Nano-scale pore structure and fractal dimension of organic-rich Wufeng-Longmaxi shale from Jiaoshiba area, Sichuan Basin: Investigations using FE-SEM, gas adsorption and helium pycnometry

A critical review of water uptake by shales

Laboratory measurements including porosity, permeability, high-pressure mercury intrusion (HPMI), nuclear magnetic resonance (NMR) measurements, and microscopic analysis of thin sections and scanning electron microscopy (SEM) were performed to provide insights into the microscopic pore structure of the Xujiahe Formation tight sandstones in Sichuan Basin. The relationships between microscopic pore structure parameters, such as pore geometry, pore size distribution, pore network, and macroscopic consequences, such as permeability, reservoir quality index, Swanson parameter, fractal dimension as well as NMR parameters, have been investigated. The results show that the pore systems are dominated by secondary dissolution porosity with minor amounts of primary porosity and microfracture. NMR T2 pore size distributions are either uni- or multimodal. Long T2 components are not frequently present due to the lack of the macropores, whereas as shorter T2 components dominate the T2 spectrum. T2gm (the geometric mean ...

Insight into the Pore Structure of Tight Sandstones Using NMR and HPMI Measurements

Heterogeneity of intergranular, intraparticle and organic pores in Longmaxi shale in Sichuan Basin, South China: Evidence from SEM digital images and fractal and multifractal geometries

Fractal characteristics of Upper Cretaceous lacustrine shale from the Songliao Basin, NE China

The effect of the variation in material composition on the heterogeneous pore structure of high-maturity shale of the Silurian Longmaxi formation in the southeastern Sichuan Basin, China

Mercury intrusion porosimetry (MIP) has been widely used to characterize the pore structure for various types of porous media. Several relationships between permeability and pore structure information (e.g., porosity and pore-size distribution) have been developed in the literature. This work is to introduce a new, and simpler, empirical equation to predict permeability by solely using the median pore-throat radius (r50), which is the pore-throat radius corresponding to 50% mercury saturation. The total of 18 samples used in this work have a wide range of permeability, from 10 −6 to 10 3 mD, which makes the new equation more

http://iopscience.iop.org/article/10.1088/1742-2132/10/2/025014/pdf

Estimating permeability using median pore-throat radius obtained from mercury intrusion porosimetry

Because of its significant impact on relative permeability, capillary pressure, stimulation methods, and ultimate recovery, the wettability of reservoir rocks is a critical factor of the petroleum recovery process. However, characterizing the wettability of shale with extremely low matrix permeabilities is a challenging task because of the dominant presence of nanopores in shale and high heterogeneity of shale compositions at multiple scales. From spontaneous imbibition behavior that uses two types of imbibing fluid (water and n-decane), the present study examines the wettability characteristics of gas-window Barnett Shale samples taken from four different depths of Texas United 1 Blakely core in Wise County in Texas. Imbibition experiments were conducted in two directions: parallel and transverse to the lamination of the samples. A scaling method was used to analyze imbibition data, and observed imbibition behaviors were interpreted to infer the different wettability conditions of four samples with different mineralogy, total organic carbon content, and pore-throat size distribution. Our results show that wettability significantly affects fluid imbibition behavior and that four tested samples can be divided into three wettability categories: more water wet, mixed wet, and more oil wet. Overall, the variable wettability of Barnett samples will affect hydrocarbon storage, distribution, and production.

Wettability of Mississippian Barnett Shale samples at different depths: Investigations from directional spontaneous imbibition

Pore structure has a signiﬁcant effect on the occurrence state of shale hydrocarbons and the hydrocarbon storage capability of shale reservoirs Consequently, it is quite meaningful to clarify the shale pore structure evolution characteristics for understanding the migration and enrichment mechanisms of hydrocarbons within shale reservoirs during different geological stages The abundant existence of organic matter within shales complicates the shale pore structure evolution process by hydrocarbon generation, migration and cracking Many studies have been conducted to reveal the shale pore structure evolution characteristics and the controlling factors Basically, these studies could be divided into two categories based on the sample source: comparing the pore structure of natural shale samples with different thermal maturities; obtaining shale samples with different thermal maturities by conducting thermal simulation experiments on low-mature shale samples and comparing the pore structure of these simulated shale samples However, no consistent viewpoint on shale pore structure evolution has been reached This review presents the state of the art of shale pore structure evolution studies It is widely recognized in the literature that both the inorganic and organic diagenesis control the shale pore structure evolution process However, it is found that the shale pore structure evolution models proposed in the literature were largely dependent on the samples used And it is recommended to conduct the two categories of studies simultaneously in order to obtain more reliable shale pore structure evolution characteristics in future investigations Cited as : Gao, Z, Fan, Y, Xuan, Q, Zheng, G A review of shale pore structure evolution characteristics with increasing thermal maturities Advances in Geo-Energy Research, 2020, 4(3): 247-259, doi: 1046690/ager20200303

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Zhiye Gao

Papers

The effect of the variation in material composition on the heterogeneous pore structure of high-maturity shale of the Silurian Longmaxi formation in the southeastern Sichuan Basin, China

Estimating permeability using median pore-throat radius obtained from mercury intrusion porosimetry

Wettability of Mississippian Barnett Shale samples at different depths: Investigations from directional spontaneous imbibition

A review of shale pore structure evolution characteristics with increasing thermal maturities

Progress and development trend of unconventional oil and gas geological research