Oil Reservoirs
    Gas Maturity


Stable isotope analysis is a critical technique for upstream reservoir exploration through well profiling. Understanding the origin of oil and gas in any new reservoir is an essential requirement for determining its feasibility and suitability for exploitation. As well as making oil-oil correlations for reservoir mapping possible, stable isotope analysis is a key function of any petrochemical service laboratory.

Beyond the exploration of conventional reservoirs, recent plays into unconventional “tight” resources such as shale gas and coal bed methane have a similar need for stable isotope analysis; evaluation of the carbon and hydrogen fingerprints enables petroleum geochemists further insight into this continuing drive for new opportunities.

Oil fractions & natural gases

Compound specific isotope analysis allows highly precise isotopic profiling of oil reservoirs and therefore evaluation of the source of the oil. Knowing the origin of the oil and the extent of its maturity allows the feasibility of any well site to be established. Combined with carbon and hydrogen isotope analysis of natural gases, our exceptional GC-IRMS system and IonOS software, you will find that these time consuming analyses are performed quickly and rapidly, improving your ROI.

Whole oils & sediments

Combining compound specific isotope analysis of oil fractions with bulk isotope analysis is highly complementary for understanding oil origins, but also allows nitrogen, sulfur and oxygen isotope analysis of NSO fractions. Our elemental analysers also offer excellent performance for more refractory samples such as sediments which are able to bring greater insight into basin geochemistry.

Carbonates & DICs

By analyzing sedimentary carbonates from a basin brings greater understanding of the burial processes and diagenesis environment that the oil reservoir has been subjected too. Our iso FLOW system is able to analyse sedimentary carbonates, dissolved inorganic carbonate as well as well waters with high precision. This flexible system is also capable of analysing dissolved nitrates allowing complete hydrogeology of the basin to be established.

Oil & Gas publications using our instruments

Our customers use our instruments to do some amazing research in the oil & gas application field. To show you how they perform their research and how they use our IRMS instruments, we have collected a range of peer-reviewed publications which cite our products. You can find the citations below and then follow the links to the publishing journal should you wish to download the publication.

If you would like to investigate our available citations in more detail, or email the citation list to yourself or your colleagues then take a look at our full citation database.

43 results:

Decoupling δ13C response to palaeoflora cycles and climatic variation in coal: A case study from the Late Permian Bowen Basin, Queensland, Australia
Palaeogeography, Palaeoclimatology, Palaeoecology (2013)
Nikola Van de Wetering, Joan Esterle, Kim Baublys

The Late Permian coal measures of the Bowen Basin, Australia express both environmental and climatic changes that occurred prior to the Permian Triassic (P–T) boundary. In order to decouple the influence of environmental factors (salinity, pH, base level and temperature) from depositional and climatic factors (atmospheric CO2) in organic δ13C, a high resolution study was performed on 24 coal seams (total 24.6 m) in the Late Permian stratigraphy in the northern Bowen Basin. The Late Permian stratigraphy of the Bowen Basin records a transition from deltaic and lacustrine conditions within the Tinowan Formation and Black Alley Shale Formation, to fluvial deposition in the Kaloola and Bandanna Formations. Intermittent volcanism is recorded by tuff layers during periods of peat accumulation. Variations of coal lithotypes were recorded and formed the basis of sampling for petrography and isotope analysis. Coal samples were etched to expose cellular anatomy, and systematically identified to recognise palaeoflora assemblages. When observed within seam, δ13C of the coal varied cyclically (13C enriched-depleted-enriched) as a response to environmental changes expressed in palaeoflora communities. The total range of δ13C was − 26.6‰ to − 21.9‰. The overall trend of δ13C progresses to increasing 13C enrichment, corresponding with dull lithotypes (rich in inertinite) which indicate fluctuations in base level. The 13C enrichment peaks at − 22.5‰ within the Kaloola Member and shifting rapidly toward a depletion (maximum − 26.6‰) of 13C in the upper Bandanna Formation, prior to the P–T boundary. These changes are expressed in palaeoflora communities where ecosystems shifted from dominant Glossopteris flora, to climax community flora including Palaeosmunda, Cycadales and Ginkgo, suited to temperate, early Mesozoic climates. The results of this study represent an insight into the effects of environmental variables on 13C uptake of plants. The identification of flora within coal gives an insight into palaeowetland evolution, and can be partnered with classic petrographical techniques for integrated analysis in coals. Both the geochemistry and the anatomical aspects of coal represent an important tool for future palaeowetland research

Authigenic carbonates from the Darwin Mud Volcano, Gulf of Cadiz: A record of palaeo-seepage of hydrocarbon bearing fluids
Chemical Geology (2012)
Heleen Vanneste, Miriam Kastner, Rachael H. James, Douglas P. Connelly, Rebecca E. Fisher, Boris a. Kelly-Gerreyn, Katja Heeschen, Matthias Haeckel, Rachel a. Mills

Hydrocarbon-rich fluids expelled at mud volcanoes (MVs) may contribute significantly to the carbon budget of the oceans, but little is known about the long-termvariation in fluid fluxes at MVs. The Darwin MV is one of more than 40 MVs located in the Gulf of Cadiz, but it is unique in that its summit is covered by a thick car- bonate crust that has the potential to provide a temporal record of seepage activity. In order to test this idea, we have conducted petrographic, chemical and isotopic analyses of the carbonate crust. In addition a 1-D transport-reaction model was applied to pore fluid data to assess fluid flow and carbonate precipitation at present. The carbonate crusts mainly comprise of aragonite, with a chaotic fabric exhibiting different gener- ations of cementation and brecciation. The crusts consist of bioclasts and lithoclasts (peloids, intraclasts and extraclasts) immersed in a micrite matrix and in a variety of cement types (microsparite, botryoidal, isopa- chous acicular, radial and splayed fibrous). The carbonates are moderately depleted in 13C(δ13C=−8.1 to −27.9‰) as are the pore fluids (δ13C=−19.1 to −28.7‰), which suggests that their carbon originated from the oxidation of methane and higher hydrocarbons, like the gases that seep from theMV today. The car- bonate δ18O values are as high as 5.1‰, and it is most likely that the crusts formed from 18O-rich fluids de- rived from dehydration of clay minerals at depth. Pore fluid modelling results indicate that the Darwin MV is currently in a nearly dormant phase (seepage velocities are b0.09 cm yr−1). Thus, the thick carbonate crust must have formed during past episodes of high fluid flow, alternating with phases of mud extrusion and uplift
Tags: carbon , oxygen , geol , oilg , gashead

Correlation of crude oils and oil components from reservoirs and source rocks using carbon isotopic compositions of individual n-alkanes in the Tazhong and Tabei Uplift of the Tarim Basin, China
Organic Geochemistry (2012)
Shuang Yu, Changchun Pan, Jinji Wang, Xiaodong Jin, Lanlan Jiang, Dayong Liu, Xiuxiang Lü, Jianzhong Qin, Yixiong Qian, Yong Ding, Honghan Chen

Carbon isotopic compositions were determined by GC–IRMS for individual n-alkanes in crude oils and the free, adsorbed and inclusion oils recovered by sequential extraction from reservoir rocks in the Tazhong Uplift and Tahe oilfield in the Tabei Uplift of Tarim Basin as well as extracts of the Cambrian–Ordovician source rocks in the basin. The variations of the δ13C values of individual n-alkanes among the 15 oils from the Tazhong Uplift and among the 15 oils from the Triassic and Carboniferous sandstone reservoirs and the 21 oils from the Ordovician carbonate reservoirs in the Tahe oilfield demonstrate that these marine oils are derived from two end member source rocks. The major proportion of these marine oils is derived from the type A source rocks with low δ13C values while a minor proportion is derived from the type B source rocks with high δ13C values. Type A source rocks are within either the Cambrian–Lower Ordovician or the Middle–Upper Ordovician strata (not drilled so far) while type B source rocks are within the Cambrian–Lower Ordovician strata, as found in boreholes TD2 and Fang 1. In addition, the three oils from the Cretaceous sandstone reservoirs in the Tahe oilfield with exceptionally high Pr/Ph ratio and δ13C values of individual n-alkanes are derived, or mainly derived, from the Triassic–Jurassic terrigenous source rocks located in Quka Depression. The difference of the δ13C values of individual n-alkanes among the free, adsorbed and inclusion oils in the reservoir rocks and corresponding crude oils reflects source variation during the reservoir filling process. In general, the initial oil charge is derived from the type B source rocks with high δ13C values while the later oil charge is derived from the type A source rocks with low δ13C values. The δ13C values of individual n-alkanes do not simply correlate with the biomarker parameters for the marine oils in the Tazhong Uplift and Tahe oilfield, suggesting that molecular parameters alone are not adequate for reliable oil-source correlation for high maturity oils with complex mixing.

Stable carbon isotopic compositions of individual aromatic hydrocarbons as source and age indicators in oils from western Australian basins
Organic Geochemistry (2011)
Ercin Maslen, Kliti Grice, Pierre. Le Métayer, Daniel Dawson, Dianne Edwards

The present study aims to establish the factors controlling the stable carbon isotopic compositions (δ13C) of individual aromatic hydrocarbons analysed by compound specific isotope analysis (CSIA) in crude oils from western Australian petroleum basins of varying age and facies type. This paper reports δ13C values of individual aromatic hydrocarbons, like alkylbenzenes, alkylnaphthalenes, alkylphenanthrenes and methylated biphenyls. The main aims are to confirm the origin (source) and age of these oils based on CSIA of selected aromatic compounds and to understand why the Sofer plot is ineffective in establishing the source of western Australian petroleum systems. The bulk δ13C of saturated and aromatic hydrocarbon fractions of crude oils have been previously used to differentiate sources, however, many Australian crude oils are not classified correctly using this method. The oils were classified as marine by the δ13C values of individual aromatic compounds and as terrigenous based on the bulk δ13C data (Sofer plot). The oils where the δ13C values of 1,6-DMN and 1,2,5-TMN isomers are most negative are indicative of a marine source, whereas oils with a less negative values for the 1,6-DMN and 1,2,5-TMN isomers are derived from marine source rocks that contain a significant terrigenous component. Similarly, oils with the least negative δ13C values for the 1-MP and 1,9-DMP isomers reflect varying inputs of terrigenous organic matter to the their marine source rocks. Plots of P/DBT and Pr/Ph concentration ratios versus δ13C values of DMP, 1,6-DMN, 1,2,5-TMN, 1-MP and 1,9-MP are constructed to establish the relative amount of terrigenous organic matter contributing to the source rock of a series of marine oils. The ratios of P/DBT and Pr/Ph plotted against the δ13C values of the aromatic isomers (such as 1,6-DMN, 1,2,5-TMN, 1-MP and 1,9-MP) provide a novel and convenient way to discriminate crude oils derived from different source rocks that contain varying amounts of marine and terrigenous organic matter.

A new application of headspace single-drop microextraction technique for compound specific carbon isotopic determination of gasoline range hydrocarbons
Organic Geochemistry (2011)
Yun Li, Yongqiang Xiong, Chenchen Fang, Qianyong Liang, Jingru Zhang, Ping’an Peng

In this study, headspace single-drop microextraction (HS-SDME) coupled with gas chromatography–isotope ratio mass spectrometry (GC–IRMS), was employed to determine compound specific carbon isotopic values (δ13C) of gasoline range hydrocarbons. The reproducibility of the method was found to be satisfactory. By comparison with the δ13C values of the twelve target compounds determined using direct injection of their n-C16 solution, no obvious isotopic fractionation was observed during the HS-SDME procedures. Some parameters that could affect the carbon isotopic fractionation, such as ionic strength of working solutions and inlet split ratio, were examined. The results also suggest that these factors had no significant effect on the carbon isotopic determination of gasoline range hydrocarbons. The application of HS-SDME to a crude oil sample proved that this method could be a promising tool for the determination of carbon isotopic values of gasoline range hydrocarbons in oils or aqueous samples.

Molecular and petrographic indicators of redox conditions and bacterial communities after the F/F mass extinction (Kowala, Holy Cross Mountains, Poland)
Palaeogeography, Palaeoclimatology, Palaeoecology (2011)
Leszek Marynowski, Michal Rakociński, Ewelina Borcuch, Barbara Kremer, Brian a. Schubert, a. Hope Jahren

Pyrite framboid diameter analysis and organic geochemistry of the triangularis/crepida boundary section at Kowala (Holy Cross Mountains, Poland) imply suboxic to oxic and sporadically euxinic bottom waters during the Lower Famennian. In addition, morphological web-like structures typical for microbial mats, as well as the recognition of 2α-methylhopanes and monomethyl-alkane cyanobacteria biomarkers is evidenced of microbial activity after the global Frasnian/Famennian (F/F) extinction event. The presence of cyanobacterial mats also suggests suboxic to oxic environments and at the same time photic bottom water conditions. However, isorenieratane and its derivatives were detected in almost all samples. The presence of this well-known biomarker of green sulfur bacteria implies that euxinic conditions were present in the upper part of the water column at least intermittently or that temporal euxinia occurred in the water column. Presence of euxinic conditions is confirmed by the occurrence of small-sized pyrite framboids which were particularly dominant in the lower part of the section. The shift towards low δ13C values in both micritic limestones and in sedimentary organic matter seen at the beginning of the period of diminished photic zone, might reflect an influx of newly respired CO2 to surface waters, caused by enhanced respiration at depth after the F/F transition in the Checiny-Zbrza basin. © 2011 Elsevier B.V.
Tags: carbon , oxygen , geol , oilg , elem , mulitcarb

The role of reservoir mediums in natural oil cracking : Preliminary experimental results in a confined system
Xiao Qilin, S U N Yongge, Zhang Yongdong

Large amounts of data regarding the influence of temperature and pressure on the thermal stability of crude oil have been published; however, the role of reservoir mediums has received little attention. Experiments involving oil cracking in the presence of montmorillonite, illite, calcite, quartz and water were conducted in closed gold tubes to investigate the effects of these reservoir mediums on oil destruction. This was done by screening variations in the chemical and stable carbon isotopic components of nC10+ and gasoline-range hydrocarbons (nC8−) present in various systems. Results indicated that reservoir mediums have an active role in oil cracking under experimental conditions. The concentrations of nC10+ in the cracked residues progressively decreased in systems containing oil+water+illite, oil+water+montmorillonite, oil+water, oil+water+quartz and oil+water+calcite. In comparison with the system containing oil+water, our results indicated a retardation effect for oil cracking in systems in the presence of illite and montmorillonite, and an acceleration effect on oil destruction in systems in the presence of calcite and quartz. nC10+ became increasingly depleted in 13C in systems with oil+water+illite, oil+water+calcite, oil+water+montmorillonite, oil+water+ quartz and oil+water. No obvious correlation was observed between concentrations and stable carbon isotopic components of nC6-nC8 and nC10+ in the individual systems. The discrepancies in chemical and stable carbon isotopic components of nC6-nC8 and nC10+ in the pyrolyzed residues highlighted the important role of reservoir mediums to control carbon-carbon cleavage of nC10+ and then the isomerization, cyclolization and aromatization reactions; as well as governing the occurrence and thermal destruction of nC6-nC8 under experimental conditions. This research may have critical implications in reconstructing chemical kinetic models for natural oil cracking

Assessment of petroleum biodegradation using stable hydrogen isotopes of individual saturated hydrocarbon and polycyclic aromatic hydrocarbon distributions in oils from the Upper Indus Basin, Pakistan
Organic Geochemistry (2009)
Muhammad Asif, Kliti Grice, Tahira Fazeelat

The stable hydrogen isotopic compositions (δD) of selected aliphatic hydrocarbons (n-alkanes and isoprenoids) in eight crude oils of similar source and thermal maturity from the Upper Indus Basin (Pakistan) were measured. The oils are derived from a source rock deposited in a shallow marine environment. The low level of biodegradation under natural reservoir conditions was established on the basis of biomarker and aromatic hydrocarbon distributions. A plot of pristane/n-C17 alkane (Pr/n-C17) and/or phytane/n-C18 alkane (Ph/n-C18) ratios against American Petroleum Institute (API) gravity shows an inverse correlation. High Pr/n-C17 and Ph/n-C18 values and low API gravity values in some of the oils are consistent with relatively low levels of biodegradation. For the same oils, δD values for the n-alkanes relative to the isoprenoids are enriched in deuterium (D). The data are consistent with the removal of D-depleted low molecular weight (LMW) n-alkanes (C14–C22) from the oils. The δD values of isoprenoids do not change with progressive biodegradation and are similar for all the samples. The average D enrichment for n-alkanes with respect to the isoprenoids is found to be as much as 35‰ for the most biodegraded sample. For example, the moderately biodegraded oils show an unresolved complex mixture (UCM), loss of LMW n-alkanes (

Carbon isotopic compositions of 1,2,3,4-tetramethylbenzene in marine oil asphaltenes from the Tarim Basin: Evidence for the source formed in a strongly reducing environment
Science in China Series D: Earth Sciences (2008)
WangLu Jia, PingAn Peng, ZhongYao Xiao

Although 1-alkyl-2,3,6-trimethylbenzenes and a high relative amount of 1,2,3,4-tetramethylbenzene have been detected in marine oils and oil asphaltenes from Tabei uplift in the Tarim Basin, their biological sources are not determined. This paper deals with the molecular characteristics of typical marine oil asphaltenes from Tabei and Tazhong uplift in the Tarim Basin and the stable carbon isotopic signatures of individual compounds in the pyrolysates of these asphaltenes using flash pyrolysis-gas chromatograph-mass spectrometer (PY-GC-MS) and gas chromatograph-stable isotope ratio mass spectrometer (GC-C-IRMS), respectively. Relatively abundant 1,2,3,4-tetramethylbenzene is detected in the pyrolysates of these marine oil asphaltenes from the Tarim Basin. δ 13C values of 1,2,3,4-tetramethylbenzene in the pyrolysates of oil asphaltenes vary from −19.6%. to −24.0%., while those of n-alkanes in the pyrolysates show a range from −33.2%. to −35.1%.. The 1,2,3,4-tetramethylbenzene in the pyrolysates of oil asphaltenes proves to be significantly enriched in 13C relative to n-alkanes in the pyrolysates and oil asphaltenes by 10.8%.–15.2%. and 8.4%.–13.4%., respectively. This result indicates a contribution from photosynthetic green sulfur bacteria Chlorobiaceae to relatively abundant 1,2,3,4-tetramethylbenzene in marine oil asphaltenes from the Tarim Basin. Hence, it can be speculated that the source of most marine oil asphaltenes from the Tarim Basin was formed in a strongly reducing water body enriched in H2S under euxinic conditions.
Tags: carbon , geol , oilg , gaschrom

Source and significance of selected polycyclic aromatic hydrocarbons in sediments (Hovea-3 well, Perth Basin, Western Australia) spanning the Permian–Triassic boundary
Organic Geochemistry (2007)
Kliti Grice, Birgit Nabbefeld, Ercin Maslen

Stable carbon isotopic data for polycyclic aromatic hydrocarbons (PAHs; chrysene and triphenylene, benzo(e)pyrene, 9-methylphenanthrene) in sediments of comparable thermal maturity from a petroleum drill core (Hovea-3 well, Perth Basin, Western Australia) spanning the largest mass extinction event in the past 500 million years (Permian–Triassic boundary) are consistent with an algal kerogen source in the basal Triassic as opposed to a combustion and/or higher-plant source in the underlying Permian sediments. The δ13C values of extractable PAHs are less negative in the Permian inertinitic interval (−24.7‰ to −29.2‰) than the Triassic sapropelic interval (−30‰ to −33.3‰). A strong correlation is evident between δ13C of individual PAHs, δ13C of kerogen and Rock-Eval pyrolysis hydrogen index providing unequivocal evidence that PAH δ13C is mainly controlled by organic matter type. Abundant algal-derived PAHs in basal Triassic sediments may be a global feature; the lack of coal globally in the basal Triassic sediments is also consistent with this observation. The Early Triassic coal gap appears to coincide with the global extinction of peat-forming plants at the end of the Permian, coal did not reappear until the Middle Triassic and Permian levels of plant diversity and thick peat deposits did not recover until the Late Triassic. The PAH isotopic data support the contention that a global anoxic event at the end of the Permian period contributed to the gradual worldwide asphyxiation and ultimate extinction of many marine and terrigenous organisms.