CO2 geological sequestration in heterogeneous binary media: Effects of geological and operational conditions

Abstract

Realistic representation of subsurface heterogeneity is essential to better understand and effectively predict the migration and trapping patterns of carbon dioxide (CO 2) during geological carbon sequestration (GCS). Many candidate aquifers for GCS have sedimentary architectures which reflect fluvial deposition, where coarser-grained facies with higher-permeability (e.g., sandstone) are juxtaposed within finer-grained facies with lower-permeability (e.g., shale). Because the subsurface is difficult to access and sample, geostatistical methods are often used to model the spatial distribution of geological facies across different scales. We use a transition-probability based approach to simulate heterogeneous systems with binary facies distributions and the resulting petrophysical properties at the field scale. The approach produces heterogeneity fields which honor observable and physical facies attributes (e.g., volumetric proportions, mean lengths, and juxtapositional tendencies). Further, we use the associated facies-dependent properties for both relative permeability and capillary pressure relations and their hysteretic behavior. Heterogeneous facies models are used to investigate the sensitivity of different trapping mechanisms (i.e., dissolution, residual trapping) as well as CO 2 plume dynamics to variability in (1) the spatial organization and connectivity of sedimentary facies types; (2) aquifer temperature; (3) CO 2 injection period; (4) perforation length; and (5) the level of impurity, represented here as methane (CH 4) present in injected CO 2 streams. Model results show that the magnitudes of residual and solubility trapping are reduced by increasing the percentage and degree of connectivity of high-permeability facies. An increase in aquifer temperature leads to a decrease in residual trapping and an increase in solubility trapping. Results also reveal that for a given volume of injected CO 2 , shorter injection times yield higher total amounts of trapped CO 2. Similarly, wells perforated over a shorter thickness of the aquifer contribute to an increase in both residual and solubility trapping. We also find that increased CH 4 concentrations in the injected CO 2 streams decrease residual trapping while increasing solubility trapping. This effect is more pronounced at shallower depths, where the pressure and temperature of the aquifer are lower.

Modelling of Transient CO2/Water Flow in Wellbore considering Multiple Mass and Heat Transfer

“…(3) A methane kick can develop more rapidly than a CO 2 kick, i.e., the velocity of gas migration and void fraction of gas in a methane kick are much larger (4) The simulation error of pit gain can reach 50% if the effect of gas dissolution is neglected in the CO 2 kick. However, it is negligible in the methane kick…”

“…Compared to the conventional working fluids, liquid or supercritical CO 2 has good properties (large density and heat capacity, low viscosity, and surface tension, etc.) for heat transfer and fluid flow and is widely used in the operations of drilling, fracturing, enhanced oil recovery (EOR), and geothermal exploitation [1][2][3][4][5]. Generally, affected by variations of the temperature and pressure in the wellbore, the thermophysical properties of CO 2 change significantly in the temporal and spatial scales, as shown in Figure 1.…”

“…Effect of Gas Dissolution. A comparison of CO 2 and CH4 kicks is conducted to analyze the effect of gas dissolution and phase transition on kick migration.…”

CO2-Fluid-Rock Interactions and the Coupled Geomechanical Response during CCUS Processes in Unconventional Reservoirs

“…When trying to understand CO 2 -oil flow through nanoscale porous media, it is essential to identify the relative importance of the processes occurring and the degree of interactions. Modeling of such highly nonlinear coupled flow should be involved, but current and predicted computational ability could not simulate all the known and physically described processes operating efficiently [237][238][239]. Although CO 2 injection has been widely used in conventional reservoirs to enhance oil and gas recovery, the interaction of CO 2 with fluids and pore surface in unconventional formations will influence phase behavior and multiphase flow, thus affecting CO 2 capture and reservoir stress redistribution.…”

CO2-Driven Hydraulic Fracturing Trajectories across a Preexisting Fracture

“…Compared to fractures induced by water, those induced by gas have rougher surfaces, more tortuous paths, and a larger potential to form a complex fracture network, in turn potentially resulting in higher surface flow-transfer surface areas and reduced conductive flow lengths [10,19,21]. Additionally, the adsorption capacity of CO 2 is 4-20 times of that of methane [22,23], enabling the competitive replacement of methane by CO 2 and the cosequestration of CO 2 .…”