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Kitty L Milliken - One of the best experts on this subject based on the ideXlab platform.
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empirical relationship between gas composition and Thermal Maturity in eagle ford shale south texas
AAPG Bulletin, 2017Co-Authors: Tongwei Zhang, Kitty L Milliken, Xun Sun, Stephen C Ruppel, Daniel EnriquezAbstract:Organic-rich and carbonate-rich Eagle Ford Shale is a self-sourced oil and gas reservoir with little alteration of gas chemistry as might be affected by petroleum expulsion and migration. As such it provides an ideal natural laboratory to quantify the compositional variation of gases generated from oil-prone type II kerogen during Thermal maturation. The chemical composition of the gas released from rock crushing was conducted and integrated with Rock-Eval pyrolysis to define the empirical relationship between gas compositional parameters and Thermal Maturity in this study. From 10 wells in the Eagle Ford Shale in south Texas, we collected 74 core samples having a range of Thermal Maturity (the measured maximum temperature [Tmax] values of hydrocarbons generated in Rock-Eval pyrolysis range from 427°C to 494°C [800°F to 921°F], and the calculated equivalent vitrinite reflectance (Roe) values range from 0.51% to 1.73% based on Tmax values). Total organic carbon content ranges from 0.3% to 8.53%, with an average of 3.12% (standard deviation of 1.77%). Burial depth is from 2989.6 to 13,827.3 ft (911.2 to 4214.6 m). Our results showed that gas composition in the Eagle Ford Shale is mainly controlled by Thermal Maturity, and three stages of gas generation are identified based on the C1 and C2 concentrations of the gases released by rock crushing from Eagle Ford Shale core samples. The three stages of gas generation correspond to the following processes of organic matter conversion: (1) kerogen and bitumen Thermal cracking to crude oil, (2) bitumen and heavy crude oil Thermal cracking to light oil, and (3) light oil cracking to gas. Methane-rich gas and an abundance of branched butane and pentane are generated in light oil cracking to gas, resulting in high C1/C2, C1/(C2 + C3), i-C4/n-C4, and i-C5/n-C5 ratios. Increased cracking of normal alkanes such as n-butane and n-pentane occurs in the light oil cracking to gas. Empirical equations between gas compositional parameters and Thermal Maturity (Tmax or Roe) are obtained for oil-prone type II. The C1, C2, C1/C2, C1/C2 + C3, and i-C4/n-C4 ratios are the five best parameters for determining Thermal Maturity with an exponentially derived R2 value of 0.74. The composition of gas produced from the Eagle Ford Shale following hydraulic fracturing is used to validate the empirical equations. Calculated Thermal regime for the oil production based on the produced gas is located at the peak of oil generation and the beginning of light oil cracking to gas, corresponding to Tmax from 454°C to 464°C (849°F to 867°F) or at an Roe ranging from 1.01% to 1.19%. Empirical equations provide a basis for interpretation of mud gas logging data and produced gas composition.
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pore types and pore size distributions across Thermal Maturity eagle ford formation southern texas
AAPG Bulletin, 2015Co-Authors: Maxwell Pommer, Kitty L MillikenAbstract:Pore types, pore size, and pore abundance vary systematically across Thermal Maturity in the Eagle Ford Formation, Maverick Basin, southern Texas. Scanning electron imaging of 20 samples from four wells is used to assess the complex response of pores to chemical and mechanical processes, entailing both destruction of primary porosity and generation of secondary pores. Primary mineral-associated pores are destroyed by compaction, cementation, and infill of secondary organic matter, whereas secondary pores are generated within organic matter (OM). Destruction of primary pores during early burial (to ∼0.5%) occurs by compaction of ductile detrital OM and clays and, to a lesser degree, as a result of cementation and infill of secondary OM. Larger pores are associated with coccolith debris. The dominant OM is spatially isolated detrital OM “stringers.” Porosity is volumetrically dominated (average 6.2%) by relatively large, mostly interparticle mineral-associated pores (median size 51.6 nm [0.000002 in.]; detection limit near 3–4 nm [0.00000012–0.00000015 in.]). At low Maturity, porosity and pore size correlate directly with calcite abundance and inversely with OM volumes. At higher Maturity, further destruction of primary pores occurs through cementation, secondary OM infill, and greater compaction. Mineral-associated pores are present at high-Maturity ( ∼1.2%–1.3%), but are smaller (median size 30.2 nm [0.0000011 in.]) and less abundant (average of 2.5%) than at low Maturity. A large portion of OM within high-Maturity samples is diagenetic in origin and has pervaded into primary pore space, coating cement crystals, and filling intraparticle pores. Substantial mineral-associated porosity is locally present in samples where incursion of primary pore space by secondary OM has not occurred. Abundant secondary porosity is generated as OM matures into the wet-gas window. Porosity in most high-Maturity samples is volumetrically dominated (average of 1.3%) by smaller, OM-hosted pores (median size 13.2 nm [0.00000051 in.]).
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Pore types and pore-size distributions across Thermal Maturity, Eagle Ford Formation, southern Texas
AAPG Bulletin, 2015Co-Authors: Maxwell Pommer, Kitty L MillikenAbstract:Pore types, pore size, and pore abundance vary systematically across Thermal Maturity in the Eagle Ford Formation, Maverick Basin, southern Texas. Scanning electron imaging of 20 samples from four wells is used to assess the complex response of pores to chemical and mechanical processes, entailing both destruction of primary porosity and generation of secondary pores. Primary mineral-associated pores are destroyed by compaction, cementation, and infill of secondary organic matter, whereas secondary pores are generated within organic matter (OM). Destruction of primary pores during early burial (to ∼0.5%) occurs by compaction of ductile detrital OM and clays and, to a lesser degree, as a result of cementation and infill of secondary OM. Larger pores are associated with coccolith debris. The dominant OM is spatially isolated detrital OM “stringers.” Porosity is volumetrically dominated (average 6.2%) by relatively large, mostly interparticle mineral-associated pores (median size 51.6 nm [0.000002 in.]; detection limit near 3–4 nm [0.00000012–0.00000015 in.]). At low Maturity, porosity and pore size correlate directly with calcite abundance and inversely with OM volumes. At higher Maturity, further destruction of primary pores occurs through cementation, secondary OM infill, and greater compaction. Mineral-associated pores are present at high-Maturity ( ∼1.2%–1.3%), but are smaller (median size 30.2 nm [0.0000011 in.]) and less abundant (average of 2.5%) than at low Maturity. A large portion of OM within high-Maturity samples is diagenetic in origin and has pervaded into primary pore space, coating cement crystals, and filling intraparticle pores. Substantial mineral-associated porosity is locally present in samples where incursion of primary pore space by secondary OM has not occurred. Abundant secondary porosity is generated as OM matures into the wet-gas window. Porosity in most high-Maturity samples is volumetrically dominated (average of 1.3%) by smaller, OM-hosted pores (median size 13.2 nm [0.00000051 in.]).
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effect of organic matter type and Thermal Maturity on methane adsorption in shale gas systems
Organic Geochemistry, 2012Co-Authors: Tongwei Zhang, Kitty L Milliken, Stephen C Ruppel, Geoffrey S Ellis, Rongsheng YangAbstract:Abstract A series of methane (CH4) adsorption experiments on bulk organic rich shales and their isolated kerogens were conducted at 35 °C, 50 °C and 65 °C and CH4 pressure of up to 15 MPa under dry conditions. Samples from the Eocene Green River Formation, Devonian–Mississippian Woodford Shale and Upper Cretaceous Cameo coal were studied to examine how differences in organic matter type affect natural gas adsorption. Vitrinite reflectance values of these samples ranged from 0.56–0.58 %Ro. In addition, Thermal Maturity effects were determined on three Mississippian Barnett Shale samples with measured vitrinite reflectance values of 0.58, 0.81 and 2.01 %Ro. For all bulk and isolated kerogen samples, the total amount of methane adsorbed was directly proportional to the total organic carbon (TOC) content of the sample and the average maximum amount of gas sorption was 1.36 mmol of methane per gram of TOC. These results indicate that sorption on organic matter plays a critical role in shale-gas storage. Under the experimental conditions, differences in Thermal Maturity showed no significant effect on the total amount of gas sorbed. Experimental sorption isotherms could be fitted with good accuracy by the Langmuir function by adjusting the Langmuir pressure (PL) and maximum sorption capacity (Γmax). The lowest Maturity sample (%Ro = 0.56) displayed a Langmuir pressure (PL) of 5.15 MPa, significantly larger than the 2.33 MPa observed for the highest Maturity (%Ro > 2.01) sample at 50 °C. The value of the Langmuir pressure (PL) changes with kerogen type in the following sequence: type I > type II > type III. The thermodynamic parameters of CH4 adsorption on organic rich shales were determined based on the experimental CH4 isotherms. For the adsorption of CH4 on organic rich shales and their isolated kerogen, the heat of adsorption (q) and the standard entropy (Δs0) range from 7.3–28.0 kJ/mol and from −36.2 to −92.2 J/mol/K, respectively.
Maxwell Pommer - One of the best experts on this subject based on the ideXlab platform.
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pore types and pore size distributions across Thermal Maturity eagle ford formation southern texas
AAPG Bulletin, 2015Co-Authors: Maxwell Pommer, Kitty L MillikenAbstract:Pore types, pore size, and pore abundance vary systematically across Thermal Maturity in the Eagle Ford Formation, Maverick Basin, southern Texas. Scanning electron imaging of 20 samples from four wells is used to assess the complex response of pores to chemical and mechanical processes, entailing both destruction of primary porosity and generation of secondary pores. Primary mineral-associated pores are destroyed by compaction, cementation, and infill of secondary organic matter, whereas secondary pores are generated within organic matter (OM). Destruction of primary pores during early burial (to ∼0.5%) occurs by compaction of ductile detrital OM and clays and, to a lesser degree, as a result of cementation and infill of secondary OM. Larger pores are associated with coccolith debris. The dominant OM is spatially isolated detrital OM “stringers.” Porosity is volumetrically dominated (average 6.2%) by relatively large, mostly interparticle mineral-associated pores (median size 51.6 nm [0.000002 in.]; detection limit near 3–4 nm [0.00000012–0.00000015 in.]). At low Maturity, porosity and pore size correlate directly with calcite abundance and inversely with OM volumes. At higher Maturity, further destruction of primary pores occurs through cementation, secondary OM infill, and greater compaction. Mineral-associated pores are present at high-Maturity ( ∼1.2%–1.3%), but are smaller (median size 30.2 nm [0.0000011 in.]) and less abundant (average of 2.5%) than at low Maturity. A large portion of OM within high-Maturity samples is diagenetic in origin and has pervaded into primary pore space, coating cement crystals, and filling intraparticle pores. Substantial mineral-associated porosity is locally present in samples where incursion of primary pore space by secondary OM has not occurred. Abundant secondary porosity is generated as OM matures into the wet-gas window. Porosity in most high-Maturity samples is volumetrically dominated (average of 1.3%) by smaller, OM-hosted pores (median size 13.2 nm [0.00000051 in.]).
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Pore types and pore-size distributions across Thermal Maturity, Eagle Ford Formation, southern Texas
AAPG Bulletin, 2015Co-Authors: Maxwell Pommer, Kitty L MillikenAbstract:Pore types, pore size, and pore abundance vary systematically across Thermal Maturity in the Eagle Ford Formation, Maverick Basin, southern Texas. Scanning electron imaging of 20 samples from four wells is used to assess the complex response of pores to chemical and mechanical processes, entailing both destruction of primary porosity and generation of secondary pores. Primary mineral-associated pores are destroyed by compaction, cementation, and infill of secondary organic matter, whereas secondary pores are generated within organic matter (OM). Destruction of primary pores during early burial (to ∼0.5%) occurs by compaction of ductile detrital OM and clays and, to a lesser degree, as a result of cementation and infill of secondary OM. Larger pores are associated with coccolith debris. The dominant OM is spatially isolated detrital OM “stringers.” Porosity is volumetrically dominated (average 6.2%) by relatively large, mostly interparticle mineral-associated pores (median size 51.6 nm [0.000002 in.]; detection limit near 3–4 nm [0.00000012–0.00000015 in.]). At low Maturity, porosity and pore size correlate directly with calcite abundance and inversely with OM volumes. At higher Maturity, further destruction of primary pores occurs through cementation, secondary OM infill, and greater compaction. Mineral-associated pores are present at high-Maturity ( ∼1.2%–1.3%), but are smaller (median size 30.2 nm [0.0000011 in.]) and less abundant (average of 2.5%) than at low Maturity. A large portion of OM within high-Maturity samples is diagenetic in origin and has pervaded into primary pore space, coating cement crystals, and filling intraparticle pores. Substantial mineral-associated porosity is locally present in samples where incursion of primary pore space by secondary OM has not occurred. Abundant secondary porosity is generated as OM matures into the wet-gas window. Porosity in most high-Maturity samples is volumetrically dominated (average of 1.3%) by smaller, OM-hosted pores (median size 13.2 nm [0.00000051 in.]).
Paul C. Hackley - One of the best experts on this subject based on the ideXlab platform.
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high microscale variability in raman Thermal Maturity estimates from shale organic matter
International Journal of Coal Geology, 2018Co-Authors: Aaron M Jubb, Paul C. Hackley, Palma J Botterell, Justin E Birdwell, Robert C Burruss, Brett J Valentine, Javin J Hatcherian, Stephen A WilsonAbstract:Abstract Raman spectroscopy has recently received attention as a means to estimate Thermal Maturity of organic matter in petroleum generating source rocks to complement more traditional approaches such as vitrinite reflectance and programmed pyrolysis. While many studies have observed positive correlations between source rock Thermal Maturity and Raman spectral parameters, little attention has been given to the degree of variation in the Raman response across individual organic grains, especially for shales or mudrocks with highly dispersed organic matter. Here the spatial variation in Raman estimates of Thermal Maturity within individual organic grains is assessed from shales from the Boquillas, Marcellus, Niobrara, and Woodford Formations. The Thermal Maturity parameters extracted from Raman spectra can vary widely across distances of ≤5 μm within the same organic grain. These results illustrate the high degree of chemical heterogeneity inherent to the organic matter within these source rocks. Additionally, the spatial pattern of the Raman parameters, as revealed by 2D Raman mapping, imply that organic matter structure is influenced by associations with mineral surfaces within the surrounding rock matrix. Chemical heterogeneity and matrix effects directly impact the Raman response from these types of materials and thus the extracted Thermal Maturity estimate. These findings highlight the care which must be adopted when making Raman measurements of organic matter within source rock matrices, especially for samples which feature highly dispersed, heterogeneous organic matter as found in petroliferous mudrocks.
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application of raman spectroscopy as Thermal Maturity probe in shale petroleum systems insights from natural and artificial maturation series
Energy & Fuels, 2018Co-Authors: Paul C. Hackley, Keno N LunsdorfAbstract:Raman spectroscopy was studied as a Thermal Maturity probe in a series of Upper Devonian Ohio Shale samples from the Appalachian Basin spanning from immature to dry gas conditions. Raman spectroscopy also was applied to samples spanning a similar Thermal range created from 72-h hydrous pyrolysis (HP) experiments of the Ohio Shale at temperatures from 300 to 360 °C and isoThermal HP experiments lasting up to 100 days of similar Devonian–Mississippian New Albany Shale. Raman spectra were treated by automated evaluation software based on iterative and simultaneous modeling of signal and baseline functions to decrease subjectivity. Spectra show robust correlation to measured solid bitumen reflectance (BRo) values and were therefore used to construct logarithmic regression relationships for calculation of BRo equivalent values. Raman spectra show considerable differences between natural samples and HP residues with similar measured BRo values, indicating as-yet undetermined differences in carbon chemistry. We ...
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assessment of Thermal Maturity trends in devonian mississippian source rocks using raman spectroscopy limitations of peak fitting method
Frontiers in Energy Research, 2017Co-Authors: Jason S Lupoi, Paul C. Hackley, Luke P Fritz, Thomas M Parris, Logan Solotky, Courtland F Eble, Steve SchlaegleAbstract:The Thermal Maturity of shale is often measured by vitrinite reflectance (VRo). VRo measurements for the Devonian-Mississippian black shale source rocks evaluated herein predicted Thermal imMaturity in areas where associated reservoir rocks are oil-producing. This limitation of the VRo method led to the current evaluation of Raman spectroscopy as a suitable alternative for developing correlations between Thermal Maturity and Raman spectra. In this study, Raman spectra of Devonian-Mississippian black shale source rocks were regressed against measured VRo or sample-depth. Attempts were made to develop quantitative correlations of Thermal Maturity. Using sample-depth as a proxy for Thermal Maturity is not without limitations either, as Thermal Maturity as a function of depth depends on Thermal gradient, which can vary through time, subsidence rate, uplift, lack of uplift, and faulting. Correlations between Raman data and Thermal Maturity metrics were quantified by peak-fitting the spectra. Various peak-fitting procedures were evaluated to determine the effects of the number of peaks and maximum peak widths on correlations between spectral metrics and Thermal Maturity. Correlations between D-frequency, G-band full-width-at-half-maximum (FWHM) and band separation between the G- and D- peaks and Thermal Maturity provided some degree of linearity throughout most peak-fitting assessments; however, these correlations and those calculated from the G-frequency, D/G FWHM ratio, and D/G peak area ratio also revealed a strong dependence on peak-fitting processes. This dependency on spectral analysis techniques raises questions about the validity of peak-fitting, particularly given the amount of subjective analyst involvement necessary to reconstruct spectra. This research shows how user interpretation and extrapolation affected the comparability of different samples, the accuracy of generated trends, and therefore, the potential of the Raman spectral method to become an industry benchmark as a Thermal Maturity probe. A Raman method devoid of extensive operator interaction and data manipulation is quintessential for creating a standard method.
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liquid hydrocarbon characterization of the lacustrine yanchang formation ordos basin china organic matter source variation and Thermal Maturity
Interpretation, 2017Co-Authors: Xun Sun, Tongwei Zhang, Daniel Enriquez, Quansheng Liang, Chengfu Jiang, Paul C. HackleyAbstract:AbstractSource-rock samples from the Upper Triassic Yanchang Formation in the Ordos Basin of China were geochemically characterized to determine variations in depositional environments, organic-matter (OM) source, and Thermal Maturity. Total organic carbon (TOC) content varies from 4 wt% to 10 wt% in the Chang 7, Chang 8, and Chang 9 members — the three OM-rich shale intervals. The Chang 7 has the highest TOC and hydrogen index values, and it is considered the best source rock in the formation. Geochemical evidence indicates that the main sources of OM in the Yanchang Formation are freshwater lacustrine phytoplanktons, aquatic macrophytes, aquatic organisms, and land plants deposited under a weakly reducing to suboxic depositional environment. The elevated C29 sterane concentration and depleted δC13 values of OM in the middle of the Chang 7 may indicate the presence of freshwater cyanobacteria blooms that corresponds to a period of maximum lake expansion. The OM deposited in deeper parts of the lake is do...
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Thermal Maturity of tasmanites microfossils from confocal laser scanning fluorescence microscopy
Fuel, 2015Co-Authors: Paul C. HackleyAbstract:Abstract We report here, for the first time, spectral properties of Tasmanites microfossils determined by confocal laser scanning fluorescence microscopy (CLSM, using Ar 458 nm excitation). The Tasmanites occur in a well-characterized natural maturation sequence (Ro 0.48–0.74%) of Devonian shale (n = 3 samples) from the Appalachian Basin. Spectral property λmax shows excellent agreement (r2 = 0.99) with extant spectra from interlaboratory studies which used conventional fluorescence microscopy techniques. This result suggests spectral measurements from CLSM can be used to infer Thermal Maturity of fluorescent organic materials in geologic samples. Spectra of regions with high fluorescence intensity at fold apices and flanks in individual Tasmanites are blue-shifted relative to less-deformed areas in the same body that have lower fluorescence intensity. This is interpreted to result from decreased quenching moiety concentration at these locations, and indicates caution is needed in the selection of measurement regions in conventional fluorescence microscopy, where it is common practice to select high intensity regions for improved signal intensity and better signal to noise ratios. This study also documents application of CLSM to microstructural characterization of Tasmanites microfossils. Finally, based on an extant empirical relation between conventional λmax values and bitumen reflectance, λmax values from CLSM of Tasmanites microfossils can be used to calculate a bitumen reflectance equivalent value. The results presented herein can be used as a basis to broaden the future application of CLSM in the geological sciences into hydrocarbon prospecting and basin analysis.
Nazmul Haque Mondol - One of the best experts on this subject based on the ideXlab platform.
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cenozoic exhumation on the southwestern barents shelf estimates and uncertainties constrained from compaction and Thermal Maturity analyses
Marine and Petroleum Geology, 2016Co-Authors: Irfan Baig, Jan Inge Faleide, Jens Jahren, Nazmul Haque MondolAbstract:Abstract The Barents Sea is believed to have been influenced in most parts by Cenozoic uplift and erosion episodes. The rocks in the area are not currently at their maximum burial depth. The exhumation of the sedimentary rocks has had large effects on rock physical properties and hydrocarbon maturation and migration. The current study seeks to estimate exhumation from shale compaction and Thermal Maturity techniques and discuss its implications for hydrocarbon exploration in the uplifted Barents Sea area. This study uses well logs and Thermal Maturity data together with widely distributed shot gather data along long-offset seismic reflection lines. The use of shale compaction techniques to estimate exhumation was focused particularly on the regionally preserved Aptian-Albian (Kolmule Formation) and Paleogene (Torsk Formation) shales. Normal compaction reference curves were established for these units in areas currently at their maximum burial depth (e.g. Sorvestsnaget Basin and Vestbakken Volcanic Province). The results suggest widespread Cenozoic exhumation throughout the southwestern Barents Sea. The exhumation magnitudes increase towards east and northeast. The average exhumation estimates from the three data sources range from ∼800 to 1400 m within the Hammerfest Basin, ∼1150–1950 m on the Loppa High, ∼1200–1400 m on the Finmark Platform and ∼1250–2400 m on the Bjarmeland Platform. The marked differences in glacial erosion from mass balance and average erosion estimates from the current study suggest a significant pre-glacial uplift and erosion in the southwestern Barents Sea area. The observed stratigraphy and presence of significant volumes of Late Oligocene-Middle Miocene sediments in basins at the outer margin, and increased erosion rates at the same time in source areas suggest that maximum burial in the southwestern Barents Sea may have occurred sometime during the Oligocene, or even earlier in the Eocene. The results from this study are useful input for modelling of source rock maturation, generation, migration and trapping of hydrocarbons in the area. These results are also an important input for the prediction of more precise reservoir and seal rock properties in frontier areas away from the exploration wells and provide valuable knowledge for the use of interval velocities in the uplifted areas.
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cenozoic exhumation on the southwestern barents shelf estimates and uncertainties constrained from compaction and Thermal Maturity analyses
Marine and Petroleum Geology, 2016Co-Authors: Irfan Baig, Jan Inge Faleide, Jens Jahren, Nazmul Haque MondolAbstract:Abstract The Barents Sea is believed to have been influenced in most parts by Cenozoic uplift and erosion episodes. The rocks in the area are not currently at their maximum burial depth. The exhumation of the sedimentary rocks has had large effects on rock physical properties and hydrocarbon maturation and migration. The current study seeks to estimate exhumation from shale compaction and Thermal Maturity techniques and discuss its implications for hydrocarbon exploration in the uplifted Barents Sea area. This study uses well logs and Thermal Maturity data together with widely distributed shot gather data along long-offset seismic reflection lines. The use of shale compaction techniques to estimate exhumation was focused particularly on the regionally preserved Aptian-Albian (Kolmule Formation) and Paleogene (Torsk Formation) shales. Normal compaction reference curves were established for these units in areas currently at their maximum burial depth (e.g. Sorvestsnaget Basin and Vestbakken Volcanic Province). The results suggest widespread Cenozoic exhumation throughout the southwestern Barents Sea. The exhumation magnitudes increase towards east and northeast. The average exhumation estimates from the three data sources range from ∼800 to 1400 m within the Hammerfest Basin, ∼1150–1950 m on the Loppa High, ∼1200–1400 m on the Finmark Platform and ∼1250–2400 m on the Bjarmeland Platform. The marked differences in glacial erosion from mass balance and average erosion estimates from the current study suggest a significant pre-glacial uplift and erosion in the southwestern Barents Sea area. The observed stratigraphy and presence of significant volumes of Late Oligocene-Middle Miocene sediments in basins at the outer margin, and increased erosion rates at the same time in source areas suggest that maximum burial in the southwestern Barents Sea may have occurred sometime during the Oligocene, or even earlier in the Eocene. The results from this study are useful input for modelling of source rock maturation, generation, migration and trapping of hydrocarbons in the area. These results are also an important input for the prediction of more precise reservoir and seal rock properties in frontier areas away from the exploration wells and provide valuable knowledge for the use of interval velocities in the uplifted areas.
Ralf Littke - One of the best experts on this subject based on the ideXlab platform.
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depositional environment and Thermal Maturity of the coal bearing longtan shale in southwest guizhou china implications for shale gas resource potential
International Journal of Coal Geology, 2020Co-Authors: Qian Zhang, Sebastian Grohmann, Ralf LittkeAbstract:Abstract Significant knowledge has been assembled on the marine Longmaxi Shale in the Sichuan Basin over the past ten years. However, the distribution of shale gas resources on the periphery of the Sichuan Basin and in other source rock formations are still not sufficiently understood. To improve our understanding on the depositional environment and Thermal Maturity, and their relevance to the source rock quality and shale gas potential of the thick, coal-bearing Longtan Shale, 36 organic-rich shale samples were selected from a single borehole located in the southwestern Guizhou Province for geochemical and petrographic analysis. Total organic carbon (TOC) contents are high with 7.7 wt% on average, reaching partly up to 28.21 wt%, while carbonate contents are low. Vitrinite reflectance (VRr) values and Rock-Eval Tmax temperatures range from 1.48 to 1.84% and 482 to 583 °C, respectively, indicating a high Thermal Maturity which is in accordance with aromatic molecular parameters. The remaining, present day hydrocarbon generation potential (Rock-Eval S2) is rather low due to the high Maturity. Microscopic investigations further show that the organic matter in the rocks is mainly composed of higher land plant particles, present as large and poorly rounded vitrinite and inertinite particles indicating a rather short transport distance. TOC vs. total sulfur (TS) relationships as well as specific hydrocarbon ratios (e.g. pristane/phytane) and framboidal pyrite size distributions indicate a variable either marine or freshwater environment for the shales in the coal-bearing sequence and suggest that original kerogen was either type III or type II-III. Bottom water during deposition was probably oxygen depleted but not anoxic. High sedimentation rates can be assumed for the now 700 m thick, compacted sequence, favorable for the preservation of organic matter. Overall, the present results are in accordance with previous studies of the Longtan Shale which initially had a high hydrocarbon (mainly gas) generation potential; furthermore the thickness of the formation is much larger in the here studied southwestern part of the Guizhou Province than in the previously studied northern parts.
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ediacaran cambrian ordovician silurian and permian shales of the upper yangtze platform south china deposition Thermal Maturity and shale gas potential
International Journal of Coal Geology, 2019Co-Authors: Qian Zhang, Ralf Littke, Xuan Tang, Laura Zieger, Mohammadebrahim Shabani, Jinchuan ZhangAbstract:Abstract For many years, the Yangtze Platform has been successfully explored and exploited for petroleum. The Lower Silurian Longmaxi Shale proved to contain commercial quantities of gas, but several other formations might also have a high potential for shale-hosted gas exploration. This paper comprises of geochemical, petrographical, petrophysical and mineralogical information on the major Proterozoic and Paleozoic gas shales in the Upper Yangtze area, which provides insights on the depositional environment, the Thermal Maturity of organic matter, shale gas storage capacity and the fracability of these rocks. The total organic carbon (TOC) content varies from 0.1 to 22.5% with an average value of 2.7% and most of these shales were deposited in an oxygen-depleted marine environment. Equivalent vitrinite reflectance (VRr) values range from 2.20 to 4.25%, indicating that all samples are in the gas generation window and lost a large amount of primary organic carbon. Porosity varies between 1.5 and 13.6% with an average value of 5.8%, while the excess sorption capacity ranges from 0.10 to 0.22 mmol/g rock. Minerology data show that quartz is the predominant mineral except for the Upper Permian Longtan Formation, in which clay minerals account for 29 to 84%. New data were combined with those from other publications and compared to information on other, well-studied shale-hosted gas systems.
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artificial Thermal maturation of source rocks at different Thermal Maturity levels application to the triassic montney and doig formations in the western canada sedimentary basin
Organic Geochemistry, 2016Co-Authors: Mariafernanda Romerosarmiento, Tristan Euzen, Sebastien Rohais, Chunqing Jiang, Ralf LittkeAbstract:Abstract Artificial Thermal maturation of petroleum source rocks is widely performed by either open- or closed-system pyrolysis. These experiments are performed usually on immature source rock or isolated kerogen samples to quantify petroleum generation potential and to calculate kinetic parameters. Here, we characterize a maturation series from the Triassic Montney and Doig formations in the Western Canada Sedimentary Basin (WCSB), in order to investigate the evolution of the source rock properties and their corresponding kerogen kinetic parameters as a function of the Thermal Maturity. Organic petrography determined the Thermal Maturity and the spatial distribution of organic matter particles. Rock-Eval Shale Play analyses were then applied to assess the presence of both free and sorbed hydrocarbons still contained in the sample as well as the hydrocarbon generation potential. Based on vitrinite reflectance values, three kerogen samples from the Doig Formation and one kerogen sample from the Montney Formation at different Thermal Maturity levels were selected for analysis of bulk kinetic parameters (e.g., activation energy distribution, frequency factor) using programmed open-system pyrolysis. Additionally, we evaluated the type of hydrocarbons and determined the molecular composition of organic compounds that comprise the first two Rock-Eval peaks (Sh0 and Sh1) obtained during the improved thermovaporization. TD–GC–MS–FID analyses were carried out on rock samples sequentially from 100 °C to 200 °C and then from 200 °C to 350 °C in order to characterize the composition of hydrocarbons represented by each Rock-Eval Shale Play peak. Free and sorbed low-to-medium molecular weight aliphatic and aromatic hydrocarbons ( 20 ) are the main hydrocarbon components released in the temperature range corresponding to the Rock-Eval Shale Play Sh0 parameter. Medium and high-molecular weight hydrocarbons (C 10 –C 30 aromatics and saturates) are predominant components Thermally released in the temperature range corresponding to the Rock-Eval Shale Play Sh1 parameter. Results show both an increasing activation energy and loss of petroleum generation potential as Thermal degradation proceeds. The Shale Play method has been developed to better discriminate the generated fluids (Sh0 + Sh1) from the residual kerogen (Sh2) providing a more accurate Rock-Eval T max . Sh0 and Sh1 parameters also offer a practical way for an early estimate of oil in place.
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shale oil potential and Thermal Maturity of the lower toarcian posidonia shale in nw europe
International Journal of Coal Geology, 2015Co-Authors: Jinli Song, Ralf Littke, Philipp Weniger, Christian Ostertaghenning, S NelskampAbstract:A suite of drilling cores and outcrop samples of the Lower Toarcian Posidonia Shale (PS) were collected from multiple locations including the Swabian Alb and Franconian Alb of Southwest-Germany, Runswick Bay of UK and Loon op Zand well (LOZ-1) of the West Netherlands Basin. In order to assess the Thermal Maturity and quantify the petroleum generation potential of the rocks, elemental analysis, Rock-Eval pyrolysis, organic petrographic investigations and molecular hydrocarbon analyses were performed. Available literature data of the Posidonia Shale from Luxembourg and northwest Germany were used for comparison in the discussion.The Lower Toarcian Shale is more carbonate-rich (about 30% on average) in SW-Germany, NW-Germany and Luxembourg, and is instead more silicate-rich in UK and NL with carbonate contents of about 15% on average. This coincides with the relative distances of the depositional settings to the clastic source areas on the continents during the early Jurassic. However, HI values are similar, approx. 500-700. mg. HC/g TOC on average at all sampling localities, exhibiting typical type II kerogen with excellent hydrocarbon generation potential. Differences in relative abundance of terrigenous organic matter input are deduced from molecular indicators, Rock-Eval data and organic petrography. The highest abundance of terrigenous organic matter is evident for Runswick Bay, UK.Samples from outcrops of the Lower Toarcian Shale from Runswick Bay, UK, have reached the early stage of the oil window, with quite uniform T max values (425-438°C, avg. 433°C) and a narrow range of PI (production index) values (0.10-0.19), substantiated by mature fluorescing characteristics of telalginite and lamalginite and vitrinite reflectance values of 0.6-0.7%. Wider ranges of T max values (421-443°C, avg. 427°C), vitrinite reflectance (0.4-0.8%) and production indices (0.06-0.29) suggest more variable Thermal maturation ranging from immature to almost peak oil generation at the LOZ-1 well, NL, although only some intervals indicate advanced Thermal Maturity there. In contrast, the Lower Toarcian marlstones from the Swabian and Franconian Alb of SW-Germany are clearly immature, similar to the samples from Luxembourg. In NW-Germany, the Posidonia Shale covers a wide spectrum of Maturity ranging from immature to overmature.Source potential index (SPI) indicates the highest value in the LOZ-1, NL followed by Wickensen, NW-Germany and Esch-sur-Alzette, LU, mainly due to differences in thickness of the studied sections. The lowest value was observed in SW-Germany. The Lower Toarcian (Jet Rock) in Runswick Bay, UK, is assumed to have a high shale oil potential because of its advanced Thermal Maturity, although its SPI is not high due to the limited thickness of the section studied. The PS in SW-Germany has low shale oil potential due to low Thermal Maturity and limited thickness. © 2015 Elsevier B.V.
