Abstract
Abstract In this study, we report a physics-based model for pore structure typing in which a generalized model is also derived to calculate the specific surface area of the grains. In this model, a new pore-structure-type indicator is defined to characterize the discrepancies of pore structures based on the fractal geometry theory and a modified Kozeny-Carman equation. We compared the proposed model with the conventional model by comprehensive experimental tests in 130 low permeability sandstone cores from the Dongfang gas reservoir in the South China Sea. The fractal dimension of the grain Dg was first accurately calculated through thin section analysis. The results show that grains of low-permeability sandstone indeed have the bifractal distribution with constant radius boundaries of approximately 30 μm, potentially accounting for the multiscale of pore spaces. Compared with the conventional model, considering the complex pore and grain size distributions as well as irreducible water saturation, the developed model as a generalized expression performs better in pore structure typing with higher correlation coefficients in porosity-permeability and structural coefficients-pore radius relationships due to the newly identified indicator with a wider range. Finally, a multiscale workflow was proposed to analyze the petrological and structural features of pore structures by two-dimensional core images, thin sections, scanning electron microscope, mercury intrusion tests and three-dimensional micro-computed tomography. This work enables us to explain the genetic types and differences of the pore structure and may help to characterize the internal connection of the grain structure-pore structure-flow mechanism in hydrocarbon exploration and development.
Published Version
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