H11J-01
Fluid Flow Simulation For CO2EOR and Sequestration Utilizing Geomechanical Constraints Teapot Dome Oil Field, Wyoming
Mature oil and gas reservoirs are attractive targets for geological sequestration of CO2 because of their potential storage capacities and the possible cost offsets from enhanced oil recovery (EOR). In this work we develop a 3D reservoir model and fluid flow simulation of the Tensleep Formation using geomechanical constraints to evaluate the feasibility of a CO2-EOR injection project at Teapot Dome Oil Field, WY. The objective of this work is to model the migration of the injected CO2 as well as to obtain limits on the rates and volumes of CO2 that can be injected without compromising seal integrity. Teapot Dome is an elongated asymmetrical, basement-cored anticline with a north-northwest axis. It is part of the Salt Creek structural trend, located in the southwestern edge of the Powder River Basin. The Tensleep Fm. in this area consists of interdune deposits such as eolian sandstones, sabkha carbonates, evaporites (mostly anhydrite), and some very low permeability dolomicrites. The average porosity is 0.10 ranging from 0.05-0.20. The average permeability is 30 mD, ranging from 10 100 mD. The average reservoir thickness is 50 ft. The reservoir has strong aquifer drive. In the area under study, the Tensleep Fm. has its structural crest at 1675 m. It presents a 3-way closure trap against a NE-SW fault to the north. We previously carried out a geomechanical stability analysis and found this fault to be able to support the increase in pressure due to the CO2 to be injected, even if the structure was "filled-to-spill". In this work we combine our previous geomechanical analysis, geostatistical reservoir modeling and fluid flow simulations to investigate critical questions regarding the feasibility of a CO2-EOR project in the Tensleep Fm. The analysis takes into consideration the initial trapping and sealing mechanisms of the reservoir, the consequences of past and present oil production on the initial properties, and the potential effect of CO2 injection on both the reservoir and the seal. Finally, we want to predict the long-term oil recovery of the injection site and what will happen in the system once oil production stops.
H11J-02
Integration of Continuous Active-Source Seismic Monitoring and Flow Modeling for CO2 Sequestration: The Frio II Brine Pilot
We present preliminary results from the integrated analysis of continuous active-source seismic monitoring (CASSM) data acquired as part of the Frio II brine pilot CO2 injection experiment. Our approach is to link retrospective 3D multiphase flow modeling (TOUGH2) to a complete suite of synthetic geophysical datasets via an accurate model of the seismic response induced by CO2 emplacement. Through detailed comparison of the Frio II field observations and our synthetic seismic dataset we were able to sequentially refine our flow model, thus gaining insight into the CO2 storage performance characteristics of the Frio site and, potentially, carbon sequestration on a larger scale. In the Frio II crosswell CASSM experiment, the seismic source was located near the top of the formation in the injection well and a string of receivers was located along the observation well, sited updip of the injection well. During the first two days of CO2 injection, seismic velocity along various crosswell raypaths decreased as the CO2 plume migrated. A 3D numerical model of the multiphase, multicomponent fluid flow was developed based on a layered permeability distribution extrapolated from wireline logs and core analyses. This model generated a time-series of simulated saturation distributions which were subsequently transformed into models of time-varying geophysical properties. The petrophysical model used for this transformation couples White's patchy fluid saturation model with NIST's CO2 equation of state and the brine property equations developed by Batzle & Wang. Synthetic seismic travel-time datasets for the true CASSM geometry were calculated using a non-linear eikonal solver, while complete waveforms were generated using a high-order acoustic time-domain finite- difference simulation system. Comparison of calculated and observed seismic travel times constrained the simulated plume evolution, and thereby improved retrospective estimates of the permeability model. In particular, the pattern of arrival of CO2 along various seismic ray paths within the reservoir suggests strongly localized flow of CO2 along preferential paths. Such localized flow may limit capillary trapping, and reduce the rates of dissolution in brine and reaction with rock minerals. http://esd.lbl.gov/co2geostorage/research/geoseq/geoseq.html
H11J-03
Fluid Mechanical Modelling of Carbon Dioxide Sequestration
The flow of supercritical carbon dioxide against an impermeable caprock will be considered from a theoretical and experimental point of view. A series of fundamental problems will be presented, along with some laboratory simulations. It will be shown that in the simplest case, when the caprock is totally impermeable and horizontal, with viscosity differences between the supercritical carbon dioxide and the fluid into which it is intruding neglected, the radius of the spreading of carbon dioxide increases like the square root of time. We will then consider the influence of a sloping caprock, where for time short compared to some critical time, τc, the spreading pool is close to axisymmetric, while for times very much greater than τc it is approximately three times larger in the upslope than cross-slope direction. For typical geological conditions, τc can vary from between days and years, and hence the observed shape will depend on details at the injection site. A discussion of the effects of different viscosities of the intruding and intruded fluid will be presented and the important non- dimensional physical parameters outlined. The talk will conclude with a discussion of very recent research on the effects of heterogeneous porosity in the ambient and an application of the results to the analysis of the observations at Sleipner. The talk will be illustrated by colour movie sequences of experiments and a real desk- top experiment. http://www.itg.cam.ac.uk/people/heh/index.html
H11J-04
Upscaling of Capillary Trapping in a Buoyant Plume: Application to CO2 Sequestration in Aquifers
CO2 sequestration refers to the capture and long-term storage of anthropogenic CO2 in order to limit its emission to the atmosphere. Injection into geological formations is one option to store CO2. Deep saline aquifers are prime candidates for CO2 storage because they have a huge storage capacity and they are widely distributed. One of the major concerns in any sequestration project is the potential leakage of the CO2 into the atmosphere. CO2 tends to migrate to the top of the geologic structure. This upward migration is sometimes delayed or suppressed by low permeability layers that impede the vertical flow of gas hydrodynamic or structural trapping. However, the success of a sequestration project relies to a great extent on the magnitude of capillary trapping (Juanes et al., Water Resour. Res. 2006), in which the CO2 phase is disconnected into an immobile (trapped) fraction. Here, we investigate, by means of laboratory experiments and numerical simulation, the scale dependence of capillary trapping. The basic flow unit is a transparent glass-bead pack a Hele-Shaw cell filled with glass beads. This design enables simple visualization techniques to be used to monitor the flow. The present paper confirms that current field-scale simulation models of CO2 storage overestimate the amount that is actually trapped, because they do not capture the small-scale variability due to viscous and gravity instabilities, and permeability channeling. http://web.mit.edu/juanes/www/
H11J-05
The effect of residual trapping and slope on gravity currents in confined aquifers
Motivated by geological CO2 storage, we present a sharp-interface vertical equilibrium model for the migration of immiscible gravity currents with constant residual trapping in a two-dimensional, sloping, confined aquifer. The continuous loss of residual saturation decreases the current volume over time until the current is exhausted, giving rise to a maximum migration distance and time. Analytic and semi-analytic solutions for the limiting hyperbolic problem are derived. Comparison with numerical solutions show that the limiting solutions are good approximations to the numerical solution for high mobility ratios, M>10, even for Peclet numbers of order unity. For high mobility currents, such as CO2 in an aquifer our analysis shows that the dimension less migration time and distance increase with increasing mobility ratio and decrease with increasing trapped saturation, but they are only a weak function of the slope as long as the slope is finite. In these cases of finite slope the current evolution is divided into two stages, an initial stage of power-law decrease of volume and a later stage when the volume decays very rapidly. This behavior contrasts strongly with the power-law volume evolution of currents in horizontal aquifers. Several large regional saline aquifers are gently sloping, but lack a structural closure. Our results suggest that the efficient residual trapping of CO2 in dipping aquifers may allow CO2 storage, if CO2 is injected far enough from the outcrop of the aquifer.
H11J-06
Measurements and Modeling of Capillary Pressure Behavior for Carbon Dioxide Sequestration Applications in Aquifers
Modeling of storage of carbon dioxide (CO2) in heterogeneous aquifers requires experiments of the capillary pressure as function of temperature and pressure. We present a method with which drainage and imbibition capillary pressures can be measured as a function of saturation at various temperature ( T) and pressure ( P) conditions. The measurements are carried out at ( T, P) conditions of practical interest. The capillary pressure curves are obtained for the unconsolidated sand-distilled-water-CO2 system. The experimental results show a decrease of drainage and imbibition capillary pressure for increasing CO2 pressures and pronounced dissolution rate effects for gaseous CO2. Significant capillary pressure fluctuations and negative values during imbibition are observed at near critical conditions. To understand the effects of dissolution on capillary pressure and the cumulative water production, a quasi-1D, fully implicit numerical model is developed. Moreover, the measurement procedure is validated by this model, which simulates the drainage experiments. The simulator is based on the upstream finite volume method that incorporates the CO2- H2O phase behavior, mass transfer and dissolution of one phase into another.
H11J-07
Detailed Numerical Modeling of Leakage of CO2 Through Wellbores Incorporating Complexities of Wellbore Details and Phase-Change in Large-Scale Reservoir Simulations
One primary measure of performance for any proposed large-scale CO2 sequestration operation will be how the system responds to potential wellbore failure and subsequent CO2 migration during injection of large volumes of CO2. This will require detailed numerical simulations which will incorporate realistic wellbore details and capture near-wellbore conditions in a coarse 3-dimensional grid. In this paper, we will present results of detailed numerical simulations of a large-scale CO2 sequestration operation. The simulations are performed using FEHM, a multi-phase, heat and mass transfer simulator. We have developed a novel, computationally efficient approach to incorporate radial wellbores in a 3-dimensional Cartesian grid. With this approach the radial solution of fluid flow in the vicinity of wellbores is obtained at high grid resolution without a need for well functions such as the Peaceman approximation. The approach provides for flexible incorporation of wellbores in a computational grid without a need for grid refinement. Our study domain includes a hypothetical field site with a heterogeneous storage aquifer and multiple impermeable and permeable strata above it. CO2 output from a typical coal-fired power plant is injected, over a period of 50 years. Simulation of injection and subsequent migration is performed while capturing the physics of non-isothermal, multi-phase fluid flow. Leakage of CO2 through a wellbore within the field is simulated, both during and after the injection period, including any potential phase-change. We explore the sensitivity of predictions of CO2 migration through wellbores to changes in values of parameters such as location of wellbore, completion properties and local rock properties.
H11J-08
Prediction of Groundwater Quality Changes in Response to CO2 Leakage from Deep Geological Storage
If carbon dioxide stored in deep saline aquifers would leak into overlying sources of potable groundwater, the intruding CO2 would lower groundwater pH and thereby enhance the solubility of hazardous inorganic constituents (such as lead or arsenic) present in the aquifer minerals. How and to what extent groundwater quality would be affected depends largely on the initial abundance and distribution of these constituents in the aquifers, as well as on the aquifer mineralogy and the oxidation state. Using the USGS NWIS data base, we are conducting a systematic evaluation of more than 38,000 groundwater quality analyses from aquifers throughout the United States that report non-zero concentrations of selected hazardous constituents. The results of the evaluation are being employed to set up an equilibrium geochemical model of the aquifer chemistry in order to estimate the distribution of various constituents between the aqueous phase and adsorption and ion exchange sites, and in solid solution in primary and secondary minerals. Important qualitative conclusions can be drawn immediately from this evaluation regarding the geochemical vulnerability of the groundwaters. For example, the majority of the samples are saturated with respect to calcite, indicating that these groundwaters may somewhat buffer CO2-related pH changes. For quantitative evaluation, we use the equilibrium geochemical model as a starting point for reactive geochemical transport simulations that predict the impact of CO2 intrusion into a fresh- water aquifer and the related changes to the host rock mineralogy and water chemistry. The resulting concentrations of hazardous constituents in the groundwater are then compared to the EPA specified health- based limits for drinking water. Various sensitivity studies are conducted for different hydrological and geochemical and mineralogical conditions, representative of some major aquifer systems in the United States. Our findings help to understand (1) which aquifer systems and regions of the country might be vulnerable in case of CO2 intrusion, and (2) which inorganic constituents might adversely affect water quality and to what extent.