Detailed parametrization of the pore space in tight clastic rocks from Poland based on laboratory measurement results

Abstract

Computed X-ray tomography (CT), together with nuclear magnetic resonance spectroscopy, pulse- and pressure-decay permeability methods, is a source of comprehensive information about the geometrical parameters of the pore space. Geological material consists of 31 samples of tight, gas-bearing, clastic rocks from different wells and formations. The purpose was to parametrize in detail the pore structure, revealing the relationships between the various parameters and estimating the equation for assessing the fluid flow ability of analyzed tight rocks. Following parameters were taken into consideration in the pore space characterization: thickness mean, equivalent diameter, anisotropy, elongation, sphericity, Feret diameter, Feret coefficient, Feret shape; shape factors: 2nd circularity coefficient, Malinowska coefficient and Danielsson coefficient; as well as parameters from 3D skeleton analysis: junctions, branches, coordination number. It was captured the dependence of logarithmic T2 mean from NMR on junction count from CT, as well as T2 cutoff from NMR on elongation from CT for the all samples. Logarithm of absolute permeability was estimated based on multiple linear regression analysis using only geometrical parameters from X-ray nanotomography, which is a benefit in the times of coring material decrease.