The presence of authigenic clay minerals is usually found in sandstones where these minerals grow in the environment itself. Authigenic clay minerals provide benefits to sandstones, especially to determine the quality of porosity and permeability in sandstones. The samples in this study were collected from an outcrop of measured section at Cipamingkis’ River. The main goal of this study was to understand the presence of authigenic clay minerals in sandstones caused by the diagenetic process using Scanning Electron Microscope and Energy Dispersive X-Ray (SEM – EDX method. The results of this study were kaolinite, smectite, and illite found in very dominant amounts in sandstones as pore linings, pore fillings, replacement, and vug fillings.

Subang Formation is one of many turbidite flow-induced sediment that built Bogor Trough, Java. Despite its marine origin, the exposure to the meteoric environment and burial process caused this formation to go under diagenesis, thus altering its primary characteristics. Intensive cementation by equant calcite, feldspar alteration, and grain dissolution indicates diagenesis in a meteoric environment. The cementation process filled primary and secondary pores, decreasing the primary porosity. On the other hand, the dissolution of the grain formed new secondary porosities. The presence of stylolites and fractured fragments indicated the formation had experienced burial. Although compaction often decreases rock’s porosity, the fracturing of the rocks due to compaction leads to fracture porosity formation, increasing rock’s porosity. Analyzing the compaction signs that destroyed the cementation and dissolution features in the rock samples, it is assumed that the diagenesis had occurred in the meteoric environment before it occurred in the burial environment. This study showed that the heterogeneity of the Subang Formation in the Cibeet River resulted from all these diagenesis processes mentioned above. Furthermore, the diagenesis study of the Subang Formation can be implemented as a preliminary stage to determine the quality of the petroleum reservoir. Diagenesis of Subang Formation in Cibeet River, Bogor, West Java.

The research focuses on the Klapanunggal Formation, composed of limestone in the West Java Basin, specifically in the Klapanunggal area, Klapanunggal District, Bogor Regency, West Java Province. A massive limestone outcrop was found in this location. The method used is field data collection, stratigraphic cross-section measurement, and petrographic analysis. It aims to determine the facies characteristics, depositional environment, and association of the limestone facies of the Klapanunggal Formation. The results obtained from macroscopic and microscopic descriptions resulted in six (6) facies: Skeletal Wackestone, Skeletal Packstone, Benthic Foram Grainstone, Skeletal Rudstone, Coral Rudstone, and Bindstone. Then, the facies are classified into facies associations, resulting in three (3) facies associations: Platform Interior (Open Marine), Platform Margin Reef, and Slope.

Depositional environment of Jatiluhur Formation is a very interesting research object to study, especially from the geological and biological aspects. This formation is very well exposed in several rivers in Bogor, especially in the Cipamingkis River. Field studies were carried out by measuring section method and ichnofossil description along the section. Stratigraphy log data shows the overall upward coarsening with a length of 66 meters. There are 4 facies associations from stratigraphy log data and the description of ichnofossil, FA1 is interpreted as a classical turbidite deposition process seen from alternating pattern of thin carbonate sandstones with carbonate siltstone in relative depths in the bathyal to sublittoral zone seen from Scolicia, Thalassinoides, and Opiomorpha seen in this section., FA2 is interpreted as a turbidite deposition process in the upper-fan section seen from the lithology of thick carbonate claystone and carbonate sandstones in the form of inserts at a relative depth in the sublittoral zone seen by ichnofossil found in the form of Circulishnis, FA3 is interpreted as an upper fan or channel fill seen from the structure The slump in this section that occurs at a sublittoral depth is seen from its ichnofossils, namely Rhizocorallium and Thalassinoides, and FA4 is interpreted as shallow marine seen from the lithology dominated by carbonate sandstones with tires That is, the sedimentary structure occurs in the relative depths of the sub-littoral to littoral zone seen from its ichnofossils, namely Planolites and Taenidium. Depositional environment of the Jatiluhur Formation shows that depth at bottom of section is deeper than upper section and deposition process from turbidite to shallow marine.

This study will focus on identifying depositional facies in uncored intervals using a gradient boosting classifier, based on electric logs: gamma-ray (GR), resistivity (ILD), neutron porosity (NPHI), and density (RHOB), as well as facies description and classification derived from cored intervals. Supervised learning with gradient boosting classifiers is the primary method that combines a lot of weak learning models to create a robust predictive model. A gradient boosting classifier was applied because the output will be in the form of images. We used nine wells such as four training data, and five testing data along with gamma-ray, resistivity, NPHI, and RHOB as input. The statistical methods were used to distribute facies on each well, and we used the F1 score and average of confusion matrix to validate the values. The result shows 0.718 or 71.8% of the F1 score and 0.6617 or 66.17% of the confusion matrix. With this level of accuracy, we conclude that the gradient boosting classifier methods are reliable enough to determine facies in the area that have limited core data with satisfying efficient results without reducing the accuracy.