NIUMAG
Pore Size Distribution Analysis
Research methods of layered pore size distribution
Nowadays, there are many methods for measuring pore size distribution, including mercury intrusion method, liquid nitrogen adsorption method, electron microscope scanning method, X-ray method, etc.
Overview of Measurement Methods for Pore Size Distribution
Mercury intrusion method: it is a method for determining the pore size distribution of some mesopores and macropores. The basic principle is that mercury does not wet general solids, and external pressure needs to be applied to allow mercury to enter the pores. The greater the external pressure, the smaller the radius of the pores that mercury can enter. The pore volume of the corresponding pore size can be known by measuring the amount of mercury entering the pores under different external pressures. However, there is a problem that small pores cannot be measured, and the process is irreversible, which will cause damage to the core, and there may be a problem that the measured value is larger than the actual value.
Liquid nitrogen adsorption method: It is a relatively mature and widely used method to measure the pore size distribution of mesopores by nitrogen adsorption method. It is the principle of volume equivalent substitution, that is, the amount of liquid nitrogen filled in the hole is equivalent to the volume of the hole. There is a bias in the test of macropores based on the principle of liquid nitrogen adsorption.
Electron microscope scanning method: slice the core, expose it under the electron microscope, photograph the cut surface with high resolution, set the threshold value to select the shadow area to define the pore, and obtain the pore size distribution after data processing of the photo. This method requires slicing the core, the process is irreversible and destroys the sample, and the threshold setting is subjective, which has a certain impact on the accuracy of the pore size distribution.
X-ray method: X-rays pass through the core and exhibit exponential attenuation. When the receiver receives the attenuated signal, after data processing, a correlation can be established between the amount of the attenuated signal and the sample pores, so as to obtain the pore size distribution of the core. . However, the size of the core penetrated by X-rays has a certain limit, and different minerals in the core will affect the attenuation of X-rays, thereby affecting the testing accuracy of the aperture.
Compared with traditional methods, NMR, as a mature pore size distribution research method, NMR has the advantages of fast, non-destructive, online monitoring, accurate, green, etc. It can realize spatial layer of cores, test the pore size distribution of each layer, and more microscopically characterize the pore size distribution.
