Evaluating the pore structure of low permeability glutenite reservoir by 3D digital core technology

In order to analyze the micro pore structure characteristics of low-permeability glutenite reservoirs more intuitively and accurately, µ-CT scanning imaging technology is used to evaluate the development characteristics of pores, fractures and high-density interstitial materials in the three-dimensional core space of samples, and the rock pore structure is analyzed from the perspective of image gray, homogeneity and pore throat connectivity. According to the maximum sphere algorithm, a digital core pore network model is extracted and established, and the probability distribution characteristics of pore radius, throat radius, pore throat ratio and core pore throat coordination number of different rock samples are studied. The results show that the reservoir space of the samples in the study area is dominated by dissolution pores and micro fractures, with pore radius ranging from 0.1 to 10 μm, throat radius from 0.1 to 7 μm, pore throat ratio from 0 to 4, and coordination number from 0 to 7. The overall pore throat ratio, throat radius and poor throat connectivity are the main reasons for the low core permeability in the study area. It is found that the 3D digital core technology can more accurately evaluate the internal heterogeneity of rocks, and the calculated pore structure parameters include both connected pore information and isolated pore information. Compared with conventional mercury injection and nuclear magnetic resonance, the 3D digital core technology has obvious advantages in the evaluation of rock micro pore structure. Article highlights This paper uses the image binary segmentation method to separate the gray images of µ-CT scans of glutenite cores, and the pore space and skeleton of different rocks are characterized. And 3D gray images of 3D digital cores are constructed by PerGeos. The pore network model is used to analyze the reservoir pore structure, and the characteristic parameters of pore structure (such as pore radius, throat radius, pore-throat ratio, shape factor and coordination number of rock) are extracted, and the porosity and permeability are calculated to quantitatively evaluate the pore structure. The experiment data reveal that the main pore space of low permeability glutenite reservoir in the study area is micro-pore, with low pore coordination number, small pore-throat ratio, small pore radius and poor pore connectivity. These characteristics contribute to the low permeability reservoir, which has no obvious law of porosit