Characterisation of Reservoir Fluid Properties and PVT Behaviour in Gas Condensate Fields of the Anambra Basin, South East Nigeria

Gas condensate reservoirs in the Anambra Basin of South East Nigeria present complex phase behaviour challenges that require careful pressure-volume-temperature characterisation to optimise field development planning and surface facility design. This study characterises the reservoir fluid properties and PVT behaviour of gas condensate samples collected from exploration wells drilled in the Anambra Basin. Compositional analysis of three separator gas and recombined wellstream samples was performed using gas chromatography to determine C1 through C10 plus fractions. PVT laboratory measurements including constant composition expansion, constant volume depletion, and separator tests were conducted on recombined samples at reservoir conditions. Cubic equations of state, specifically the Peng-Robinson equation, were tuned to match measured PVT data using regression on binary interaction parameters and volume shift corrections. Results indicate dew point pressures ranging from 3,850 to 4,200 psia at reservoir temperatures of 195 to 210 degrees Fahrenheit, classifying the fluids as lean to moderate gas condensates with condensate-gas ratios between 45 and 85 stock tank barrels per million standard cubic feet. Retrograde condensate banking behaviour is confirmed through constant volume depletion tests, which predict maximum liquid dropout of 12 percent by pore volume at pressures 600 psi below dew point. Implications for surface separator design and gas processing train specifications are discussed. Keywords: PVT analysis, gas condensate, Anambra Basin, equation of state, dew point pressure.