Natural Fractures and Their Effects on Reservoir Reconstruction in Lower Cambrian Shale, Southeast Chongqing, China

Li, Dahua; Jiao, Weiwei; Yuan, Feng; Xiang, Xiaojun; Pan, Linhua

doi:10.1260/0144-5987.33.6.769

Cited by 7 publications

(7 citation statements)

References 21 publications

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“…This type of structure is defined as a dilatational or tensile fracture with a decrease in the total volume of the rock. Diagenetic fractures are a type of nearhorizontal fractures caused by pressure solution, compaction, and pressure release [33][34][35]. These fractures, which are developed in the outcrop shale of the Longmaxi Formation, are predominantly horizontal foliation fractures and bedding slip joints.…”

Section: Diageneticmentioning

confidence: 99%

Quantitative Characterization and Determination of the Main Factors That Control Fracture Development in the Lower Paleozoic Shale in Southeastern Chongqing, China

Zhang

Kong

Chen³

et al. 2021

Geofluids

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The Longmaxi and Niutitang Formations are typical shale reservoirs in southeastern Chongqing. Since the Paleozoic, southeastern Chongqing has experienced multistage tectonic movement and diagenesis, resulting in the formation of a large number of natural fractures. In shale reservoirs, fractures not only provide seepage channels for oil and gas migration but also play an important role in the oil and gas reservoir space. Natural fractures provide a flow path from source rock to reservoir during oil filling and connect hydraulic fractures, matrix pores, and boreholes during production. Therefore, identifying the main factors that control the development of natural fractures in the Longmaxi and Niutitang Formations in southeastern Chongqing has a guiding significance for the efficient development of shale reservoirs in this area. By considering the Longmaxi and Niutitang Formation shales as case studies, using field outcrops, drilling cores, and other data, and conducting X-ray diffraction (XRD) analysis as well as total organic carbon (TOC) measurements, the quantitative parameter characteristics and main factors that control the development of natural fractures in reservoir shales were examined in detail. The results obtained showed that there are three types of fractures in the lower Paleozoic shale in southeastern Chongqing, which are structural, diagenetic, and abnormal high-pressure fractures. Among them, the fractures in the Longmaxi Formation shale, which are relatively abundant, predominantly consist of low-angle and high-angle inclined fractures, while the Niutitang Formation predominantly consists of high-angle fractures. Additionally, the investigation of fracture size and fracture density, as well as correlation analyses, showed that the fractures of the Lower Paleozoic shale are predominantly micro fractures that play a key role in improving reservoir seepage. It was also noted that the development of fractures is affected by several factors, including tectonic stress, mineral composition, organic carbon content, and rock thickness. The degree of fracture development was found to be positively correlated with brittle mineral and quartz contents, and high organic matter contents also significantly favored the formation micro fractures.

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Section: Diageneticmentioning

confidence: 99%

Quantitative Characterization and Determination of the Main Factors That Control Fracture Development in the Lower Paleozoic Shale in Southeastern Chongqing, China

Zhang

Kong

Chen³

et al. 2021

Geofluids

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“…Depth/km ( He et al, 2011;Li et al, 2015;Liu et al, 2011;Zeng and Guo, 2015). The Permian Basin is located on the south edge of the North America platform and is a Paleozoic cratonic basin formed on Precambrian crystalline basement.…”

Section: Tectonic and Sedimentary Characteristics Basin Tectonic Evolmentioning

confidence: 99%

“…It is a large multicycle superimposed basin consisting of stably developed Paleozoic marine cratonic basin and Mesozoic–Cenozoic foreland basin developed from thrust structures and has experienced multistage tectonic disturbances and depositional superimpositions (Figure 2(b)) (He et al., 2005; Jia and Wei, 2002; Zhang et al., 2007); the Sichuan Basin is located northwest of the Yangtze tectonic plate. It is on the Proterozoic crystalline basement, resulting from superimpositions of cratonic basin between the Sinian and middle Triassic, foreland basin in later Triassic, and depression basin between the early Jurassic to middle Cretaceous (Figure 2(c)) (He et al., 2011; Li et al., 2015; Liu et al., 2011; Zeng and Guo, 2015). The Permian Basin is located on the south edge of the North America platform and is a Paleozoic cratonic basin formed on Precambrian crystalline basement.…”

Section: Tectonic and Sedimentary Characteristicsmentioning

confidence: 99%

A comparative study of salient petroleum features of the Proterozoic–Lower Paleozoic succession in major petroliferous basins in the world

Liu

Jin

Bai

et al. 2016

Energy Exploration & Exploitation

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The Proterozoic-Lower Paleozoic marine facies successions are developed in more than 20 basins with low exploration degree in the world. Some large-scale carbonate oil and gas fields have been found in the oldest succession in the Tarim Basin, Ordos Basin, Sichuan Basin, Permian Basin, Williston Basin, Michigan Basin, East Siberia Basin, and the Oman Basin. In order to reveal the hydrocarbon enrichment roles in the oldest succession, basin formation and evolution, hydrocarbon accumulation elements, and processes in the eight major basins are studied comparatively. The Williston Basin and Michigan Basin remained as stable cratonic basins after formation in the early Paleozoic, while the others developed into superimposed basins undergone multistage tectonic movements. The eight basins were mainly carbonate deposits in the Proterozoic-early Paleozoic having different sizes, frequent uplift, and subsidence leading to several regional unconformities. The main source rock is shale with total organic carbon content of generally greater than 1% and type I/II organic matters. Various types of reservoirs, such as karst reservoir, dolomite reservoir, reef-beach body reservoirs are developed. The reservoir spaces are mainly intergranular pore, intercrystalline pore, dissolved pore, and fracture. The reservoirs are highly heterogeneous with physical property changing greatly and consist mainly of gypsum-salt and shale cap rocks. The trap types can be divided into structural, stratigraphic, lithological, and complex types. The oil and gas reservoir types are classified according to trap types where the structural reservoirs are mostly developed. Many sets of source rocks are developed in theseCreative Commons CC-BY: This article is distributed under the terms of the Creative Commons Attribution 3.0 License (http://www.creativecommons.org/licenses/by/3.0/) which permits any use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/open-access-at-sage). basins and experienced multistage hydrocarbon generation and expulsion processes. In different basins, the hydrocarbon accumulation processes are different and can be classified into two types, one is the process through multistage hydrocarbon accumulation with multistage adjustment and the other is the process through early hydrocarbon accumulation and late preservation.

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“…But the mineralogy distribution dominates the etching patterns. Unlike hydraulic fractures with basically orthonormal and symmetrical distribution, high conductivity because of proppant placement, and longer fracture length, the etched fracture exhibits a radial distribution with shorter fracture length and lower conductivity due to fracture closure (Li et al., 2015; Lee et al., 2016; He et al., 2016; Qin et al., 2018). The presence of multiple etched fractures makes pressure transient analysis more complex and difficult, especially the radial distribution of multiple etched fractures.…”

Section: Introductionmentioning

confidence: 99%

Pressure transient analysis of a vertical well with multiple etched fractures in carbonate reservoirs

Luo

Fan

et al. 2019

Energy Exploration & Exploitation

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Acid fracturing has been widely used as an industry practice in explored and developed carbonate reservoirs. It is very important to understand responses of reservoirs and improve production performance of a well due to the presence of fracture networks by stimulation treatments. Pressure transient analysis is one of the most effective diagnostic techniques available to enhance our understanding of natural and artificial-etched fracture behavior. This work presented a novel mathematical model for unsteady state flow of naturally fractured porous medium into multiple etched fractures intersecting a vertical well, and three different geometric shapes of matrix blocks containing slabs, cylinders and spheres were considered. The new solution was derived by using the Laplace transformation and the point source function integral approach. The polar coordinate transformation was used to deal with the radial distribution of arbitrary fracture number and angle. Then the model was validated by comparison with three published cases. Finally, type curves were plotted to identify flow regimes: linear flow, transitional flow, pseudoradial flow, and boundary dominant flow if the closed or constant pressure boundary exists. Furthermore, sensitivity analysis was investigated. The results showed that the acid-etched fracture parameters containing fracture number, fracture distribution and conductivity had a significant impact on pressure behavior at early times. However, natural fracture storativity coefficient and interporosity flow parameter mainly affected the transitional flow at intermediate times. Moreover, the shape of matrix blocks had a little influence on transient responses at intermediate times. It is found that multiple etched fractures existing near the wellbore consume less pressure drop and increase the productivity of a well as a whole.

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Natural Fractures and Their Effects on Reservoir Reconstruction in Lower Cambrian Shale, Southeast Chongqing, China

Cited by 7 publications

References 21 publications

Quantitative Characterization and Determination of the Main Factors That Control Fracture Development in the Lower Paleozoic Shale in Southeastern Chongqing, China

Quantitative Characterization and Determination of the Main Factors That Control Fracture Development in the Lower Paleozoic Shale in Southeastern Chongqing, China

A comparative study of salient petroleum features of the Proterozoic–Lower Paleozoic succession in major petroliferous basins in the world

Pressure transient analysis of a vertical well with multiple etched fractures in carbonate reservoirs

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