Complex Characterization of Organic-Rich Carbonate Shales Saturation

Mukhametdinova, Aliya

doi:10.5593/sgem2019/1.2/s06.091

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“…Sample #551 was an organic-rich wackestone (Figure 7) because the matrix held the immersed calcite detritus. Our experience and observations showed that the petrographical description of the formation distinguished lithotypes, but did not provide reliable information on the void space structure [55,56]. Following down along the scale bar, we attempted to characterize the void space using whole-core CT and mini-plug micro-CT. We found that, similarly to the petrographic analysis of thin-sections, CT did not reveal natural voids and, thus, turned out to be a meaningless tool for the target rock (Figure 8).…”

Section: Microstructural Characterizationmentioning

confidence: 99%

Reservoir Properties of Low-Permeable Carbonate Rocks: Experimental Features

et al. 2020

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This paper presents an integrated petrophysical characterization of a representative set of complex carbonate reservoir rock samples with a porosity of less than 3% and permeability of less than 1 mD. Laboratory methods used in this study included both bulk measurements and multiscale void space characterization. Bulk techniques included gas volumetric nuclear magnetic resonance (NMR), liquid saturation (LS), porosity, pressure-pulse decay (PDP), and pseudo-steady-state permeability (PSS). Imaging consisted of thin-section petrography, computed X-ray macro- and microtomography, and scanning electron microscopy (SEM). Mercury injection capillary pressure (MICP) porosimetry was a proxy technique between bulk measurements and imaging. The target set of rock samples included whole cores, core plugs, mini cores, rock chips, and crushed rock. The research yielded several findings for the target rock samples. NMR was the most appropriate technique for total porosity determination. MICP porosity matched both NMR and imaging results and highlighted the different effects of solvent extraction on throat size distribution. PDP core-plug gas permeability measurements were consistent but overestimated in comparison to PSS results, with the difference reaching two orders of magnitude. SEM proved to be the only feasible method for void-scale imaging with a spatial resolution up to 5 nm. The results confirmed the presence of natural voids of two major types. The first type was organic matter (OM)-hosted pores, with dimensions of less than 500 nm. The second type was sporadic voids in the mineral matrix (biogenic clasts), rarely larger than 250 nm. Comparisons between whole-core and core-plug reservoir properties showed substantial differences in both porosity (by a factor of 2) and permeability (up to 4 orders of magnitude) caused by spatial heterogeneity and scaling.

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Section: Microstructural Characterizationmentioning

confidence: 99%