Validating Subsurface Samples of Volatile Black Oil through PVT Calculations of Surface Separator Samples for Enhanced Reservoir Characterization

This study investigates black oil's pressure, volume, and temperature (PVT) properties from well X, analyzed using subsurface and surface recombination samples. Black oil samples were collected from the Q oil field and subjected to PVT analysis at the Reservoir Fluid Laboratory in Port Harcourt. Key findings include bubble point pressure (Pb) of 2000 psi, with a standing correlation value of 1934.3 psi, resulting in a 3.3% difference. The solution gas/oil ratio was measured at 647.3 SCF/STB, compared to 671.0 SCF/STB from correlations, a difference of 3.5%. The oil formation volume factor (Bo) was 1.456 res Bbl/STB, while standing correlations indicated 1.0675 res Bbl/STB, showing a 3.6% difference. The isothermal compressibility ranged from 10.12 x 10<sup>-6</sup> psi<sup>-1</sup> at 4500 psi to 4.1309 x 10<sup>18</sup> cp at 15 psi. Gas evolution began at 2000 psig and increased with decreasing pressure. Viscosity varied significantly, recorded at 0.54 cp at 4500 psig and 1.38 cp at 15 psig. The reservoir contains heavy crude oil with an API rating of 30 and an average absolute error of 3.5% (0.035). These results enhance reservoir characterization and validate the use of PVT calculations in analyzing volatile black oil samples.