Paleoenvironments and Hydrocarbon Potential of Upper Cretaceous Shales in Agbabu-1 Well, Dahomey Basin SW Nigeria

Upper Cretaceous shales partially exposed in the northern fringes of the Dahomey Basin are well developed in the subsurface in Southwestern part of the basin where Agbau-1 well is sited. These shales were evaluated in respect to their paleoenvironments and potentials for hydrocarbon using foraminiferal assemblages, biomarkers and Rock Eval pyrolysis studies. The dominance of benthonic foraminifera species suggests a shallow marine environment and high percentage of calcareous to arenaceous benthic www.eujournal.org 195foraminifera indicate high water salinity and hypersline environment. Dysoxic oxygen condition is also prevalent probably because most of the benthic foraminifera recovered are epifauna that live in a reduced oxygen condition. 1.90 wt%, 244 mgHC/gTOC and 429℃ average values of total organic carbon, hydrogen index and Tmax reveal that the Upper Cretaceous shales have relatively fair to good organic matter, predominantly Type II-III kerogen and currently immature. Though three is a trend of an increase in maturity down the hole. All the steranes have uniform distributions (C27>C28>C29), suggesting a relatively higher input from the marine red algae and a low level of land plant contribution to the source organic matter. Pristane/phytane ratios and C29/C27 steranes confirmed the organic matter type to be a Type II/III and anoxic source rock depositional condition as well as a reducing diagenetic system in the sediment water column. The Upper Cretaceous shales in Dahomey Basin can be targeted for exploration as an unconventional petroleum resource.

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Source Rock Evaluation of Paleocene Akinbo shale, Eastern Dahomey Basin

International Journal of Advanced Geosciences ◽

10.14419/ijag.v6i1.8236 ◽

2017 ◽

Vol 6 (1) ◽

pp. 34

Author(s):

Dairo Victoria ◽

Asue Onenu

Keyword(s):

Organic Matter ◽

Source Rock ◽

Oil Content ◽

Oxygen Index ◽

Hydrogen Index ◽

Mean Values ◽

Average Value ◽

Dahomey Basin ◽

Source Rock Evaluation ◽

Rock Eval

Selected subsurface core samples of the shale of Akinbo Formation as penetrated by an exploratory well in Ibese, Eastern Dahomey basin were investigated to ascertain the quality and quantity of organic matter, the hydrocarbon potential and kerogen type.The samples were subjected to Total Organic Carbon (TOC) and Rock Eval analyses and various cross plots were generated from the data obtained.The TOC and Free oil content (S1) of all the shale samples range from 0.96wt% to 2.82wt% and 0.07mgHC/g to 0.17mgHC/g with mean values of 1.67wt% and 0.11mgHC/g respectively while the source rock potential (S2) ranges from 0.01mgHC/g to 0.17mgHC/g with an average value of 0.08mgHC/g. Also, the Hydrogen Index (HI) and the Oxygen Index (OI), ranges from 0.35mgHC/g TOC to 16.7mgHC/g TOC and 11.4mgCO/g TOC to 38.33mgCO/g TOC with an average value of 5.77mgHC/g TOC and 19.04mgCO/g TOC respectively. The Production Index (PI) and the Generative Potential (GP) range from 0.38 to 0.94 and 0.12mgHC/g to 0.34mgHC/g with mean values of 0.61 and 0.19mgHC/g respectively.The results obtained from the cross plots of HI versus OI, S2 versus TOC and TOC versus GP; It shows that the shale samples from the Akinbo Formation have good organic matter richness to generate hydrocarbon, dominantly gas prone and from a Type III kerogen.

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Paleoenvironmental Reconstructions using Organic Source Indicators: A Summary of Examples from Sri Lanka

Journal of Tropical Forestry and Environment ◽

10.31357/jtfe.v8i2.3759 ◽

2019 ◽

Vol 8 (2) ◽

Author(s):

A.S. Ratnayake

Keyword(s):

Organic Matter ◽

Sri Lanka ◽

Algal Growth ◽

Land Plant ◽

Model Studies ◽

Paleoclimatic Changes ◽

Past Life ◽

Rock Eval ◽

Analytical Approaches ◽

Paleoenvironmental Reconstructions

The qualitative and quantitative analysis of sedimentary organic matter (i.e., the residue of past biota) provides integrated histories of marine and continental past life and paleoenvironmental /paleoclimatic changes. Organic geochemical investigations are possible by combining (i) bulk properties such as elemental compositions, stable isotope ratios, and Rock-Eval pyrolysis data, and (ii) biomarker molecular compositions such as n-alkanes, sterol, and polycyclic aromatic hydrocarbons compositions. The analytical approaches described in this overview illustrate the published examples of lacustrine and marine organic geochemical studies in Sri Lanka. In summary, the Jurassic Andigama and Tabbowa Basins provide different sources of organic matter, followed by availability of nutrient for algal growth and the amount of land runoff to the basins. Rock-Eval analysis of the Cretaceous to Paleogene sedimentary rocks in the offshore Mannar Basin reveal the presence of gas-prone land-plant organic matter mainly and minor oil-prone algal organic matter. The amounts and types of organic matter variations in Bolgoda Lake sediments indicate changes in Holocene sea-level, coastal geomorphology, and continental climates during the last 7,000 years. In future directions, applications of novel organic geochemical proxies and understanding of original biologically synthesized materials in tropics would improve interpretations of paleoenvironmental changes. Besides, local and regional paleoclimatic proxy and model studies would refine future paleoenvironmental reconstructions in Sri Lanka.

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Use of Rock-Eval Pyrolysis and Vitrinite Reflectance Data in Characterizing Type and Maturity of Organic Matter in Coal, Upper Cretaceous Fruitland Formation, San Juan Basin, New Mexico and Colorado: ABSTRACT

AAPG Bulletin ◽

10.1306/20b22c1f-170d-11d7-8645000102c1865d ◽

1990 ◽

Vol 74 ◽

Author(s):

B. E. Law, D. E. Anders, G. E. Mich

Keyword(s):

Organic Matter ◽

New Mexico ◽

Upper Cretaceous ◽

Vitrinite Reflectance ◽

San Juan ◽

San Juan Basin ◽

Rock Eval ◽

Reflectance Data

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Assessment of the hydrocarbon potentiality of the Late Jurassic formations of NW Iraq: A case study based on TOC and Rock-Eval pyrolysis in selected oil-wells

Open Geosciences ◽

10.1515/geo-2019-0071 ◽

2019 ◽

Vol 11 (1) ◽

pp. 918-928

Author(s):

Swar J. Al-Atroshi ◽

Govand H. Sherwani ◽

Srood F. Al-Naqshbandi

Keyword(s):

Organic Matter ◽

Late Jurassic ◽

Immature Stage ◽

Mature Stage ◽

Organic Carbon Content ◽

Hydrocarbon Generation ◽

Type Ii ◽

Kerogen Type ◽

Two Samples ◽

Rock Eval

Abstract The Late Jurassic Naokelekan and Barsarin formations of northwestern Iraq have been investigated in three wells to assess their potentiality for hydrocarbon generation. The results of Total Organic Carbon content (TOC) and Rock-Eval Pyrolysis reveal fair to excellent content of hydrocarbon and suggest that the depositional conditions were suitable for the production and preservation of organic matter. The Thermal Maturity Proxy indicates that the studied formations were mature stage of hydrocarbon generation, with an exception of three samples from the Naokelekan Formation in Shaikhan-8 well, and two samples from the Barsarin Formation in Atrush-1 and Shaikhan-8 wells were at an immature stage. The S1 and TOC relationship shows that all the samples are indigenous in nature. Most of samples from the Naokelekan Formation belong to kerogen Type II/III, and that in the Barsarin Formation belongs to kerogen Type II is dominant. The Pr/Ph, Pr/n-C17 and Ph/n-C18 ratios for the extracted bitumen of both the formations indicate that they were originated from marine organic matter under reducing conditions. The δ13CSat and δ13CAro range from −28.7 to −27.7‰ and −28.8 to −27.7‰ respectively. These biomarkers show high contribution of marine organic matters preserved under relatively anoxic conditions in the studied formations.

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Composition of Sedimentary Organic Matter across the Laptev Sea Shelf: Evidences from Rock-Eval Parameters and Molecular Indicators

Water ◽

10.3390/w12123511 ◽

2020 ◽

Vol 12 (12) ◽

pp. 3511

Author(s):

Elena Gershelis ◽

Andrey Grinko ◽

Irina Oberemok ◽

Elizaveta Klevantseva ◽

Natalina Poltavskaya ◽

...

Keyword(s):

Organic Matter ◽

Surface Sediments ◽

Continental Margins ◽

Laptev Sea ◽

Lena River ◽

Nearshore Sediments ◽

Rock Eval ◽

Molecular Indicators ◽

Sedimentation Regime ◽

The Laptev Sea

Global warming in high latitudes causes destabilization of vulnerable permafrost deposits followed by massive thaw-release of organic carbon. Permafrost-derived carbon may be buried in the nearshore sediments, transported towards the deeper basins or degraded into the greenhouse gases, potentially initiating a positive feedback to climate change. In the present study, we aim to identify the sources, distribution and degradation state of organic matter (OM) stored in the surface sediments of the Laptev Sea (LS), which receives a large input of terrestrial carbon from both Lena River discharge and intense coastal erosion. We applied a suite of geochemical indicators including the Rock Eval parameters, traditionally used for the matured OM characterization, and terrestrial lipid biomarkers. In addition, we analyzed a comprehensive grain size data in order to assess hydrodynamic sedimentation regime across the LS shelf. Rock-Eval (RE) data characterize LS sedimentary OM with generally low hydrogen index (100–200 mg HC/g TOC) and oxygen index (200 and 300 CO2/g TOC) both increasing off to the continental slope. According to Tpeak values, there is a clear regional distinction between two groups (369–401 °C for the inner and mid shelf; 451–464 °C for the outer shelf). We suggest that permafrost-derived OM is traced across the shallow and mid depths with high Tpeak and slightly elevated HI values if compared to other Arctic continental margins. Molecular-based degradation indicators show a trend to more degraded terrestrial OC with increasing distance from the coast corroborating with RE results. However, we observed much less variation of the degradation markers down to the deeper sampling horizons, which supports the notion that the most active OM degradation in LS land-shelf system takes part during the cross-shelf transport, not while getting buried deeper.

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What happened to the organic matter from the Upper Cretaceous succession in Guatemala, Central America?

Marine and Petroleum Geology ◽

10.1016/j.marpetgeo.2021.105246 ◽

2021 ◽

pp. 105246

Author(s):

Wiesława Radmacher ◽

Osmín J. Vásquez ◽

Mario Tzalam ◽

Mireya Jolomná ◽

Anny Molineros ◽

...

Keyword(s):

Organic Matter ◽

Central America ◽

Upper Cretaceous

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Droplet infiltration dynamics and soil wettability related to soil organic matter of soil aggregate coatings and interiors

Journal of Hydrology and Hydromechanics ◽

10.1515/johh-2016-0021 ◽

2016 ◽

Vol 64 (2) ◽

pp. 111-120 ◽

Cited By ~ 16

Author(s):

Miroslav Fér ◽

Martin Leue ◽

Radka Kodešová ◽

Horst H. Gerke ◽

Ruth H. Ellerbrock

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Preferential Flow ◽

Water Drop ◽

Soil Aggregates ◽

High Water ◽

Contact Angles ◽

Surface Wettability ◽

Mineral Coatings ◽

Droplet Infiltration

Abstract The organo-mineral coatings of soil aggregates, cracks, and biopores control sorption and macropore-matrix exchange during preferential flow, in particular in the clay-illuvial Bt-horizon of Luvisols. The soil organic matter (SOM) composition has been hypothesized to explain temporal changes in the hydraulic properties of aggregate surfaces. The objective of this research was to find relations between the temporal change in wettability, in terms of droplet infiltration dynamics, and the SOM composition of coated and uncoated aggregate surfaces. We used 20 to 40 mm sized soil aggregates from the Bt2 horizon of a Haplic Luvisol from loess that were (i) coated, (ii) not coated (both intact), and (iii) aggregates from which coatings were removed (cut). The SOM composition of the aggregate surfaces was characterized by infrared spectroscopy in the diffuse reflection mode (DRIFT). A potential wettability index (PWI) was calculated from the ratio of hydrophobic and hydrophilic functional groups in SOM. The water drop penetration times (WDPT) and contact angles (CA) during droplet infiltration experiments were determined on dry and moist aggregate samples of the three types. The decrease in the CA with time was described using the power function (CA(t) = at−b). For dry aggregates, the WDPT values were larger for coated as compared to uncoated regions on the aggregate surfaces, and increased with increasing PWI value (R2 = 0.75). The a parameter was significantly related to the WDPT (R2 = 0.84) and to the PWI (R2 = 0.64). The relations between the b parameter and the WDPT (R2 = 0.61) and the PWI (R2 = 0.53) were also significant. The WDPT values of wet soil aggregates were higher than those of dry aggregates due to high water contents, which limited the droplet infiltration potential. At the wet aggregate surfaces, the WDPT values increased with the PWI of the SOM (R2 = 0.64). In contrast to dry samples, no significant relationships were found between parameters a or b of CA(t) and WDPT or PWI for wet aggregate surfaces. The results suggest that the effect of the SOM composition of coatings on surface wettability decreases with increasing soil moisture. In addition to the dominant impact of SOM, the wettability of aggregate surfaces could be affected by different mineralogical compositions of clay in coatings and interiors of aggregates. Particularly, wettability of coatings could be decreased by illite which was the dominant clay type in coatings. However, the influence of different clay mineral fractions on surface wettability was not due to small number of measurements (2 and 1 samples from coatings and interiors, respectively) quantified.

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Source rock characterization of mesozoic to cenozoic organic matter rich marls and shales of the Eratosthenes Seamount, Eastern Mediterranean Sea

Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles ◽

10.2516/ogst/2018036 ◽

2018 ◽

Vol 73 ◽

pp. 49 ◽

Cited By ~ 8

Author(s):

Sebastian Grohmann ◽

Susanne W. Fietz ◽

Ralf Littke ◽

Samer Bou Daher ◽

Maria Fernanda Romero-Sarmiento ◽

...

Keyword(s):

Organic Matter ◽

Mediterranean Sea ◽

Source Rock ◽

Eastern Mediterranean ◽

Source Rocks ◽

Eastern Mediterranean Sea ◽

Potential Source Rock ◽

Levant Basin ◽

Rock Characterization ◽

Rock Eval

Several significant hydrocarbon accumulations were discovered over the past decade in the Levant Basin, Eastern Mediterranean Sea. Onshore studies have investigated potential source rock intervals to the east and south of the Levant Basin, whereas its offshore western margin is still relatively underexplored. Only a few cores were recovered from four boreholes offshore southern Cyprus by the Ocean Drilling Program (ODP) during the drilling campaign Leg 160 in 1995. These wells transect the Eratosthenes Seamount, a drowned bathymetric high, and recovered a thick sequence of both pre- and post-Messinian sedimentary rocks, containing mainly marine marls and shales. In this study, 122 core samples of Late Cretaceous to Messinian age were analyzed in order to identify organic-matter-rich intervals and to determine their depositional environment as well as their source rock potential and thermal maturity. Both Total Organic and Inorganic Carbon (TOC, TIC) analyses as well as Rock-Eval pyrolysis were firstly performed for the complete set of samples whereas Total Sulfur (TS) analysis was only carried out on samples containing significant amount of organic matter (>0.3 wt.% TOC). Based on the Rock-Eval results, eight samples were selected for organic petrographic investigations and twelve samples for analysis of major aliphatic hydrocarbon compounds. The organic content is highly variable in the analyzed samples (0–9.3 wt.%). TS/TOC as well as several biomarker ratios (e.g. Pr/Ph < 2) indicate a deposition under dysoxic conditions for the organic matter-rich sections, which were probably reached during sporadically active upwelling periods. Results prove potential oil prone Type II kerogen source rock intervals of fair to very good quality being present in Turonian to Coniacian (average: TOC = 0.93 wt.%, HI = 319 mg HC/g TOC) and in Bartonian to Priabonian (average: TOC = 4.8 wt.%, HI = 469 mg HC/g TOC) intervals. A precise determination of the actual source rock thickness is prevented by low core recovery rates for the respective intervals. All analyzed samples are immature to early mature. However, the presence of deeper buried, thermally mature source rocks and hydrocarbon migration is indicated by the observation of solid bitumen impregnation in one Upper Cretaceous and in one Lower Eocene sample.

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