A full-scale characterization method and application for pore-throat radius distribution in tight oil reservoirs

Xiao, Qi; Yang, Zhengming; Wang, Zhiyuan; Zhang, Qi; Wang, Xuewu; Xiong, Shengwu

doi:10.1016/j.petrol.2019.106857

Cited by 26 publications

(13 citation statements)

References 17 publications

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“…Under the actual drilling differential pressure, macropores contribute the most to the permeability of the reservoir [ 26 ]. Mud filtrate primarily invades the macropores to displace the movable fluid (including movable water and oil and gas) within the detection range, while mud filtrate invades the small pores less, and the bound fluid will not change basically.…”

Section: Methodsmentioning

confidence: 99%

Study on Nuclear Magnetic Resonance Logging T2 Spectrum Shape Correction of Sandstone Reservoirs in Oil-Based Mud Wells

Sun

Cai²,

Feng

et al. 2021

Molecules

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The oil-based mud filtrate will invade the formation under the overbalanced pressure during drilling operations. As a result, alterations will occur to the nuclear magnetic resonance (NMR) response characteristics of the original formation, causing the relaxation time of the NMR T2 spectrum of the free fluid part to move towards a slower relaxation time. Consequently, the subsequent interpretation and petrophysical evaluation will be heavily impacted. Therefore, the actual measured T2 spectrum needs to be corrected for invasion. For this reason, considering the low-porosity and low-permeability of sandstone gas formations in the East China Sea as the research object, a new method to correct the incorrect shape of the NMR logging T2 spectrum was proposed in three main steps. First, the differences in the morphology of the NMR logging T2 spectrum between oil-based mud wells and water-based mud wells in adjacent wells were analyzed based on the NMR relaxation mechanism. Second, rocks were divided into four categories according to the pore structure, and the NMR logging T2 spectrum was extracted using the multidimensional matrix method to establish the T2 spectrum of water-based mud wells and oil-based mud wells. Finally, the correctness of the method was verified by two T2 spectrum correction examples of oil-based mud wells in the study area. The results show that the corrected NMR T2 spectrum eliminates the influence of oil-based mud filtrate and improves the accuracy of NMR logging for calculating permeability.

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Section: Methodsmentioning

confidence: 99%

Study on Nuclear Magnetic Resonance Logging T2 Spectrum Shape Correction of Sandstone Reservoirs in Oil-Based Mud Wells

Sun

Cai²,

Feng

et al. 2021

Molecules

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“…At present, some new technologies and methods have been applied to the characterization of tight oil reservoirs, such as mercury injection (constant rate mercury injection, conventional mercury injection, etc. ), low-temperature nitrogen adsorption, low-field nuclear magnetic resonance, small-angle scattering, focused ion beam (FIB), computed tomography (CT) scanning, casting thin sections, scanning electron microscopy (SEM), and other techniques. − However, as far as the current research is concerned, all of the research methods and methods listed above have their limitations or disadvantages. For instance, the minimum effective pore radius detected by constant rate mercury injection technology can only reach 0.12 μm, while, as known to all, a majority of pore throat radii in tight oil reservoirs are less than 1 μm.…”

Section: Introductionmentioning

confidence: 99%

Research on Characterization and Heterogeneity of Microscopic Pore Throat Structures in Tight Oil Reservoirs

et al. 2021

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The key to the efficient development of a tight reservoir is its accurate evaluation. In this study, the pore throat structure characteristics of sandstone samples in the study block were analyzed by high-pressure mercury injection technology. According to the characteristics of the capillary pressure curve, the sandstone samples in the study block were divided into three types: the first type has a reservoir permeability greater than 0.7 mD and a core mercury injection saturation of 96% with a good reservoir quality; the second type has a reservoir permeability ranging from 0.4 to 0.7 mD and a core mercury injection saturation of 80% with a moderate reservoir quality; and the third type has a reservoir permeability between 0.1 and 0.4 mD and a core mercury injection saturation of 50% with a poor reservoir quality. Also, high-resolution synchrotron radiation imaging and scanning electron microscopy were used to observe the pore throat structure, connectivity, and microscopic heterogeneity of sandstone samples, showing an increasing level of pore disconnection, serious microscopic heterogeneity, and poor reservoir performance as reservoir permeability declines. As mineral composition tests show, the lithology of the tight sandstone in the target block is mainly medium-grained and fine-grained feldspar lithic sandstone and the longitudinal heterogeneity of lithology and mineral components of tight sandstone is relatively weak at above the centimeter level. Besides, based on the high-pressure mercury injection test data, fractal theory is applied to calculate the fractal dimensions of the three types of reservoirs. The result shows a gradual increase in fractal dimensions with the decrease of reservoir quality, in which the closer the fractal dimension is to 3, the more serious the microscopic heterogeneity is, and the stronger the roughness of the pore surface is. As a result, the more heterogeneous the tight reservoir gets, the more likely the injected fluid is to flow along the developed and connected pore regions.

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“…Because of the different effective testing range of different methods, the characterization of tight sandstone reservoirs has strong limitations, and the multifaceted comprehensive full-scale pore-throat characterization became the key content of the current study of the size distribution characteristics of a pore-throat in tight sandstone. − Zhao et al generated a full-scale map of the pore-throat radius by combining low-temperature nitrogen adsorption, high-pressure mercury intrusion, and rate-controlled mercury intrusion. Xiao et al proposes a full-scale pore structure characterization method that involves interpolation of mesopore data characterized by low-temperature nitrogen adsorption into mercury-injection coordinates and combined with macropore characterized by high-pressure mercury intrusion at a pore radius of 25 nm.…”

Section: Introductionmentioning

confidence: 99%

“…21−23 Zhao et al 24 generated a full-scale map of the pore-throat radius by combining low-temperature nitrogen adsorption, high-pressure mercury intrusion, and rate-controlled mercury intrusion. Xiao et al 25 proposes a full-scale pore structure characterization method that involves interpolation of mesopore data characterized by low-temperature nitrogen adsorption into mercury-injection coordinates and combined with macropore characterized by high-pressure mercury intrusion at a pore radius of 25 nm.…”

Section: Introductionmentioning

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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A full-scale characterization method and application for pore-throat radius distribution in tight oil reservoirs

Cited by 26 publications

References 17 publications

Study on Nuclear Magnetic Resonance Logging T2 Spectrum Shape Correction of Sandstone Reservoirs in Oil-Based Mud Wells

Study on Nuclear Magnetic Resonance Logging T2 Spectrum Shape Correction of Sandstone Reservoirs in Oil-Based Mud Wells

Research on Characterization and Heterogeneity of Microscopic Pore Throat Structures in Tight Oil Reservoirs

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

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