ANALISIS POTENSI RESERVOIR BASEMENT FRACTURE: STUDI KASUS POST-DRILLING ANALYSIS SUMUR

• Main Author: Qosim Ghozali, Nur
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/86916
• Institution: Institut Teknologi Bandung

The South Sumatra Basin is one of the major oil dan gas-producing basins in Indonesia, classified as a "super basin" with an estimated remaining potential reserve of at least 5 BBOE. Many significant discoveries in the South Sumatra Basin originate from basement reservoirs that contain natural fractures. Understanding the spatial dan temporal distribution of these fractures, dan their relationship with the reservoir fractures, is essential to identify the orientation of the primary fractures that act as the main permeability pathways. Geomechanical evaluation, which includes critical fracture analysis, can be utilized to gain this understanding, particularly in the PPP structure, which has not yielded hydrocarbons from its basement reservoir target. It is known that the PPP-1 structure is surrounded by wells that have successfully produced hydrocarbons from the basement, making it a puzzle why this structure has not shown hydrocarbon accumulation. Geomechanical analysis was conducted on several surrounding wells, including PPP-1, Bungin-1, Bungin-2, dan Rayun-2. The methods used in this study include 1D geomechanical analysis, image log analysis, dan paleostress inversion. These methods were employed to determine the characteristics dan distribution of critical fractures, the history of fracture formation, dan the stresses responsible for their formation. The assumption is that the fractures found in the basement have not been significantly affected by intensive diagenesis processes that alter the rock properties, dan the dynamic stress calculation results are valid dan close to their original values. Subsurface mapping results indicate that the study area is dominated by northwest-southeast dan northeast-southwest structural trends within the basement interval. The northeast-southwest structural trend is predominantly characterized by normal faults, while the northwest-southeast trend consists of reverse faults. The SHmax direction in Well PPP-1 is oriented northeast-southwest, consistent with the orientation of the extensional fractures. The evaluation of the principal stress directions in the surrounding structures dan references shows that the local stress orientation in the PPP structure is also aligned northeast-southwest. Geomechanical modelling results from Well PPP suggest that the tectonic regime in the study area is strike-slip, with the principal stress direction oriented northeast-southwest. The comparison of in-situ stress gradient values, indicating the magnitude of stresses, can be used to analyze the active fault regime. The study area is influenced by a strike-slip fault regime, characterized by SHmax > Sv > SHmin. Geomechanical evaluation also indicates the potential for the Talangakar Formation to act as an effective seal rock, as evidenced by overpressure conditions. The critical fracture evaluation, conducted using several critical coefficients, shows the potential for both the presence dan absence of critical fractures. The major critical fracture orientation is N 105–115°E, while the minor orientation is N 45–50°E. Petroleum system analysis results indicate that the failure of hydrocarbon accumulation in the PPP structure is not due to trap formation, reservoir conditions, or seal rock. The source rock evaluation suggests that the hydrocarbon charge potential is favorable in the Plajawan area, but poor timing of the accumulation charge may have prevented hydrocarbon accumulation in the PPP structure.