Data/Analytical Interpretation Report

Basic Interpretation – Standard interpretation of your specific sample data ONLY; does not include any contextual data for the regional area or Basin, or final written report. Includes Projected Source Rock Type, Age, Thermal Maturity Level, and Degree of Biodegradation. Not recommended for companies that do not have a Geochemist on staff.

Complete and Comprehensive Interpretation – Includes standard interpretation of samples analyzed plus comparison/contrast to the associated GeoMark Interpretive Study, or RFDbase data; your data is put into context of the larger Basin/Play to look for trends, oil family identification, source, migration pathways, etc.; includes one detailed digital report.

Biomarkers & Alkyl Aromatics via GCMS/MS (QQQ)

Measures 200+ compounds, with a single injection of crude oil, to determine reservoir or source rock and fluid maturity, giving you and early understanding of parent-child well relationships, well spacing, zonal contribution and production allocation.

Biomarkers via Gas Chromatography Mass Spectrometry

Saturate (branched/cyclic) biomarkers

Aromatic biomarkers

SARA & Molecular Sieve required as a prerequisite

Oil/Extract required sample amount is 0.1 mg for each Saturate and Aromatic

Compound Specific Isotope Analysis

Compound-specific stable isotope measurements, primarily δ13C, are a crucial tool in oil-oil and oil-source rock correlations as well as for understanding the origins and histories of oil reservoirs. At GeoMark we can analyze whole crude oil samples via direct injection into a GC-IRMS allowing us to readily identify a full suite of n-alkanes (>nC-25+) along with the associated cycloalkane, aromatic and isoprenoid peaks. Isotopic evaluation of these additional compound classes reveals trends in maturity and origins which are not identifiable when exclusively assessing the traditional n-alkane package (>n-C12).

Sulfur Isotopes

NSO fraction

Whole Oil

Sulfur isotope signatures (δ34S) are a subtle, yet underused, tool for characterizing and correlating crude oil samples and systems. These signatures are indicative of the origin of the sulfur in oil samples and given that the source of most sulfur in oils is contemporaneous seawater sulfate these signatures can also be indicative of geologic age.  At GeoMark we can analyze sulfur isotope signatures in whole oil samples with a weight % composition as low as 0.05%.

Carbon Isotopes

Sat fraction (requires SARA as a prerequisite)

Aro fraction (requires SARA as a prerequisite)

NSO fraction (requires SARA as a prerequisite)

Asph fraction (requires SARA as a prerequisite)

Whole Oil (does not require SARA as a prerequisite)

Depending on kerogen content, required amount of material is 10mg.

Liquid Chromatography (LC) SARA separation



%Resin (NSO)


Can be done on an oil or extracted rock material. 50 to 100 mg of sample required.

SARA serves as the prerequisite to Saturate and Aromatic GCMS

Metals concentration



Weight % Sulfur

The weight % Sulfur for a given oil is another common ‘bulk property’ and can reflect the oil’s source and quality. Sources containing low concentrations of free iron (i.e. carbonate source rocks) frequently produce oils rich in sulfur. Typically, the amount of sulfur in oils usually decreases with increasing thermal maturity and increases as a result of bacterial degradation. The % Sulfur content is independent of H2S content of an oil sample.

API gravity

API Gravity is a fundamental ‘bulk property’ measurement of an oil’s density and is a metric that’s used across many sub-disciplines within the Oil & Gas Industry. An oil’s API Gravity can reflect the source organic matter or thermal maturity. Typically, higher API gravities indicate advanced thermal maturities while lower API gravities may result from secondary alteration or primary migration of oils of lower relative maturity. When using API data, it’s important to remember that it is typically measured and calculated at “surface conditions” as opposed to other fluid property measurements that simulate reservoir or downhole conditions.