Petroleum Geochemistry Division – Characterisation of Liquid & Extracted Hydrocarbons...

Whole Oil Analysis

GEOTECH’s whole oil GC-MS protocol provides a fingerprint of the entire oil from C4 to C31. The technique is tailored primarily to the analysis of gasoline range components. Several parameters are calculated from the gasoline range data to characterise the extent of alteration of a crude oil by secondary processes such as water washing and biodegradation. Wax content can also be determined from whole oil GC-MS, though detailed analysis of waxes is more accurately carried out by HTGC (high temperature GC). This technique is routinely performed at GEOTECH and determines hydrocarbons up to C100+.

Whole Extract GC-MS

Whole extract GC-MS provides a chromatogram of all compounds which are solvent extractable and GC-able. This analysis is particularly useful for identifying the presence of polar contaminants which are removed by liquid chromatographic separation prior to saturate GC-MS analysis.

Saturate GC-MS Analysis

Calculated parameters derived from saturate GC-MS analysis of an oil or sediment extract yield useful information regarding depositional environment, source of organic matter, extent of biodegradation and alteration via water washing. Saturate GC-MS can also provide an indication as to a samples’ level of thermal maturation.

Branched/Cyclic GC-MS Analysis

Branched / cyclic compounds are isolated from the saturate fraction using molecular sieving techniques and are analysed by GC-MS (SIM). Biomarker distributions and various calculated parameters provide detailed information regarding source, maturity, level of biodegradation and depositional environment. Mass fragmentograms are provided to illustrate the key biomarker distributions.

Aromatic GC-MS Analysis

The aromatic fraction of an oil or extract is analysed by GC-MS (SIM). Calculated parameters derived from aromatic data, such as the Methylphenanthrene Index (MPI) and calculated vitrinite reflectance equivalence, provide useful information about sample maturity. The contribution of higher plant material can be inferred via calculation of the Higher Plant Index (HPI). The distribution of aromatic components also allows for determination of extent of alteration through in-reservoir mixing, migration contamination and biodegradation. Mass fragmentograms are provided to illustrate the distributions key aromatic components.

More specialised analyses can also be conducted to provide more comprehensive information regarding water contact history, maturity and biodegradation. These include analysis of selected components, for example phenols and mono- and triaromatic steranes.

Compound Specific and Bulk Isotope Analysis

Compound specific isotope analysis (CSIA) and bulk carbon isotope determination can be performed on both sediment extracts and crude oils. Isotope data provide information pertaining to source and maturity of organic matter and are particularly useful for incorporation into oil-oil and oil-to source rock correlation studies.