ANALYSIS OF SEAL CAPACITY AND RELATION WITH HEIGHT OF HYDROCARBON COLUMN IN JS-1 RIDGE AREA, NORTH EAST JAVA BASIN

• Main Author: Khadafi
• Format: Theses
• Language: Indonesia
• Subjects: Karya Umum
• Online Access: https://digilib.itb.ac.id/gdl/view/53173
• Institution: Institut Teknologi Bandung

The Early Miocene reefal carbonate of Kujung-1 is the main hydrocarbon reservoir in JS-1 Ridge Area, North East Java Basin. The varying heights of hydrocarbon columns affect the success rate of exploration in Kujung-1 Formation. The shale of Rancak Unit acts as a regional seal dan determines the height of the hydrocarbon column in the Kujung-1 Reservoir. This study aims to understand the character, capacity of seal, and its relation with hydrocarbon column height to improve the chances of exploration success. The methodology in this study includes estimation of pore pressures, capillary seals, hydrofracturing seals, and natural fractures modeling. The data used included 41 wells, laboratory data (Mercury injection capillary pressure, vitrinite reflectance and X-ray diffraction), and 3D seismic data. The pore pressure of Rancak Unit indicates that it is slight overpressure by loading mechanism, while formations below Rancak Unit are related to the unloading mechanism. The presence of slight overpressure increases sealing capacity of Rancak Unit to 1.95 MPa or 221 m gas column equivalent. Rancak has greater hydrofracturing seal capabillity than the thickness of the Kujung-1 reservoir. Interpretation of borehole breakout and drilling induced tensile were performed in KD-1 and KD-3 Wells. The fractures have average maximum horizontal stress direction is northeast-southwest. The geomechanical model shows that predominant stress regime at KD-1 and KD-3 Wells is normal stressregime. Fracture distribution based on natural fracture modeling is consistent with the percentage of hydrocarbon filling in Kujung-1 Reservoir. However, the fractures are in a stable condition under present-day stress. Based on futher analysis, the natural fractures in the Rancak Unit are the main factor affecting the height of the hydrocarbon column in the Kujung-1 Reservoir. The Neogen compressional tectonic period is thought to be a period of fracture in the study area in critical condition, and leakage occurred in the Kujung-1 Reservoir at that time.