Characterization of plus fractions for low gas-oil ratio black oil samples in Turkey

Türkmenoğlu, Artuğ
Pressure - Volume - Temperature (PVT) analyses simulate the reservoir fluid behavior while flowing from the reservoir to the surface under varying pressure, volume and temperature conditions. There are several PVT simulators that perform PVT calculations. Accurate characterization of a fluid is very important for further studies and reservoir simulations in all reservoir engineering aspects. Because there are a few equations of state and many types of reservoir and reservoir fluids, experimental data does not perfectly match with the PVT simulation results. Low API black oils include heavy hydrocarbons. Therefore, regression and characterization of plus fractions are needed in order to get better results from the PVT simulators. PVT data is usually used for field development program, reserve calculations, and EOR/IOR implementations such as gas flooding. In this study, PVT experiments, which are Constant Composition Experiment, 0 - Flash Experiment, Gas and Oil Compositional Analysis and Viscosity Measurement at reservoir temperature, are conducted on low GOR (20.7 scf/STB < GOR < 62.3 scf/STB) black oil samples. Reservoir fluid samples are obtained from different fields in Turkey. After laboratory experiments, in order to compare the experimental data, PVT simulation studies are performed. During simulation study, with respect to EOS models (SRK and PR with Peneloux Correction), bubble points, oil densities and oil viscosities are used as regression data. Heavier hydrocarbons are lumped together as C7+, C10+ and C20+, which is called as pseudoization process. Effects of critical properties and degree of pseudoization of plus fractions are investigated. Also, correlations to predict critical properties are used. The predictive ability of EOS models after tuning is analysed also by comparing simulational and experimental oil formation volume factors at bubble point pressure. The reason of selecting these parameters is that those are not used as inputs into compositional simulator for regression. PR - Pen EoS is more successful in density predictions than SRK - Pen EoS. Also, pseudoization is highly effective on density predictions. However, for heavy hydrocarbons, small degree of pseudoization gives acceptable results. Viscosity predictions are not effected by both EoS models and pseudoization but, they depend on viscosity correction factors of CSP model. Good agreements with experimental data suggest that PVT simulators can be used as a good alternative, especially when there is no possibility to conduct the experiments.


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Citation Formats
A. Türkmenoğlu, “Characterization of plus fractions for low gas-oil ratio black oil samples in Turkey,” M.S. - Master of Science, Middle East Technical University, 2016.