Research project

Project fact sheet

Clumped isotopes in natural samples from industry wells with independent temperature control

Project researcher(s): 
Dr John MacDonald
Project supervisor(s): 
Dr Cédric M. John
February, 2013 - January, 2015

One fundamental parameter in subsurface studies, notably for oil/gas exploration, lies in the reconstruction of the paleo-temperature to which rocks have been submitted during burial. The main paleo-thermometers for carbonates are fluid inclusion (Th)  and oxygen isotopes (δ18O). Both approaches have limitations however.  Fluid inclusions thermometry  requires the occurrence of two-phase (rare below 50°C), rather large inclusions (>10µm), and an evaluation of pressure correction (critical in over-pressured context). The δ18O method can be applied to very small samples (<10µg carbonate) but it requires to know/estimate the δ18O value of the parent diagenetic fluid in order to derive the temperature of formation. The dual dependency of δ18O on both temperature and water composition is often a major challenge in the interperetation of conventional stable isotope studies of carbonates, because in order to calculate one of the two parameters the second parameter (either temperature of fluid composition) needs to be known. 

The carbonate clumped isotope paleothermometer is a novel tool that offers several advantages over conventional isotopes and fluid inclusions. Notably, it is independent of the isotopic composition of the parent fluid, and can be applied even on lithologies where fluid inclusions are absent.  This removes many uncertainties in subsurface interpretation of diagenetic paragenesis and thermal history of rocks/basins.  Clumped isotopes thermometry is a promising new technique for the study of deeply buried reservoirs, and this project aims at testing clumped isotopes in well characterized natural samples taken at reservoir conditions in order to validate theoretical and/or experimental calibrations.