Laboratory Measurements of CO2-H2O Interfacial Tension at HP/HT Conditions: Implications for CO2 Sequestration in Deep Aquifers

Abstract

Disposal of carbon dioxide (CO 2 ) in permeable, porous subsurface rock formations (i.e., geological sequestration) has been identified as a viable option for reducing greenhouse gas emissions into the Earth's atmosphere. Potential subsurface systems considered for geological sequestration include depleted oil and gas reservoirs, coalbed methane and shale gas reservoirs, and deep aquifers. Though each of these disposal systems has their advantages, deep aquifers (mostly filled with non-potable or brackish waters) have the greatest potential for large CO 2 sequestration programs primarily because of their relative abundance in most sedimentary basins and their large effective capacities.Successful selection of potential of CO 2 deep aquifer sequestration sites, however, requires an understanding of all physical and chemical trapping mechanisms by which CO 2 may be retained. Principle retention mechanisms in aquifers include structural/stratigraphic (CO 2 immobilization or trapping below an impermeable confining layer), residual fluid (trapped as immobile fluid phase in aquifer pore spaces), solubility (immobilized as fluid phase dissolved in in-situ water), mineral (immobilized as solid carbonate minerals formed from reaction with aquifer rock), and hydrodynamic (CO 2 dissolved in slow-moving water) trapping. While all of these mechanisms contribute to CO 2 sequestration, the structural/stratigraphic and residual fluid mechanisms have the largest and most immediate impact on trapping or retaining CO 2 in aquifers.The effectiveness of both structural/stratigraphic and residual fluid trapping mechanisms is dependent on the capillary pressure characteristics of the aquifer seal and formation, respectively. And, the capillary pressure characteristics are strong functions of the interfacial tension (IFT) properties of the carbon dioxide-water (CO 2 -H 2 O) system. Unfortunately, there is a general lack of understanding of the CO 2 -H 2 O IFTs, particularly at high-pressure/high-temperature (HP/HT) conditions typical of many potential deep aquifer sites. The vast majority of published CO 2 -H 2 O IFT data were obtained at pressures less than 10,000 psia and temperature less than about 250 o F. Additionally, there are often inconsistencies among the existing data published in the literature, thereby making it difficult to create predictive models.To address these inadequacies in the existing technical literature data base, we conducted laboratory studies to measure CO 2 -H 2 O IFTs using a pendant drop method at pressures between 1,000 and 18,000 psia and temperatures up to 400 o F. Rather than relying on correlations or previously published data, we also measured water-vapor-saturated CO 2 as well as CO 2saturated water densities directly at each pressure and temperature. General observations from our laboratory study include:• CO 2 -H 2 O IFTs demonstrated a strong dependence on temperature (decreasing with increasing temperature);• For a given temperature, CO 2 -H 2 O IFTs were relatively insensitive to pressure with ...

Study of the impact of high temperatures and pressures on the equilibrium densities and interfacial tension of the carbon dioxide/water system

“…[85], 298 K ( ); Yaginuma et al [27], 304 K ( ); Hebach et al [28], 313 K ( ) and 333 K ( ); Kvamme et al [19], 323 K ( ); Tabasinejad et al [29], 423 K ( ); Shariat et al [25], 373 K ( ), 423 K ( ) and 477 K ( ). Solid lines represent pure density of CO 2 (a) and water (b) at pertinent temperatures obtained from correlations given in REFPROP [30].…”

“…The measured equilibrium densities values were compared to those of pure components [30] and to selected data available in the literature [19,25,[27][28][29]85] and the results are plotted in figure 5 and listed in tables S1 and S2 in supporting information. [85], 298 K ( ); Yaginuma et al [27], 304 K ( ); Hebach et al [28], 313 K ( ) and 333 K ( ); Kvamme et al [19], 323 K ( ); Tabasinejad et al [29], 423 K ( ); Shariat et al [25], 373 K ( ), 423 K ( ) and 477 K ( ).…”

“…Chiquet et al [6], Bachu and Bennion [21], Tabasinejad et al [29] and Shariat et al [25] measured the densities of the saturated phases with a vibrating-tube and the results showed that the approximation of the water-saturated vapour phase density to that of pure CO 2 [30] is in fact valid for temperatures and pressures up to 473 K and 140 MPa, respectively. However, as demonstrated by Chiquet et al [6], the effect of dissolved CO 2 on the density of the liquid aqueous phase can cause severe underestimation of the IFTs close to the density inverse conditions, where the deviations of the real (measured) density difference from that of pure substances are greatest.…”

“…At these conditions, pure CO 2 will be in a supercritical state (T c ~ 304.13 K and P c ~ 7.38 MPa) and with densities higher than 662 kg·m -3 . Due to its key role in the design of the processes mentioned above, many studies have been conducted on the experimental measurement of the IFT of the CO 2 /H 2 O system during the last two decades [6,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. In most of these studies the pendant drop method has been used to perform these measurements over a wide range of experimental conditions.…”

Study of Shale Wettability for CO2 Storage

“…Other trapping mechanisms are mineral trapping, where CO 2 reacts with minerals in the rock, and solubility trapping, where CO 2 dissolves in the aqueous phase. In general, different trapping mechanisms occur simultaneously (Basbug et al 2007, Salimi et al 2012, Shariat et al 2012). …”