Elements and gas enrichment laws of sweet spots in shale gas reservoir: A case study of the Longmaxi Fm in Changning block, Sichuan Basin

Pan, Renfang; Gong, Qiyong; Yan, Jie; Jin, Jineng

doi:10.1016/j.ngib.2016.05.003

Cited by 11 publications

(8 citation statements)

References 6 publications

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“…Radiating from the core to the margin, the Cambrian, Ordovician, Silurian, Permian, Triassic, and Jurassic strata crop out in turn. A series of thrust faults, mostly in the NE and NNW directions, often penetrate the Cambrian in the core. ,, Within the anticline, there are well-developed secondary folds. At the steep NE flank, the Dongguancun nosing structure extends in the NE direction, and the east end plunges into the Yingpanshan anticline and Xuyong syncline and vanishes into the nearly E-W-trending Xuyong syncline.…”

Section: Geological Settingmentioning

confidence: 99%

“…The Changning Block is located at the intersection of the southern Sichuan fold belt and the Loushan faulted fold belt, the major part of which lies in the Jianwu syncline. Structurally, it is adjacent to the Changning anticline, Xuyong syncline, and Gaomuding structures on the east, the Baiyanglin and Dazhai anticlinal structures on the south, the Jiacunxi structure on the west, and the Lianhuasi, Laowengchang, and Fujiamiao structures on the north (Figure A). ,− The study area experienced multi-phase, multi-directional tectonic movements in the Caledonian, Hercynian, Indosinian, Yanshanian, and Himalayan, with the structural style finalized at the end of the Himalayan. , It is in a structural triangle against compressive stress from the eastern Sichuan-western Hunan and Hubei structural belt on the east, remote compressive stress transfer from the Longmenshan Mountains on the west, the constraint of the Sichuan Basin and Huayingshan fracture zone on the north, and compression and uplifting caused by structural transformation in the Ziyun-Luodian fracture zone on the south, where there are diverse and complex structural systems, including folds, faults, and fractures. ,, …”

Section: Geological Settingmentioning

confidence: 99%

“…In the Sichuan Basin, a major shale gas province in China, organic-rich shales occur in the Upper Sinian Doushantuo Formation, Lower Cambrian Shuijingtuo Formation (Niutitang Formation, Jiulaodong Formation, and Qiongzhusi Formation), and Upper Ordovician Wufeng Formation to Lower Silurian Longmaxi Formation (“Wufeng Formation–Longmaxi Formation”). − The Wufeng Formation–Longmaxi Formation organic-rich marine shales feature high TOC, large thickness, high maturity, a high brittleness index, and high gas content. Some shale gas fields, including Jiaoshiba, Changning, Zhaotong, Weirong, and Luzhou, have been established. − The age-old over-mature shales in the Longmaxi Formation underwent multi-phase structural deformation; − thus, shale gas preservation conditions vary greatly from area to area. Owing to the dual effects of the Tethyan tectonic and Circum Pacific tectonic domains, the Sichuan Basin (especially the basin margin) experienced complicated structural evolution and severe structural deformation, giving rise to diverse structural styles, which led to various complicated preservation conditions. − There are many factors affecting shale gas preservation, and the most dominant factor is the occurrence of fractures (including faults and fractures). − The formation of fractures is governed by the mechanical properties and stress loads acting on rocks.…”

Section: Introductionmentioning

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%

Section: Introductionmentioning

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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“…In general, gas is contained in mature shale. However, commercial shale gas reservoirs are formed by the effective allocation of multiple spatiotemporal factors instead of a single factor (Pan et al, 2016;Wang et al, 2018). Shale is a special rock type that integrates the source, storage and coverage.…”

Section: Coupled Control Of "Source and Storage" Accumulationmentioning

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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“…Previous research on this area's black shale has mainly been concentrated on the Sichuan Basin. The Changning-Weiyuan block is mainly composed of organic-rich black shales enriched in graptolites, brachiopods, and other fossils, along with good organic matter types, relatively high thermal maturity, moderate content of brittle mineral components in shale matrix, and the presence of diverse types of pores and fractures, all of which make the Longmaxi Formation shale favorable for shale gas accumulation (Pu et al, 2010;Pan et al, 2016). Most research into black shale has focused on the Jiaoshiba shale gas reservoir in Fuling, southeastern Sichuan, including studies on the division of graptolite belts, sedimentary responses, shale distribution laws, accumulation models, and structural influences (Su et al, 2007;Mu et al, 2011;Guo, 2014;Guo et al, 2014a;Chen et al, 2015;Wang, 2015;Nie et al, 2016;Jin et al, 2018;Zhou et al, 2018;Gao et al, 2019;Gou and Xu, 2019;Liang et al, 2018;Lv et al, 2019Lv et al, , 2020Tang et al, 2019;Wang R. Y. et al, 2019;Wang et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Characteristics and Genetic Mechanisms of Normal-Pressure Fractured Shale Reservoirs: A Case Study From the Wufeng–Longmaxi Formation in Southeastern Chongqing, China

Wang

Tan²,

Wang³

et al. 2021

Front. Earth Sci.

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Compared with the overpressure conditions of shale reservoirs in the Jiaoshiba area, exploring the controlling factors of changes in shale reservoir physical properties under normal-pressure accumulation is of great significance to shale gas exploration. To achieve this, X-ray powder diffraction, nitrogen adsorption, and scanning electron microscopy were carried out to determine mineral content, permeability, porosity, and pore structure for well core and outcrop samples of the Wufeng–Longmaxi Formation in southeastern Chongqing, China. Field observations and drilling cores revealed abundant structural fractures in southeastern Chongqing, offering potential main storage space for shale gas. Findings also determined that high-quality source rocks are located in the lower part of the Wufeng–Longmaxi Formation, which features low porosity and low permeability, yet existing structural fractures could potentially improve permeability to a certain extent. The main factors controlling the shale reservoir with the above characteristics include the depositional environment, mineral components, total organic carbon content, and tectonic movement. The deep-water anoxic depositional environment was conducive to the complete preservation of organic matter and sedimentation of the biogenic siliceous minerals, which had a strong effect on improving the porosity of organic matter and brittleness of the rocks. The high content of quartz was found to improve rock compression resistance and brittleness, and increasing clay proportion was found to enhance the interlayer pores of clay minerals. Total organic carbon content, specific surface area, pore volume, and fracture development were all found to have direct contributions to shale gas entrapment. Overall, the most important factor resulting in normal-pressure accumulation in southeastern Chongqing was the intense tectonic movements since the Late Jurassic period which destroyed the original overpressure accumulation conditions.

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Elements and gas enrichment laws of sweet spots in shale gas reservoir: A case study of the Longmaxi Fm in Changning block, Sichuan Basin

Cited by 11 publications

References 6 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

Geological Characteristics of Deep Shale Gas in the Silurian Longmaxi Formation in the Southern Sichuan Basin, China

Characteristics and Genetic Mechanisms of Normal-Pressure Fractured Shale Reservoirs: A Case Study From the Wufeng–Longmaxi Formation in Southeastern Chongqing, China

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