TUDY OF DEPTH ESTIMATION CALCULATION OF GRAVITY DATA USING 2-D SPECTRAL ANALYSIS CASE STUDY: SANGALLA GEOTHERMAL FIELD, TANA TORAJA, SOUTH SULAWESI

• Main Author: Affianto, Rizky
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/53410
• Institution: Institut Teknologi Bandung

The gravity method can be used to study horizontal and vertical changes in subsurface rock structures. In studying the vertical changes in the gravity method, research with spectral analysis can be used. Spectral analysis is performed to obtain an estimated value for the depth or thickness of a layer. The most commonly used spectral analysis is one-dimensional. This study aims to perform spectral analysis calculations using different methods, namely in two dimensions. To obtain the estimated depth value, a program is compiled to calculate the depth estimate using the two-dimensional spectral analysis method. Testing was carried out using synthetic models to test the success of the program. The testing results show that the developed program has succeeded in calculating the depth estimate. In addition, the synthesis model is also used to study the effect of several gravity measurement parameters on the depth estimation results. Three information is obtained related to this test, namely (1) the dimension of the measurement area affects the depth estimation results, (2) The distance of the measuring point or the optimum data spacing is smaller or equal to the target anomaly depth, (3) If the measuring point covers the area the gravity anomaly response from an anomaly, then the direction of the path at the spread of the measuring point does not really affect the calculation of the depth estimate. (4) Depth estimation using spectral analysis on anomalies with thin layers results in inaccurate results, (5) Depth Estimation of the anomaly body is calculated from the surface of the measuring station. Then, the program was applied to gravity data in the Sangalla, South Sulawesi. Through the calculation of the estimated depth, the reservoir is estimated to be at a depth of more than 845 m.