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 samplesobtained 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 asplagioclase, 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.
Highlights
The main issues in rock typing of a sandstone is to link the geological processes forming the sandstone pore architecture - pore geometry and pore structure - with petrophysical properties
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
After plotting J-Function against water saturation Sw, identification of the microscopic geological features is made by integrating the thin section petrography, SEM and XRD data for each corresponding rock sample for the purpose of J-Function grouping on the basis of similarity in the microscopic features
Summary
The main issues in rock typing of a sandstone is to link the geological processes forming the sandstone pore architecture - pore geometry and pore structure - with petrophysical properties. Previous research on carbonate rocks was conducted by Gomes et al, (2008) in an attempt to understand the original facies, depositional environments and the diagenetic events affecting the original textures. They looked at the connection between rocks and fluids with purpose to recognize the connection among lithofacies, petrophysical groups, and rock type. El Khatib (1995) showed mathematicaly that rock pore tortuosity was inversely related to Leverett JFunction This relation can be interpreted as an indication of similarity in pore tortuosity for a number of rock samples with capillary pressure data sets that can be represented by a single J-Function curve. Archie (1950) – who firstly introduced the term of rock type cited by other researchers (Gunter et al, 1997, Guo et al, 2005, Gomes et al, 2008, Rushing et al, 2008, Permadi & Susilo, 2009, and Wibowo & Permadi, 2013) defined that a rock type as a formation, which was deposited under similar condition and went through similar diagenesis, gave a specific porosity-permeability relationship with a particular group of capillary pressure curves and water mas.ccsenet.org
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