Research Projects
Fundamental processes at the interface between dissimiliar mineral surfaces in fluids - applications to quartz-clay interaction (pressure solution) and precipitation of carbonates on mica: with Prof Jaccob Israelachvili, UCSB Engineering. Clay minerals have been shown to enhance pressure solution of quartz and carbonates. Carbonate minerals and other phases have also been shown to grow selectively within biotite cleavages but not in muscovite. We are using geologic observation to constrain a series of Surface Force Apparatus (SFA), modified SFA to measure and control electrical properties, and AFM laboratory experiments. These results will allow us to understand the cause of enhanced pressure solution at clay-quartz interfaces as well as other effects at clay -fluid interfaces.
Cementation related to fluid flow in faults and fractures, Southern California: constraining the timing, duration, magnitude, and origin: Fluid flow in fracture/faults has been shown as important mechanism for basin scale mass transfer and cementation in coastal Califronia and the San Joaquin basin.. see publications. We are currently studying similar issues in the LA basin and are concentrating on the Newport-Ingelwood fault zone using data from oil fields along the fault.
Mantle Helium Along the
Newport-Inglewood fault
Effect of rapid carbonate crystallization
on isotopic signatures of carbonate
We are investigating the fractionation of stable isotopes (13/12C, 18/16O) between CO2 gas, aqueous CO2 species and carbonate (mainly calcite and the polymorph vaterite). In geologic systems, stable isotopes of carbon are traditionally used for determining the origin or source of the carbon whereas oxygen isotopes are used to determine the temperature of crystallization and/or isotopic composition of the water from which the carbonate formed. In situations where crystallization is rapid, the isotopic systems may be out of equilibrium for the isotopic composition of the fluid and temperature of crystallization. The relevance of the disequilibrium case is interpreting isotopic signatures from carbonate precipitates associated with CO2 sequestration as well as leakage and degassing associated with hydrocarbon systems.
In our studies we have investigated proxies of natural systems including well scales in hydrocarbon production tubing and recently formed calcite speleothems in a man-made tunnel. Crystallization rates are difficult to quantify but resultant precipitates typically have grown at mm/year rates. Results from calcite scales indicate that disequilibrium in the isotopic system results in 1) covariance in 13/12C and 18/16O of the precipitate for CO2 degassing systems in which the CO2 content of the system is limited (degassing of thin fluid film). Carbon isotopes in the precipitate of these systems are typically positive due to loss of the light carbon in the escaping CO2. Surprisingly, oxygen isotopes are more positive than expected for equilibrium with the water due to light isotopes being stripped by the rapid loss of CO2 .
Our newest results are from experiments by Calera Corporation to artificially sequester CO2 from coal combustion. In contrast to the proxies described above, precipitation is extremely rapid, (e.g. mixing of calcium into a high pH, CO3= charged fluid) and the precipitate has extremely light carbon and oxygen values, up to 20 per mil lighter than expected for equilibrium. We have observed these extreme cases in both the Calera experiments (calcite precipitate) and in a few well bores (vaterite precipitate). The latter involves changing fluid composition whereas the latter appears to involve degassing. In both cases the carbon and oxygen isotopic values of the precipitates are more than 10 to 20 per mil lighter than equilibrium with the fluid. These observations suggest that during extremely rapid crystallization rates the low mass light isotopes are preferentially incorporated into the carbonate. Apparently, the light isotopes can reach the reaction site more readily than the heavier isotopes once crystallization rates exceed some threshold rate. We are currently conducting experiments to determine the relation between crystallization rate, carbonate poly morph type, and stable isotopic composition, by precipitating via one of three precipitation methods: CO2 off-gassing, supersaturation of CO3= in strongly basic solutions, or addition of CO2(g) at neutral pH.
Spontaneous combustion in landslides
Spontaneous combustion can occur in landslides as a result of rapid oxidation of newly exposed material undergoes net oxidation exothermic reactions. Several natural examples of these have been studied one which heated to 250C and another to in excess of 800C. Potential reactions involve oxidation of Fe sulphides and organic matter in the shale. The process of spontaneous combustion is being studied in these field examples and some laboratory experiments are being planned.
Hydrocarbon Production from the South Ellwood Oil Field (Platform Holly) and the Effects on Naturally Occurring Oil and Gas Seeps