Experimental investigations of heterogeneous effect on supercritical pressure CO 2 and water flow in sintered porous media AIP Conf.The in-situ mixing zone represents dynamic characteristics of CO 2 miscible displacement flows, which is important for carbon dioxide enhanced oil recovery (CO 2 -EOR) projects. However, the migration characteristics of the in-situ mixing zone under reservoir conditions has been neither well studied nor fully understood. The in-situ mixing zone with the flowing mixture of supercritical CO 2 and n-decane (nC 10 ) was investigated by using a magnetic resonance imaging apparatus at a reservoir condition of 8.5 MPa and 37.8 C in porous media. The experimental results showed that the CO 2 -frontal velocity was larger than the mixing-frontal velocity. The mixing zone length was linearly declined in the miscible displacement process. And the declining rate of the mixing zone length was increased with injection rate. It indicates that the mixing zone length is not constant in a vertically stable CO 2 misible displacement and a volume contraction due to phase behavior effects may occur. Then, an error function based on the convection-dispersion equation was fitted with CO 2 miscible displacement experiments. The error function was well fitted both at a series of fixed core positions and a series of fixed displacement times. Furthermore, the longitudinal dispersion coefficients (K lx and K lt ) and the longitudinal Peclet numbers (Pe d and Pe L ) were quantified from the fitting results. The evolutions of the longitudinal dispersion coefficient were reduced along the displacement time. And the declining rate was increased with injection rate. And with proceeding, the longitudinal dispersion coefficient was tending towards stability and constant. But the evolutions of the longitudinal Peclet numbers were increased along the displacement time. And the increasing rate was increased with injection rate. V C 2014 AIP Publishing LLC.

No abstract

Graphical AbstractThe dynamic stability characteristics of fluid flows in miscible displacement processes were investigated by using a magnetic resonance imaging apparatus under reservoir conditions of 8.5 to 9.5 MPa and 37.8°C. It was found that although the whole mixing zone length had no obvious change with pressure, a higher pressure compressed the mixing zone and led to an unstable mixing front above the critical velocity.2 much as 60% OOIP, which is more than water displacement (44% OOIP). 5 During tertiary oil recovery, miscible CO 2 displacement can reduce the residual oil by 8 to 25% OOIP in a field-scale pilot test. [6][7][8] Additionally, CO 2 EOR is an environmentally friendly technology that can reduce greenhouse gas effects. 9,10 Understanding the dynamic characteristics of fluid flow in CO 2 miscible displacement is important for predicting the in situ mixing position and oil production in oilfields. For example, in Chevron's McElroy Field 11 in West Texas, USA, a variety of porosities, permeability and heterogeneity cause the field to have various flooded zones and oil recovery efficiencies. 12 The effects of CO 2 miscible displacements have been previously discussed in various numerical and experimental studies, such as flow rate, heterogeneity, diffusion, viscosity and density differences, grain size distribution and grain shapes. 13 Experimental studies have been performed to investigate the flow characteristics of miscible displacement processes. Al-Wahaibi et al. 14 studied the effects of the flow rate, the gravity effect, the bead size and the length scale on gas-oil non-equilibrium oil recoveries for multi-contact miscible (MCM) displacement at normal pressures and temperatures. The miscible non-equilibrium increased with flow rate but independent of the permeability and the length of the bead-pack. Torabi and Asghari 15 investigated the effects of connate water saturation, the matrix permeability and the oil viscosity on the performance of gravity drainage from the matrix into the fractures. The ultimate oil recovery was less sensitive to the matrix permeability at pressures near or above the minimum miscibility pressure (MMP).Rashid et al. 16 focused on the factors affecting oil and gas recovery in CO 2 -EOR processes. Core-flooding experiments showed that reservoir permeability differences of up to 1 order of magnitude did not affect the CO 2 -EOR factor. Wylie and Mohanty 17, 18 investigated the effects of water saturation and wettability on the bypassing and mass transfer under near miscible conditions of gas displacements. Torabi and Asghari 19 measured the effects of the operating pressure, matrix permeability and oil in place and the connate water saturation on oil recoveries for CO 2 huff-and-puff processes. They observed a drastic increase in the recovery factor from immiscible to the near-miscible/miscible pressures 20 and found that the recovery may decrease far above the miscibility. Trivedi and Babadagli 20 examined the effects of flow rate and reservoir back-pressure on the c...

No abstract