Characterization, Pressure–Volume–Temperature Properties, and Phase Behavior of a Condensate Gas and Crude Oil

Abstract

The oil reservoirs are underground and have the oil and gas contained in the porous rock at high temperatures and pressures. Only 5−20% of the oil is withdrawn in primary production. Further recovery can be achieved by injecting carbon dioxide (CO 2 ) that displaces and dissolves part of the remaining oil; this process is called enhanced oil recovery. Although the characterization and fractionation of petroleum are well-known and studied, each oil sample represents a unique multicomponent system; therefore, an individual study of the sample is required. Real samples of condensate gas (CG) and light crude oil (LCO) were collected and analyzed for density, viscosity, atmospheric distillation and fractionation, and aiming characterization. Synthetic visual and non-visual methods for high pressure were successfully applied for bubble point measurements of the systems composed of supercritical CO 2 and CG or LCO. Phase envelope calculations were developed on the basis of pseudocomponents obtained by atmospheric distillation and density values using the Adachi−Lu−Sugie equation of state with van der Waals mixing rule with one interaction parameter (k ij ) from the literature. Pressure−volume−temperature (PVT) measurements are reported for the systems CG + CO 2 and LCO + CO 2 as a function of the temperature and pressure and in a wide range of CO 2 composition. Crude oil characterization using atmospheric distillation and density measurements was demonstrated to be feasible with accuracy, because the boiling points and specific mass obtained allowed us to propose a series of pseudocomponents to represent the sample phase behavior studied experimentally. Thus, results suggest that the characterization and fractioning of the samples were effective. Thermodynamic modeling and experimental data presented an average deviation of 3.1% to CG + CO 2 and 2.5% to LCO + CO 2 systems, indicating reasonable accuracy for petroleum samples.

Interfacial Tension Measured at Nitrogen–Liquid and Liquid–Liquid Interfaces Using Model Microemulsions at High-Pressure and High-Temperature Conditions

“…Increasing pressures did not impact its phase behavior, contrary to expected phase changes reported from related studies. 49 However, it has also been reported that the solubilization capacities of certain surfactants did not deteriorate at temperatures several degrees above the determined cloud points. 51 Literature data and studies on adverse effects of temperature and pressure on the phase behaviors of surfactants and microemulsions apply to some extent at the liquid−liquid phase.…”

Phase Behavior Identification and Formation Mechanisms of the BZ19-6 Condensate Gas Reservoir in the Deep Bozhong Sag, Bohai Bay Basin, Eastern China

“…However, regardless of the influence of organic matter type and maturity, the presence of an unusually high or abnormally low content of low-carbon aromatic hydrocarbons in the crude oil or condensate gas, could potentially indicate whether the crude oil or condensate gas experienced a secondary alteration and whether evaporation fractionation was the reason [38]. The late charging of the natural gas transforms the early oil reservoirs into condensate gas reservoirs and increases the wax content of condensate oil and paraffinicity of the heavy hydrocarbon gas, ensuring that the oil quality is higher than that of the normal condensate [13]. The average condensate density of the BZ19-6 structure is 0.798 g/cm 3 (at 20°C), which is higher than the normal condensate density (approximately 0.74 g/cm 3 ); the wax content and the paraffinicity is high, with an average of 9 Geofluids 13.7% and 1.57 (Tables 2 and 5), respectively.…”

“…A condensate gas reservoir is a special hydrocarbon deposit located between oil and gas reservoirs and is more valuable compared with conventional oil and gas reservoirs. Condensate gas exhibits the characteristics of complex genesis, complex thermodynamics, and multiple phase behaviors [10][11][12][13], of which phase behavior and formation mechanism are of great significance in the evaluation of deep oil and gas resources. The study on the phase behavior of condensate gas reservoirs began in the 1930s.…”

“…Carbon isotope data of natural gas of the BZ19-6 and BZ21-22 structures 13. C 1 δ 13 C 2 δ 13 C 3 δ 13 C 1 -δ 13 C 2 δ 13 CO 2 By Pedersen et al[27] By Manafi et al[28] …”

Experimental and modeling studies of density and viscosity behavior of a live fluid due to CO2injection at reservoir condition

“…As the injection of CO 2 causes changes in crude and gas thermophysical properties and phase equilibria [15][16][17][18][19], it is necessary to recalculate the equilibrium of the CO 2 -oil system for the CO 2 injection scenario as well as assessing the viscosity-pressure behavior. Thus, it is required additional experimental data of density and viscosity as a function of temperature and pressure of the mixture comprising oil with dissolved CO 2 .…”