Effective Permeability 3D Model Unlock the Uncertainty Production in Low Perm Fluvial-deltaic Reservoirs, Nilam Field, Kutai Basin, Indonesia

Abstract

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.