CO2 Injection in Vertical and Horizontal Cores: Measurements and Numerical Simulation

Abstract

Summary In certain high-pressure and low-temperature reservoirs, the density of CO2 may be substantially higher than the oil density. Upon mixing of CO2 and oil, a gas phase with a high content of methane (C1) may also appear. When the C1 content is high, this gas phase may have a lower density than the oil. In relation to this phenomenon, we have conducted three comprehensive experiments studying CO2 injection from the top and bottom of a vertical core and injection in a horizontal core. The injection rate is 1 PV/day. This low rate allows the study of diffusion. The core diameter used in this work is 3.8 cm and the length is 27.3 cm. The tests are conducted at a pressure of 441 bar and a temperature of 60°C. At 2.6 hydrocarbon pore volume injection (PVI), the coreflood results give a recovery of 98% for bottom injection, 84% for top injection, and 92% for horizontal injection. We have also conducted an extensive set of measurements to determine swelling, viscosity, and density for the calibration of an equation of state. We simulate the experiments using a state-of-the-art higher-order finite-element three-phase compositional model. The simulations suggest that the endpoint relative permeability of the CO2-rich phase may be lower than the oil phase. The results also show that Fickian diffusion should be taken into account, but that the diffusion coefficients are reduced, because the CO2/oil mixtures are in the near-critical region for much of the injection. Even for a horizontal core there is a considerable gravity effect. One main conclusion is that there may be vast differences between CO2 injection in a 1D slim tube and in a core where there may be a 2D flow. A related conclusion is that analysis of CO2 coreflooding may provide important parameters for field-scale problems.

Effect of Flow Direction on Relative Permeability Curves in Water/Gas Reservoir System: Implications in Geological CO2 Sequestration

“…The gravity number in horizontal flow is higher than that in vertical flow. Moortgat et al [24] observed a similar gravitational effect during their study in which oil recovery was compared between core flooding in horizontal, vertical up, and vertical down CO 2 flooding. In their study, CO 2 density was higher than the oil density used; hence, gravitational frontal instability was observed during vertical CO 2 injection from top to bottom.…”

Phase Behavior of a United Arab Emirates Stock-Tank Oil and Carbon Dioxide at Reservoir Conditions: Experiments and Thermodynamic Modeling

“…These changes are mainly attributed to physics and chemical interaction between the two fluids and also to the fluid injection rate and pressure [1]. The many advantages of CO 2 injection over those of water and nitrogen injection are summarized in [2]. CO 2 flooding is among the most promising enhanced oil recovery (EOR) methods in heavy oil reservoirs and has been successfully used in a number of worldwide basins where other EOR techniques are not applicable [3].…”

“…The swelling depends on the amount of methane in the oil. Because the CO 2 does not displace all of the methane when it contacts a reservoir fluid, the more methane there is in the oil, the less is the swelling of the oil [4].…”

“…Oil mobility is improved because the solubility of CO 2 in the oil increases the oil volume and at the same time causes a reduction in the oil viscosity [5]. Characterization of produced and residual oils in the CO 2 flooding process has been recently carried out by [6]. This kind of study provides a deep understanding of the changes of properties of the produced and residual oils in CO 2 -EOR processes.…”

Effect of Miscibility Condition for CO2 Flooding on Gravity Drainage in 2D Vertical System

“…Nasrabadi et al [6] conducted the simulation study to investigate the effect of density in the 2D vertical reservoir and shown significant effect of gravity and heterogeneity. Although a number of researchers [1][2][3][4][5][6][7][8][9][10] have investigated about CO 2 flooding under the various miscibility conditions and the gravity drainage mechanism, none of researches have been done in vertical oil reservoir.…”