No abstract

Understanding the impact of saturation levels on the mechanical and physical properties of limestone and marly limestone deposits is very critical for geotechnical and mechanical studies in the energy and construction industries. This research aims to link the strength characteristics of carbonate rock (limestone and marly limestone) with physical and mechanical properties at saturation levels of 0, 0.25, 50%, 75% and 100%. To complete this work, 100 samples were collected and analysed employing an orderly research facility testing. According to experimental findings, the strength and durability of the limestone and marly limestone declined with rising saturation levels, while the P‐wave velocity Vp showed an upward trend from 0% to 100%. The uniaxial compressive strength (UCS) of the limestones employed in this research significantly decreased (up to 36%) between the dry and saturated stages for limestone samples. While marly limestone, there is a drop (up to 32%) in UCS. The findings of a straightforward regression study show that it is possible to predict the strength properties of rocks directly from various saturation levels. Additionally, a number of various estimate connections were created utilizing independent variables like Vp and saturation level. The experimental outcomes showed that Vp showed an upward tendency with an increasing degree of saturation. The deformability and strength parameters of the samples declined with increasing saturation degrees. The elastic modulus and strength both decrease as clay and water amounts increase. The quality index (QI) number for limestone is 45, which indicates that it has extremely good quality and can be used as a building material at 0% saturation. At 25%, 50%, 75% and 100% saturation, it is evaluated at 43, 40, 33 and 31, respectively. The marly limestone samples have high quality at 0% (QI = 36), but poor quality at 25%, 50%, 75% and 100% saturation (QI = 33, 30, 27 and 23). This research provides a better understanding of the relationship between saturation levels and the mechanical, physical and depositional characteristics of marly limestone and limestone, which might be helpful in industrial studies. Advance examination of distinctive sorts of carbonate rocks can be more supportive of broadening our understanding of this idea.

Diagenetic understandings tied to depositional sequences that developed over the past decades help to predict the reservoir quality in oil and gas exploration. Understanding the lithologic characteristics and diagenetic alterations is key to decipher the various complex controls on its porosity and permeability. This diagenetic heterogeneity is a product of a complex history of diagenetic modifications, however, there are not many studies addressing this problem. The results show that the exposed sections around Bintulu town comprise of massive sandstones intervals, laminated clays, and brackish-shales and lignite. Five main types of lithologies are identified in the stratigraphic sections: sandstones, shales, coal, siltstones, and mudstones. These rock types are further sub-divided into fifteen lithofacies based on sedimentary structures and other characteristics. Petrographic studies revealed that the sandstones are well-sorted quartz arenite, with fine to medium grained sand. The diagenetic processes recognized include compaction, dissolution and cementation. The early, middle, and late diagenetic stages are present in the lithostratigraphy. Bioturbation marks the start of post-depositional changes, and allowed rapid exchange of pore waters with overlying depositional water. Iron oxide occurred in early diagenesis rapidly after the sediments were buried. However, later grain dissolution provided the secondary porosity and permeability. Compaction rates were high in muddy sediments. Sandstone samples with high mud content have less diagenetic signatures. Later, quartz and calcite cement stabilizes the grains and decreases porosity generated by early dissolution. Middle stages of diagenesis involved the growth of chlorite perpendicular to quartz grains. The late diagenetic changes involved the growth of pyrite crystals associated with chemical composition of deep burial pore fluids. The cement types that have been observed in this formation include clay, calcite, quartz overgrowth and iron oxides whereas, the later phases destroyed the early generated porosity. The calcite cement in the early stage of diagenesis, though, resisted the compaction of sediments and aids to preserve the porosity. Dominant porosity is interparticle porosity that is present depositionally and later enhanced by secondary grain dissolution.

No abstract

No abstract