Characterization of Depleted Hydrocarbon Reservoir AA-01 of KOKA Field in the Niger Delta Basin for Sustainable Sub-Sea Carbon Dioxide Storage

This study characterized the AA-01 depleted hydrocarbon reservoir in the KOKA field, Niger Delta, using a multidimensional approach. This investigation involved data validation analysis, evaluation of site suitability for CO2 storage, and compositional simulation of hydrocarbon components. The primary objective was to determine the initial components and behavior of the hydrocarbon system required to optimize the injection of CO2 and accompanying impurities, establishing a robust basis for subsequent sequestration efforts in the six wells in the depleted KOKA AA-01 reservoir. The process, simulated using industry software such as ECLIPSE, PVTi, SCAL, and Petrel, included a compositional fluid analysis to confirm the pressure volume temperature (PVT) hydrocarbon phases and components. This involved performing a material balance on the quality of the measured data and matching the initial reservoir pressure with the supplied data source. The compositional PVT analysis adopted the Peng-Robinson equation of state to model fluid flow in porous media and estimate the necessary number of phases and components to describe the system accurately. Results from this investigation indicate that the KOKA AA-01 reservoir is suitable for CO2 sequestration. This conclusion is based on the reservoir's good quality, evidenced by an average porosity of 0.21 and permeability of 1 111.0 mD, a measured lithological depth of 9 300 ft, and characteristic reservoir - seal properties correlated from well logs. The study confirmed that volumetric behavior predictions are directly linked to compositional behavior predictions, which are essential during reservoir initialization and data quality checks. Additionally, it highlighted that a safe design for CO2 storage relies on accurately representing multiphase behaviour across wide-ranging pressure-temperature-composition conditions.