Fluid and Gas Geochemistry

During exploration for economic accumulations of hydrocarbons, the chemical and stable isotopic compositions of hydrocarbon and non-hydrocarbon gases have proved to offer great value in reducing risks in both frontier and well-explored basins. Deeply buried source rocks produce natural gas molecules that are preferentially enriched in the heavier isotopes of carbon (13C), nitrogen (15N), and hydrogen (2H), providing the gases with an isotopic fingerprint distinct from that of gases produced by near-surface microbial metabolisms or inorganic sources. In addition to isotopic fingerprints, deeply sourced thermogenic accumulations of methane usually contain minor to moderate proportions of C2+ hydrocarbon gases, assisting in differentiation from microbially produced methane.


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Geological Sciences

Gas Stable Isotope Geochemistry

Gas Origin

Reducing risk depends on finding a trap and determining the probability that migrating petroleum from a mature source rock into a trap has not escaped or is not destroyed. The chemical and isotopic composition of natural gas allows a clear genetic distinction between biogenic (microbial) and thermogenic sources due to the unique fingerprint of each process.

Reservoir Continuity and Frac evaluation

Natural gas data also contains information concerning reservoir connectivity between producing intervals. The stable isotopic composition of discrete intervals can be used to evaluate the fracking height as well as the effectiveness of the fracking process. Stable isotope gas geochemistry typically provides inexpensive data to interpret uncertain geological and/or engineering information. The geochemical approach for assessing gas reservoir compartmentalization is similar to the methods applied to oil accumulations.

Shale Gas and Oil Associated Gas

•Identifying migrated vs. in-situ gas origin.

•Compositional and isotopic ratios from hydrocarbon gas (C1-C5) can predict gas vs. liquid abundance with depth

•Characterizing fracture height stray gas

•Constraining source maturity (in vitrinite-poor intervals).

•Anomalies in Shale Gas (“positive Shift”, isotope reversals- “rollover” effect).

•Ethane Isotope “Reversals” within a single well demonstrates overpressure / effective seals.

•Production allocation from multiple frac stages.

•Identifying Reservoir compartmentalization

•Characterizing gas in shallow non-pay zones (stray gas in aquifers).

Oil Geochemistry

Geochemical characterization of hydrocarbon fluids provides valuable information during exploration, development, and production stages. For example, biomarker molecules (complex molecular fossils derived from known, once-living organisms) can be measured in both crude oils and extracts, allowing the interpretation of their distributions as a function of the type of organic matter, environmental conditions during their deposition, lithology, thermal maturity, biodegradation, etc.

Geochemical fingerprinting

In addition to a myriad of Core Labs’ analytical capabilities, our Geoscience team can help assess the different risk elements of a petroleum system. Expert geochemists can tailor analytical and interpretive programs (covering oil quality-source-maturity-age-alteration history aspects) to cover stringent requirements

Exploration geochemistry

A typical program requires the implementation of oil inversions, oil-oil, and oil-source rock correlations using key biomarkers and stable isotope parameters to create a unique fingerprint for each fluid, a function of their unique genetic and post-genetic histories.

Development and production geochemistry: fluid continuity of reservoirs and allocation of Commingled Production

·Define vertical and lateral reservoir continuity and understand reservoir compartmentalization in oil fields, vertically in a single well or laterally between multiple wells.

·Production allocation in commingled or multi-zone production.

·Graphical and algebraic allocation based on key GC, biomarkers, non biomarkers, and stable Isotope parameters.

·Time-lapse geochemistry over the life of the reservoir.