Influence of Particle Size on the Low-Temperature Nitrogen Adsorption of Deep Shale in Southern Sichuan, China

Abstract

Pore characteristics are one of the most important elements in the study of shale reservoir properties and are a key parameter for the evaluation of the potential of shale oil and gas resources. Low-temperature nitrogen adsorption is a common laboratory method that is used to characterize the pore structure of shale. However, the effect of shale’s particle size on the experimental results of the nitrogen adsorption of deep shale samples is still unclear. In this paper, using deep shale samples of different mesh sizes from the Luzhou Block as an example, we studied the effect of particle size on the pore structure of deep shale, as characterized by nitrogen adsorption experiments. The results showed that the pore volume of deep shale is mainly distributed in the mesoporous range, with a pore size ranging from 2 to 20 nm. The pore volume, as measured by nitrogen adsorption, increases slowly as the particle size decreases and then it increases rapidly. The particle size of shale has no obvious effect on the measurement of the specific surface area. The fractal dimension of deep shale gradually increases as the particle size of the shale samples increases and the smaller the particle size, the higher the correlation coefficient, R2, of the fractal dimension fitting. In this paper, different recommended sizes are given for selecting suitable particle sizes in nitrogen adsorption experiments on deep shale with different structural parameters, which will increase the accuracy of the study of the pore structure of deep shale.

Shale’s Pore Structure and Sorption-Diffusion Characteristics: Effect of Analyzing Methods and Particle Size

“…They show a discrepancy in the early mesopore region and below 2 nm. These pores mainly contribute to the gas adsorption in shale rocks and clays. ,, As the pore size decreases, the deviations of various BJH methods become progressively more and more substantial. It demonstrates the limitation of the BJH approach to analyze the PSAD of shale rocks and clays.…”

“…These novel, theoretically based methods provide a much more accurate pore size analysis over the complete micro/mesopore size range. 29,30 DFT uses statistical thermodynamics to construct model isotherms that account for gas− solid and gas−gas interactions along with the geometric configuration of pore walls during adsorption. 23 Landers, Gor, and Neimark 25 also stated that DFT models provide important corrections to the Kelvin equation on the nanoscale for more reliable pore size analysis, as confirmed by the broad experimental validation.…”

Determination of Apparent Pore Size Distributions of Organic Matter and Inorganic Matter in Shale Rocks Based on Water and N2 Adsorption

“…Before the experiments, samples were crushed into a 100–150 mesh with a particle size of 150–100 μm, which is considered as a suitable particle size for the shale pore structure characterization with N 2 adsorption–desorption experiments. A discussion about the effect of particle size can be seen in refs and . Then, a quantitative analysis of mineral composition was conducted on the D8 discover X-ray diffraction (XRD) instrument with the scanning range 2–75° and a scanning speed of 2 deg/min, and the proportion of minerals was estimated by the typical diffraction peak of each crystal.…”

Optimization and Application of XGBoost Logging Prediction Model for Porosity and Permeability Based on K-means Method

“…This method is more accurate in characterizing micropores than other techniques [3]. In sandstone reservoirs with predominantly medium porosity distribution (2-50 nm), the use of the low-temperature nitrogen (N 2 ) adsorption method is a more common approach for porosity determination [4][5][6][7]. Some scholars have applied constant-rate mercury injection technology to measure porosity in tight porous sandstone reservoirs.…”