Complex Fluid of South Mahakam: A Fluid Synthesis Case Studies with Overpressure and Gas Striping Phenomena, of Multilayer Reservoirs for Marginal Offshore Gas Field Development in the Manpatu Field

Abstract

Abstract Manpatu Field was discovered in 2022. It will provide a transition to green energy supply for the future capital of Indonesia, which will be located in the same region of East Kalimantan. A fluid synthesis studies methodology of the retrograde gas-condensate with gas striping phenomena on the overpressure multilayer reservoir fluid vertical distribution was introduced to rectify volumetric calculations in both static and dynamic geomodel simulation. This was done to justify the economics of the offshore marginal gas field development. The new approach is based on generating a specific fluid model - EOS pseudo component methodology for Gas Striping that is in agreement with the geochemistry analysis. It involves integrating the surrounding panel with exploration well data to control the fluid model based on Gas Liquid Ratio (GLR) and hydrocarbon column occurrence in the overpressure vertical distribution of the Manpatu Field compared to other panels of the South Mahakam Field. The aim is to provide a base-minimum-maximum case scenario in reducing uncertainties of the fluid, in order to economically justify the volumetric hydrocarbon calculation in static and dynamic simulations. A fluid model with 5 pseudo components, following a specific trend based on the geochemistry analysis of the hydrocarbon with gas stripping phenomena, was generated to match all the fluid behavior from the PVT samples. However, this is only half of the journey. Saturation pressure and GLR vertical distribution from the available samples taken from the exploration wells are not sufficient to determine fluid evolution with the overpressure regime in the Manpatu Field. Therefore, combining the data with the surrounding produced panel is taken into account. The result deviated, even contradicted, the classical gravitational segregation vertical fluid distribution. Specific GLR and Saturation Pressure evolution trends vs. depth scenarios and assumptions in the overpressure regime were made to govern fluid vertical distribution and reduce uncertainties in static and dynamic geomodel simulation to mimic the phenomena in the field. Gas striping and overpressure need to be considered in order to have a reliable multilayer reservoir gas condensate-oil fluid model for reliable OOIP and IGIIP volumetric calculations and development scenarios. Using classical gravitational segregations vertical fluid distributions would lead to misleading conclusions. The results of volumetric calculations and uncertainties are rectified for the justification of the project's economic feasibility for the Manpatu's marginal gas field development FID's.