Connecting Microscopic Geological Features to Pore Geometry and Pore Structure: Case Study - Sandstone Reservoir of Balikpapan Formation, Kutai Basin

Abstract

Understanding geological features with engineering aspect has been done by previous studies and remains attractive by both geologists and engineers. This study employed data of a total of one hundred and seventy-nine (179) sandstone samples obtained from the Middle Miocene to Late Miocene Balikpapan Formation in Kutai Basin, Indonesia. The data includes thin section porosity, scanning electron microscope (SEM), x-ray diffraction (XRD), and capillary pressure (Pc). All samples are mainly dominated by quartz with additional rock fragment and feldspar, and additional component such as plagioclase, heavy minerals, occasional carbonaceous materials, micas and opaque minerals. Detrital clays, pseudomatrix and laminated clays occurred locally in minor quantity. Porosity ranges from 6 to 28.8.9%, whereas permeability ranging from 0.02 and 4,718 mD. This study investigates the relationship of microscopic geological features with pore geometry and pore structures. Kozeny equation and Leverette's J-Function are implemented to characterize the pore geometry and structure in correlation with microscopic geologic features. The main findings of the study are that: i) combination of quartz content, texture, clay content, and the diagenetic history of quartz cementation strongly relates to both pore geometry and structure of the sandstone samples, ii) the content of cements does not show a systematic effect on either pore geometry or pore structure, and iii) in general, for all the sandstone samples employed here, the higher quartz and lower clay contents tend to give both a larger pore geometry and lower pore structure in terms of pore tortuosity.

On the Pore Geometry and Structure Rock Typing

“…Interestingly, there is also a good trend with the grain size distribution GSD measured by thin section: a larger grain size distribution GSD correlates with a smaller rock type number (GSD ↑ → RT # ↓). 34 Note: The upward arrow ↑ indicates increased values. The downward arrow ↓ means decreased values.…”