An Integrated Core, Reservoir Characterization and PVT for Hybrid Enhanced Oil Recovery in Unconsolidated Sandstone Reservoir
Authors: Gibrata Muhammad A , Ameish Giamal , Eldali Magdi , Huang Qingfeng , Rouis Lamia , Dernika Moustafa , Bashar  , Nizarudin  , Klemin D 
Published: October 2024

The enhanced oil recovery (EOR) is important to be implemented, in matured unconsolidated sandstone reservoir. It is to ensure oil production with optimum recovery from the reservoir. It requires an integration multi disciplines rock and fluid properties evaluation. In this EOR study with water injection, gas injection, water alternating gas and ongoing alkaline surfactant polymer (ASP) have been used for EOR displacement analysis, it has used engineering of gas injection in advanced PVT analysis to properly understand the injection reservoir fluid phase behavior and the EOR displacements in core flooding.

The PVT study has been performed, initially on the gas miscibility and phase behavior that consists swelling test, minimum miscibility pressure (MMP), vapour liquid equilibrium (VLE), multi-contact evaluation and flow assurance studies. The oil and water from the particular reservoir conditions have been used in the analysis. Then it continued with reservoir characterization, water injection, gas injection, water alternating gas (WAG) and ongoing ASP for hybrid EOR displacements analysis. It has involved an in-house integrated petrophysical, geological, reservoir characterization and model in the EOR study. A 3D computed tomography (CT) image and the available RRT-SHM model have been used for core plugs selection of the EOR study.

The unconsolidated core samples have been plugged successfully by liquid nitrogen and cleaned, injection high to low water salinity and the wettability restoration a steady-state relative permeability with the selected fluids. The steady-state floods (water-oil, gas-oil and gas-water) have been designed to obtain relative permeability on plugs representing selected reservoir rock types at reservoir conditions. A digital rock analysis with steady state floods on the same rock types is validated, then digital rock analysis is used to obtain relative permeability data on all remaining rock types for fast time and effective cost. The saturation is determined by in situ saturation monitoring (ISSM) with X-Ray attenuation. Injection continues until the pressure drop across the core sample and the measured saturation are stable. The oil and gas are injected into a sample initially at initial water saturation to maximum gas injection and at residual oil saturation. The optimum conditions for EOR and related parameters controlled by the core properties on the EOR displacement analysis are defined.

The innovative integrated approach of reservoir characterization and EOR have provided the reliable technical basis and assurance for the development of unconsolidated sandstone reservoirs. The oil recovery with recent reservoir conditions range has been measured. It has benefits to maximize oil recovery from current main producing reservoir with utilizing the available gas, fluids, core, logs, production and reservoir data which is important for a successful field development plan.