VOLUMETRIC RECONSTRUCTION OF INDIVIDUAL OIL INCLUSIONS BY CONFOCAL SCANNING LASER MICROSCOPY

The composition of oil trapped in fluid inclusions cannot be accuratel y determined with conventional techniques. Consequently, pressure and temperature trapping conditions in petroleum environments will only be established by a combination of volumetric and homogenisation-tempera ture data. Therefore, analytical procedures and limitations of Confoca l Scanning Laser Microscopy (CSLM) have been determined for the volume tric approximation of oil inclusions. The volumetric analysis of an oi l inclusion has been obtained using a confocal BIG-RAD inverted scanni ng laser microscope. 68 focus planes spaced at 1 mu m have been acquir ed and computerised. Fluorescence image processing (thresholding) allo ws the oil volume to be estimated. Contouring of each focus plane and surface modelling by GOCAD software to produce a three-dimensional mod el of the inclusion revealed optical aberration at the level of the va pour bubble. Consequently, the vapour bubble may be approximated as a sphere and a gas vol.% can be calculated from different estimate proce dures (voxel counting, surface modelling). The result has shown that t he average n-alkane composition corresponding to the estimated gas vol .% of the inclusion is close to the average n-alkane composition deduc ed by FT-IR analysis. This work has demonstrated the ability of CSLM t o estimate the volume of the cavity of an oil inclusion to an accuracy better than 95%.