ELASTIC AND ANISOTROPY PARAMETERS OF THE TALANG AKAR FORMATION – SOUTH SUMATRA BASIN BASED ON ULTRASONIC TOMOGRAPHY OF CORE PLUGS

• Main Author: Mutia Sari, Vani
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/37138
• Institution: Institut Teknologi Bandung

Talang Akar Formation (TAF) is the main source and reservoir rocks in South Sumatra Basin, which is one of the hidrocarbon-rich basins in western Indonesia. A good seismic data processing, modeling and interpretation needs to account the rock anisotropy effect, and its relationship to the physical parameters of the source and reservoir rocks. However, up to now there is no solid study on the seismic anisotropy of the TAF reservoir and source rocks. Anisotropy study is difficult to be done in the South Sumatra Basin’s TAF due to the unavailability of dipole sonic log and three-component seismic data. Therefore, the anisotropy parameters in this study were obtained from laboratory measurements on core plug samples. As the limited core plug samples were friable, fissured, and its microstructure is below the seismic wave resolution, then the ultrasonic wave was used to measure the TAF core plugs anisotropies. Furthermore, the ultrasonic tomography measurements with 3600 source-receiver configurations and high-resolution ultrasound gives a more precise results of elastic properties and anisotropy parameters. This study is divided into four main steps: ultrasonic tomography measurements, analysis of elastic properties, shear wave splitting analysis and anisotropy, and analysis on the relationships of elastic properties and anisotropy parameters with rock-type, core-plug porosity, thin-section porosity, and sand-volume ratio. The study was done on 21 core-plug samples collected from 6 wells in the South Sumatra Basin. Petrographic analysis shows that the rock types of the 21 samples are mud, silt, sandy silt, sandy clay, and clayey sand. The relationship of several parameters shows that all of the samples are anisotropic, and there is a linear relationship between the P-wave anisotropy parameter (?) and the S-wave anisotropy (?). The cross-plots of the anisotropy parameters ? and ? to the sand-volume ratio show that they have linear relationships and can be classified into two groups: low sand-volume ratio (<0.50), and high sand-volume ratio (>0.50). Anisotropy parameter ? give better correlation for both groups. The anisotropy parameters of the samples were also affected by the position of core samples to the geology structures around it.