Burgess Shale-type deposits provide a wealth of information on the early evolution of animals.Questions that are central to understanding the exceptional preservation of these biotas and the paleoenvironments they inh...Burgess Shale-type deposits provide a wealth of information on the early evolution of animals.Questions that are central to understanding the exceptional preservation of these biotas and the paleoenvironments they inhabited may be obscured by the post-depositional alteration due to metamorphism at depth and weathering near the Earth’s surface.Among over 50 Cambrian BST biotas,the Chengjiang and Qingjiang deposits are well known for their richness of soft-bodied taxa,fidelity of preservation,and Early Cambrian Age.While alteration via weathering has been well-investigated,the thermal maturity of the units bearing the two biotas has not yet been elucidated.Here we investigate peak metamorphic temperatures of the two deposits using two independent methods.Paleogeotemperature gradient analyses demonstrate that the most fossiliferous sections of the Chengjiang were buried at a maximum depth of∼8500 m in the Early Triassic,corresponding to∼300°C,while the type area of the Qingjiang biota was buried at a maximum depth of∼8700 m in the Early Jurassic,corresponding to∼240°C.Raman geothermometer analyses of fossil carbonaceous material demonstrate that peak temperatures varied across localities with different burial depth.The two productive sections of the Chengjiang biota were thermally altered at a peak temperature of approximately 300°C,and the main locality of the Qingjiang biota experienced a peak temperature of 238±22°C.These results from two independent methods are concordant.Among BST deposits for which thermal maturity has been documented,the Qingjiang biota is the least thermally mature,and therefore holds promise for enriching our understanding of BST deposits.展开更多
This work restored the erosion thickness of the top surface of each Cretaceous formations penetrated by the typical well in the Hari sag, and simulated the subsidence burial history of this well with software BasinMod...This work restored the erosion thickness of the top surface of each Cretaceous formations penetrated by the typical well in the Hari sag, and simulated the subsidence burial history of this well with software BasinMod. It is firstly pointed out that the tectonic subsidence evolution of the Hari sag since the Cretaceous can be divided into four phases: initial subsidence phase, rapid subsidence phase,uplift and erosion phase, and stable slow subsidence phase. A detailed reconstruction of the tectonothermal evolution and hydrocarbon generation histories of typical well was undertaken using the EASY R% model, which is constrained by vitrinite reflectance(R) and homogenization temperatures of fluid inclusions. In the rapid subsidence phase, the peak period of hydrocarbon generation was reached at c.a.105.59 Ma with the increasing thermal evolution degree. A concomitant rapid increase in paleotemperatures occurred and reached a maximum geothermal gradient of about 43-45℃/km. The main hydrocarbon generation period ensued around 105.59-80.00 Ma and the greatest buried depth of the Hari sag was reached at c.a. 80.00 Ma, when the maximum paleo-temperature was over 180℃.Subsequently, the sag entered an uplift and erosion phase followed by a stable slow subsidence phase during which the temperature gradient, thermal evolution, and hydrocarbon generation decreased gradually. The hydrocarbon accumulation period was discussed based on homogenization temperatures of inclusions and it is believed that two periods of rapid hydrocarbon accumulation events occurred during the Cretaceous rapid subsidence phase. The first accumulation period observed in the Bayingebi Formation(Kb) occurred primarily around 105.59-103.50 Ma with temperatures of 125-150℃. The second accumulation period observed in the Suhongtu Formation(Ks) occurred primarily around84.00-80.00 Ma with temperatures of 120-130℃. The second is the major accumulation period, and the accumulation mainly occurred in the Late Cretaceous. The hydrocarbon accumulation process was comprehensively controlled by tectono-thermal evolution and hydrocarbon generation history. During the rapid subsidence phase, the paleo temperature and geothermal gradient increased rapidly and resulted in increasing thermal evolution extending into the peak period of hydrocarbon generation,which is the key reason for hydrocarbon filling and accumulation.展开更多
Thermal maturity indices and modelling based on Arrhenius-equation reaction kinetics have played an important role in oil and gas exploration and provided petroleum generation insight for many kerogenrich source rocks...Thermal maturity indices and modelling based on Arrhenius-equation reaction kinetics have played an important role in oil and gas exploration and provided petroleum generation insight for many kerogenrich source rocks.Debate continues concerning how best to integrate the Arrhenius equation and which activation energies(E)and frequency factors(A)values to apply.A case is made for the strong theoretical basis and practical advantages of the time-temperature index(∑TTIARR)method,first published in 1998,using a single,carefully selected E-A set(E?218 kJ/mol(52.1 kcal/mol);A?5.45Et26/my)from the well-established A-E trend for published kerogen kinetics.An updated correlation between ∑TTIARR and vitrinite reflectance(Ro)is provided in which the P TTIARR scale spans some 18 orders of magnitude.The method is readily calculated in spreadsheets and can be further enhanced by visual basic for application code to provide optimization.Optimization is useful for identifying possible geothermal gradients and erosion intervals covering multiple burial intervals that can match calculated thermal maturities with measured Ro data.A memetic optimizer with firefly and dynamic local search memes is described that flexibly conducts exploration and exploitation of the feasible,multi-dimensional,thermal history solution space to find high-performing solutions to complex burial and thermal histories.A complex deep burial history example,with several periods of uplift and erosion and fluctuating heat flow is used to demonstrate what can be achieved with the memetic optimizer.By carefully layering in constraints to the models specific insights to episodes in their thermal history can be exposed,leading to better characterization of the timing of petroleum generation.The objective function found to be most effective for this type of optimization is the mean square error(MSE)of multiple burial intervals for the difference between calculated and measure Ro.The sensitively-scaled P TTIARR methodology,coupled with the memetic optimizer,is well suited for rapidly conducting basin-wide thermal maturity modelling involving multiple pseudo-wells to provide thermal maturity analysis at fine degrees of granularity.展开更多
The Yong＇an-Meitai area is the focus of the present exploration in the Fushan Depression, Beibuwan Basin, South China Sea. All oils from this area are geochemically characterized by higher Pr/Ph ratio, higher proport...The Yong＇an-Meitai area is the focus of the present exploration in the Fushan Depression, Beibuwan Basin, South China Sea. All oils from this area are geochemically characterized by higher Pr/Ph ratio, higher proportion of heavy molecular weight hydrocarbons, and higher proportion of C29 regular steranes, which indicate that the organic matter of source rocks might have been deposited in an oxidizing palaeoenvironment and be dominated by higher plant organic matter input. The oil from E3w2 （the second member of Weizhou Fro. of the Oligocene） has a much higher density, relatively higher Pr/nC17 and Ph/nC18 ratios, and a ＂UCM--unresolved complex mixture＂ on gas chromatograms, which indicate that it has been slightly biodegraded. CPI and other terpane and sterane isomer ratios suggest they are all mature oils. The timing of oil charging in E3w2 and E2I1 （the first member of the Liushagang Fro. of the Eocene） determined by the homogenization temperatures of fluid inclusions and thermal evolution history are from 9-3 Ma and 8-3 Ma, respectively. Thus, the interpretation of E3w2 as a secondary reservoir is unlikely. The timing of oil charging is later than that of hydrocarbon generating and expulsion of Liushagang Fin. source rocks and trap formation, which is favorable for oil accumulation in this area. All molecular parameters that are used for tracing oil filling direction decrease with shallower burial depth, which suggests vertical oil migration. The widely occurring faults that penetrate through the source rocks of the Liushagang Fro. may serve as a fine oil charging conduit.展开更多
Pre-existing models for thermal history modelling have shown deficiency in explicit algorithms to establish the quantitative relationship between maturity indices and thermal gradients in some sedimentary basins that ...Pre-existing models for thermal history modelling have shown deficiency in explicit algorithms to establish the quantitative relationship between maturity indices and thermal gradients in some sedimentary basins that experienced multi-episodic rifting evolution. In this study, a forward and inverse combination model（FICM） is proposed to estimate the vitrinite reflectance（Ro） and thermal gradients. The forward module is used to calculate Ro values. It couples the EASY%Ro model with burial history reconstruction with consideration of thermal gradient variations during basin evolution. The inverse module reconstructs histoical thermal gradients by calibrating cmputed Ro against measured Ro data. The time-temperature series is a necessary input for both forward and inverse modules. Sample density is a profound factor influencing the accuracy of modelling results. In order to obtain satisfying outputs, a sufficient sample density is required. Thermal gradients are assumed to vary linearly between two given samples. Modelling results of case studies indicate that the sensitivity of heating time to Ro evlution is differnt with thermal gradients depending on geolgoical setting. Three difffernt districts, which include the time-sensitive area, the temperature-sensitive area and the non-sensitive area, can be recognized on the the relationship map among Ro variations, heating time and geothermal gradients. This model can be applied to reconstruct the thermal history and maturation evolution in a basin that has undergone complex multi-episodic rifting.展开更多
The average geothermal gradient in the Qin-shui Basin, Shanxi Province, North China, estimated from temperature logging data of 20 boreholes is 28.2±1.03℃/km. The thermal conductivities of 39 rock samples are me...The average geothermal gradient in the Qin-shui Basin, Shanxi Province, North China, estimated from temperature logging data of 20 boreholes is 28.2±1.03℃/km. The thermal conductivities of 39 rock samples are measured and 20 heat flow values are obtained. The estimated heat flow ranges from 44.75 mW7m2 to 101.81 mW/m2, with a mean of 62.69±15.20 mW/m2. The thermal history reconstruction from the inversion of vitrinite data, using Ther-model for Windows 2004, reveals that the average paleo-heat flow at the time of maximum burial in late Jurassic to early Cretaceous is 158.41 mW/m2 for the north part, 119.57 mW/m2 for the central part and 169.43 mW/m2for the south part of the basin respectively. The reconstruction of the buried history of the strata indicates that the age for the end of sedimentation and the beginning of erosion for the basin is 108-156 Ma, and that the eroded thickness of the strata is 2603 m in the north, 2291 m in the central, and 2528.9 m in the south of the basin respectively. The 'higher in the north and the south, lower in the central' distribution pattern of the paleo-heat flow coincides with the distribution of the coal-bed methane spatially and temporally, which shows that the coal-bed methane is controlled by the paleo-geotem-perature field in the basin.展开更多
Three types of practical data are used for basin simulation: stratigraphic column thicknesses interpreted in the light of the common seismic reflecting layers, the percentage of mudy rocks in the column and the statis...Three types of practical data are used for basin simulation: stratigraphic column thicknesses interpreted in the light of the common seismic reflecting layers, the percentage of mudy rocks in the column and the statistical heat flow values. A mesh point data read-in technique is used for the region covered by Tertiary strata in the basin A B-T-M computer software is developed for simulating the burial, thermal and oil-gas maturation histories on 703 mesh points. Furthermore, five typical types of oil-gas evolution trends are summarized on the basis of the characteristics of B-T-M evolution graph of each single mesh point. A careful analysis shows that the sedimentation-burial history through differentiated stratum thermal history in the different parts of the basin ultimately controls the temporal sequence and the threshold temperature and depth of oil-gas maturation, as well as the whole evolutionary process of petroleum formation of oil-source rocks from low-maturation, high-maturation through over-maturation to the limit of wet-gas preservation at different development stages. All this would provide an important basis for the prediction of oil-gas resource prospect in the Qaidam Basin.展开更多
基金supported by the Natural Science Foundation of China(Nos.41930319,41621003,and EAR-1554897)the 111 Project(No.D17013)the Natural Science Basic Research Plan of Shaanxi Province(No.2022JC-DW5-01).
文摘Burgess Shale-type deposits provide a wealth of information on the early evolution of animals.Questions that are central to understanding the exceptional preservation of these biotas and the paleoenvironments they inhabited may be obscured by the post-depositional alteration due to metamorphism at depth and weathering near the Earth’s surface.Among over 50 Cambrian BST biotas,the Chengjiang and Qingjiang deposits are well known for their richness of soft-bodied taxa,fidelity of preservation,and Early Cambrian Age.While alteration via weathering has been well-investigated,the thermal maturity of the units bearing the two biotas has not yet been elucidated.Here we investigate peak metamorphic temperatures of the two deposits using two independent methods.Paleogeotemperature gradient analyses demonstrate that the most fossiliferous sections of the Chengjiang were buried at a maximum depth of∼8500 m in the Early Triassic,corresponding to∼300°C,while the type area of the Qingjiang biota was buried at a maximum depth of∼8700 m in the Early Jurassic,corresponding to∼240°C.Raman geothermometer analyses of fossil carbonaceous material demonstrate that peak temperatures varied across localities with different burial depth.The two productive sections of the Chengjiang biota were thermally altered at a peak temperature of approximately 300°C,and the main locality of the Qingjiang biota experienced a peak temperature of 238±22°C.These results from two independent methods are concordant.Among BST deposits for which thermal maturity has been documented,the Qingjiang biota is the least thermally mature,and therefore holds promise for enriching our understanding of BST deposits.
基金supported by the project of "Constraints on Lithospheric Dynamic Evolution and Hydrocarbon Accumulation from Late Mesozoic Paleo-geothermal Field in Ordos and Qinshui Basins" (grant No. 41630312)the National Nature Science Foundation of China (grants No. 41372208 and 40534019)+1 种基金the Open Found of the State Key Laboratory of Ore Deposit Geochemistry, CAS (grant No. 201304)supported by international program for Ph.D. candidates, Sun Yat-Sen University
文摘This work restored the erosion thickness of the top surface of each Cretaceous formations penetrated by the typical well in the Hari sag, and simulated the subsidence burial history of this well with software BasinMod. It is firstly pointed out that the tectonic subsidence evolution of the Hari sag since the Cretaceous can be divided into four phases: initial subsidence phase, rapid subsidence phase,uplift and erosion phase, and stable slow subsidence phase. A detailed reconstruction of the tectonothermal evolution and hydrocarbon generation histories of typical well was undertaken using the EASY R% model, which is constrained by vitrinite reflectance(R) and homogenization temperatures of fluid inclusions. In the rapid subsidence phase, the peak period of hydrocarbon generation was reached at c.a.105.59 Ma with the increasing thermal evolution degree. A concomitant rapid increase in paleotemperatures occurred and reached a maximum geothermal gradient of about 43-45℃/km. The main hydrocarbon generation period ensued around 105.59-80.00 Ma and the greatest buried depth of the Hari sag was reached at c.a. 80.00 Ma, when the maximum paleo-temperature was over 180℃.Subsequently, the sag entered an uplift and erosion phase followed by a stable slow subsidence phase during which the temperature gradient, thermal evolution, and hydrocarbon generation decreased gradually. The hydrocarbon accumulation period was discussed based on homogenization temperatures of inclusions and it is believed that two periods of rapid hydrocarbon accumulation events occurred during the Cretaceous rapid subsidence phase. The first accumulation period observed in the Bayingebi Formation(Kb) occurred primarily around 105.59-103.50 Ma with temperatures of 125-150℃. The second accumulation period observed in the Suhongtu Formation(Ks) occurred primarily around84.00-80.00 Ma with temperatures of 120-130℃. The second is the major accumulation period, and the accumulation mainly occurred in the Late Cretaceous. The hydrocarbon accumulation process was comprehensively controlled by tectono-thermal evolution and hydrocarbon generation history. During the rapid subsidence phase, the paleo temperature and geothermal gradient increased rapidly and resulted in increasing thermal evolution extending into the peak period of hydrocarbon generation,which is the key reason for hydrocarbon filling and accumulation.
文摘Thermal maturity indices and modelling based on Arrhenius-equation reaction kinetics have played an important role in oil and gas exploration and provided petroleum generation insight for many kerogenrich source rocks.Debate continues concerning how best to integrate the Arrhenius equation and which activation energies(E)and frequency factors(A)values to apply.A case is made for the strong theoretical basis and practical advantages of the time-temperature index(∑TTIARR)method,first published in 1998,using a single,carefully selected E-A set(E?218 kJ/mol(52.1 kcal/mol);A?5.45Et26/my)from the well-established A-E trend for published kerogen kinetics.An updated correlation between ∑TTIARR and vitrinite reflectance(Ro)is provided in which the P TTIARR scale spans some 18 orders of magnitude.The method is readily calculated in spreadsheets and can be further enhanced by visual basic for application code to provide optimization.Optimization is useful for identifying possible geothermal gradients and erosion intervals covering multiple burial intervals that can match calculated thermal maturities with measured Ro data.A memetic optimizer with firefly and dynamic local search memes is described that flexibly conducts exploration and exploitation of the feasible,multi-dimensional,thermal history solution space to find high-performing solutions to complex burial and thermal histories.A complex deep burial history example,with several periods of uplift and erosion and fluctuating heat flow is used to demonstrate what can be achieved with the memetic optimizer.By carefully layering in constraints to the models specific insights to episodes in their thermal history can be exposed,leading to better characterization of the timing of petroleum generation.The objective function found to be most effective for this type of optimization is the mean square error(MSE)of multiple burial intervals for the difference between calculated and measure Ro.The sensitively-scaled P TTIARR methodology,coupled with the memetic optimizer,is well suited for rapidly conducting basin-wide thermal maturity modelling involving multiple pseudo-wells to provide thermal maturity analysis at fine degrees of granularity.
基金This research was financially supported by the Natural Science Foundation of China(Grant No.40672093)CNPC Innovation Fund(07El001)the ESS-China Hydrocarborn Geoscience Collaboration Project under Natural Resources Canada's International 0pportunities Program.We extend our thanks to South 0il Exploration and Development Company of PetroChina for samples collection.
文摘The Yong＇an-Meitai area is the focus of the present exploration in the Fushan Depression, Beibuwan Basin, South China Sea. All oils from this area are geochemically characterized by higher Pr/Ph ratio, higher proportion of heavy molecular weight hydrocarbons, and higher proportion of C29 regular steranes, which indicate that the organic matter of source rocks might have been deposited in an oxidizing palaeoenvironment and be dominated by higher plant organic matter input. The oil from E3w2 （the second member of Weizhou Fro. of the Oligocene） has a much higher density, relatively higher Pr/nC17 and Ph/nC18 ratios, and a ＂UCM--unresolved complex mixture＂ on gas chromatograms, which indicate that it has been slightly biodegraded. CPI and other terpane and sterane isomer ratios suggest they are all mature oils. The timing of oil charging in E3w2 and E2I1 （the first member of the Liushagang Fro. of the Eocene） determined by the homogenization temperatures of fluid inclusions and thermal evolution history are from 9-3 Ma and 8-3 Ma, respectively. Thus, the interpretation of E3w2 as a secondary reservoir is unlikely. The timing of oil charging is later than that of hydrocarbon generating and expulsion of Liushagang Fin. source rocks and trap formation, which is favorable for oil accumulation in this area. All molecular parameters that are used for tracing oil filling direction decrease with shallower burial depth, which suggests vertical oil migration. The widely occurring faults that penetrate through the source rocks of the Liushagang Fro. may serve as a fine oil charging conduit.
基金the National Natural Science Foundation of China (Nos. 91028009 and 41372112)the Key Project of Hubei Natural Science Foundation (No. 2008CDA095)the Funding of Key Laboratory of Tectonics and Petroleum Resources of the Ministry of Education (No. TPR-2012-02)
文摘Pre-existing models for thermal history modelling have shown deficiency in explicit algorithms to establish the quantitative relationship between maturity indices and thermal gradients in some sedimentary basins that experienced multi-episodic rifting evolution. In this study, a forward and inverse combination model（FICM） is proposed to estimate the vitrinite reflectance（Ro） and thermal gradients. The forward module is used to calculate Ro values. It couples the EASY%Ro model with burial history reconstruction with consideration of thermal gradient variations during basin evolution. The inverse module reconstructs histoical thermal gradients by calibrating cmputed Ro against measured Ro data. The time-temperature series is a necessary input for both forward and inverse modules. Sample density is a profound factor influencing the accuracy of modelling results. In order to obtain satisfying outputs, a sufficient sample density is required. Thermal gradients are assumed to vary linearly between two given samples. Modelling results of case studies indicate that the sensitivity of heating time to Ro evlution is differnt with thermal gradients depending on geolgoical setting. Three difffernt districts, which include the time-sensitive area, the temperature-sensitive area and the non-sensitive area, can be recognized on the the relationship map among Ro variations, heating time and geothermal gradients. This model can be applied to reconstruct the thermal history and maturation evolution in a basin that has undergone complex multi-episodic rifting.
文摘The average geothermal gradient in the Qin-shui Basin, Shanxi Province, North China, estimated from temperature logging data of 20 boreholes is 28.2±1.03℃/km. The thermal conductivities of 39 rock samples are measured and 20 heat flow values are obtained. The estimated heat flow ranges from 44.75 mW7m2 to 101.81 mW/m2, with a mean of 62.69±15.20 mW/m2. The thermal history reconstruction from the inversion of vitrinite data, using Ther-model for Windows 2004, reveals that the average paleo-heat flow at the time of maximum burial in late Jurassic to early Cretaceous is 158.41 mW/m2 for the north part, 119.57 mW/m2 for the central part and 169.43 mW/m2for the south part of the basin respectively. The reconstruction of the buried history of the strata indicates that the age for the end of sedimentation and the beginning of erosion for the basin is 108-156 Ma, and that the eroded thickness of the strata is 2603 m in the north, 2291 m in the central, and 2528.9 m in the south of the basin respectively. The 'higher in the north and the south, lower in the central' distribution pattern of the paleo-heat flow coincides with the distribution of the coal-bed methane spatially and temporally, which shows that the coal-bed methane is controlled by the paleo-geotem-perature field in the basin.
基金Project supported by the National Natural Science Foundation of China.
文摘Three types of practical data are used for basin simulation: stratigraphic column thicknesses interpreted in the light of the common seismic reflecting layers, the percentage of mudy rocks in the column and the statistical heat flow values. A mesh point data read-in technique is used for the region covered by Tertiary strata in the basin A B-T-M computer software is developed for simulating the burial, thermal and oil-gas maturation histories on 703 mesh points. Furthermore, five typical types of oil-gas evolution trends are summarized on the basis of the characteristics of B-T-M evolution graph of each single mesh point. A careful analysis shows that the sedimentation-burial history through differentiated stratum thermal history in the different parts of the basin ultimately controls the temporal sequence and the threshold temperature and depth of oil-gas maturation, as well as the whole evolutionary process of petroleum formation of oil-source rocks from low-maturation, high-maturation through over-maturation to the limit of wet-gas preservation at different development stages. All this would provide an important basis for the prediction of oil-gas resource prospect in the Qaidam Basin.
