NEW APPROACHES TO DETECTION AND CORRECTION OF SUPPRESSED VITRINITE REFLECTANCE

1997 ◽  
Vol 37 (1) ◽  
pp. 524 ◽  
Author(s):  
J. Newman
Keyword(s):  
Organic Matter ◽  
Vitrinite Reflectance ◽  
Sedimentary Rocks ◽  
Nitrogen Atmosphere ◽  
Source Rocks ◽  
Coal Seams ◽  
A New Technique ◽  
Thermal Indicators ◽  
Bulk Chemistry ◽  
Made In

Vitrinite reflectance is commonly used as an indicator of thermal history and the likely maturity of source rocks. However, comparison of reflectance with other thermal indicators, and assessment of downhole gradients, indicate that vitrinites sometimes have anomalously low reflectance. This phenomenon is referred to as suppression, and can affect vitrinite in both marine and terrestrial sedimentary rocks, and in coal seams. For coals it is possible to diagnose and correct reflectance suppression using bulk chemistry; however, dispersed organic matter in sedimentary rocks requires a petro- logical approach. Therefore, a new technique has been developed combining reflectance with quantitative vitrinite fluorescence (VRF). A VRF plot allows objective differentiation of sedimentary Type III and IV organic matter into suppressed vitrinite, normal vitrinite, recycled vitrinite, and inertinite, based on graphical relationships. This takes the guesswork out of vitrinite identification and overcomes the problem of suppression. Measurements are made in a nitrogen atmosphere to avoid fluorescence alteration. Examples of VRF plots show that fresh samples are not essential for vitrinite fluorescence, as previously assumed.

COAL AS A SOURCE OF OIL AND GAS: A CASE STUDY FROM THE BASS BASIN, AUSTRALIA

2003 ◽  
Vol 43 (1) ◽  
pp. 117 ◽  
Author(s):  
C.J. Boreham ◽  
J.E. Blevin ◽  
A.P. Radlinski ◽  
K.R. Trigg
Keyword(s):  
Organic Matter ◽  
Oil And Gas ◽  
Middle Eocene ◽  
Vitrinite Reflectance ◽  
Mineral Resources ◽  
Sedimentary Basins ◽  
Source Rocks ◽  
Gas Generation ◽  
Australian Context ◽  
Effective Source

Only a few published geochemical studies have demonstrated that coals have sourced significant volumes of oil, while none have clearly implicated coals in the Australian context. As part of a broader collaborative project with Mineral Resources Tasmania on the petroleum prospectivity of the Bass Basin, this geochemical study has yielded strong evidence that Paleocene–Eocene coals have sourced the oil and gas in the Yolla, Pelican and Cormorant accumulations in the Bass Basin.Potential oil-prone source rocks in the Bass Basin have Hydrogen Indices (HIs) greater than 300 mg HC/g TOC. The coals within the Early–Middle Eocene succession commonly have HIs up to 500 mg HC/g TOC, and are associated with disseminated organic matter in claystones that are more gas-prone with HIs generally less than 300 mg HC/g TOC. Maturity of the coals is sufficient for oil and gas generation, with vitrinite reflectance (VR) up to 1.8 % at the base of Pelican–5. Igneous intrusions, mainly within Paleocene, Oligocene and Miocene sediments, produced locally elevated maturity levels with VR up to 5%.The key events in the process of petroleum generation and migration from the effective coaly source rocks in the Bass Basin are:the onset of oil generation at a VR of 0.65% (e.g. 2,450 m in Pelican–5);the onset of oil expulsion (primary migration) at a VR of 0.75% (e.g. 2,700–3,200 m in the Bass Basin; 2,850 m in Pelican–5);the main oil window between VR of 0.75 and 0.95% (e.g. 2,850–3,300 m in Pelican–5); and;the main gas window at VR >1.2% (e.g. >3,650 m in Pelican–5).Oils in the Bass Basin form a single oil population, although biodegradation of the Cormorant oil has resulted in its statistical placement in a separate oil family from that of the Pelican and Yolla crudes. Oil-to-source correlations show that the Paleocene–Early Eocene coals are effective source rocks in the Bass Basin, in contrast to previous work, which favoured disseminated organic matter in claystone as the sole potential source kerogen. This result represents the first demonstrated case of significant oil from coal in the Australian context. Natural gases at White Ibis–1 and Yolla–2 are associated with the liquid hydrocarbons in their respective fields, although the former gas is generated from a more mature source rock.The application of the methodologies used in this study to other Australian sedimentary basins where commercial oil is thought to be sourced from coaly kerogens (e.g. Bowen, Cooper and Gippsland basins) may further implicate coal as an effective source rock for oil.

scholarly journals Organic geochemical and palynological studies of the Maastrichtian source rock intervals in Bida Basin, Nigeria: implications for hydrocarbon prospectivity

2020 ◽  
Vol 10 (8) ◽  
pp. 3191-3206
Author(s):  
Olusola J. Ojo ◽  
Ayoola Y. Jimoh ◽  
Juliet C. Umelo ◽  
Samuel O. Akande
Keyword(s):  
Organic Matter ◽  
Source Rock ◽  
Vitrinite Reflectance ◽  
Source Rocks ◽  
High Yield ◽  
Thermal Maturity ◽  
Hydrocarbon Source Rock ◽  
Moderate Amount ◽  
Oxic Condition ◽  
Freshwater Swamp

Abstract The Patti Formation which consists of sandstone and shale offers the best potential source beds in the Bida Basin. This inland basin is one of the basins currently being tested for hydrocarbon prospectivity in Nigeria. Fresh samples of shale from Agbaja borehole, Ahoko quarry and Geheku road cut were analysed using organic geochemical and palynological techniques to unravel their age, paleoecology, palynofacies and source bed hydrocarbon potential. Palynological data suggest Maastrichtian age for the sediments based on the abundance of microfloral assemblage; Retidiporites magdalenensis, Echitriporites trianguliformis and Buttinia andreevi. Dinocysts belonging to the Spiniferites, Deflandrea and Dinogymnium genera from some of the analysed intervals are indicative of freshwater swamp and normal sea conditions. Palynological evidence further suggests mangrove paleovegetation and humid climate. Relatively high total organic carbon TOC (0.77–8.95 wt%) was obtained for the shales which implies substantial concentration of organic matter in the source beds. Hydrocarbon source rock potential ranges from 0.19 to 0.70 mgHC/g.rock except for a certain source rock interval in the Agbaja borehole with high yield of 25.18 mgHC/g.rock. This interval also presents exceptionally high HI of 274 mgHC/g.TOC and moderate amount of amorphous organic matter. The data suggests that in spite of the favourable organic matter quantity, the thermal maturity is low as indicated by vitrinite reflectance and Tmax (0.46 to 0.48 Ro% and 413 to 475 °C, respectively). The hydrocarbon extracts show abundance of odd number alkanes C27–C33, low sterane/hopane ratio and Pr/Ph > 2. We conclude that the source rocks were terrestrially derived under oxic condition and dominated by type III kerogen. Type II organic matter with oil and gas potential is a possibility in Agbaja area of Bida Basin. Thermal maturity is low and little, or no hydrocarbon has been generated from the source rocks.

UPPER CAMBRIAN AND TREMADOCIAN SEDIMENTS IN THE NAROL AREA (SOUTHERN LUBLIN REGION) – SOURCE AND RESERVOIR OF SHALE GAS?

2016 ◽  
pp. 61-86
Author(s):  
Magdalena Sikorska-Jaworowska
Keyword(s):  
Organic Matter ◽  
Shale Gas ◽  
Vitrinite Reflectance ◽  
Clay Fraction ◽  
Source Rocks ◽  
Hydrocarbon Migration ◽  
Upper Cambrian ◽  
Carbonate Cement ◽  
Small Admixture ◽  
Quartz Cement

Petrologic investigations of Upper Cambrian and Tremadocian deposits were carried out in the Narol region (southern Lublin region) in prospecting for shale gas accumulations. The observations and analyses were made using a polarizing microscope, luminoscope (CL) and scanning microscope (BSE, SE, EDS, SEM-CL). The following analyses were performed: CL-spectral analysis of quartz, X-ray structural analysis of clay fraction, and pyrolytic analysis of organic matter. The rocks under study are represented mainly by clay-silt shales with sandy interbeds. They belong to the epicontinental siliciclastic association deposited on an extensive shelf subjected to tidal and storm action. The shales consist largely of illite, and the silt fraction is represented by quartz with a small admixture of feldspars. Quartz cement is common (growths and aggregates of authigenic quartz), while carbonate cement (calcite, Fe-dolomite/ ankerite and siderite), as well as pyrite, kaolinite and phosphate cements are rare. The shales reveal microporosity in the form of “microchannels” paralleling illite plates, and within mica packets. The micropores (1–2 µm in size) are observed in both the carbonate cement and organic matter. As a result of deep burial and intense diagenetic processes, the organic matter has undergone strong alteration (max. Ro = 2.5%). The vitrinite reflectance index and pyrolitic analysis of organic matter, as well as the highly ordered illite structure, indicate the maximum palaeotemperatures in the range of 120–150°C. The rocks show numerous fractures healed with carbonates and/or quartz. Some of the fractures that run parallel to the lamination (or more rarely those running perpendicular or at a high angle) have remained open and are potential pathways of hydrocarbon migration. Pyrolytic analysis shows that the shales do not represent source rocks. It is supposed that they do not represent reservoirs for unconventional hydrocarbon accumulations.

The Scotian Basin offshore Nova Scotia: thermal history and provenance of sandstones from apatite fission track and 40Ar/39Ar data

1992 ◽  
Vol 29 (5) ◽  
pp. 909-924 ◽  
Author(s):  
A. M. Grist ◽  
P. H. Reynolds ◽  
M. Zentilli ◽  
C. Beaumont
Keyword(s):  
Nova Scotia ◽  
Thermal History ◽  
Fission Track ◽  
Vitrinite Reflectance ◽  
Source Rocks ◽  
Apatite Fission Track ◽  
Eastern Canada ◽  
Grenville Province ◽  
Thermal Indicators ◽  
Fission Track Ages

Apatite fission track and 40Ar/39Ar age spectrum data from sandstone drill-core minerals taken from depths of 2–5 km in nine wells from the Scotian Basin are presented and interpreted in terms of the thermal history of the basin and the provenance of its sediments. The focus of the study is a comparison of the data from these thermochronometers with each other and with previously published vitrinite reflectance and aromatization–isomerization (A–I) reactions in biomarker compounds from the same or nearby wells.Apatite fission track ages are generally in agreement with expectations in that they trend to zero at a depth of ~4 km (corrected bottom-hole temperature ~120 °C). Shallower (lower present temperature) samples are partially annealed; the degree of partial annealing correlates closely with the degree of A–I reactions. Both thermal indicators are activated over the temperature range 60–120 °C.Samples from two wells, Mic Mac J-77 and Erie D-26, are anomalous. They are more annealed than present formation temperatures would predict, an anomaly that is also indicated by the A–I data. These samples are interpreted as having experienced higher than present temperatures subsequent to deposition, possibly resulting from the passage of hot fluids related to localized volcanism or the sudden venting of an overpressured reservoir.K-feldspars record minor (< 20%) argon loss as a result of burial heating in the basin only at the greatest depths of the sampled range (> 4.3 km). This result is in agreement with the thermal models of the Scotian Basin and extrapolation of the A–I and fission track data to greater depths. The inferred argon loss implies an activation energy of 40 ± 4 kcal/mol for the smallest diffusion domains.The argon age spectra for samples that have not lost argon during residence in the basin provide evidence on the provenance of the sediments. K-feldspars from the Early Cretaceous Missisauga Formation have spectra that are similar to those obtained from K-feldspars from the Grenville Province of the Canadian Shield, whereas muscovites from the same formation give Cambrian to Carboniferous argon ages (mean 387 Ma), an indication of contributions from other source rocks. Corresponding data from the Jurassic Mohican Formation are similar to those reported for plutons from the southern Nova Scotia mainland (ca. 250–350 Ma argon ages). By implication, the Mohican Formation, which is the earliest postrift deposit, was derived from local sources inferred to be adjacent flank uplifts, whereas the Missisauga Formation was derived in part either directly or indirectly from the Grenvillian-aged interior of eastern Canada.

Origin of hydrocarbons in the Bach Ho field (The Vietnamese shelf)

2021 ◽  
pp. 4-13
Author(s):  
V. Kerimov ◽  
◽  
R. Mustaev ◽  
Vu Nam Hai ◽  
◽  
...  
Keyword(s):  
Organic Matter ◽  
Distinctive Feature ◽  
Sedimentary Rocks ◽  
Crystalline Basement ◽  
Source Rocks ◽  
Sedimentary Sequences ◽  
Geochemical Study ◽  
The World ◽  
Sedimentary Source ◽  
Hydrocarbon Distribution

This article presents the results of a geochemical study of oil on the Vietnam shelf (Cuu Long basin), including those in the crystalline basement. The Bach Ho field oils in the basement have a hydrocarbon distribution that is no different than oil of numerous accumulations in Oligocene and Miocene sedimentary sequences. Similar to the organic origin oils of the world, oils from the Bach Ho field lack regular isoprenanes С12 and С17 and cheilanthanes (tri-cyclic terpanes) С22 and С27. A distinctive feature of these oils is a large amount of cheilanthanes С19-С29, and large neo-adiantane to adiantane and hopanes to steranes ratios. All these parameters indicate a large bacterial contribution in the generation of these oils. Studies have shown the similarity between oil biomarker parameters and the organic matter of sedimentary rocks, which supports the organic nature of the oils in the basement fields on the Vietnam shelf. It is shown that the hydrocarbon accumulations in the basement complexes of the Cuu Long basin are in a secondary occurrence, and their origin was the organic matter of the sedimentary source rocks.

scholarly journals Burial history, thermal history and hydrocarbon generation modelling of the Jurassic source rocks in the basement of the Polish Carpathian Foredeep and Outer Carpathians (SE Poland)

2012 ◽  
Vol 63 (4) ◽  
pp. 335-342 ◽  
Author(s):  
Paweł Kosakowski ◽  
Magdalena Wróbel
Keyword(s):  
Organic Matter ◽  
Thermal History ◽  
Vitrinite Reflectance ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Thermal Maturity ◽  
Burial History ◽  
Se Poland ◽  
Carpathian Foredeep ◽  
Outer Carpathians

Burial history, thermal history and hydrocarbon generation modelling of the Jurassic source rocks in the basement of the Polish Carpathian Foredeep and Outer Carpathians (SE Poland)Burial history, thermal maturity, and timing of hydrocarbon generation were modelled for the Jurassic source rocks in the basement of the Carpathian Foredeep and marginal part of the Outer Carpathians. The area of investigation was bounded to the west by Kraków, to the east by Rzeszów. The modelling was carried out in profiles of wells: Będzienica 2, Dębica 10K, Góra Ropczycka 1K, Goleszów 5, Nawsie 1, Pławowice E1 and Pilzno 40. The organic matter, containing gas-prone Type III kerogen with an admixture of Type II kerogen, is immature or at most, early mature to 0.7 % in the vitrinite reflectance scale. The highest thermal maturity is recorded in the south-eastern part of the study area, where the Jurassic strata are buried deeper. The thermal modelling showed that the obtained organic matter maturity in the initial phase of the "oil window" is connected with the stage of the Carpathian overthrusting. The numerical modelling indicated that the onset of hydrocarbon generation from the Middle Jurassic source rocks was also connected with the Carpathian thrust belt. The peak of hydrocarbon generation took place in the orogenic stage of the overthrusting. The amount of generated hydrocarbons is generally small, which is a consequence of the low maturity and low transformation degree of kerogen. The generated hydrocarbons were not expelled from their source rock. An analysis of maturity distribution and transformation degree of the Jurassic organic matter shows that the best conditions for hydrocarbon generation occurred most probably in areas deeply buried under the Outer Carpathians. It is most probable that the "generation kitchen" should be searched for there.

scholarly journals Geochemistry and petrology of selected sediments from Bukit Song, Miri, Sarawak, Malaysia, with emphasis on organic matter characterization

2021 ◽  
Vol 11 (10) ◽  
pp. 3663-3688
Author(s):  
Amin Tavakoli
Keyword(s):  
Organic Matter ◽  
Depositional Environment ◽  
Vitrinite Reflectance ◽  
Xrd Analysis ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Thermal Maturity ◽  
Petroleum Potential ◽  
Type Iv ◽  
Two Samples

AbstractThe aim of this study is to provide a better understanding of the type of source input, quality, quantity, the condition of depositional environment and thermal maturity of the organic matter from Bukit Song, Sarawak, which has not been extensively studied for hydrocarbon generation potential. Petrological and geochemical analyses were performed on 13 outcrop samples of the study location. Two samples, having type III and mixed kerogen, showed very-good-to-excellent petroleum potential based on bitumen extraction and data from Rock–Eval analysis. The rest of the samples are inert—kerogen type IV. In terms of thermal maturity based on vitrinite reflectance, the results of this paper are akin to previous studies done in the nearby region reported as either immature or early mature. Ph/n-C18 versus Pr/n-C17 data showed that the major concentration of samples is within peat coal environment, whilst two samples were associated with anoxic marine depositional environment, confirmed by maceral content as well. Macerals mainly indicated terrestrial precursors and, overall, a dominance of vitrinite. Quality of the source rock based on TOC parameter indicated above 2 wt. % content for the majority of samples. However, consideration of TOC and S2 together showed only two samples to have better source rocks. Existence of cutinite, sporinite and greenish fluorescing resinite macerals corroborated with the immaturity of the analysed coaly samples. Varying degrees of the bitumen staining existed in a few samples. Kaolinite and illite were the major clays based on XRD analysis, which potentially indicate low porosity. This study revealed that hydrocarbon-generating potential of Bukit Song in Sarawak is low.

PETROLEUM GEOCHEMISTRY OF THE MURTA MEMBER, MOOGA FORMATION, AND ASSOCIATED OILS, EROMANGA BASIN

1989 ◽  
Vol 29 (1) ◽  
pp. 114 ◽  
Author(s):  
T.G. Powell ◽  
C.J. Boreham ◽  
D.M. McKirdy ◽  
B.H. Michaelsen ◽  
R.E. Summons
Keyword(s):  
Organic Matter ◽  
Vitrinite Reflectance ◽  
Hydrocarbon Composition ◽  
Source Rocks ◽  
Marine Oils ◽  
Algal Organic Matter ◽  
Conventional Oil ◽  
Effective Source ◽  
Eromanga Basin ◽  
Chemical Evidence

An investigation has been made of the source potential, degree of maturation and hydrocarbon composition of selected oils and sediments in the Murta Member in ATP 267P and the Moomba and Napacoongee- Murteree Blocks (PEL 5 and 6), Eromanga Basin. Shales in the Murta Member contain low amounts (up to 2.5% TOC) of terrestrial oil- prone organic matter (Types II–III) which consists predominantly of sporinite, lipto- detrinite and inertinite with lower amounts of vitrinite, although some samples contain relatively abundant telalginite. Extractable hydrocarbon yields demonstrate that parts of the Murta Member are effective source rocks at present maturation levels, which are at the threshold of the conventional oil window (vitrinite reflectance = 0.5- 0.6% Ro).Oils from Murta reservoirs in ATP 267P (Kihee, Nockatunga and Thungo) all show the characteristics found by previous analyses of many Murta oils, namely paraffinic, low wax, and high pristane- to- phytane ratios. In contrast Murta oils from Limestone Creek and Biala are waxy. All oils show chemical evidence of generation at relatively low maturation levels. Gas chromatograms of the saturate fractions from the best source facies show the same characteristics noted for the low- wax oils. Samples with lower source potential in contrast contain relatively abundant waxy n- alkanes. Methylphenan- threne Indices and biomarker maturation indicators obtained from the oils show the same values as were measured on sediment samples from the Murta. Hence the oils could not have been derived from deeper, more mature source rocks. The distribution of biomarkers in the low- wax oils is also consistent with an origin from the Murta Member. A corresponding source facies for the high- wax oils has not yet been located. However, chemical maturation indices also suggest a source in the Murta Member or in immediately adjacent strata.The unusual circumstances represented by the Murta oils (low maturity, low- wax terrestrial oils) provide evidence for bacterial contribution to the source material for non- marine oils. Both the low- wax oils and the best source facies contain abundant hydrocarbons derived from bacterial precursors. This bacterial organic matter appears to yield hydrocarbons at an earlier stage of maturation than the predominantly terrestrial plant and algal organic matter with which it is associated. In the case of the Murta Member there are sufficient hydrocarbons generated at relatively low maturity to allow migration to occur. Chemical evidence suggests a low contribution from algal organic matter to the generated hydrocarbons.

scholarly journals Evaluation of Shale Source Rocks and Clay Mineral Diagenesis in the Permian Basin, USA: Inferences on Basin Thermal Maturity and Source Rock Potential

Geosciences ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 381
Author(s):  
Hunter Green ◽  
Branimir Šegvić ◽  
Giovanni Zanoni ◽  
Silvia Omodeo-Salé ◽  
Thierry Adatte
Keyword(s):  
Organic Matter ◽  
Clay Mineral ◽  
Vitrinite Reflectance ◽  
Sedimentary Basins ◽  
Source Rocks ◽  
Petroleum Exploration ◽  
Peak Oil ◽  
Permian Basin ◽  
Thermal Indices ◽  
Rock Eval

The use of mineral diagenetic indices and organic matter maturity is useful for reconstructing the evolution of sedimentary basins and critical assessments for potential source rocks for petroleum exploration. In this study, the relationship of clay mineral diagenesis and organic matter thermal indices (Rock-Eval Tmax) and calculated vitrinite reflectance (%Ro) were used to constrain the maximum burial depths and temperatures of three distinct intervals within the northern Permian Basin, USA. X-ray diffraction of clay fractions (<2 µm) consists of illite, chlorite, and illite-smectite intermediates. Primary clay mineral diagenetic changes progressively increase in ordering from R0 to R1 I-S between 2359.5 and 2485.9 m and the appearance of chlorite at 2338.7 m. Rock-Eval pyrolysis data show 0 to 14 wt% TOC, HI values of 40 to 520 mgHC/g TOC, and S2 values of 0 to 62 mg HC/g, with primarily type II kerogen with calculated %Ro within the early to peak oil maturation window. Evaluation of the potential for oil generation is relatively good throughout the Tonya 401 and JP Chilton wells. Organic maturation indices (Tmax, %Ro) and peak burial temperatures correlate well with clay mineral diagenesis (R0–R1 I-S), indicating that maximum burial depths and temperatures were between 2.5 and 4 km and <100 °C and 140 °C, respectively. Additionally, the use of clay mineral-derived temperatures provides insight into discrepancies between several calculated %Ro equations and thus should be further investigated for use in the Permian Basin. Accordingly, these findings show that clay mineral diagenesis, combined with other paleothermal proxies, can considerably improve the understanding of the complex burial history of the Permian Basin in the context of the evolution of the southern margin of Laurentia.

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