Fractal Analysis of Donghetang Sandstones Using NMR Measurements

Abstract

Routine core analysis, thin section epifluorescence and scanning electron microscopy (SEM) analyses were performed to delineate the reservoir qualities, pore systems, and pore network characteristics of the Devonian Donghetang sandstone samples. Nuclear magnetic resonance (NMR) measurements were used to gain insight into pore size distributions of these sandstones. Fractal analysis was performed on the NMR T2 spectrum measured at echo spacings of 0.6 and 1.2 ms. Then the relationships between NMR parameters and fractal dimension were investigated. The results show that the pore systems are dominated by primary intergranular pores with a combination of secondary dissolution pores, micropores, and microfractures. Samples with the highest reservoir quality are characterized by a coexistence of primary intergranular and secondary dissolution pores. The parameter T2gm (the geometric mean of the T2 distribution) is a sensitive one for characterizing the pore size distribution and microscopic pore structure sinc...