Browsing by Subject "Dew point"

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Parametric Study of Relative Permeability Effects on Gas-Condensate Core Floods and Wells
(2003-12) Rai, Rakesh Roshan; Pope, Gary A.; Sharma, Mukul Mani
A simulation study was done to systematically evaluate the effects of relative permeability parameters on both laboratory corefloods and gas-condensate wells producing below the dew point pressure. A Corey-type relative permeability model was used including the effect of interfacial tension (trapping number or capillary number dependence). The field simulations have been done using five different gas-condensate fluids ranging from lean to rich. The decrease in PI was studied for each case. The simulations of laboratory experiments were carried out to compare and understand the condensate buildup and better understand and interpret these experiments. The University of Texas compositional simulator UTCOMP was used in this study. The coreflood simulations included both condensate accumulation and methanol treatment stages. The three-phase flash capability of UTCOMP was needed to simulate the corefloods in some cases since the water-methanol-hydrocarbon mixtures are liquid-liquid-gas systems under the conditions studied. The sensitivity of the productivity index for both gas and condensate phases differed for all five single-well cases that were simulated and was substantially different for the 8 relative permeability parameters that were studied. The gas PI decreases in direct proportion to the gas relative permeability. The parameters that have the most effect on the gas relative permeability are the gas endpoint, the gas exponent, and the trapping parameter controlling the residual condensate saturation since the gas relative permeability increases as the condensate saturation decreases. Since the gas endpoint decreases as the residual water saturation increases, it also has a direct and significant affect on the gas PI. The gas PI changed on the order of 5 fold with both gas endpoint and residual water saturation. The gas PI changed on the order of 2 fold with both the gas exponent and the oil trapping number parameter. Changes in condensate PI follow similar trends as for gas PI because higher gas rates result in more condensate under surface conditions. A comparison between several high-rate corefloods and the compositional simulations indicated that the residence times were too short in the corefloods for the fluids to achieve local equilibrium. Good history matches were obtained for most of the steady state pressure drops even at high flow rates, but agreement between the simulation results and the experimental data was good for the transient flow period only at the lowest flow rate of 2 cc/hr. The simulations predict that all of the condensate and water (if initially present) is removed from the cores after a few pore volumes of methanol injection. During subsequent gas injection below the dew point pressure, condensate drops out but at a reduced rate until the methanol is stripped out of the core by the flowing gas, and then the pressure drop increases again just as observed in the experiments.