Ray Kevin, M. Burhannudinnur

ANALISIS LITOFASIES DAN REEF SYSTEM BATUAN KARBONAT BERDASARKAN DATA WELL LOG DAN CORE PADA FORMASI BATURAJA, CEKUNGAN SUMATERA SELATAN

Introduction

Analisis litofasies dan reef system batuan karbonat berdasarkan data well log dan core pada formasi baturaja, cekungan sumatera selatan. Analisis litofasies & sistem terumbu batuan karbonat Formasi Baturaja, Cekungan Sumatera Selatan. Identifikasi fasies, lingkungan pengendapan, dan geometri isolated reef dari data well log & core.

Abstract

Abstrak Daerah penelitian berlokasi pada lapangan “RKS” yang terletak pada Formasi Baturaja, Cekungan Sumatera Selatan. Tujuan dari penelitian ini adalah mengidentifikasi fasies dan lingkungan pengendapan yang berkembang pada Formasi Baturaja yang berada di Cekungan Sumatera Selatan yang merupakan suatu sistem terumbu pada batuan karbonat. Metodologi penelitian yang dilakukan yaitu dengan cara analisis kuantitatif menggunakan data log dan analisis fasies menggunakan data petrografi dan mudlog. Dari hasil analisis kuantitatif meliputi peta kedalaman daerah penelitian, serta hasil analisis litofasies menurutdeksripsi dari litologi yang ada pada seluruh sumur terbagi menjadi beberapa fasies yaitu fasies coral packstone, fasies coralwackstone, fasies coral framestone, fasies skeletal packstone, fasies coarse skeletal packstone, dan fasies skeletal wackestone. Lingkungan pengendapan pada sistem terumbu yang berkembang berdasarkan jenis dari fasies dan biota yang hadir pada daerah penelitian diperkirakan diendapakan pada lingkungan core reef dan back reef lagoon. Berdasarkan hasil analisis lingkungan pengendapan tersebut menunjukan geometri dari sistem terumbu yaitu isolated reef.Kata-kata kunci : Formasi Baturaja, Batuan Karbonat, Fasies, Lingkungan Pengendapan, Sistem Terumbu. AbstractThe research area is located on the "RKS" field located in the Baturaja Formation, South Sumatra Basin. The purpose of this study is to identify the facies and depositional environment that developed in the Baturaja Formation in the South Sumatra Basin which is a reef system in carbonate rocks. Research methodology carried out by means of quantitative analysis using log data and facies analysis using petrographic data and mudlogs. From the results of quantitative analysis covering depth maps of the study area, as well as the analysis results of lithofacies according to the description of lithology in all wells divided into several facies, namely coral packstone facies, coral wackstone facies, coral framestone facies, skeletal packstone facies, coarse facies skeletal packstone, and skeletal wackestone facies. The depositional environment on the reef system that develops based on the type of facies and biota present in the study area is estimated to be deposited in the core reef and back reef lagoon environment. Based on the results of the depositional environment analysis shows the geometry of the reef system that is isolated reef.Keywords: Baturaja Formation, Carbonate Rocks, Facies, Depositional Environment, Reef System.

Review

This paper presents a focused investigation into the lithofacies and reef system architecture of the Baturaja Formation within the South Sumatra Basin, specifically at the "RKS" field. The primary objective is to delineate the carbonate facies and associated depositional environments that characterize this reef system. Through a multi-proxy approach integrating well log data, petrographic analysis, and mudlog interpretation, the study identifies a range of facies including various coral and skeletal packstones, wackstones, and framestones. The findings suggest a depositional setting encompassing core reef and back reef lagoon environments, ultimately pointing towards an isolated reef geometry for the Baturaja Formation in the study area. The methodology employed, combining quantitative well log analysis with detailed core-based facies interpretation (petrography and mudlogs), is a commendable strength, offering a comprehensive dataset for understanding carbonate systems. The identification and detailed naming of multiple carbonate facies, from coral framestones to skeletal wackestones, significantly contribute to the geological understanding of the Baturaja Formation, which is a known hydrocarbon reservoir in the region. Furthermore, the robust interpretation of specific depositional environments (core reef, back reef lagoon) and the determination of the isolated reef geometry provide valuable insights into the paleogeographic and paleoenvironmental conditions that prevailed during the formation's deposition. These findings are directly relevant for reservoir characterization and exploration efforts in the South Sumatra Basin. While the abstract effectively outlines the study's scope and key findings, certain aspects could benefit from further elaboration in the full manuscript. The "quantitative analysis using log data" is primarily described as yielding "depth maps," and it would be valuable to understand how specific log responses (e.g., gamma ray, resistivity, density, sonic) were quantitatively tied to the identified lithofacies and environmental interpretations. Similarly, while petrography is mentioned, a more explicit description of the specific petrographic analyses performed (e.g., thin section analysis for texture, composition, pore system, and diagenetic features) would enhance the scientific rigor and allow for a deeper understanding of the facies characteristics. Future work could also explore the diagenetic overprint on these reef systems and its implications for reservoir quality, as well as integrating seismic data to further validate and refine the interpreted isolated reef geometry.

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