Binary pore structure characteristics of tight sandstone reservoirs

Zhu, Haihua; Zhang, Tingshan; Li, Yaoyu; Zhang, Jingxuan; Chen, Xiaohui

doi:10.1016/s1876-3804(19)60283-1

Cited by 32 publications

(17 citation statements)

References 25 publications

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“…Of note, the structure fracture had higher porosity than the pores (Figure 6I), significantly improving the physical properties of the marl reservoir (Kong et al, 2019). After the marl diagenesis, Shulu Sag underwent many tectonic movements, and many faults were formed (Zhao et al, 2015;Zhu et al, 2018;Zhu et al, 2019b;Zhu et al, 2020;He et al, 2022). The vicinity of these faults tended to be characterized by a concentration of stress, which was conducive to the occurrence of microfractures associated with faults, which played a key role in improving the physical features of the reservoir.…”

Section: Tectonismmentioning

confidence: 99%

Reservoir characteristics and factors influencing shahejie marl in the shulu sag, bohai bay basin, eastern China

Fu²,

Zhu³

et al. 2022

Front. Earth Sci.

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Shahejie marl in the Shulu Sag is a crucial resource for unconventional hydrocarbon exploration in China. Although breakthroughs have been made in tight oil exploration in this area, the mechanisms underlying the formation of this marl reservoir and factors controlling its ‘sweet spots’ have not been thoroughly studied. To understand the pore structure characteristics and factors influencing the marl reservoir, we analyzed core samples from Wells ST1 and ST3. A series of experiments was conducted on the samples, such as X-ray diffraction, focused ion beam scanning electron microscopy, micro-CT, and total organic carbon test. Additionally, the physical properties of different marl rock fabrics were studied with auxiliary tests, such as mercury intrusion capillary pressure analyses, nuclear magnetic resonance, porosity and permeability tests, and thin-section observation. The results revealed that the marl reservoir is characterized by low porosity (1.61%) and low permeability (2.56mD). The porosity and permeability (1.61% and 3.26mD) of laminated marl were better than those (0.92% and 1.68mD) of massive marl. Clay minerals and quartz content in laminated (11.8 and 8.2%) was less than in massive marl (16.2 and 13.3%). The marl pores include intercrystalline pores, dissolution pores, and microfractures. Additionally, the laminated marl pores were primarily distributed along the dark lamina, with good connectivity. A few isolated and uniform holes were observed in the massive marl. Influenced by rock fabric and mineral composition, layered fractures were mainly developed in the laminated marl, while structural fractures were the main type of microfractures in the massive marl. The primary sedimentary mechanism was the main geological action underlying the differences in marl rock fabric; this mechanism affects the physical properties of the marl reservoir, which are key factors to be considered when searching for the marl reservoir ‘sweet spots’. Particular attention should be paid to these factors during tight oil exploration and development in similar sedimentary basins.

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Section: Tectonismmentioning

confidence: 99%

Reservoir characteristics and factors influencing shahejie marl in the shulu sag, bohai bay basin, eastern China

Fu²,

Zhu³

et al. 2022

Front. Earth Sci.

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“…Thin section analysis was used in combination with other analytical tests to further determine the clastic composition and pore-throat structure characteristics of tight sandstone. The thin sections were 30 μm in thickness and impregnated with blue-dye resin to highlight the porosity. − The AXIO SKOP40 microscope was used for observation, photography, and analysis. We measured the mass fraction of terrigenous clastic and interstitial materials as well as structure characteristics such as the cementation type, contact mode, density, sorting, and roundness features of each clastic rock thin section.…”

Section: Samples and Experimentsmentioning

confidence: 99%

Pore-Throat Size Distribution and Classification of the Paleogene Tight Sandstone in Lishui Sag, East China Sea Shelf Basin, China

Zhao

Ma³

2020

Energy Fuels

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The characteristics of tight sandstone reservoirs are closely influenced by the complex pore structure and the widths of pore-throat size distributions (P-TSDs). Because of the limitations of various techniques, it is difficult to characterize the morphology and size distribution jointly of the pore-throat structure. In this study, thin section, scanning electron microscopy, X-ray fluorescence diffraction, high-pressure mercury injection, and constant speed mercury injection were combined to analyze the pore throat structure characteristics of the Lishui tight sandstone reservoir in the southern East China Sea Shelf Basin, and joint characterization of morphology and size distribution of the pore-throat structure was established based on X-ray computed tomography (XCT) analysis. The results showed that the Paleocene tight sandstone in Lishui Sag generally has a high content of lithic and feldspar, which provides a good material basis for the development of clay minerals in the reservoir. Autogenic illite and kaolinite occupy the majority of pore-throat space in tight sandstone reservoirs and form intergranular micropores of clay minerals with a radius less than 1 μm, which are important factors for the development of micropores and throats in tight sandstone. XCT scanning showed that as the content of clay mineral increased, the number of throats developed per unit volume decreased, the isolated point-like micropores significantly increased, and the connectivity between micropores deteriorated. Based on the pore and throat information obtained by XCT scanning, the pore and throat radius frequency and volume distribution curves were generated. According to the distribution characteristics of the curves, the pore size distribution types of tight sandstone are divided into two types: peak type and flat type, and throat size distribution types are divided into three types: right peak type, left peak type, and bimodal type.

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“…The microporous structure is an umbrella term for pore throat distribution, size, morphology, connectivity and configuration (Qiao et al, 2019;Song et al, 2019;Zhu et al, 2019). These parameters are usually obtained by scanning electron microscopy (SEM), Nano/Micro-CT imaging, mercury injection, nitrogen adsorption and other experimental methods (Guo et al, 2018;Sui et al, 2018;Gou et al, 2019;Viktorovich et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

The investigation of microporous structure and fluid distribution mechanism in tight sandstone gas reservoirs: A case study on the second member of Xujiahe gas reservoirs in Yuanba area

Guo

Fu²,

Li³

et al. 2022

Front. Energy Res.

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Tight sandstone reservoir is characterized by ultra-low porosity, complex microporous structure and water residues, which shows different gas storage and transport mechanism from conventional reservoirs. Therefore, effective development of tight sandstone gas reservoirs is faced with technical challenges. Microporous structures, distribution mechanism of fluid is a basic issue in gas reservoir evaluation. In this work, we take gas reservoir in the 2nd member of Xujiahe Formation in Yuanba area as an example to analyze the microscopic feature of pore structure and fluid distribution. The three-dimensional digital core has been applied to represent the real microporous structure. Specifically, a digital core reconstruction method based on SEM and casting slice images has been proposed. Ultimately, the mechanism of distribution, mode of occurrence of water residues in tight sandstone reservoirs has been simulated and quantitatively analyzed. The results show that the water residues could been visualized and categorized into three modes, water mass in corner, water film on surface, and water column in throat. The water residues could cause dramatic influence on pore structures, active pore size could be decreased with rising residual water saturation, the magnitude falls by over 50%. In addition, grain size would affect the distribution of water residues, which shows different percentage in medium and fine sand. Pore connectivity is another characteristic factor to describe the microporous structures. In this study, cluster marking algorithm has been applied to obtain the pore connectivity in tight sandstone with different grain size. In medium sand, the pore connectivity is dramatically decreased with rising water saturation, the downward trend become slower when water saturation reaches to 60%. Compared to fine sand, the tendency variation appears when water saturation reaches to 40%. This paper provides an applicable method to reveal the micro-scale reservoir properties and fluid distribution mechanisms in tight sandstone gas reservoirs.

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Binary pore structure characteristics of tight sandstone reservoirs

Cited by 32 publications

References 25 publications

Reservoir characteristics and factors influencing shahejie marl in the shulu sag, bohai bay basin, eastern China

Reservoir characteristics and factors influencing shahejie marl in the shulu sag, bohai bay basin, eastern China

Pore-Throat Size Distribution and Classification of the Paleogene Tight Sandstone in Lishui Sag, East China Sea Shelf Basin, China

The investigation of microporous structure and fluid distribution mechanism in tight sandstone gas reservoirs: A case study on the second member of Xujiahe gas reservoirs in Yuanba area

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