Characterizing small-scale migration behavior of sequestered CO2 in a realistic geological fabric

For typical reservoir conditions, buoyancy and capillary forces grow dominant over viscous forces within a few hundred meters of the injection wells as the pressure gradient due to injection decreases, resulting in qualitatively different plume migration regimes. The migration regime depends on two factors: the capillary pressure of the leading edge of the plume and the range of threshold entry pressures within the rock at the leading edge of the plume. A capillary channel regime arises when these two factors have the same magnitude. Flow patterns within this regime vary from finger-like structures with minimal rock contact to back-filling structures with compact volumes of saturation distributed between fingers. Reservoir heterogeneity is one of the principal factors influencing CO2 migration pathway in the capillary channel regime. Here we characterize buoyancy-driven migration in a natural 2D geologic domain (1 m × 0.5 m peel from an alluvium) in which sedimentologic heterogeneity has been resolved at sub-millimeter (depositional) resolution. The relevant features of the heterogeneity are grain size distribution, which determines the mean and range of threshold pressures and correlation lengths of threshold pressures in horizontal and vertical directions. The relevant physics for this migration regime is invasion percolation, and simulations indicate that CO2 migrates through the peel in a few narrow pathways which cannot be captured by conventional coarse-grid simulations. The storage efficiency of the capillary channel regime would be low and consequently CO2 would also migrate greater distances than expected from models or simulations that neglect the capillary channel flow regime.Bureau of Economic Geolog

Semi-analytical model to determine perforation interval for secure CO2 storage in saline aquifers

AbstractDue to density difference between injected CO2 and in-situ brine, the pressure difference between wellbore and formation varies with depth in a CO2 injection well. Consequently the flux distribution along a vertical well is not uniform during the early stages of injection. For injection rates below a certain threshold, this can lead to only a fraction of the perforations contributing to injection. Generally this reduces the efficiency of CO2 immobilization by dissolution in brine and by residual trapping because less volume of rock and brine comes in contact with injected CO2. Thus for injection rates below the threshold, optimization of the length of the perforated interval is required to maximize trapping. We describe a semi-analytical algorithm that finds the optimum interval of injection for a given flow rate so that all the perforations contribute throughout the injection period. Although bottomhole pressure rises while injecting in smaller perforation interval, the greater mobility of the CO2 phase upstream of the drying front reduces this increase and enables the use of smaller interval. In the case of a horizontal well, the length of well plays an important role in determining the CO2 trapping. The two competing effects, trapping along the well length and along lateral direction, determine the optimum well length required. Greater well length increases the trapping in direction of well path but reduces in lateral direction because of the ratio of gravity forces to viscous forces becomes larger. Thus dominance of either of these competing effects and cost of drilling determine optimal well length. This study illustrates the effect of different injection strategies on multiple objectives of CO2 sequestration including maximizing trapping and minimizing leakage potential. We find that the benefits of a strategy to maximize injectivity may be offset by less CO2 entering secure modes of storage

Pressure perturbations from geologic carbon sequestration: Area-of-review boundaries and borehole leakage driving forces

We investigate the possibility that brine could be displaced upward into potable water through wells. Because of the large volumes of CO2 to be injected, the influence of the zone of elevated pressure on potential conduits such as well boreholes could extend many kilometers from the injection site—farther than the CO2 plume itself. The traditional approach to address potential brine leakage related to fluid injection is to set an area of fixed radius around the injection well/zone and to examine wells and other potentially open pathways located in the “Area-of-Review” (AoR). This suggests that the AoR needs to be defined in terms of the potential for a given pressure perturbation to drive upward fluid flow in any given system rather than on some arbitrary pressure rise. We present an analysis that focuses on the changes in density/salinity of the fluids in the potentially leaking wellbore.Bureau of Economic Geolog

Characterizing Small-scale Migration Behavior of Sequestered CO2 in a Realistic Geologic Fabric

AbstractFor typical field conditions, buoyancy and capillary forces grow dominant over viscous forces within a few hundred meters of the injection wells resulting in remarkably different fluid migration patterns. Reservoir heterogeneity and fluid properties are principal factors influencing CO2 migration pathways in the buoyancy/capillarity regime. We study the effect of small-scale heterogeneity on buoyant migration of CO2 in this regime. Capillary channel flow patterns emerge in this regime, as characterized by invasion-percolation simulations in a real meter-scale 2D geologic domain in which sedimentologic heterogeneity has been resolved at sub-millimeter resolution. As the degree of heterogeneity increased in synthetic media, CO2 migration patterns exhibited a spectrum of structures, from ‘dispersed’ capil lary fingers with minimal rock contact to back-filled’compact’ distributions of saturation with much larger storage efficiency

Generalized adhesion maps for predicting thin film transitions

Abstract Ž . Thin film transition TFT phenomena are of special interest to the petroleum industry. After crude-oil is trapped in reservoir rocks, it can alter the wettability of the rock surface, with profound implications for the subsequent transport of fluids. Correlation between the TFT and wettability alteration is qualitatively evident from many experiments. It is not clear, however, whether the TFT is a sufficient condition for wettability alteration. In this work we describe a generalized adhesion map, which locates the TFT in parameter space. Comparison of these maps with laboratory studies indicates that wettability alteration involves other mechanisms in addition to the TFT.

Representative Farms Economic Outlook for the December 2007 FAPRI/AFPC Baseline

The farm level economic impacts of the Farm Security and Rural Investment Act of 2002 (2002 Farm Bill) on representative crop, dairy, and livestock operations are projected in this report. The analysis was conducted over the 2007-2012 planning horizon using FLIPSIM, AFPC’s whole farm simulation model. Data to simulate agricultural operations in the nation’s major production regions came from two sources: • Producer panel cooperation to develop economic information to describe and simulate representative crop, livestock, and dairy farms. • Projected prices, policy variables, and input inflation rates from the Food and Agricultural Policy Research Institute (FAPRI) December 2007 Baseline. The FLIPSIM policy simulation model incorporates the historical risk faced by agricultural producers for prices and production. This report presents the results of the December 2007 Baseline in a risk context using selected simulated probabilities and ranges for annual net cash farm income values. The probability of a farm experiencing a negative ending cash balance and the probability of a farm losing real net worth are included as indicators of the cash flow and equity risks facing producers through the year 2012. This report is organized into ten sections. The first section summarizes the process used to develop the representative farms and the key assumptions utilized for the farm level analysis. The second section summarizes the FAPRI December 2007 Baseline and the policy and price assumptions used for the representative farm analyses. The third through sixth sections present the results of the simulation analyses for feed grain, wheat, cotton, and rice farms. The seventh and eighth sections summarize simulation results for dairy and cattle. Two appendices constitute the final sections of the report. Appendix A provides tables to summarize the physical and financial characteristics for each of the representative farms. Appendix B provides the names of producers, land grant faculty, and industry leaders who cooperated in the panel interview process to develop the representative farms.

Development of Reacted Channel During Flow of CO2 Rich Water Along a Cement Fracture

AbstractLab scale experiments were performed to characterize how coupling between reaction and flow affect time-dependent flux of CO2-rich water along leaky wells. The core flow system applies confining stress to a cement core with a single tensile fracture while CO2-rich water is injected at constant rate and elevated pore pressure. Results show no significant variation in pressure differential, despite the development of a texturally distinct calcium depleted channel along the fracture surfaces which is bounded by thin rims of precipitation. Silicon rich material remains in the channel and prevents wormhole development and large increases in aperture. Implications for time-dependent CO2 leakage are that even with high fluid flux, the leak does not get appreciably worse

Walking and Walkability: Is Wayfinding a Missing Link? Implications for Public Health Practice

Research on walking and walkability has yet to focus on wayfinding, the interactive, problem-solving process by which people use environmental information to locate themselves and navigate through various settings