U41C-0020
Stratigraphy of Citronelle Oil Field, AL: Perspectives from Enhanced Oil Recovery and Potential CO2 Sequestration
The Citronelle Dome is a giant salt-cored anticline in the eastern Mississippi Interior Salt Basin of south Alabama. The dome forms an elliptical structural closure containing multiple opportunities for enhanced oil recovery (EOR) and large-capacity saline reservoir CO2 sequestration. The Citronelle Oil Field, which is on the crest of the dome, has produced more than 168 MMbbl of 42° gravity oil from marginal marine sandstone in the Lower Cretaceous Donovan Sand. Recently, EOR field tests have begun in the northeastern part of the oil field. Citronelle Unit B-19-10 #2 well (Alabama State Oil and Gas Board Permit No. 3232) will serve as the CO2 injector for the first field test. CO2 will be injected into the Upper Donovan 14-1 and 16-2 sandstone units. All well logs in the 4-square-mile area surrounding the test site have been digitized and used to construct a network of nineteen stratigraphic cross sections correlating Sands 12 through 20A in the Upper Donovan. Detailed study of Citronelle cores has shown that depositional environments in the Donovan Sand differed significantly from the earlier model that has guided past development of the Citronelle Field. The cross sections demonstrate the extreme facies heterogeneity of the Upper Donovan, and this heterogeneity is well expressed within the five-spot well pattern where the field test will be conducted. Many other features bearing on the performance of the CO2 injection test have been discovered. Of particular interest is the 16-2 sand, which is interpreted as a composite of two tiers of channel fills. Pay strata are typically developed in the lower tier, and this is where CO2 will be injected. The upper tier is highly heterogeneous and is interpreted to contain sandstone fills of variable reservoir quality, as well as mudstone plugs.
U41C-0021
CO2 Releases from Deep Storage Formations into Drinking Water Aquifers - Assessment of Impacts on Drinking Water Quality
Geological storage of supercritical CO2 is envisioned as a means of mitigating the release of greenhouse gases into the atmosphere. However, the potential exists for CO2 to migrate from the deep geologic formations to overlying aquifers that serve as sources of drinking water, which could lead to geochemical alterations that have detrimental effects on drinking water quality. For example, elevated CO2 levels in drinking water aquifers can enhance the solubility and decrease the sorbed fraction of trace metals and radionuclides to an extent that concentrations may reach undesirable levels at the local scale. Therefore, an assessment of these effects is necessary to determine the risks associated with geologic sequestration of CO2. In this study, the effects of CO2 intrusion into a sandstone aquifer (with and without calcite cement present) on the water chemistry and on the mobility of trace metals and radionuclides were investigated. The aquifer was assumed to be unpolluted such that sorption, not solubility, was likely to be the predominant process controlling heavy metal and radionuclide mobility. Four elements with very different geochemical behaviors were selected for the study - lead, copper, arsenic, and uranium - and sorption was assumed to occur on ferric oxyhydroxides coating the sandstone matrix. Two-dimensional simulations were conducted using the coupled reactive-transport code MULTIFLO to determine the changes in aquifer water chemistry - spatially and temporally - as a function of CO2 flux from a leaking CO2 sequestration aquifer. Lead, copper, arsenic, and uranium Kd values as a function of pH and pCO2 were derived using equilibrium thermodynamic calculations and used to assess the impact of CO2 leakage on heavy metal and radionuclide mobility based on the MULTIFLO results. This work was funded by the Southwest Research Institute Internal Research and Development Project 20- R9826.
U41C-0022
Preliminary results of numerical investigations at SECARB Cranfield, MS field test site
The Southeast Regional Carbon Sequestration partnership sponsored by DOE has chosen the Cranfield, MS field as a test site for its Phase II experiment. It will provide information on CO2 storage in oil and gas fields, in particular on storage permanence, storage capacity, and pressure buildup as well as on sweep efficiency. The 10,300 ft-deep reservoir produced 38 MMbbl of oil and 677 MMSCF of gas from the 1940's to the 1960's and is being retrofitted by Denbury Resources for tertiary recovery. CO2 injection started in July 2008 with a scheduled ramp up during the next few months. The Cranfield modeling team selected the northern section of the field for development of a numerical model using the multiphase-flow, compositional CMG-GEM software. Model structure was determined through interpretation of logs from old and recently-drilled wells and geophysical data. PETREL was used to upscale and export permeability and porosity data to the GEM model. Preliminary sensitivity analyses determined that relative permeability parameters and oil composition had the largest impact on CO2 behavior. The first modeling step consisted in history-matching the total oil, gas, and water production out of the reservoir starting from its natural state to determine the approximate current conditions of the reservoir. The fact that pressure recovered in the 40 year interval since end of initial production helps in constraining boundary conditions. In a second step, the modeling focused on understanding pressure evolution and CO2 transport in the reservoir. The presentation will introduce preliminary results of the simulations and confirm/explain discrepancies with field measurements.
U41C-0023
Carbon Dioxide Stable Isotope Detection of Geological Sequestration Seepage
A priority for geological sequestration measurement, mitigation and verification (MMV) is a means of tracking seepage at concentrations at or below ambient CO2 concentrations. The carbon stable isotope ratio (13C16O2/12C16O2) is a sensitive diagnostic signature of anthropogenic and natural sources of CO2. However, the concentration of 13CO2 is approximately 100 times smaller than 12CO2 and sensitive analytical tools are required to measure the ratio in the field. Frequency modulated spectroscopy (FMS) is an ultra sensitive means of detecting the stable isotopes of CO2 that is conservatively 100x more sensitive than standard absorption spectroscopy. FMS involves directing a tunable diode laser (TDL) through an electro- optical modulator operating in the radio frequency regime producing the original carrier frequency from the TDL (wc) and evenly spaced sidebands (wc plus,minus wm). The species of interest is detected by tuning the TDL and the modulation frequency such that one of the sidebands (wc) interacts with a specific spectral feature. This paper will include experiments involving field measurements using both an in situ and remote FMS prototype instruments. The field site is located in a remote location on the Los Alamos National Laboratory campus were the instruments could monitor natural fluctuations. The in situ instrument was placed in the field site next to the remote instrument. The remote instrument was directed towards a retroreflector located 50m from the laser source signal and back to detector positioned next to the laser. The stable isotope ratio is monitored as the carrier frequency is scanned and the sidebands interact with both CO2 isotopes.
U41C-0024
Continuous Greenhouse Gas and Isotopic Carbon Dioxide Measurements via WS-CRDS Analyzers: Investigations in Real-Time Monitoring at CO2 Geological Storage Sites
A principal risk associated with geologic sequestration of carbon dioxide is leakage of the CO2 back to
the atmosphere (Wilson and Gerard 2007). Since atmospheric CO2 has a large and varying
background concentration, atmospheric monitoring of only CO2 at geologic CO2 storage sites will
be a weak monitoring strategy, with poor detection limits for any leakage of CO2 that may occur. The
sensitivity of leak detection will be greatly improved by including continuous atmospheric measurements of
tracers in the stored fluid body, such as CH4 and isotopes of CO2.
Two analyzers, based on Wavelength-Scanned Cavity Ring Down Spectroscopy (WS-CRDS), one for
simultaneous CH4 and CO2 measurements and one for 13C isotope measurements of
CO2, were recently deployed by CSIRO at the CO2CRC Otway geological storage pilot project in
Victoria, Australia (see link below). At this site, the plan is to pump up to 100,000 tonnes of magmatic
CO2 discovered during natural gas exploration, into an abandoned natural gas well nearby. The
presence of residual natural gas at both source and sink results in a substantial mole fraction of CH4 in
the stored fluid body, making methane an excellent natural tracer for any CO2 that may leak. As
atmospheric CH4 has both a lower background concentration and exhibits less diurnal variability than
CO2, simultaneous measurements of CH4 with CO2 should greatly enhance the sensitivity of
CO2 leak identification.
Continuous monitoring of the stable carbon isotopic ratio (13C) of atmospheric CO2 near the
storage site is also being assessed for its suitability to discriminate between natural variations due to the
local C3-type vegetation (respiring CO2 with δ13C ≈ -26‰) and changes that
might occur if any of the injected CO2 (which has δ13C ≈ -6‰) leaked to the
atmosphere.
Wilson, E. J. and D. Gerard (2007). Risk Assessment and Management for Geologic Sequestration of Carbon
Dioxide. Carbon Capture and Sequestration: integrating technology, monitoring and regulation. E. J. Wilson
and D. Gerard, Blackwell Publishing: 101-125.
http://www.CO2crc.com.au/otway/index.html
U41C-0025
Carbon Dioxide Sequestration Capacity of the Mt Simon Formation
A technique has been developed to better predict the quantity of carbon dioxide that can be sequestered in a formation through solubility or free phase trapping. The technique is being improved to incorporate the potential for carbonate mineral precipitation. The current study evaluates the extent to which the Mt. Simon formation can serve as a trapping reservoir. The Mt. Simon formation was selected for this study because it meets many of the criteria required for sequestration. To determine the capacity of the Mt. Simon formation to trap carbon dioxide as a soluble component, an experiment was conducted in natural Mt. Simon formation brine. The experiment was conducted at 55 degrees Celsius and pressures from 50 to 350 bars, conditions that fall within the range expected for the entire formation. The data collected compare well to existing models that only account for carbon dioxide solubility. Thus, the solubility model can be reliably used to predict dissolved carbon dioxide concentrations for the range of temperatures and pressures expected to be encountered. The capacity of the Mt. Simon formation to sequester dissolved carbon dioxide was calculated using results of the solubility model, estimation of the density of carbon dioxide saturated brine, estimation of the formation porosity, and geographic information system data on the extent of the formation. Results indicate that the Mt. Simon formation can sequester as much as 26 Gt of dissolved carbon dioxide or 255 Gt of free phase carbon dioxide depending on the efficiency of the system. The current estimated annual production of carbon dioxide from power plant emissions of IL, IA and MI is 0.24 Gt. This indicates that the basin could accept the annual emissions of these power plants for approximately 100 years or more if current carbon dioxide production does not increase.
U41C-0026
Northeast Regional Carbon Sequestration Partnership Investigation
Geologic carbon storage is a viable option for the electric power industry in the "Northeast" region to meet
regional and forthcoming federal CO2 cap-and-trade programs. Capturing CO2 emissions and
storing the gas in underground geological formations could significantly reduce the amount of CO2
released to the atmosphere. However, before this can be implemented, site-specific geological research
needs to be conducted to determine which formations are potentially capable of storing the quantity of
CO2 emitted by power plants in the Northeast region. While the target geosequestration formations in
the Northeast may have less storage capacity than those in the Midwest, Southeast or Southwest, the
available capacities may be large enough to sequester a significant fraction of the CO2 produced by
some regional power plants (which are also smaller, individually and in total, than those in the other regions).
The study will also conduct baseline assessments of electric power producer plants and CO2 emission
estimates and create first level screening on potential geologic structures for CO2 sequestration. The
work will establish a general database of "Other Uses" (current industrial and technological
innovations/options), characterize transport issues, both on land and offshore, and, provide general
guidance on the physical and land-use constraint factors of "add-on" capture technologies at existing power
plants.
http://www.epri.com
U41C-0027
Experimental Measurement of Vertical and Horizontal Permeability of Caprocks from the Krechba Field, Algeria and the Controls on their Permeability
Caprock properties play a crucial role in determining the seal capacity of a structure and so are important during exploration, appraisal and field development. Less attention has been paid to caprocks than reservoirs since if petroleum is present, then the seal must be working. However, injection of CO2 to underlying reservoirs will alter the reservoir conditions from those against which the caprock was previously effective. Increased knowledge of the petrological and petrophysical characteristics of caprocks is required in order to lay a foundation to predict the effect of the altered conditions caused by CO2 injection. Vertical (kv) and horizontal (kh) permeability were measured experimentally across a range of effective pressures for an unusually coarse grained, heterogeneous caprock (siltstone) to a natural gas reservoir and current CO2 storage reservoir, from the Krechba Field, Algeria. Permeabilities as low as 10-23m2 were recorded and were in the range of, or lower than typical fine grained siliciclastic caprock lithologies. The permeability was analysed in conjunction with mercury injection porosimetry data, and textural and mineralogical data from traditional light microscopy, backscatter secondary electron microscopy (BSEM) and cathode luminescence (CL) techniques as well as new QEMSCAN techniques to elucidate the controls on permeability. As predicted and measured by previous experimental work on fine grained siliciclastic lithologies, permeability is effectively controlled by porosity, pore size distribution and clay fraction. Permeability generally decreases with decreasing porosity and poresize distribution and increasing clay content. However, scatter in the trends was caused by heterogeneity of the sample leading to large kv and kh ratios. Primary depositional features led to layers of relatively low and high permeability in the samples, with kv controlled by the lowest permeability layer, and kh controlled by highest permeability layer. Thus kh and kv in heterogeneous rocks is not a simple relationship between porosity, pore size distribution and clay fraction, and is dependent upon their distribution.