An Integrated Reservoir Characterization in Overpressure and Complex Sandstone Reservoirs for Hybrid Reservoir Modeling and Oil Productivity
Authors: Gibrata Muhammad A. , Ameish Giamal , Djanuar Yanfidra , Lamine Mohammad , Lozano Jose 
Published: March 2023

A Reliable reservoir characterization and model are useful for reservoir development in overpressure and complex reservoirs. The field has overpressure, multi fluid contacts, multi reservoir subunits, structural and stratigraphic sand discontinuities. The reservoir properties and quality decrease with increase of depth due to overburden compaction. However rock quality is useful for oil in place and productivity. Therefore, reliable reservoir characterization in deep reservoirs and estimation of fluids in place requires an integrated subsurface data approach.

Overpressure reservoir has been observed and evaluated in some reservoirs, it tends to preserve porosity and has sufficient permeability for oil productivity from the deep reservoirs. Image resistivity/density log and chromatography data have been used to identify minor fault, gas/fluid evaluation and update the reservoir model. An integrated petrophysical evaluation has been implemented in reservoir characterization. A reliable in-house permeability log has been developed from porosity, clay bound, pore size, core and mobility data. It has used the of hybrid saturation height model that based on SCAL data including capillary pressure and Relative Permeability data for every reservoir rock type and fluid contacts for subunits.

The advanced evaluation approach of subsurface and well test data has been used to provide reliable and good of reservoir properties and results on porosity, permeability, fluid contacts, reservoir rock type and initial water saturation in deep and overpressure reservoirs. The saturation height model (SHM) has been used, a quasi-SHM for unavailable core data in deep reservoir and PVT data have been used in the evaluation. The suitable open and cased hole logs data such as image resistivity/density, chromatography, pulse-neutron capture and production logs have been used to verify fault, fluid contacts, contribution, water saturation changes and production optimization. For every reservoir subunits, the formation pressure has been used to identify an initial oil water contact, reservoir subunits evaluation and thus it has provided SHM for complex reservoir modeling. The study has provided reliable reservoir characterization, reservoir modeling and for the development for multi-layers, over pressure and complex sandstone reservoirs. The high overpressure deep reservoirs have contributed for good oil productivity. It provides support to improve oil recovery from reservoirs and future plan for reservoir development target. Therefore the integrated reservoir evaluation approach has provided reliable assurance and important benefits for reservoir characterization, optimization and reservoir management.

The integrated hybrid approach in this paper shows the value of advanced reservoir characterization in overpressure and faulted complex reservoirs. It has utilized the integration updated open and cased-hole data, gas/fluid contacts, stress direction, advanced permeability, saturation height model and gas-fluid evaluation. The evaluation also has provided the reliable for reservoir modeling, oil in place volume and field development purposes.