Dense CO2 (dense + co2)

Distribution by Scientific Domains


Selected Abstracts


Wettability alteration of caprock minerals by carbon dioxide

GEOFLUIDS (ELECTRONIC), Issue 2 2007
P. CHIQUET
Abstract One of the critical factors that control the efficiency of CO2 geological storage process in aquifers and hydrocarbon reservoirs is the capillary-sealing potential of the caprock. This potential can be expressed in terms of the maximum reservoir overpressure that the brine-saturated caprock can sustain, i.e. of the CO2 capillary entry pressure. It is controlled by the brine/CO2 interfacial tension, the water-wettability of caprock minerals, and the pore size distribution within the caprock. By means of contact angle measurements, experimental evidence was obtained showing that the water-wettability of mica and quartz is altered in the presence of CO2 under pressures typical of geological storage conditions. The alteration is more pronounced in the case of mica. Both minerals are representative of shaly caprocks and are strongly water-wet in the presence of hydrocarbons. A careful analysis of the available literature data on breakthrough pressure measurements in caprock samples confirms the existence of a wettability alteration by dense CO2, both in shaly and in evaporitic caprocks. The consequences of this effect on the maximum CO2 storage pressure and on CO2 storage capacity in the underground reservoir are discussed. For hydrocarbon reservoirs that were initially close to capillary leakage, the maximum allowable CO2 storage pressure is only a fraction of the initial reservoir pressure. [source]


Reactive flow of mixed CO2,H2O fluid and progress of calc-silicate reactions in contact metamorphic aureoles: insights from two-dimensional numerical modelling

JOURNAL OF METAMORPHIC GEOLOGY, Issue 7 2003
X. Cui
Abstract Previous models of hydrodynamics in contact metamorphic aureoles assumed flow of aqueous fluids, whereas CO2 and other species are also common fluid components in contact metamorphic aureoles. We investigated flow of mixed CO2,H2O fluid and kinetically controlled progress of calc-silicate reactions using a two-dimensional, finite-element model constrained by the geological relations in the Notch Peak aureole, Utah. Results show that CO2 strongly affects fluid-flow patterns in contact aureoles. Infiltration of magmatic water into a homogeneous aureole containing CO2,H2O sedimentary fluid facilitates upward, thermally driven flow in the inner aureole and causes downward flow of the relatively dense CO2 -poor fluid in the outer aureole. Metamorphic CO2 -rich fluid tends to promote upward flow in the inner aureole and the progress of devolatilization reactions causes local fluid expulsion at reacting fronts. We also tracked the temporal evolution of P-T-XCO2conditions of calc-silicate reactions. The progress of low- to medium-grade (phlogopite- to diopside-forming) reactions is mainly driven by heat as the CO2 concentration and fluid pressure and temperature increase simultaneously. In contrast, the progress of the high-grade wollastonite-forming reaction is mainly driven by infiltration of chemically out-of-equilibrium, CO2 -poor fluid during late-stage heating and early cooling of the inner aureole and thus it is significantly enhanced when magmatic water is involved. CO2 -rich fluid dominates in the inner aureole during early heating, whereas CO2 -poor fluid prevails at or after peak temperature is reached. Low-grade metamorphic rocks are predicted to record the presence of CO2 -rich fluid, and high-grade rocks reflect the presence of CO2 -poor fluid, consistent with geological observations in many calc-silicate aureoles. The distribution of mineral assemblages predicted by our model matches those observed in the Notch Peak aureole. [source]


Synthesis of gradient copolymers with complexing groups by RAFT polymerization and their solubility in supercritical CO2

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2009
Tiphaine Ribaut
Abstract We report the synthesis of new gradient fluorinated copolymers with complexing groups and soluble in supercritical carbon dioxide (scCO2). Poly(1,1,2,2-tetrahydroperfluorodecyl acrylate- co -acetoacetoxyethyl methacrylate) (poly(FDA- co -AAEM)) and poly(1,1,2,2-tetrahydroperfluorodecyl acrylate- co -vinylbenzylphosphonic acid diethylester) (poly(FDA- co -VBPDE)) gradient copolymers were synthesized by reversible addition fragmentation chain transfer polymerization in ,,,,,-trifluorotoluene. Poly(1,1,2,2-tetrahydroperfluorodecyl acrylate- co -vinylbenzylphosphonic diacid) (poly(FDA- co -VBPDA)) gradient copolymer was efficiently obtained by cleavage of the phosphonic ester groups of poly(FDA- co -VBPDE). The cloud points of these gradient copolymers in dense CO2 were measured in a variable volume view cell at temperatures between 25 and 65 °C. The gradient copolymers show very good solubility in compressed CO2 with the decreasing order: poly(FDA- co -AAEM) , poly(FDA- co -VBPDE) > poly(FDA- co -VBPDA). Following a green chemistry strategy, poly(FDA- co -AAEM) gradient copolymer was successfully synthesized in scCO2 with a good control over number-average molecular weight and composition. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5448,5460, 2009 [source]


Non-thermal bacterial inactivation with dense CO2

BIOTECHNOLOGY & BIOENGINEERING, Issue 6 2003
S. Spilimbergo
Abstract The use of CO2 under pressure (dense CO2) is one of the most promising techniques to achieve cold pasteurization and/or sterilization of liquid and solid materials, and is likely to replace or partially substitute currently and widely applied thermal processes. Although the ability of CO2 to inactivate microorganisms has been known since the 1950's, only within the last 15 years it has received special attention, and the scientific and economic interest towards practical applications is presently growing more and more. Here we collect and discuss the relevant current knowledge about the potentials of dense CO2 as a non-thermal technology in the field of microbial inactivation. We summarize the state of the art, including definitions, description of the equipment, relevant applications, in both simple suspensions and complex media, for the treatment of a wide range of microorganisms in both liquid and solid substrates. Finally, we also summarize and discuss the different hypotheses about the mechanisms of inactivation © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng84: 627,638, 2003. [source]