Molecular analysis of petroleum in fluid inclusions: a practical methodology

A method is described for extracting the petroleum from petroleum-bearing fluid inclusions hosted in the diagenetic cements of sedimentary rocks, whilst minimising contamination from petroleum in the pore space. A clean-up technique, involving the addition of extraction standards to the rock prior to analysis, has been developed that allows increased confidence that the hydrocarbons extracted are only from included petroleum and are not mixtures of included petroleum and petroleum (or other organic material) adhering to the surface of the host minerals within the sample. Replicate quantitative analyses indicate that the technique produces highly reproducible results. The problems of analysing included petroleum and the clean-up method development are discussed and examples of analyses of included petroleums from carbonate reservoir and carrier units are given.