EVALUATION OF SHALE GAS POTENTIAL IN TALANG AKAR AND LEMAT FORMATION INTERVALS IN ADS AREA SOUTH SUMATRA

• Main Author: Pebrimaryanti
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/78809
• Institution: Institut Teknologi Bandung

Shale gas is a natural gas trapped in fine-grained sedimentary rock (shale formation) that plays a role as source rock in the oil and gas industry. Along with the technology development, gas in shale formation now has a potential to be produced in large quantities. ADS area located in the South Sumatra Basin has source rock that has been proven as a producer of hydrocarbons. However, shale potential as a shale gas in the shale play system is still unknown. Evaluation of the shale gas potential was performed in Talangakar and Lemat Formation intervals. Evaluation was initiated with analyzing the depositional environment by conducting some reviews of these available data: biostratigraphy reports, core description reports of ADS-4 wells, geochemical analyses to determine the source rock depositional environments, and performing electrofacies interpretation. Research area is interpreted as estuarine - shallow marine environment. The next stage was well analyses that constituted of petrophysical interpretation and geochemical analyses. The petrophysical interpretation was performed by determining the volume shale, total porosity, TOC, and brittleness index. Meanwhile, the geochemical analyses were carried out by reviewing the laboratory analysis results to identify the richness and maturity level of the rock. The TOC values were determined by applying the Passey method using porosity and resistivity log. The application of Passey method was conducted to obtain the TOC values continuously in a well, with or without TOC analysis from the laboratory. The TOC values generated from log data were then calibrated with TOC values obtained from the laboratory. Brittleness index analysis was performed based on the presence of clay minerals and quartz minerals contained in the rock. This matter will be related to fracturing and production of hydrocarbons. The results of petrophysical analyses that have been performed on each well were then spread throughout the field using geostatistical methods in seismic data. Seismic data and seismic attributes were used to model the distribution of: volume shale, total organic content, maturity level, and brittleness index. The distribution maps generated from those four parameters were then overlaid using cutoff values. The cutoff values for each parameter were volume of shale Vsh > 0.35, TOC > 1, maturity level Ro > 0.9 and rock brittleness level BI > 0.5. The overlay and the cutoff of each parameter gave result that the shale in Lemat Formation has a potential to be resource shale on unconventional energy. In general, the potential of shale gas is located on zone 4 (top of basement - FS1) at a depth of 7501.34 feet - 10059 feet.