RESERVOIR CHARACTERIZATION OF C INTERVALS FOR FIELD DEVELOPMENT OPTIMALIZATION OF FIELD TT, BARITO BASIN SOUTH KALIMANTAN PROVINCE

• Main Author: Pradana, Aulia
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/77662
• Institution: Institut Teknologi Bandung

Field TT is one of the oil-producing fields in the Barito Basin. One of the major reservoirs in this field is sandstone C intervals. Currently the field’s status is “brown field”, due to the significant declining of production level from its peak approximately 2800 BOPD to only about 200 BOPD in 2011. Recovery factor of this field has reached 17.78% until mid-2011. In order to increase oil production and maximize recovery factor, several attempts will be conducted such as the addition of wells and perform the initial stage of water injection. To support those attempts, some researches are needed in order to understand the character of the reservoir in this field. This research also involves new data as an additional 3 wells with one of them has a core data. Reservoir characterization includes a more detailed understanding of the facies, facies associations and the environment of deposition, and also its relationship with existing rock properties based on the well and seismic data. Reservoir characterization performed on sandstone reservoir which is included in the Warukin Formation with a primary focus on the C intervals. C intervals is divided into three intervals called Ca, Cb, and Cc. Reservoir characterization begins with the observation of core at the well TT-27 in order to get lithofacies and lithofacies association. Further analysis is description of a thin section combined with x-ray diffraction (XRD) data. All the results of the analysis is associated with the pattern of gamma-ray logs in order to get a log model that can be used for all of the well correlation of facies associations. The next stage is to perform 3D reservoir modeling for structural, facies, and petrophysical data. Petrophysical analysis performed to obtain reservoir property values include the value of shale volume, porosity, water saturation, and permeability. The results of petrophysical analysis in each well were then distributed throughout the field using geostatistical methods. The results of the characterization are reservoir depth structure maps, thickness maps, and 3D reservoir models. Selection of scenarios increase the number of wells is done by analyzing the reservoir quality and hydrocarbon pore volume observed map (HCPV), while the choice of doing a water injection started by looking the composition of reservoir rocks and the injection well position will be aligned with the direction of deposition. This study concluded that the depositional environment of C intervals is fluvial systems. The sedimentation direction is northwest to south east. Based on Galloway channel classification, Ca and Cc interval interpreted as bedload channel and Cb as a mixed load channel. This reservoir is divided into three facies associations: channel axis, bar head unit bar, and channel margin. Channel axis mainly develops at northern part of the field, bar head unit bar develop at central area, and channel margin at the southern part of the field. These three facies associations have different reservoir quality described from log gamma ray pattern, porosity and permeability relationships, and also the value of irreducible water saturation. Channel axis facies association is best reservoir as indicated by a highest average porosity (19%), the most optimistic relationship between porosity and permeability, and the smallest irreducible water saturation which is 20%. The second best reservoir is bar head unit bar with an average porosity 16%, the relationship between porosity and permeability is medium, and the irreducible water saturation value reaches 40%. Channel margin is the worst reservoir with average porosity of 14%, the most pessimistic relationship between porosity and permeability, and the highest value of the bound water saturation in the rock (52%). By knowing the reservoir properties, then the best development scenario is drilling 1 infill well, reopen suspended wells primarily at the point where the oil is still abundantly accumulated (from HCPV maps) and conduct the peripheral water injection in the same direction of reservoir deposition.