TOC content and siliceous content are conducive to the formation of microfractures, while the development of fracture contributes to the total gas-bearing property, especially to the increase in free gas content. To be concrete, the free gas content in the fracture development member accounts for more than 55% of the total gas content, thanks to a channel provided by fractures for the desorption of shale gas.

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Overview and prospect of fracture propagation and conductivity characteristics in deep shale gas wells

Cited by 7 publications

References 10 publications

Multi-scale Fractures and Their Influence on Shale Gas Deliverability in the Longmaxi Formation of the Changning Block, Southern Sichuan Basin, China

Multi-scale Fractures and Their Influence on Shale Gas Deliverability in the Longmaxi Formation of the Changning Block, Southern Sichuan Basin, China

Analysis of the difference between the test and production in Well Z202-H1

Natural Fracture Development Characteristics and Their Relationship with Gas Contents─A Case Study of Wufeng–Longmaxi Formation in Luzhou Area, Southern Sichuan Basin, China

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