2010 Vol. 28, No. 1
Display Method:
2010, 28(1): 1-9.
Abstract:
In this paper, the equilibrium constant of the reactions related to the H2S (g) /H2S (aq) / HS / H+ / S2 system at various temperatures has been calculated as a foundation of increment of Gibbs free energy. The relationship between pH, fluid pressure and buried depth during the dissolution of calcite and dolomite in acetic medium are attained. The different contributions of CO2 and H2S to \[H+\] and different dissolution ability to carbonate of the two media under the conditions from surface to deep buried are described as follow: 1) Temperature and (or) PCO2 increasing will lead to the elevation of \[H+\] that need to dissolve the calcite and dolomite whether CO2 or H2S as a dissolvent. At relatively deep burial conditions, high PCO2 led by high fluid pressure would make the carbonate dissolution more difficult. CO2 increasing may cause the precipitation of carbonate minerals instead of the dissolution if \[H+\] was buffered; 2) The retrograde solubility model of carbonate minerals is tenable on chemistry no matter what type of acid medium. Low temperature diagenesis environment, upward migration of deep hydrothermal and the tectonic uplift would result in the temperature decreasing (ΔT) and improve the solution ability of H2S and CO2 (including other acid medium) to carbonate minerals; 3) In surface and near surface (the depth range of several hundred meters), the \[H+\] contributed by dissolved CO2 is slightly higher than that contributed by dissolved H2S when CO2 and H2S coexist. Acid fluid related to CO2 is relatively important for the dissolution of carbonate minerals, however, the \[H+\] contributed by dissolved H2S is much greater than that contributed by dissolved CO2 in deep burial, especially when the depth is more than 4000 m. Deep dissolution of carbonate would be more developed in deep buried condition where sulfate reduction exists, which could be one of the important reasons why secondary porosity develop in deep burial, NE Sichuan.
In this paper, the equilibrium constant of the reactions related to the H2S (g) /H2S (aq) / HS / H+ / S2 system at various temperatures has been calculated as a foundation of increment of Gibbs free energy. The relationship between pH, fluid pressure and buried depth during the dissolution of calcite and dolomite in acetic medium are attained. The different contributions of CO2 and H2S to \[H+\] and different dissolution ability to carbonate of the two media under the conditions from surface to deep buried are described as follow: 1) Temperature and (or) PCO2 increasing will lead to the elevation of \[H+\] that need to dissolve the calcite and dolomite whether CO2 or H2S as a dissolvent. At relatively deep burial conditions, high PCO2 led by high fluid pressure would make the carbonate dissolution more difficult. CO2 increasing may cause the precipitation of carbonate minerals instead of the dissolution if \[H+\] was buffered; 2) The retrograde solubility model of carbonate minerals is tenable on chemistry no matter what type of acid medium. Low temperature diagenesis environment, upward migration of deep hydrothermal and the tectonic uplift would result in the temperature decreasing (ΔT) and improve the solution ability of H2S and CO2 (including other acid medium) to carbonate minerals; 3) In surface and near surface (the depth range of several hundred meters), the \[H+\] contributed by dissolved CO2 is slightly higher than that contributed by dissolved H2S when CO2 and H2S coexist. Acid fluid related to CO2 is relatively important for the dissolution of carbonate minerals, however, the \[H+\] contributed by dissolved H2S is much greater than that contributed by dissolved CO2 in deep burial, especially when the depth is more than 4000 m. Deep dissolution of carbonate would be more developed in deep buried condition where sulfate reduction exists, which could be one of the important reasons why secondary porosity develop in deep burial, NE Sichuan.
2010, 28(1): 17-25.
Abstract:
In recent years, a great progress in hydrocarbon exploration has been achieved in dolomite reservoirs in which several large scale hydrocarbon pools were discovered in China. In view of which most of these dolomite reservoirs were formed during burial period, together with the high abundance of burial dolostones in stratigraphic columns, this paper aims to focus on classification of genetic texture in burial dolomite without consideration for relatively simple textures of primary or penecontemporaneous micritic dolomite. In international academic community, the classification of genetic texture of burial dolomite were well documented, but were less paid attentions in Chinese academic circle. In order to improve further study in this field, it is necessary to distinguish the different textures of dolomite formed in buried period, so that to understand the different characters of dolomization liquid. We here introduce a modified classification scheme for genetic texture of burial dolomite with references of classification about this field in international academe and combining the actual situation of dolomite researching in China. First of all, on the basis of dolomite occurrence, the dolomite texture is divided into two types: matrix dolomite and cement dolomite, Then according as crystal size, crystal shape, crystal surface and contact relation, burial dolomite is classified into six types, in which four are matrix: 1)finely crystalline, planare(s), floating dolomite; 2)finely crystalline, planare(s) dolomite; 3)finelycoarsely crystalline, nonplanara dolomite matrix; 4)coarsely crystalline, nonplanar saddle dolomite matrix, and the remanent two are cement: 1)finelymedium crystalline, planare(s) dolomite cement; 2)coarsely crystalline, nonplanar saddle dolomite cement. These texture classification provides a basis on which the dolomites formed in different diagenetic stages can be sorted out properly in the context of physicalchemical conditions of dolomitisiting fluids from which they formed，which provides effective approach of dolomite studying.
In recent years, a great progress in hydrocarbon exploration has been achieved in dolomite reservoirs in which several large scale hydrocarbon pools were discovered in China. In view of which most of these dolomite reservoirs were formed during burial period, together with the high abundance of burial dolostones in stratigraphic columns, this paper aims to focus on classification of genetic texture in burial dolomite without consideration for relatively simple textures of primary or penecontemporaneous micritic dolomite. In international academic community, the classification of genetic texture of burial dolomite were well documented, but were less paid attentions in Chinese academic circle. In order to improve further study in this field, it is necessary to distinguish the different textures of dolomite formed in buried period, so that to understand the different characters of dolomization liquid. We here introduce a modified classification scheme for genetic texture of burial dolomite with references of classification about this field in international academe and combining the actual situation of dolomite researching in China. First of all, on the basis of dolomite occurrence, the dolomite texture is divided into two types: matrix dolomite and cement dolomite, Then according as crystal size, crystal shape, crystal surface and contact relation, burial dolomite is classified into six types, in which four are matrix: 1)finely crystalline, planare(s), floating dolomite; 2)finely crystalline, planare(s) dolomite; 3)finelycoarsely crystalline, nonplanara dolomite matrix; 4)coarsely crystalline, nonplanar saddle dolomite matrix, and the remanent two are cement: 1)finelymedium crystalline, planare(s) dolomite cement; 2)coarsely crystalline, nonplanar saddle dolomite cement. These texture classification provides a basis on which the dolomites formed in different diagenetic stages can be sorted out properly in the context of physicalchemical conditions of dolomitisiting fluids from which they formed，which provides effective approach of dolomite studying.
2010, 28(1): 33-41.
Abstract:
Based on the data of cross sections and observation of thin sections,the Xiejiawan Member of Ganxi Formation ,Lower Devonian in the Longmenshan is considered to be generated from hybrid type Ⅰsediments dominative of shelf shales. Its genetic mechanisms include the major intermittent mixing mode, which is resulted from the storm flow, and the autochthonous mixing mode. The sedimentary facies of the Xiejiawan Member can be divided into following microfacies, hybrid shore,hybrid clastic shelf, hybrid carbonate shelf,shore peritidal residual + hybrid tidal flat,hybrid shelf shale + distal storm flow,hybrid continental shelf shale intercalated with proximal sandy storm flow,hybrid shelf shale intercalated with proximal sandy hybrid storm flow,and hybrid shelf shale intercalated with organic bank and point reef. Meanwhile, the Xiejiawan Member is characteristic of type Ⅱhybrid sequence and can be classified into 4 depositional system tracts of SMST,TST,EHST and LHST. Each system tract is superimposed by subsequences of different sedimentary sequences,textural styles and hybrid intensity. Among the all above mentioned sedimentary tracts,the SMST and LHST are of the most intensive intermittent mixing and autochthonous mixing,the intermittent mixing of TST is the weakest one,and the EHST is of weak intermittent mixing and autochthonous mixing.
Based on the data of cross sections and observation of thin sections,the Xiejiawan Member of Ganxi Formation ,Lower Devonian in the Longmenshan is considered to be generated from hybrid type Ⅰsediments dominative of shelf shales. Its genetic mechanisms include the major intermittent mixing mode, which is resulted from the storm flow, and the autochthonous mixing mode. The sedimentary facies of the Xiejiawan Member can be divided into following microfacies, hybrid shore,hybrid clastic shelf, hybrid carbonate shelf,shore peritidal residual + hybrid tidal flat,hybrid shelf shale + distal storm flow,hybrid continental shelf shale intercalated with proximal sandy storm flow,hybrid shelf shale intercalated with proximal sandy hybrid storm flow,and hybrid shelf shale intercalated with organic bank and point reef. Meanwhile, the Xiejiawan Member is characteristic of type Ⅱhybrid sequence and can be classified into 4 depositional system tracts of SMST,TST,EHST and LHST. Each system tract is superimposed by subsequences of different sedimentary sequences,textural styles and hybrid intensity. Among the all above mentioned sedimentary tracts,the SMST and LHST are of the most intensive intermittent mixing and autochthonous mixing,the intermittent mixing of TST is the weakest one,and the EHST is of weak intermittent mixing and autochthonous mixing.
2010, 28(1): 50-57.
Abstract:
Diagenetic facies are results of diagenetic evolutions under special depositionl and diagenetic environments, including grains, cements, and textures integrated features. The study of diagenetic facies is important to low porosity and permeability sandstones in current exploration phases. This paper divided forth member of Xujiahe system of Guangan region into five diagenetic types, and set up the logging characteristics of each diagenetic facies. After single wells diagenetic facies analysis, this paper has semiquantitatively evaluated forth member of Xujiahe Formation of Guangan area by authorizing thickenss percentage content contour diagrams, thickenss content contour diagrams, areal distribution graph of diagenetic facies.
Diagenetic facies are results of diagenetic evolutions under special depositionl and diagenetic environments, including grains, cements, and textures integrated features. The study of diagenetic facies is important to low porosity and permeability sandstones in current exploration phases. This paper divided forth member of Xujiahe system of Guangan region into five diagenetic types, and set up the logging characteristics of each diagenetic facies. After single wells diagenetic facies analysis, this paper has semiquantitatively evaluated forth member of Xujiahe Formation of Guangan area by authorizing thickenss percentage content contour diagrams, thickenss content contour diagrams, areal distribution graph of diagenetic facies.
2010, 28(1): 68-75.
Abstract:
The deepwater channel is one important element of deepwater sedimentary system, and is becoming more important to the oil industry for its potential hydrocarbon reserve. Most of the deepwater channels were buried in the submarine sedimentary formation, and are difficult to observe and study directly. Based on the new required 2D and 3D seismic data, this paper used attribute analysis technologies, likewise 3D ESP coherence time slices(flattened on the seafloor), RMS and 3D visualization to realize and study the deepwater channel developed on the slope of northern South China Sea. This channel was a deepwater sinuous channel developed in Pleistocene period, and was formed by the turbidite flow from the IndoChina peninsula. The channel is SWNE extend, the lateral erosional features is apparent. The 3D amplitude visualization map shows that the axis fill of the channel is high amplitude reflection, and was supposed to be sandrich fill, the other part of the channel fill is low amplitude reflection, and was supposed to be mudrich fill, which are similar with the deepwater channel drilled in the world. The deepwater sinuous channel has complex inner fill and composition architecture, the sand and shale layer are always interbedded, the shale layer could either hinder the migration of the flow and form overpressure or be a better seal to the flow, and we should pay more attention to this problem under the exploration and development to deepwater sinuous channel.
The deepwater channel is one important element of deepwater sedimentary system, and is becoming more important to the oil industry for its potential hydrocarbon reserve. Most of the deepwater channels were buried in the submarine sedimentary formation, and are difficult to observe and study directly. Based on the new required 2D and 3D seismic data, this paper used attribute analysis technologies, likewise 3D ESP coherence time slices(flattened on the seafloor), RMS and 3D visualization to realize and study the deepwater channel developed on the slope of northern South China Sea. This channel was a deepwater sinuous channel developed in Pleistocene period, and was formed by the turbidite flow from the IndoChina peninsula. The channel is SWNE extend, the lateral erosional features is apparent. The 3D amplitude visualization map shows that the axis fill of the channel is high amplitude reflection, and was supposed to be sandrich fill, the other part of the channel fill is low amplitude reflection, and was supposed to be mudrich fill, which are similar with the deepwater channel drilled in the world. The deepwater sinuous channel has complex inner fill and composition architecture, the sand and shale layer are always interbedded, the shale layer could either hinder the migration of the flow and form overpressure or be a better seal to the flow, and we should pay more attention to this problem under the exploration and development to deepwater sinuous channel.
2010, 28(1): 83-90.
Abstract:
Sandstones of the lower member of Dongying formation of paleogene system in Zhuangxi oilfield, Zhanhua sag, Jiyang depression are of stringbelt shaped extension, which are extremely similar to the geometry of sandstones deposited by meandering fluvial. Depositional genesis of the sandstone is one of the key basis for high resolution stratigraphic framework construction, reservoir properties distribution prediction and remainingoil redevelopment. Combined with regional geological setting, stratigraphic succession, petrological features, depositional features association, and sand body geometries of this member, it is considered that the sandstone of lower member of Dongying formation, which extends along the long axis of faulted basin, was deposited by slumpingtyped gravity flowturbidity current channel of long distance sediments source in the semideep to deep lacustrine environment with the confine of lacustrine bottom configuration. The sediment sources were from the fandeltas, sublacustrine fans in Chengdao area in the northern part. In terms of the depositonal regime of gravity flow channel, the turbidity channel was subdivided into three types of microfacies: central channel, channel margin, and subaqueous overflow. Sedimentary succession of individual central channel equals to members association of AB, ABD and AC of Bouma sequence. Reservoir rocks in the channel center are dominated by gravelly sandstone with normal graded bedding and hybrid sandstone with massive bedding, which are medium porosity and permeability. The external controls on the slumpingtyped turbidity current channel in study area is of the long term base level fall caused by volcanic eruption, episodic activity of faults controlled basin, the internal controls of the abundant sediments source, stepped faults perpendicular to the long axis of faulted basin, and negative lacustrine bottom configurations. A depositional model of tubidity current channel is established based on the depositional features and conditions of sediments.
Sandstones of the lower member of Dongying formation of paleogene system in Zhuangxi oilfield, Zhanhua sag, Jiyang depression are of stringbelt shaped extension, which are extremely similar to the geometry of sandstones deposited by meandering fluvial. Depositional genesis of the sandstone is one of the key basis for high resolution stratigraphic framework construction, reservoir properties distribution prediction and remainingoil redevelopment. Combined with regional geological setting, stratigraphic succession, petrological features, depositional features association, and sand body geometries of this member, it is considered that the sandstone of lower member of Dongying formation, which extends along the long axis of faulted basin, was deposited by slumpingtyped gravity flowturbidity current channel of long distance sediments source in the semideep to deep lacustrine environment with the confine of lacustrine bottom configuration. The sediment sources were from the fandeltas, sublacustrine fans in Chengdao area in the northern part. In terms of the depositonal regime of gravity flow channel, the turbidity channel was subdivided into three types of microfacies: central channel, channel margin, and subaqueous overflow. Sedimentary succession of individual central channel equals to members association of AB, ABD and AC of Bouma sequence. Reservoir rocks in the channel center are dominated by gravelly sandstone with normal graded bedding and hybrid sandstone with massive bedding, which are medium porosity and permeability. The external controls on the slumpingtyped turbidity current channel in study area is of the long term base level fall caused by volcanic eruption, episodic activity of faults controlled basin, the internal controls of the abundant sediments source, stepped faults perpendicular to the long axis of faulted basin, and negative lacustrine bottom configurations. A depositional model of tubidity current channel is established based on the depositional features and conditions of sediments.
2010, 28(1): 102-117.
Abstract:
Application of single grain detrital minerals to the provenance analysis of the adjacent basins to Dabie Shan is described in this paper. Correlation of the modern river sediments to the Dabie Shan source area shows that the chemical compositions of detrital garnet, Kwhite mica and tourmaline are useful indicators for provenance analysis. The characteristics of their chemical composition in the JurassicCretaceousPaleogene sediments reveal the complication of rock composition of Dabie Shan as the source area. The exhumed high pressureultrahigh pressure metamorphic rocks formed due to the deep subduction of Yangtze Block became an important source rock of the sedimentary basins adjacent to southeastern Dabie Shan during the CretaceousPaleogene, gradually. They were mainly located in the source area of the sedimentary basins adjacent to north Dabie Shan during the Jurassic. The detrital Crspinel composition and detrital zircon age structure of the Carboniferous sediments in the northern margin of Dabie Shan show that the source area is characteristic of the southern active continental margin of the North China Block during the early Paleozoic. In addition, it is characteristic of detrital zircon age of the Yangtze Block.
Application of single grain detrital minerals to the provenance analysis of the adjacent basins to Dabie Shan is described in this paper. Correlation of the modern river sediments to the Dabie Shan source area shows that the chemical compositions of detrital garnet, Kwhite mica and tourmaline are useful indicators for provenance analysis. The characteristics of their chemical composition in the JurassicCretaceousPaleogene sediments reveal the complication of rock composition of Dabie Shan as the source area. The exhumed high pressureultrahigh pressure metamorphic rocks formed due to the deep subduction of Yangtze Block became an important source rock of the sedimentary basins adjacent to southeastern Dabie Shan during the CretaceousPaleogene, gradually. They were mainly located in the source area of the sedimentary basins adjacent to north Dabie Shan during the Jurassic. The detrital Crspinel composition and detrital zircon age structure of the Carboniferous sediments in the northern margin of Dabie Shan show that the source area is characteristic of the southern active continental margin of the North China Block during the early Paleozoic. In addition, it is characteristic of detrital zircon age of the Yangtze Block.
2010, 28(1): 128-139.
Abstract:
Typical sedimentary facies are identified through integrated studies of outcrops, cores, well logging data, and combined with single factor analysis and comprehensive mapping, lithofacies paleogeography of each period of Cambrian in Sichuan Basin is determined. Depositional topography is higher in the west of the basin than in the east. Land source clastic rocks are mainly deposited in west basin and carbonate sediments are developed in the centraleast of the basin. There exist two and a half transgressionregression circles in the Cambrian in Sichuan Basin. The first transgression took place in Qiongzhusi period of the early Cambrian, hydrocarbon source rocks are deposited in shallow continental shelf. The first regression took place in Changlangpu period of the early Cambrian, land source clastic supply is sufficient and delta, clastic shoreland sedimentary facies are developed. Bank facies carbonate reservoirs are mainly deposited in Longwangmiao period of the early Cambrian (the second transgression) and Xixiangchi period of the middlelate Cambrian (the third transgression), in the higher topography of the restricted platform psammitic bank and oolitic beach carbonates are deposited, with the psammitic bank mainly developed in the centralwest basin and oolitic beach mainly developed in centraleast basin, and in the westsouth of the basin there exist inherited lagoon sediments.
Typical sedimentary facies are identified through integrated studies of outcrops, cores, well logging data, and combined with single factor analysis and comprehensive mapping, lithofacies paleogeography of each period of Cambrian in Sichuan Basin is determined. Depositional topography is higher in the west of the basin than in the east. Land source clastic rocks are mainly deposited in west basin and carbonate sediments are developed in the centraleast of the basin. There exist two and a half transgressionregression circles in the Cambrian in Sichuan Basin. The first transgression took place in Qiongzhusi period of the early Cambrian, hydrocarbon source rocks are deposited in shallow continental shelf. The first regression took place in Changlangpu period of the early Cambrian, land source clastic supply is sufficient and delta, clastic shoreland sedimentary facies are developed. Bank facies carbonate reservoirs are mainly deposited in Longwangmiao period of the early Cambrian (the second transgression) and Xixiangchi period of the middlelate Cambrian (the third transgression), in the higher topography of the restricted platform psammitic bank and oolitic beach carbonates are deposited, with the psammitic bank mainly developed in the centralwest basin and oolitic beach mainly developed in centraleast basin, and in the westsouth of the basin there exist inherited lagoon sediments.
2010, 28(1): 150-157.
Abstract:
Samples of surface sediments at 15 stations in the mud depocenter off the southern ZhejiangFujian coast were collected in both summer and winter seasons. The distribution pattern, seasonal variability of grainsize of the surface sediments in this area and their influential factors were discussed based on the grainsize measurements. The results indicate that surface sediments were mainly clayey silts with slight variations in the grain size parameters such as median grain size (Mz), standard deviation (SD), skewness (Sk) and kurtosis (Kg). There exists an evidently negative correlation between Mz and SD, while a weakly negative correlation is found between Sk and Kg. Two peak values around 4.92～6.46 and 25.32～33.27 μm, and a low value around 11.16～13.39 μm are identified from the SD of grainsize curves. Meanwhile, significant seasonal variability is found as indicated by the large differences between the parameters of surface sediments collected in summer and winter season. The ranges of all the four parameters in the winter samples are higher than those in the summer samples, while the values of Mz in winter samples are generally smaller than those in the summer samples. And the gradients of Sk and Kg are larger than those in the summer samples at the same station. The variability in SD of grain size in the winter samples was evidently higher than that in the summer samples. The variations of the parameters of surface sediments in this area are mostly attributed to sediment sources and the seasonal difference in marine dynamic environment.
Samples of surface sediments at 15 stations in the mud depocenter off the southern ZhejiangFujian coast were collected in both summer and winter seasons. The distribution pattern, seasonal variability of grainsize of the surface sediments in this area and their influential factors were discussed based on the grainsize measurements. The results indicate that surface sediments were mainly clayey silts with slight variations in the grain size parameters such as median grain size (Mz), standard deviation (SD), skewness (Sk) and kurtosis (Kg). There exists an evidently negative correlation between Mz and SD, while a weakly negative correlation is found between Sk and Kg. Two peak values around 4.92～6.46 and 25.32～33.27 μm, and a low value around 11.16～13.39 μm are identified from the SD of grainsize curves. Meanwhile, significant seasonal variability is found as indicated by the large differences between the parameters of surface sediments collected in summer and winter season. The ranges of all the four parameters in the winter samples are higher than those in the summer samples, while the values of Mz in winter samples are generally smaller than those in the summer samples. And the gradients of Sk and Kg are larger than those in the summer samples at the same station. The variability in SD of grain size in the winter samples was evidently higher than that in the summer samples. The variations of the parameters of surface sediments in this area are mostly attributed to sediment sources and the seasonal difference in marine dynamic environment.
2010, 28(1): 166-175.
Abstract:
Based on the principle of lead 210 excess decaying and the characteristics of modern lead 210 sediment profiles of 14 sediment cores from the Pearl River mouth and its adjacent areas, a Fourier series based model for counting variation sediment rates was built. Sediment series was analyzed at the Pearl River mouth within 50 sediment years. The lead 210 of each sediment cores was calculated in the model for counting variation sedimentation rates and gained more specific data of the sedimentation process. Sedimentation rates, dating results and those relations between the sedimentary environmental at the same time were analyzed. The result shows that sedimentation rates are distinct from each other greatly at different stations. The average sediment rates of the stations were 7.25cm/a,5.36cm/a,3.26cm/a,3.03cm/a,1.58cm/a, respectively. The sedimentation rates variation at different stations has good correlation with the flooding, storms, anthropological activities, geomorphologic evolvement and other environmental elements at the estuary within the same periods. It verified that the characteristic of lead 210 of the sediment profiles calculated from the Fourier series based model for counting variation sediment rates can explain the environmental statues/changes at the same time. The model also made experiences for other estuaries which would analyses the sediment rates from the characteristic of lead 210 of the sediment cores.
Based on the principle of lead 210 excess decaying and the characteristics of modern lead 210 sediment profiles of 14 sediment cores from the Pearl River mouth and its adjacent areas, a Fourier series based model for counting variation sediment rates was built. Sediment series was analyzed at the Pearl River mouth within 50 sediment years. The lead 210 of each sediment cores was calculated in the model for counting variation sedimentation rates and gained more specific data of the sedimentation process. Sedimentation rates, dating results and those relations between the sedimentary environmental at the same time were analyzed. The result shows that sedimentation rates are distinct from each other greatly at different stations. The average sediment rates of the stations were 7.25cm/a,5.36cm/a,3.26cm/a,3.03cm/a,1.58cm/a, respectively. The sedimentation rates variation at different stations has good correlation with the flooding, storms, anthropological activities, geomorphologic evolvement and other environmental elements at the estuary within the same periods. It verified that the characteristic of lead 210 of the sediment profiles calculated from the Fourier series based model for counting variation sediment rates can explain the environmental statues/changes at the same time. The model also made experiences for other estuaries which would analyses the sediment rates from the characteristic of lead 210 of the sediment cores.
2010, 28(1): 183-187.
Abstract:
The carbon and hydrogen isotopic composition of biogenic gas could indicate its forming mechanism and poolforming characteristics. In this paper, the forming ways and poolforming characteristics of the biogenic gas are researched according to the carbon and hydrogen isotopic composition of thirtyone samples from ten biogenic gas reservoirs. The studies show that the hydrogen isotopic composition of these biogenic gas reservoirs can be divided into three zones, i.e. δDCH4>200‰, 200‰>δDCH4<250‰, and δDCH4<250‰. The research results of forerunner showed that the main way of biogenic gas forming under the condition of continental fresh water facies is acetate fermentation. Our research results show that the typical way of biogenic gas forming under marine and saline lake facies is CO2 reduction, and the biogenic gas have heavy hydrogen isotopic composition, such as the values of δDCH4 are greater than 200‰; however, the main way of biogenic gas forming under the condition of land facies is the same way too, but they have light hydrogen isotopic composition which may relate to salty degree of ancient lakes as water medium, such as the values of δDCH4 are between 200‰ and 250‰. As compared with the relational data of Qaidam Basin, it is showed that the hydrogen isotope composition of the biogenic methane has the same trend as salty degree of water medium increases. The biogenic gas reservoir formed in continental transition region, in which CO2 reduction generated CH4 in company with fermentation together, may relate to constant salinity of ancient water medium and relatively high geothermal gradient，such as Baoshan basin. It has light hydrogen isotope, such as the value of δDCH4 less than 250‰, and heavy carbon isotope, which result in a negative correlation between its carbon and hydrogen isotope. The carbon and hydrogen isotope composition of biogenic gas controlled by the formation mechanism and ways can be used to identify whether it has industrial utilization value. In general, the biogenic gas from acetate fermentation is not favorable for the formation of gas reservoir.
The carbon and hydrogen isotopic composition of biogenic gas could indicate its forming mechanism and poolforming characteristics. In this paper, the forming ways and poolforming characteristics of the biogenic gas are researched according to the carbon and hydrogen isotopic composition of thirtyone samples from ten biogenic gas reservoirs. The studies show that the hydrogen isotopic composition of these biogenic gas reservoirs can be divided into three zones, i.e. δDCH4>200‰, 200‰>δDCH4<250‰, and δDCH4<250‰. The research results of forerunner showed that the main way of biogenic gas forming under the condition of continental fresh water facies is acetate fermentation. Our research results show that the typical way of biogenic gas forming under marine and saline lake facies is CO2 reduction, and the biogenic gas have heavy hydrogen isotopic composition, such as the values of δDCH4 are greater than 200‰; however, the main way of biogenic gas forming under the condition of land facies is the same way too, but they have light hydrogen isotopic composition which may relate to salty degree of ancient lakes as water medium, such as the values of δDCH4 are between 200‰ and 250‰. As compared with the relational data of Qaidam Basin, it is showed that the hydrogen isotope composition of the biogenic methane has the same trend as salty degree of water medium increases. The biogenic gas reservoir formed in continental transition region, in which CO2 reduction generated CH4 in company with fermentation together, may relate to constant salinity of ancient water medium and relatively high geothermal gradient，such as Baoshan basin. It has light hydrogen isotope, such as the value of δDCH4 less than 250‰, and heavy carbon isotope, which result in a negative correlation between its carbon and hydrogen isotope. The carbon and hydrogen isotope composition of biogenic gas controlled by the formation mechanism and ways can be used to identify whether it has industrial utilization value. In general, the biogenic gas from acetate fermentation is not favorable for the formation of gas reservoir.
2010, 28(1): 194-200.
Abstract:
The concentrations and the relative proportions of fluorene, dibenzofuran and dibenzothiophene and their methyl homologues(Fs,OFs and SFs) in a series of crude oils with different degrees of biodegradation from the Liaohe basin have been quantified and studied by GC—MS. The results show that fluorene, dibenzofuran and dibenzothiophene and their methyl homologuesare sensitive to biodegradation influence. In slightly biodegraded oils, the concentrations of fluorene, dibenzofuran and dibenzothiophene without alkyl side chain decreased at almost similar rate, but their relative proportions could remain constant and could be used as depositional environment indicator. In moderate or severely biodegraded oils, because of the variation of their ability to resistant biodegradation, their relative proportions have been altered and lost their original geochemical significance. However, as for their methyl homologues, the ability to resist biodegradation of methyl dibenzothiophene is more than methyl fluorene and methyl dibenzofuran, resulting in differently biodegraded rate, their relative proportions varied from slightly to severely biodegraded oils and could not be used to indicate the features of depositional environment. Although the concentrations of Fs,OFs and SFs in differently biodegraded oils were decreased during biodegradation, their rates differed significantly, their relative proportions varied with biodegradation all time. Therefore, for biodegraded oils, the cautions should be taken when their relative proportions of Fs,OFs and SFs are used to determine the depositional environment.
The concentrations and the relative proportions of fluorene, dibenzofuran and dibenzothiophene and their methyl homologues(Fs,OFs and SFs) in a series of crude oils with different degrees of biodegradation from the Liaohe basin have been quantified and studied by GC—MS. The results show that fluorene, dibenzofuran and dibenzothiophene and their methyl homologuesare sensitive to biodegradation influence. In slightly biodegraded oils, the concentrations of fluorene, dibenzofuran and dibenzothiophene without alkyl side chain decreased at almost similar rate, but their relative proportions could remain constant and could be used as depositional environment indicator. In moderate or severely biodegraded oils, because of the variation of their ability to resistant biodegradation, their relative proportions have been altered and lost their original geochemical significance. However, as for their methyl homologues, the ability to resist biodegradation of methyl dibenzothiophene is more than methyl fluorene and methyl dibenzofuran, resulting in differently biodegraded rate, their relative proportions varied from slightly to severely biodegraded oils and could not be used to indicate the features of depositional environment. Although the concentrations of Fs,OFs and SFs in differently biodegraded oils were decreased during biodegradation, their rates differed significantly, their relative proportions varied with biodegradation all time. Therefore, for biodegraded oils, the cautions should be taken when their relative proportions of Fs,OFs and SFs are used to determine the depositional environment.
2010, 28(1): 10-16.
Abstract:
The most common types of pores in the oolite dolomite reservoirs of the Lower Triassic Feixianguan Formation are moldic pores, crescentiform dissolution pores, lune dissolution pores and annular dissolution pores in Well Puguang 2 in Puguang Gasfield. The pores are directionally arranged. It was always believed that the pores were formed in early meteoric freshwater environments. However, the dissolution pores, with no clear deformation, are often associated with extrusion fractures, disintegration or crushed particles, indicating origin of burial dissolution after tectonic compression. The dissolution pores can be divided into two stages: the first one filling bitumen was formed before oil emplacement, the second one without bitumen occurred after oil turning into bitumen. It was considered that if structural compressional stress acted on the rocks, it could firstly cause cracks among the concentric layers of oolites where was the weak structural positions. When the stress was concentrated on the upper part of the oolites, it would develop cracks along the concentric layers by priority. The cracks were extended downward along the concentric layers as the stress increased, and which even circular and uncoating cracks could be formed. The late acidic fluids prefer to dissolute the oolites along the fractures, resulting in the formation of directional pores in the upper part of the concentric layers. With downwards dissolution along the fractures, the crescentiform pores and annular pores were developed and even moldic pores were formed as a result of increasing pressure and (or) stronger dissolution.
The most common types of pores in the oolite dolomite reservoirs of the Lower Triassic Feixianguan Formation are moldic pores, crescentiform dissolution pores, lune dissolution pores and annular dissolution pores in Well Puguang 2 in Puguang Gasfield. The pores are directionally arranged. It was always believed that the pores were formed in early meteoric freshwater environments. However, the dissolution pores, with no clear deformation, are often associated with extrusion fractures, disintegration or crushed particles, indicating origin of burial dissolution after tectonic compression. The dissolution pores can be divided into two stages: the first one filling bitumen was formed before oil emplacement, the second one without bitumen occurred after oil turning into bitumen. It was considered that if structural compressional stress acted on the rocks, it could firstly cause cracks among the concentric layers of oolites where was the weak structural positions. When the stress was concentrated on the upper part of the oolites, it would develop cracks along the concentric layers by priority. The cracks were extended downward along the concentric layers as the stress increased, and which even circular and uncoating cracks could be formed. The late acidic fluids prefer to dissolute the oolites along the fractures, resulting in the formation of directional pores in the upper part of the concentric layers. With downwards dissolution along the fractures, the crescentiform pores and annular pores were developed and even moldic pores were formed as a result of increasing pressure and (or) stronger dissolution.
2010, 28(1): 26-32.
Abstract:
The late Carboniferous phylloid aglal reef occurs in the carbonate platform margin. In this paper the phylloid reef's microfacies characteristic and sedimentary environment are analyzed by the way of detailed section microfacies analysis.We summed up 6 carbonate microfacies，i.e. bioclastic wackstone, bioclastic packstone, pelleted bioclastic packstone, phylloid algal wackstone and packstone, brachiopod packstone, bioclastic grainstone. We sums up a part sedimentary facies model, transfers from the depth open carbonate platform facies, phylloid algal reef facies, inner carbonate platform slope facies, inner carbonate platform shallow slope facies, shallow open carbonate platform facies, to intraplatform shoal facies, analyzing sedimentary environment of phylloid aglal reef. Based on the distribution of microfacies in the section, we can speculate it is the open carbonate platform environment in subtidal zone.
The late Carboniferous phylloid aglal reef occurs in the carbonate platform margin. In this paper the phylloid reef's microfacies characteristic and sedimentary environment are analyzed by the way of detailed section microfacies analysis.We summed up 6 carbonate microfacies，i.e. bioclastic wackstone, bioclastic packstone, pelleted bioclastic packstone, phylloid algal wackstone and packstone, brachiopod packstone, bioclastic grainstone. We sums up a part sedimentary facies model, transfers from the depth open carbonate platform facies, phylloid algal reef facies, inner carbonate platform slope facies, inner carbonate platform shallow slope facies, shallow open carbonate platform facies, to intraplatform shoal facies, analyzing sedimentary environment of phylloid aglal reef. Based on the distribution of microfacies in the section, we can speculate it is the open carbonate platform environment in subtidal zone.
2010, 28(1): 42-49.
Abstract:
Based on observations on the macromicro features of outcrop sections and the drilling cores of the Leikoupo Formation of Middle Triassic in the northwest of Sichuan Basin, and combining with the conventional physical property, this paper profoundly studies the types, features, reservoir capacity, influencing factors on bank reservoir property and distribution of the banks within study area. It is considered that there are four types of bank intraclast bank, algalbounding grain bank, oncolite bank and oolitic bank , of which the intraclast bank and algalbounding grain bank widely distribute in member 3 of Leikoupo from Zhong well 46Yangjia yan, oncolite bank concentrate in lower submember of member 3 of Leikoupo Formation in Jiangyou Guanyin bank, and oolitic bank concentrate in the middle-upper part of member 4 of Leikoupo Formation in Mianzhu. The high energy bank is the results of the environment of the limited eperic sea and Open shelf sea. By the joint action of krastification of hypergence period and burial dissolution for intraclast bank and algalbounding grain bank in the middleupper submember of member 3 of Leikoupo Formation, the gypsum, halite and calcite filled in the reservoir space are dissolved, intercrystalline solution pores, intergranular dissolution pore, intragranular dissolved pore, algaebounding framework dissolved pore and small cave develop well, and they are of the best reservoir body, which mainly distribute in the Zhong Well 46Yu Well 1 block.
Based on observations on the macromicro features of outcrop sections and the drilling cores of the Leikoupo Formation of Middle Triassic in the northwest of Sichuan Basin, and combining with the conventional physical property, this paper profoundly studies the types, features, reservoir capacity, influencing factors on bank reservoir property and distribution of the banks within study area. It is considered that there are four types of bank intraclast bank, algalbounding grain bank, oncolite bank and oolitic bank , of which the intraclast bank and algalbounding grain bank widely distribute in member 3 of Leikoupo from Zhong well 46Yangjia yan, oncolite bank concentrate in lower submember of member 3 of Leikoupo Formation in Jiangyou Guanyin bank, and oolitic bank concentrate in the middle-upper part of member 4 of Leikoupo Formation in Mianzhu. The high energy bank is the results of the environment of the limited eperic sea and Open shelf sea. By the joint action of krastification of hypergence period and burial dissolution for intraclast bank and algalbounding grain bank in the middleupper submember of member 3 of Leikoupo Formation, the gypsum, halite and calcite filled in the reservoir space are dissolved, intercrystalline solution pores, intergranular dissolution pore, intragranular dissolved pore, algaebounding framework dissolved pore and small cave develop well, and they are of the best reservoir body, which mainly distribute in the Zhong Well 46Yu Well 1 block.
2010, 28(1): 58-67.
Abstract:
Delta sandbody is the most important largescale continentalbasin hydrocarbon reservoir in China,The analysis of delta sandbody framework is very important to the prediction of delta sandbody. Based on the synthetical analysis the outcrops profile and grain size analysis data, delta outcrops along the eastern margin of Ordos Basin. Detailed study has been carried out on grain size and river Pattern at the Upper Triassic delta, the study demonstrate that the sandbody architecture and channel morphology should be happen to evolve regularly from the Chang 7 Member to Chang 4+5 Member in Yanchang Formation,and delta sand body framework is build including meandering distributary channel, braided distributary channel, and submarginal subsurface distributary channel,distant subsurface distributary channel and sheetlike subsurface distributary channel.The study suggests that lies different grain size parameter and SkKg in different river Pattern.
Delta sandbody is the most important largescale continentalbasin hydrocarbon reservoir in China,The analysis of delta sandbody framework is very important to the prediction of delta sandbody. Based on the synthetical analysis the outcrops profile and grain size analysis data, delta outcrops along the eastern margin of Ordos Basin. Detailed study has been carried out on grain size and river Pattern at the Upper Triassic delta, the study demonstrate that the sandbody architecture and channel morphology should be happen to evolve regularly from the Chang 7 Member to Chang 4+5 Member in Yanchang Formation,and delta sand body framework is build including meandering distributary channel, braided distributary channel, and submarginal subsurface distributary channel,distant subsurface distributary channel and sheetlike subsurface distributary channel.The study suggests that lies different grain size parameter and SkKg in different river Pattern.
2010, 28(1): 76-82.
Abstract:
Research on Mass transport complexes (MTCs) can help disclosure the distribution and evolution of gravity flow sediments, especially for reservoir predicting and reservoirseal evaluating in deepwater exploration. In this paper, high quality 3D seismic data are used to study seismic characters and evolution of the MTCs. There are three main conclusions from this research. (1) MTCs are characterized by low amplitude, chaotic, mounded seismic facies, fanlike geometry and linear basal scours;(2)They are commonly embedded in a cyclic stratigraphic succession that is composed of leveechannel complexes and hemipelagic drapes.(3)Remnants of these complexs are formed by the erosive power of mass transport from older turbidite deposits.The remnants with portions of older turbidite sediments can form potential stratigraphic traps for deepwater deposits. Although the MTCs themselves may not prove viable reservoirs, the accuracy of reservoir predicting in deepwater turbidite channels can be improved from the identification of MTCs. Various erosive processes and subsequent stratigraphic relationships surrounding mass transport deposits development may have provided the opportunities for stratigraphic trapping.
Research on Mass transport complexes (MTCs) can help disclosure the distribution and evolution of gravity flow sediments, especially for reservoir predicting and reservoirseal evaluating in deepwater exploration. In this paper, high quality 3D seismic data are used to study seismic characters and evolution of the MTCs. There are three main conclusions from this research. (1) MTCs are characterized by low amplitude, chaotic, mounded seismic facies, fanlike geometry and linear basal scours;(2)They are commonly embedded in a cyclic stratigraphic succession that is composed of leveechannel complexes and hemipelagic drapes.(3)Remnants of these complexs are formed by the erosive power of mass transport from older turbidite deposits.The remnants with portions of older turbidite sediments can form potential stratigraphic traps for deepwater deposits. Although the MTCs themselves may not prove viable reservoirs, the accuracy of reservoir predicting in deepwater turbidite channels can be improved from the identification of MTCs. Various erosive processes and subsequent stratigraphic relationships surrounding mass transport deposits development may have provided the opportunities for stratigraphic trapping.
2010, 28(1): 91-101.
Abstract:
Based on boreholes and stratigraphic sections, we draw maps about uniformly thick residual formation in the Longmen Shan Foreland Basin with Surfer 8.0 software, work out the total amount of sediment of residual formation, and figure out the sediment flux in each phase: 21.4t/(m2·Ma),184.2t/(m2·Ma),278.0t/(m2·Ma), 147.6t/(m2·Ma),703.5t/(m2·Ma), and 272.0t/(m2·Ma). Then we denude back the sediment to the orogenic belt based on material balance method and carry out depressure correction. We can work out the aggregate thickness denuded is about 2 514 m on Longmen Shan during the late Triassic Epoch, and the speeds of denudation in each phase are: 0.009 mm/a,0.114 mm/a,0.13
Based on boreholes and stratigraphic sections, we draw maps about uniformly thick residual formation in the Longmen Shan Foreland Basin with Surfer 8.0 software, work out the total amount of sediment of residual formation, and figure out the sediment flux in each phase: 21.4t/(m2·Ma),184.2t/(m2·Ma),278.0t/(m2·Ma), 147.6t/(m2·Ma),703.5t/(m2·Ma), and 272.0t/(m2·Ma). Then we denude back the sediment to the orogenic belt based on material balance method and carry out depressure correction. We can work out the aggregate thickness denuded is about 2 514 m on Longmen Shan during the late Triassic Epoch, and the speeds of denudation in each phase are: 0.009 mm/a,0.114 mm/a,0.13
2010, 28(1): 118-127.
Abstract:
The outcrops of Roda SandstoneⅢ are located in the southern Pyrenean Foreland Basin, in the northeast of Spain. The key sedimentary structures of the tidal ridges or waves are stacked sets of large scale wedge and tabular crossstrata as well as planeparallel lamination, ripple lamination. In vertical section, the tidal ridges or waves show a trend of thickening and coarsening upwards. The thickness of tidal bunches vary periodically and the reactivation surfaces are common; double mud drapes are rare, but herringbone crossstrata can be. Bioturbation can be intense in the bottomsets of the crossbedding. Shell fragments and mud clasts are common. The directions of paleocurrent were polydirectional, but most concentrated on westward direction, which is parallel to acute angle with the orientation of the progradation of delta front. The result suggests the tidal ridges and waves coexisted.
The outcrops of Roda SandstoneⅢ are located in the southern Pyrenean Foreland Basin, in the northeast of Spain. The key sedimentary structures of the tidal ridges or waves are stacked sets of large scale wedge and tabular crossstrata as well as planeparallel lamination, ripple lamination. In vertical section, the tidal ridges or waves show a trend of thickening and coarsening upwards. The thickness of tidal bunches vary periodically and the reactivation surfaces are common; double mud drapes are rare, but herringbone crossstrata can be. Bioturbation can be intense in the bottomsets of the crossbedding. Shell fragments and mud clasts are common. The directions of paleocurrent were polydirectional, but most concentrated on westward direction, which is parallel to acute angle with the orientation of the progradation of delta front. The result suggests the tidal ridges and waves coexisted.
2010, 28(1): 140-149.
Abstract:
This paper researched sedimentary styles and characteristics and discussed about Carboniferous sedimentary evolution of different stages as well as relationship between Carboniferous sedimentary facies and source rock . It is epicontinental sea in Carboniferous of Qaidam. Sedimentary environment can be divided into three sedimentary facies: shore facies, carbonate plateau facies, neritic marine basin facies and six subfacies: shallows subfacies, tidal flat subfacies, swamp subfacies, open platform facies, restricted platform subfacies and inner shelf subfacies. There are two marine ingression in Early Carboniferous and everlasting transgression in Late Carboniferous. Sedimentary environment evolves from offshore to epeiric sea and mainly develops paralic sedimentary environment. The overlapping phenomenon arose in the north foreland because of wide area transgression. The distribution of source rock is controlled by sedimentary facies: mudstone, carbargilite and carbonate are favourable source rocks, which develop in swamp subfacies or inner shelf subfacies of carboniferous in the northeast of Qaidam basin; restricted platform subfacies is also a favourable source rock distributed area because of deeper water, smaller kinetic energy, abundant organic material, which develop in relatively restricted area of Lower Carboniferous in the southwestern margin of Qaidam basin.
This paper researched sedimentary styles and characteristics and discussed about Carboniferous sedimentary evolution of different stages as well as relationship between Carboniferous sedimentary facies and source rock . It is epicontinental sea in Carboniferous of Qaidam. Sedimentary environment can be divided into three sedimentary facies: shore facies, carbonate plateau facies, neritic marine basin facies and six subfacies: shallows subfacies, tidal flat subfacies, swamp subfacies, open platform facies, restricted platform subfacies and inner shelf subfacies. There are two marine ingression in Early Carboniferous and everlasting transgression in Late Carboniferous. Sedimentary environment evolves from offshore to epeiric sea and mainly develops paralic sedimentary environment. The overlapping phenomenon arose in the north foreland because of wide area transgression. The distribution of source rock is controlled by sedimentary facies: mudstone, carbargilite and carbonate are favourable source rocks, which develop in swamp subfacies or inner shelf subfacies of carboniferous in the northeast of Qaidam basin; restricted platform subfacies is also a favourable source rock distributed area because of deeper water, smaller kinetic energy, abundant organic material, which develop in relatively restricted area of Lower Carboniferous in the southwestern margin of Qaidam basin.
2010, 28(1): 158-165.
Abstract:
Hasuhai Lake is one of the representative shallow lakes in grassland areas of China, and its eutrophication is becoming more serious. The study on the character of spatial distribution and pollution of the nitrogen forms and organic matter revealed that the content of the total nitrogen (TN), the organic nitrogen (OrgN), the ammonium nitrogen and the organic matter in the surface sediment of the lake had an obvious differentiation in longitudinal direction. The distribution characteristics of TN in surface sediments were mainly dominated by the distribution characteristics of OrgN, and TN had a significant correlation with organic matter content. In the sediment cores, the TN content and the organic nitrogen content both had the same trend that their content decreases with the increasing depth. The vertical distribution of ammonium nitrogen in the sediment core was various, but it was also enriched in the surface sediments. The organic nitrogen is the main exiting form of nitrogen in surface sediments and sediment core, and ammonium nitrogen is the main exiting form of inorganic nitrogen. There was very little TN mineralized in the diagenesis. The typical sources of organic matter in surface sediment of Hasuhai Lake may be macrophytes such as reed and terrestrial source. The pollution of nitrogen in the surface sediments of Hasuhai Lake has serious biology toxicity effect on the bottom biology communities and aquatic ecosystem.
Hasuhai Lake is one of the representative shallow lakes in grassland areas of China, and its eutrophication is becoming more serious. The study on the character of spatial distribution and pollution of the nitrogen forms and organic matter revealed that the content of the total nitrogen (TN), the organic nitrogen (OrgN), the ammonium nitrogen and the organic matter in the surface sediment of the lake had an obvious differentiation in longitudinal direction. The distribution characteristics of TN in surface sediments were mainly dominated by the distribution characteristics of OrgN, and TN had a significant correlation with organic matter content. In the sediment cores, the TN content and the organic nitrogen content both had the same trend that their content decreases with the increasing depth. The vertical distribution of ammonium nitrogen in the sediment core was various, but it was also enriched in the surface sediments. The organic nitrogen is the main exiting form of nitrogen in surface sediments and sediment core, and ammonium nitrogen is the main exiting form of inorganic nitrogen. There was very little TN mineralized in the diagenesis. The typical sources of organic matter in surface sediment of Hasuhai Lake may be macrophytes such as reed and terrestrial source. The pollution of nitrogen in the surface sediments of Hasuhai Lake has serious biology toxicity effect on the bottom biology communities and aquatic ecosystem.
2010, 28(1): 176-182.
Abstract:
Based upon AMS14C dating (calibrated CY) and inferred dating by archaeological relics, the layers of Yuxi profile in Fengdu, Chongqing can be confirmed a basically sequential deposition during approximately 8 500～4 800 aBP. There is a sharp contrast between the underpart alternating layers consisting of siltsand and deluvium (31～10 layers) and the upper deluvium (9～3 layers), which reflects that the sediment sources and environment changed in the past. The research suggests that, the consistency of sedimental structure and curvilinear characteristics of proxy Rb and Sr indicators reveals that the difference of sediment structure of Yuxi profile is mainly related to the different climate backgrounds; the underpart alternating layers which the accumulation is thicker, the persistent period is shorter and the sedimentary rate is higher are the result of abnormal changes of hydrologic phenomena under the background of unstable climate. Further analyzing, we think that the consistency between the sedimentary structure on the macroscopic level and the proxy indicators on the microscopic level of Yuxi profile stratum reflects also that the climate of Megatherma in Holocene existed a obvious phased change in study area, namely approximately 8 500～7 200 aBP, it was at the stage of unstable climate in Megatherma; and approximately 7 200～4 800 aBP, it showed the wetwarm climatic characteristics at the peak of Megatherma, which the turning point occurred in 7 200aBP.
Based upon AMS14C dating (calibrated CY) and inferred dating by archaeological relics, the layers of Yuxi profile in Fengdu, Chongqing can be confirmed a basically sequential deposition during approximately 8 500～4 800 aBP. There is a sharp contrast between the underpart alternating layers consisting of siltsand and deluvium (31～10 layers) and the upper deluvium (9～3 layers), which reflects that the sediment sources and environment changed in the past. The research suggests that, the consistency of sedimental structure and curvilinear characteristics of proxy Rb and Sr indicators reveals that the difference of sediment structure of Yuxi profile is mainly related to the different climate backgrounds; the underpart alternating layers which the accumulation is thicker, the persistent period is shorter and the sedimentary rate is higher are the result of abnormal changes of hydrologic phenomena under the background of unstable climate. Further analyzing, we think that the consistency between the sedimentary structure on the macroscopic level and the proxy indicators on the microscopic level of Yuxi profile stratum reflects also that the climate of Megatherma in Holocene existed a obvious phased change in study area, namely approximately 8 500～7 200 aBP, it was at the stage of unstable climate in Megatherma; and approximately 7 200～4 800 aBP, it showed the wetwarm climatic characteristics at the peak of Megatherma, which the turning point occurred in 7 200aBP.
2010, 28(1): 188-193.
Abstract:
It is discovered that series of carbazole compounds, including carbazole, lmethylcarbazole, 2methylcarbazole, 3methylcarbazole, 4methylcarbazole, 5methylcarbazole, 6methylcarbazole, which are affluent in the pyrolysis product of Dunaliella Salina. The relative content of the series of carbazole compounds in the aromatic hydrocarbon fraction mounts to 30.97％ at 300℃,while it is only 15.44％ at 350℃, and it rarely occured at 250℃.
On one hand, it indicates that Dunaliella Salina is one of the primary parent materials of carbazole compounds in source rock and crude oil; On the other hand, it suggests that the crude oil derived from Dunaliella Salina is probably rich in carbazole compounds under a highlyrich salt environment, which provides strong evidence to contrast crude oil with original source rock in this environment.
It is discovered that series of carbazole compounds, including carbazole, lmethylcarbazole, 2methylcarbazole, 3methylcarbazole, 4methylcarbazole, 5methylcarbazole, 6methylcarbazole, which are affluent in the pyrolysis product of Dunaliella Salina. The relative content of the series of carbazole compounds in the aromatic hydrocarbon fraction mounts to 30.97％ at 300℃,while it is only 15.44％ at 350℃, and it rarely occured at 250℃.
On one hand, it indicates that Dunaliella Salina is one of the primary parent materials of carbazole compounds in source rock and crude oil; On the other hand, it suggests that the crude oil derived from Dunaliella Salina is probably rich in carbazole compounds under a highlyrich salt environment, which provides strong evidence to contrast crude oil with original source rock in this environment.
2010, 28(1): 201-207.
Abstract:
Through oil reservoir anatomization and analyzing its spatialtemporal relationship with reservoir forming condition, migration pathways and the control on oil accumulation and distribution were studied on the basis of summarizing oil migration mechanism and mode in Fuyu oil layer in Chang 10 block. It was considered that oil migration pathways of Fuyu oil layer in Chang 10 block were as follows in main. ①T2 source faults are transporting pathways through which oil that generated by K1qn1 source rock migrated downward into underlying F, Y oil layers in Sanzhao depression. ②Faults combining with sand bodies are transporting pathways of oil in Fuyu oil layer in Sanzhao depression migrating laterally to Chang 10 block. The controlling roles of oil migration pathways of Fuyu oil layer in Chang 10 block to oil accumulation and distribution are mainly manifested as: ①Development degree of T2 source faults controls oil supply amount of Fuyu oil layer in Chang 10 block. ②Fault concentrated belts are main oil accumulation areas of Fuyu oil layer in Chang 10 block, and high fault block connected by transporting pathways that formed by faults combing with sand bodies are main oil accumulation positions.
Through oil reservoir anatomization and analyzing its spatialtemporal relationship with reservoir forming condition, migration pathways and the control on oil accumulation and distribution were studied on the basis of summarizing oil migration mechanism and mode in Fuyu oil layer in Chang 10 block. It was considered that oil migration pathways of Fuyu oil layer in Chang 10 block were as follows in main. ①T2 source faults are transporting pathways through which oil that generated by K1qn1 source rock migrated downward into underlying F, Y oil layers in Sanzhao depression. ②Faults combining with sand bodies are transporting pathways of oil in Fuyu oil layer in Sanzhao depression migrating laterally to Chang 10 block. The controlling roles of oil migration pathways of Fuyu oil layer in Chang 10 block to oil accumulation and distribution are mainly manifested as: ①Development degree of T2 source faults controls oil supply amount of Fuyu oil layer in Chang 10 block. ②Fault concentrated belts are main oil accumulation areas of Fuyu oil layer in Chang 10 block, and high fault block connected by transporting pathways that formed by faults combing with sand bodies are main oil accumulation positions.
