Nilam Field is located in Kutai Basin, East Kalimantan, Indonesia, which even more than 40 years of exploitation, these fluvial deltaic reservoirs, of age Early-Middle Miocene, still have significant reserves of gas, that occur in poor quality reservoir rocks in structural, stratigraphic or combination traps, that were not entirely examined. This case history describes some works carried out in this field over these low permeability reservoirs, locally known as G's sandstones, in order to understand the root of the erratic production results, evaluate the formation damage, identify the potential areas and present the right solution for recovering the undeveloped accumulations.Seventeen cores were taken in these horizons, with the main purpose to obtain the necessary information for determination and characterization of rocks and the explanation of trapped phase. An understanding of multiphase properties as capillary pressure, water-gas relative permeability, fluid compatibility and the right model for effective permeability, calibrated by nodal analysis techniques, are mandatory to properly define the input for the 3D petrophysical models. In the past, the failure to fully understand these concepts, especially the effective permeability model and its relationship with the critical water saturation, less than 40% for these reservoirs, has led to a not clear understanding the controls on gas-field distribution. Therefore, effective permeability to gas as function of varying water saturation is the key factor to understand the reservoir productivity.The integration of critical petrophysical aspects with geology using geostatistical methods had produced comprehensive overlay models that were used to delineate the best areas for developing the significant amounts of un-recovered reserves with minimum uncertainty in production. The use of this methodology has arrived not only to achieve this target but also has shown an incremental gas production as much as 10 times, in some areas of the field, during the last 2 years.For this study, two sources of information were available: Core data and Log data. Both were analyzed to get reliable information to characterize the G Reservoirs.

The fluvial deltaic VICO's Reservoirs are located in the eastern part of Kutai Basin, Indonesia, being Badak one of their biggest and most prolific Fields that has been producing gas for more than 35 years. Badak, the first gas field discovered in the Basin, presents the concentrations of hydrocarbon in fluvial sediments, mainly in channels and bars deposits. These bodies are distributed through a vertical interval of thousands feet over various areas of the structure. At present, we face the challenge of developing the remaining gas reserves in these low permeability deep reservoirs. These reservoirs locally known as G and H levels are at depths between 11,000ft to 13,000ft. During last couples of years considerable efforts have been done on developing fluvial facies model based on sedimentary environment and core data. The key factor, for better understanding the potential areas was an integrated 3D Model including also a detailed petrophysical analysis. Based on core data cut-off values of porosity, permeability and water saturation were calculated and used for selection of the best well candidates, with the higher flow rates. The same cut-off values were applied in the 3D model in order to identify and characterize the main productive areas with high storage and flow capacity. The 3D model helped to understand the areal and vertical distribution of these petrophysical properties as well as porosity and water saturation. As a result, confident locations for development of these low permeability reservoirs can be presented in order to increase the current recovery factor. Right applications of a reliable 3D model allows to identify of best areas and potential reservoir characteristics from limited quantity of data, obtainable from conventional cores and well logs to maximize the success of the project. Drilling in these reservoirs already contributed with 30 MMCFD of gas equivalent to 30% of field production.