ARCHITECTURAL ELEMENT ANALYSIS AND ITS IMPLICATIONS TO RESERVOIR QUALITY IN A DEEPWATER SLOPE CHANNEL COMPLEX, OFFSHORE KUTAI BASIN

• Main Author: Muhammad, Wahid
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/82525
• Institution: Institut Teknologi Bandung

Deepwater exploration success of Field X in the offshore Kutai Basin had resulted in the discovery of significant natural gas reserves coming from several reservoir segments. In this research, the reservoir segment that is being studied is segment BSN, which is a Pliocene-aged deepwater turbidite slope channel complex deposit. The reservoir is characterized by complex stratigraphic relationships of its architectural elements and heterogeneity of its facies distribution. In the study area, these reservoirs are hydraulically connected, but production performance data show that there are different production rates from the three production wells (BSN-5, BSN-6 and BSN-9). Therefore, this study aims to analyze the relationship of geometrical complexity of architectural elements in affecting the reservoir quality distribution within the reservoir segment BSN. This research implements several methods that are systematic and integrated with the availability data such as 3D seismic data, 3D inversion seismic data, core data, well logs data, and dynamic data. These data are then used to analyze the depositional environment, petrophysical calculations and interpretation of architectural elements to 3D geological modeling. Architectural element analysis was conducted using a fundamental method based on the seismic stratigraphic method to map and understand the geometry, distribution and sedimentological framework of the deepwater slope channel complex. Then, 3D static reservoir modeling is performed using Sequential Indicator Simulation (SIS) and Sequential Gaussian Simulation (SGS) methods using well data and trend modeling in the form of seismic inversion data of sand probability to determine the population of facies distribution and reservoir properties beyond the existing well data in the research area. Thus, the relationship to reservoir quality is analyzed based on architectural elements characteristics, net reservoir thickness and reservoir property values. This study successfully interpreted the depositional processes and mapped 6 individual channel elements with architectural element geometries divided into channel axis, channel margin, and slope mudstones. The sedimentation process in this channel complex was deposited by turbidite current mechanisms and on steep slope gradients in the deepwater slope geometry with all channel elements deposited in amalgamation with progradational stacking patterns that are connected to each other due to the eroding nature of the channels. Reservoir quality analysis also shows that BSN-5 and BSN-6 have excellent reservoir quality with average porosity and permeability of 0.20% and 97 mD, respectively, which is reflected in the high production performance as both wells penetrate the channel axis. Meanwhile, the BSN-9 production well shows a low production performance as it penetrates the channel margin with poor reservoir quality with average porosity and permeability values of 0.15% and 32 mD.