Modified low field NMR method for in-depth pore space analysis and Fe-containing minerals influence mitigation in tight siliciclastic and extrusive rocks

Precise evaluation of rock filtration and capacity properties is challenging, particularly in unconventional reservoir formations containing para- and ferromagnetic minerals. This data set contains T2 relaxation time data of two different Low-Field Nuclear Magnetic resonance (LF-NMR) approaches, standard and modified differential, along with the Mercury Injection Capillary Pressure (MICP) and X-Ray Diffraction (XRD) data. The modified differential approach employs the subtraction of the dried sample signal from the signal of the 100 % water-saturated sample before taking the Laplace transform, giving a differential distribution devoid of the unwanted signals from rock matrix, closed porosity and clay-bound water. This method skips the background subtraction step characteristic of the standard approach, achieving a higher Signal-to-noise ratio. In the proposed PSD conversion workflow based on the percolation theory, a power function relationship between differential LF-NMR T2 relaxation time and MICP pore-throat diameter can be established, enabling the determination of LF-NMR absolute pore size distribution and pseudo capillary pressure (Pc) curves for samples with Fe-containing minerals.