2015 Vol. 33, No. 5
Display Method:
2015, 33(5): 845-854.
doi: 10.14027/j.cnki.cjxb.2015.05.001
Abstract:
According to the "water-transgression caused filling sand-bodies" found in Yangtze delta investigation in 1980s, based on the other investigation data and ancient sand-body features, the "water-transgression delta model" has been established. More than 30 years, more and more data have been showen that the model is correct. The modern deposition investigations and satellite pictures from Yangtze delta, Erhai in Yunnan, Daihai in Inner Mongolia et al., have revealed the recent popular model of "underwater distributary channel" is absent, but according to sedimentary theory (such as the cycle stratigraphy and sequence stratigraphy) analysis, the water-transgression deposition is widely developed. The flume simulation experiment has also confirmed that delta is developed in transgression period, so water-transgression sand-body micro-facies should have replaced the underwater distributary channel micro-facies. Great thickness and largely distributed sandstone in member 2 and member 4 of Xujiahe Formation have been caused by the superimposition of multi-channel river mouth progradation (mouth sand bar), retrogradation (water-transgression channel sand-body),channel lateral migration and piecing together with multi-deltas. Water-transgression deltas have formed in transgression period of lake or sea level, and the tectonism, climate changing, particular geological events, topography and depositional rate and so on. could have caused the up and down of water level, and the water-transgression delta has been developed when the water level have went up.
According to the "water-transgression caused filling sand-bodies" found in Yangtze delta investigation in 1980s, based on the other investigation data and ancient sand-body features, the "water-transgression delta model" has been established. More than 30 years, more and more data have been showen that the model is correct. The modern deposition investigations and satellite pictures from Yangtze delta, Erhai in Yunnan, Daihai in Inner Mongolia et al., have revealed the recent popular model of "underwater distributary channel" is absent, but according to sedimentary theory (such as the cycle stratigraphy and sequence stratigraphy) analysis, the water-transgression deposition is widely developed. The flume simulation experiment has also confirmed that delta is developed in transgression period, so water-transgression sand-body micro-facies should have replaced the underwater distributary channel micro-facies. Great thickness and largely distributed sandstone in member 2 and member 4 of Xujiahe Formation have been caused by the superimposition of multi-channel river mouth progradation (mouth sand bar), retrogradation (water-transgression channel sand-body),channel lateral migration and piecing together with multi-deltas. Water-transgression deltas have formed in transgression period of lake or sea level, and the tectonism, climate changing, particular geological events, topography and depositional rate and so on. could have caused the up and down of water level, and the water-transgression delta has been developed when the water level have went up.
2015, 33(5): 855-864.
doi: 10.14027/j.cnki.cjxb.2015.05.002
Abstract:
The rhythmic sandstone and mudstone cycles are common lithologic units in terrigenous stratigraphic system. Wireline log curves of sandstone and mudstone cycles can be described in term of sinusoidal waves in depth domains. Amplitude variations of wellline logs reflect grain sizes in a sedimentary cycle, and wavelength changes are a measure scale to mark cyclic thickness. The cumulative residual curves from average amplitude variations of well logs are introduced and demonstrated as a valid graphical method to define depositional regime transformation and check boundary surfaces of cyclic sequences. The numerical simulation results shows the positive half waves and negative half waves of cumulative residual curves are respectively corresponding to coarsening-upward and fining-upward sedimentary successions in low frequency cyclic sequences in a well interval. Transform points of positive half waves and negative half waves are calibrated to boundary surface depth of cyclic sequences. The spectral analysis and filter methods are adopted to divide cyclic sequence hierarchy and then discuss depositional mechanism. The GR log data from Xian Well 3 of Qaidam Basin as a case, cumulative residual curves are calculated and constructed on well log data. The low and high frequency cyclic sequences are distinguished and its procedure and methods are illustrated in detail. The significance and interpretation of amplitudes and wavelength changes of sedimentary cycles is discussed in this paper.
The rhythmic sandstone and mudstone cycles are common lithologic units in terrigenous stratigraphic system. Wireline log curves of sandstone and mudstone cycles can be described in term of sinusoidal waves in depth domains. Amplitude variations of wellline logs reflect grain sizes in a sedimentary cycle, and wavelength changes are a measure scale to mark cyclic thickness. The cumulative residual curves from average amplitude variations of well logs are introduced and demonstrated as a valid graphical method to define depositional regime transformation and check boundary surfaces of cyclic sequences. The numerical simulation results shows the positive half waves and negative half waves of cumulative residual curves are respectively corresponding to coarsening-upward and fining-upward sedimentary successions in low frequency cyclic sequences in a well interval. Transform points of positive half waves and negative half waves are calibrated to boundary surface depth of cyclic sequences. The spectral analysis and filter methods are adopted to divide cyclic sequence hierarchy and then discuss depositional mechanism. The GR log data from Xian Well 3 of Qaidam Basin as a case, cumulative residual curves are calculated and constructed on well log data. The low and high frequency cyclic sequences are distinguished and its procedure and methods are illustrated in detail. The significance and interpretation of amplitudes and wavelength changes of sedimentary cycles is discussed in this paper.
2015, 33(5): 865-877.
doi: 10.14027/j.cnki.cjxb.2015.05.003
Abstract:
Based on the sedimentary characteristics of the Permian-Triassic boundary (PTB) strata in Xianfeng, combined with analysis from boreholes lithofacies, the stratum was divided into two kinds of sedimentary facies, including homoclinal carbonate ramp and rimmed carbonate platform, and seven kinds of subfacies, such as high-energy bioclastic shoal, inner ramp and intertidal flat and so on. Then analyzing microfacies characters of the carbonate rocks, such as biotic assemblage, grain composition and supported type. Boundary strata of the studied section can be mainly divided into fourteen microfacies types. From this, the sedimentary facies sequences and evolution of this period were established. The studied section outputs one layer of microbialites. From observations of plain microscope, the following results were obtained: microbialites consist of stromatolites; in most of these microbialites, coccoid cyanobacterias, calcified sheaths and microsparry cladding layer were found largely. Characteristics of the biotic assemblage were be analyzed after grinding the thin sections continuously for rock core of K9 limestone which is 0.58 m long and comes from borehole ZK1501. There are abundant fossils in this place where 6 cm away from the bottom of the admitted major extinction horizon, such as Trilobites, Gastropods and Phylloid Algae. Above the stratum, miniaturized Ostracods(<200 μm) were found. We concluded obviously that the major extinction horizon of Permian should be located at the place, while PTB is at the middle and lower segments of the miniaturized Ostracods layer.
Based on the sedimentary characteristics of the Permian-Triassic boundary (PTB) strata in Xianfeng, combined with analysis from boreholes lithofacies, the stratum was divided into two kinds of sedimentary facies, including homoclinal carbonate ramp and rimmed carbonate platform, and seven kinds of subfacies, such as high-energy bioclastic shoal, inner ramp and intertidal flat and so on. Then analyzing microfacies characters of the carbonate rocks, such as biotic assemblage, grain composition and supported type. Boundary strata of the studied section can be mainly divided into fourteen microfacies types. From this, the sedimentary facies sequences and evolution of this period were established. The studied section outputs one layer of microbialites. From observations of plain microscope, the following results were obtained: microbialites consist of stromatolites; in most of these microbialites, coccoid cyanobacterias, calcified sheaths and microsparry cladding layer were found largely. Characteristics of the biotic assemblage were be analyzed after grinding the thin sections continuously for rock core of K9 limestone which is 0.58 m long and comes from borehole ZK1501. There are abundant fossils in this place where 6 cm away from the bottom of the admitted major extinction horizon, such as Trilobites, Gastropods and Phylloid Algae. Above the stratum, miniaturized Ostracods(<200 μm) were found. We concluded obviously that the major extinction horizon of Permian should be located at the place, while PTB is at the middle and lower segments of the miniaturized Ostracods layer.
2015, 33(5): 878-890.
doi: 10.14027/j.cnki.cjxb.2015.05.004
Abstract:
In the Early Cretaceous, controlled by the uplift of Qilianshan Mountains and the climate, a set of clastic rocks developed in the continental basins before Qilianshan Mountains. The Cretaceous strata develope and outcrop well in Zhangye city of Gansu province, which are made up of particular sedimentary facies successions under the concept framework of the unconventional system tracts, and are very important to the study of Qilianshan Mountains uplift and its impacts on the environment of Asia. The Lower Cretaceous strata of Yinggezui cross-section include the Chijinpu Formation, the Xiagou Formation, and the Zhougou Formation, which can be divided into 10 third-order sequences (S.1-S.10). Generally speaking, the LAST is composed of alluvial fan facies and fluvial facies coarse clastic rocks, while lacustrine facies fine clastic rocks constitute the HAST. The eolian sandstones in the middle-low Chijinpu Formation and the Xiagou Formation, are the products of "foehn effect" caused by Qilianshan Mountains uplift, which are meaningful to the study of the Qilianshan Mountains uplift. In the Early Cretaceous, the climate experienced a series of changes, from semi-arid climate to arid climate to wet climate, which reflects that the Qilianshan Mountains uplift in this period can be charactered by four different stages, i.e. the early episodic uplift stage, the middle fast uplift stage, and the last isostatic uplift stage. In the transition period of Early to Late Cretaceous, the Qilianshan Mountains uplifted fast and intensively, which caused the study area turned into a denuded zone, so the Upper Cretaceous strata have not developed. The Lower Cretaceous sequences of Yinggezui cross-section, not only are the material records of Qilianshan Mountains uplift, but also can provide an important record to the reconstruction of the pattern of the atmospheric circle in the East Asia.
In the Early Cretaceous, controlled by the uplift of Qilianshan Mountains and the climate, a set of clastic rocks developed in the continental basins before Qilianshan Mountains. The Cretaceous strata develope and outcrop well in Zhangye city of Gansu province, which are made up of particular sedimentary facies successions under the concept framework of the unconventional system tracts, and are very important to the study of Qilianshan Mountains uplift and its impacts on the environment of Asia. The Lower Cretaceous strata of Yinggezui cross-section include the Chijinpu Formation, the Xiagou Formation, and the Zhougou Formation, which can be divided into 10 third-order sequences (S.1-S.10). Generally speaking, the LAST is composed of alluvial fan facies and fluvial facies coarse clastic rocks, while lacustrine facies fine clastic rocks constitute the HAST. The eolian sandstones in the middle-low Chijinpu Formation and the Xiagou Formation, are the products of "foehn effect" caused by Qilianshan Mountains uplift, which are meaningful to the study of the Qilianshan Mountains uplift. In the Early Cretaceous, the climate experienced a series of changes, from semi-arid climate to arid climate to wet climate, which reflects that the Qilianshan Mountains uplift in this period can be charactered by four different stages, i.e. the early episodic uplift stage, the middle fast uplift stage, and the last isostatic uplift stage. In the transition period of Early to Late Cretaceous, the Qilianshan Mountains uplifted fast and intensively, which caused the study area turned into a denuded zone, so the Upper Cretaceous strata have not developed. The Lower Cretaceous sequences of Yinggezui cross-section, not only are the material records of Qilianshan Mountains uplift, but also can provide an important record to the reconstruction of the pattern of the atmospheric circle in the East Asia.
2015, 33(5): 891-898.
doi: 10.14027/j.cnki.cjxb.2015.05.005
Abstract:
This article reveals the mechanism and significance of the condensed section developed in the Nenjiang Formation of Songliao Basin by applying the methods of sequence stratigraphy, sedimentary geology and basin dynamics analysis.10~15 m thick condensed section developed at the bottom of the Nenjiang Formation in Songliao Basin was formed under the action of shrinking process of the lake basin caused by the forced regression. When the water body in the distal end of the progradational sequence became into the highly-salinity and strong-reduced environment, the condensed section deposited as oil shale and was marked by the high bell shaped resistance in the well log. And the bottom of the condensed section took the SB07 maximum lake flooding surface as the isochronal boundary. The upward progradational sequence last a long time span and had no isochronism, meanwhile the strong progradation from the east to west blocked the transgression channel. Therefore, the inference that "transgression event" ever happened in the Nenjiang Formation of the Songliao Basin is false. Consequently, the study of the mechanism of the condensed section in Songliao Basin makes sense for sequence stratigraphy and sedimentary geology. By the analysis of hydrocarbon accumulation, we come to the conclusion that the condensed section in the Nenjiang Formation is both the source rock and the regional cap. There are abundant oil and gas resource covering and underlying this layer, which can be easily identified from the seismic data and well log as forced regression sequence. The condensed section is also a good structural mark to evaluate petroleum basins and to optimize the sequence. Thus, the awareness of the condensed section has theoretic and practical meaning for sequence stratigraphy, sedimentary environment and hydrocarbon accumulation analysis.
This article reveals the mechanism and significance of the condensed section developed in the Nenjiang Formation of Songliao Basin by applying the methods of sequence stratigraphy, sedimentary geology and basin dynamics analysis.10~15 m thick condensed section developed at the bottom of the Nenjiang Formation in Songliao Basin was formed under the action of shrinking process of the lake basin caused by the forced regression. When the water body in the distal end of the progradational sequence became into the highly-salinity and strong-reduced environment, the condensed section deposited as oil shale and was marked by the high bell shaped resistance in the well log. And the bottom of the condensed section took the SB07 maximum lake flooding surface as the isochronal boundary. The upward progradational sequence last a long time span and had no isochronism, meanwhile the strong progradation from the east to west blocked the transgression channel. Therefore, the inference that "transgression event" ever happened in the Nenjiang Formation of the Songliao Basin is false. Consequently, the study of the mechanism of the condensed section in Songliao Basin makes sense for sequence stratigraphy and sedimentary geology. By the analysis of hydrocarbon accumulation, we come to the conclusion that the condensed section in the Nenjiang Formation is both the source rock and the regional cap. There are abundant oil and gas resource covering and underlying this layer, which can be easily identified from the seismic data and well log as forced regression sequence. The condensed section is also a good structural mark to evaluate petroleum basins and to optimize the sequence. Thus, the awareness of the condensed section has theoretic and practical meaning for sequence stratigraphy, sedimentary environment and hydrocarbon accumulation analysis.
2015, 33(5): 899-908.
doi: 10.14027/j.cnki.cjxb.2015.05.006
Abstract:
To further explore the significance of the tempestites that exposed near the boundary of Permian and Triassic at Nanjiang section, and investigate the effect of Early Triassic monsoon on the sedimentary characteristic in northern Sichuan Basin, several set of tempestites have been researched in this article. The paper focuses on the characteristics of sedimentary and petrology in both outcrop section and thin sections of the storm deposits at Nanjiang section. According to the different sedimentary characteristic, each set of tempestite can be divided into three section: Section a is developed at storm active period, Section b is developed at storm energy declining period, Section c is developed at storm rest period. Depending on the combination of Sa, Sb, Sc, tempestites can be divided into four kinds of storm sequence structure type to represent different sedimentary environment. Then based on the grain-size analysis of storm particles and the comparison of sedimentary thickness, we found that the storm energy gradually increased upward. Furthermore, when the tempestites at Nanjiang section are contrasted with Shangsi section, showed that the thickness and the characteristic of them is similar and that they are both developed at the Early Triassic sedimentary strata near the boundary of P/T. Therefore, a conclusion can be made that they are the same deposition and both of them are influenced by frequent storm events under the giant monsoon system at Early Triassic Period. What`s more, they reveal the deposit process that the shelf margin gradually was in movement in the direction of the wide sea at Early Triassic, and the Trough gradually being filled simultaneously.
To further explore the significance of the tempestites that exposed near the boundary of Permian and Triassic at Nanjiang section, and investigate the effect of Early Triassic monsoon on the sedimentary characteristic in northern Sichuan Basin, several set of tempestites have been researched in this article. The paper focuses on the characteristics of sedimentary and petrology in both outcrop section and thin sections of the storm deposits at Nanjiang section. According to the different sedimentary characteristic, each set of tempestite can be divided into three section: Section a is developed at storm active period, Section b is developed at storm energy declining period, Section c is developed at storm rest period. Depending on the combination of Sa, Sb, Sc, tempestites can be divided into four kinds of storm sequence structure type to represent different sedimentary environment. Then based on the grain-size analysis of storm particles and the comparison of sedimentary thickness, we found that the storm energy gradually increased upward. Furthermore, when the tempestites at Nanjiang section are contrasted with Shangsi section, showed that the thickness and the characteristic of them is similar and that they are both developed at the Early Triassic sedimentary strata near the boundary of P/T. Therefore, a conclusion can be made that they are the same deposition and both of them are influenced by frequent storm events under the giant monsoon system at Early Triassic Period. What`s more, they reveal the deposit process that the shelf margin gradually was in movement in the direction of the wide sea at Early Triassic, and the Trough gradually being filled simultaneously.
2015, 33(5): 909-918.
doi: 10.14027/j.cnki.cjxb.2015.05.007
Abstract:
Storm deposits are commonly found in Da'anzhai Member, Lower Jurassic. We have studied the storm deposition's sedimentary structure, and then found that, notwithstanding the absence of hummocky cross-stratification, we can found top structure, bottom structure and the bedding structure are numerous, which can be symbols of storm deposition. After comprehensively analyzed the depositional features, we built an ideal deposition facies sequence, that is, gutter cast, surface of scour, gravel shell fragment bedding, graded bedding, ripple bedding, float thin shell bedding, silt bedding and the top surface structure, cut structure and ripple ridge. The hydrodynamic force and preservation condition variation in different microfacies, so the storm facies sequence in every microfacies are different. Graded bedding are the main residual structure in high energy microfacies, namely fore shell beach and the core shell beach, and the rear shell beach. Silt bedding can be found in littoral to shallow area, but the deep shallow lake reserve more structures, containing ripple bedding, float thin shell bedding, and silt bedding. The research of storm deposition can help us get more precise understanding on the depositional model of the shell limestone, what's more, it can give us a guide for tight oil exploration. The storm deposition in deep shallow lake and the fore shell beach have relatively high porosity, and the reservoir adjacent to source rock and has good preservation condition. So the two microfacies are the tight oil advantage facies.
Storm deposits are commonly found in Da'anzhai Member, Lower Jurassic. We have studied the storm deposition's sedimentary structure, and then found that, notwithstanding the absence of hummocky cross-stratification, we can found top structure, bottom structure and the bedding structure are numerous, which can be symbols of storm deposition. After comprehensively analyzed the depositional features, we built an ideal deposition facies sequence, that is, gutter cast, surface of scour, gravel shell fragment bedding, graded bedding, ripple bedding, float thin shell bedding, silt bedding and the top surface structure, cut structure and ripple ridge. The hydrodynamic force and preservation condition variation in different microfacies, so the storm facies sequence in every microfacies are different. Graded bedding are the main residual structure in high energy microfacies, namely fore shell beach and the core shell beach, and the rear shell beach. Silt bedding can be found in littoral to shallow area, but the deep shallow lake reserve more structures, containing ripple bedding, float thin shell bedding, and silt bedding. The research of storm deposition can help us get more precise understanding on the depositional model of the shell limestone, what's more, it can give us a guide for tight oil exploration. The storm deposition in deep shallow lake and the fore shell beach have relatively high porosity, and the reservoir adjacent to source rock and has good preservation condition. So the two microfacies are the tight oil advantage facies.
2015, 33(5): 919-931.
doi: 10.14027/j.cnki.cjxb.2015.05.008
Abstract:
Many earthquake-related seismites were discovered in Paleogene in Liaodong Bay depression. According to the observation of well core, we identified 11 indicators of seismites of Paleogene in Liaodong Bay depression, including micro-fold, step micro-fault, seismic fall-masses, liquefied breccias, liquefied fold, pinch and swell structure, ball and pillow structure, flamy structure, liquefaction sandy-silty dyke, seismic-related fracture and seismic breccias. They all distribute in delt-front or the slope toe near prodelta. We establish the seismite succession through the degree of deformation. The seismites succession has been divided into I, II and III three units from weak to strong which reflect the intensity of Paleoseismic. Through the analysis of the seismites space-time distribution and its reflection on ancient earthquake intensity by geostatistical methods, we assume Tan-Lu Fault of Paleogene in Liaodong Bay depression was in the orientation of NNE. The tectonic activity can be divided into three stages. The first stage is E2s3. The tectonic activity mainly distribute in the northern of Liaoxi Low salient. The second stage is E3s2-E3s1. The tectonic activity mainly distribute in A oilfield of Liaozhong sag. The third stage is E3d. The tectonic activity mainly distribute in A oilfield and the neighbouring area of Liaoxi Low salient, thinly distributed in the southern and northern of Liaozhong sag. The first and third stages are intense tectonic activity periods. The results show that through seismites time-space distribution to inverse the tectonic activity is feasible and it provides a new way of thinking for basin analysis.
Many earthquake-related seismites were discovered in Paleogene in Liaodong Bay depression. According to the observation of well core, we identified 11 indicators of seismites of Paleogene in Liaodong Bay depression, including micro-fold, step micro-fault, seismic fall-masses, liquefied breccias, liquefied fold, pinch and swell structure, ball and pillow structure, flamy structure, liquefaction sandy-silty dyke, seismic-related fracture and seismic breccias. They all distribute in delt-front or the slope toe near prodelta. We establish the seismite succession through the degree of deformation. The seismites succession has been divided into I, II and III three units from weak to strong which reflect the intensity of Paleoseismic. Through the analysis of the seismites space-time distribution and its reflection on ancient earthquake intensity by geostatistical methods, we assume Tan-Lu Fault of Paleogene in Liaodong Bay depression was in the orientation of NNE. The tectonic activity can be divided into three stages. The first stage is E2s3. The tectonic activity mainly distribute in the northern of Liaoxi Low salient. The second stage is E3s2-E3s1. The tectonic activity mainly distribute in A oilfield of Liaozhong sag. The third stage is E3d. The tectonic activity mainly distribute in A oilfield and the neighbouring area of Liaoxi Low salient, thinly distributed in the southern and northern of Liaozhong sag. The first and third stages are intense tectonic activity periods. The results show that through seismites time-space distribution to inverse the tectonic activity is feasible and it provides a new way of thinking for basin analysis.
2015, 33(5): 932-940.
doi: 10.14027/j.cnki.cjxb.2015.05.009
Abstract:
The sandy hill sand and loess deposits constitute the regional sand-loess system,which are widely distributed in the middle reach of Yangtze River especially in the Poyang Lake area since the last interglacial. A transect named D-D transect was set from north to south along with the winter monsoon direction. The <20 mm grains extracted from bulk sample on the basis of wet-sieve methods were used to measure major and trace element abundances by XRF. Our results reveal that: (1)The content of major element has a systemic change from north to south.The changes are most pronounced within the range of 5 to 20 km away from the Yangtze River,and then level off. SrO,Na2O,CaO,K2O,MnO,CaO are of negative logarithmic function changes, SiO2,ZrO2,Al2O3,TiO2 and CIA are of positive logarithmic function changes ; The profiles of D-D transect seem to have a similar source displayed by the scatter diagrams of ZrO2/Al2O3 vs. ZrO2/TiO2, TiO2/Al2O3vs. TiO2/ZrO2, K2O/Al2O3vs. ZrO2/TiO2, K2O/TiO2vs. ZrO2/Al2O3,SrO/TiO2vs. SrO/Al2O3,Base/ZrO2vs. Base/TiO2,ect. These characteristics further reveals that all of the profiles in D-D transect belong to the same aeolian deposits system. (2) The stable elemental compositions of the D-D transect are similar to the WN loess, Xiashu loess, and sediment of flood land of the Yangtze River, these results reveal that aeolian deposits and the Yangtze River sediment have a rich source and over-commixing. Therefore, it is suggested that the factors on chemical composition of clastic sediment should be fully studied when geochemistry methods are used to analyze the province and depositional setting, and multiple methods can be synthetically used and the study on regional geology should be paid more attention.
The sandy hill sand and loess deposits constitute the regional sand-loess system,which are widely distributed in the middle reach of Yangtze River especially in the Poyang Lake area since the last interglacial. A transect named D-D transect was set from north to south along with the winter monsoon direction. The <20 mm grains extracted from bulk sample on the basis of wet-sieve methods were used to measure major and trace element abundances by XRF. Our results reveal that: (1)The content of major element has a systemic change from north to south.The changes are most pronounced within the range of 5 to 20 km away from the Yangtze River,and then level off. SrO,Na2O,CaO,K2O,MnO,CaO are of negative logarithmic function changes, SiO2,ZrO2,Al2O3,TiO2 and CIA are of positive logarithmic function changes ; The profiles of D-D transect seem to have a similar source displayed by the scatter diagrams of ZrO2/Al2O3 vs. ZrO2/TiO2, TiO2/Al2O3vs. TiO2/ZrO2, K2O/Al2O3vs. ZrO2/TiO2, K2O/TiO2vs. ZrO2/Al2O3,SrO/TiO2vs. SrO/Al2O3,Base/ZrO2vs. Base/TiO2,ect. These characteristics further reveals that all of the profiles in D-D transect belong to the same aeolian deposits system. (2) The stable elemental compositions of the D-D transect are similar to the WN loess, Xiashu loess, and sediment of flood land of the Yangtze River, these results reveal that aeolian deposits and the Yangtze River sediment have a rich source and over-commixing. Therefore, it is suggested that the factors on chemical composition of clastic sediment should be fully studied when geochemistry methods are used to analyze the province and depositional setting, and multiple methods can be synthetically used and the study on regional geology should be paid more attention.
2015, 33(5): 941-950.
doi: 10.14027/j.cnki.cjxb.2015.05.010
Abstract:
Loess deposit can be formed at geological periods during sandstorm weather and its grain size characteristics can record the atmospheric circulation patterns and paleoenvironmental evolution information during the dust removal process. The Yangchang (YC) loess section in the village of Pulu is situated on the fifth terrace of a tributary of the Keriya River. YC loess is mainly composed of coarse silt and sand with high degree of sorting. The grain size analyses of YC loess indicate that the loess belongs to aeolian deposits from the Taklimakan Desert. Grain-size distribution of YC loess section is mainly controlled by the aridification of the source area, and thus, can indicate the drying process of the south edge of the Tarim Basin. Analysis of the grain-size distribution indicates that the southern margin of the Tarim Basin was relatively humid and stable during 8.5~3.6 ka, and during 3.6~0 ka the climate became dramatically arid with several millennial-scale events, which is in accordance with records from other study areas. We think that the climate at the southern margin of the Tarim Basin has features of both the Monsoon mode and millennial-scale climate oscillation, and might be controlled by both the low latitude Asian Monsoon and high latitude climate from Northern Hemisphere. We speculate that decrease of the ASM intensity in relation to weakening of the solar activity might have caused the aridification of the Tarim Basin since 3.6 ka. And the climate change in high latitude of the Northern Hemisphere might have further strengthened the drying trend and the climate instability since 3.6 ka through intensifying the Westerlies and its amplitude.
Loess deposit can be formed at geological periods during sandstorm weather and its grain size characteristics can record the atmospheric circulation patterns and paleoenvironmental evolution information during the dust removal process. The Yangchang (YC) loess section in the village of Pulu is situated on the fifth terrace of a tributary of the Keriya River. YC loess is mainly composed of coarse silt and sand with high degree of sorting. The grain size analyses of YC loess indicate that the loess belongs to aeolian deposits from the Taklimakan Desert. Grain-size distribution of YC loess section is mainly controlled by the aridification of the source area, and thus, can indicate the drying process of the south edge of the Tarim Basin. Analysis of the grain-size distribution indicates that the southern margin of the Tarim Basin was relatively humid and stable during 8.5~3.6 ka, and during 3.6~0 ka the climate became dramatically arid with several millennial-scale events, which is in accordance with records from other study areas. We think that the climate at the southern margin of the Tarim Basin has features of both the Monsoon mode and millennial-scale climate oscillation, and might be controlled by both the low latitude Asian Monsoon and high latitude climate from Northern Hemisphere. We speculate that decrease of the ASM intensity in relation to weakening of the solar activity might have caused the aridification of the Tarim Basin since 3.6 ka. And the climate change in high latitude of the Northern Hemisphere might have further strengthened the drying trend and the climate instability since 3.6 ka through intensifying the Westerlies and its amplitude.
2015, 33(5): 951-964.
doi: 10.14027/j.cnki.cjxb.2015.05.011
Abstract:
A big controversy about the sedimentary environment of Shawan Formation in Chepaizi area, of Junggar Basin is still existed in the previous views, the main view about that is considered most likely braided river delta or beach bar sand deposition. A further analysis based on the borehole, paleontology data and physical geography data was deemed that rather than the previous sedimentary model,the Chunguang block was likely exposed, alluvial fan and fluvial deposition. The alluvial fan system developed from the northern part of the study area and fluvial system was found in the south central area. Moreover, in different sedimentary period, the sedimentary system was changed: in member 1 of the Shawan Formation, alluvial-braided river sedimentation was formed and in member 2 of the Shawan Formation, alluvial-meandering river deposit existed,however,in member 3 of the Shawan Formation, Chunguang area lack of typical fluvial deposits,mainly alluvial fan system and the flood plain deposited. All in all,in the shawan sedimentary period, Chunguang block has the character whith multi-source deposition and multiple sedimentary system.In the vertical profile,two different alluvial-braided river sedimentary model have been built up.
A big controversy about the sedimentary environment of Shawan Formation in Chepaizi area, of Junggar Basin is still existed in the previous views, the main view about that is considered most likely braided river delta or beach bar sand deposition. A further analysis based on the borehole, paleontology data and physical geography data was deemed that rather than the previous sedimentary model,the Chunguang block was likely exposed, alluvial fan and fluvial deposition. The alluvial fan system developed from the northern part of the study area and fluvial system was found in the south central area. Moreover, in different sedimentary period, the sedimentary system was changed: in member 1 of the Shawan Formation, alluvial-braided river sedimentation was formed and in member 2 of the Shawan Formation, alluvial-meandering river deposit existed,however,in member 3 of the Shawan Formation, Chunguang area lack of typical fluvial deposits,mainly alluvial fan system and the flood plain deposited. All in all,in the shawan sedimentary period, Chunguang block has the character whith multi-source deposition and multiple sedimentary system.In the vertical profile,two different alluvial-braided river sedimentary model have been built up.
2015, 33(5): 965-971.
doi: 10.14027/j.cnki.cjxb.2015.05.012
Abstract:
The lower member of formation Oficina of H block in Venezuela's Orinoco heavy oil belt is dominated with extensively distributed sandy braided river deposits. The heavy oil resources within the reservoir is rich and has a huge potential for development. At present, the oilfield is at the stage of reservoir evaluation before the development and it has relatively large well spacing with no 3D seismic coverage, only a limited number of newly drilled horizontal wells exist within part of the block. According to the existing data available in the study area, first of all, the paper analyzes the formation and evolution of the sand bar and channel from the dynamic point of view, focusing on the differences between the three statuses of active channel, sandy channel fill and the abandoned channel fill. On this basis, study methods such as modern sedimentation analogy, empirical formula utilization, application of horizontal well data are used to characterize the key parameters of the main units in braided river and to restore its scale. Based on the above research results, this paper summarizes the depositional model of sandy braided river and accomplishes the establishment of a 3D geological model under its guidance. This model is combined with prediction of reservoir distribution in the study area and good application results have been achieved. It is of great importance to guide the implementation of subsequent development plan and to improve the sand encountering ratio for the new wells to be drilled.
The lower member of formation Oficina of H block in Venezuela's Orinoco heavy oil belt is dominated with extensively distributed sandy braided river deposits. The heavy oil resources within the reservoir is rich and has a huge potential for development. At present, the oilfield is at the stage of reservoir evaluation before the development and it has relatively large well spacing with no 3D seismic coverage, only a limited number of newly drilled horizontal wells exist within part of the block. According to the existing data available in the study area, first of all, the paper analyzes the formation and evolution of the sand bar and channel from the dynamic point of view, focusing on the differences between the three statuses of active channel, sandy channel fill and the abandoned channel fill. On this basis, study methods such as modern sedimentation analogy, empirical formula utilization, application of horizontal well data are used to characterize the key parameters of the main units in braided river and to restore its scale. Based on the above research results, this paper summarizes the depositional model of sandy braided river and accomplishes the establishment of a 3D geological model under its guidance. This model is combined with prediction of reservoir distribution in the study area and good application results have been achieved. It is of great importance to guide the implementation of subsequent development plan and to improve the sand encountering ratio for the new wells to be drilled.
2015, 33(5): 972-982.
doi: 10.14027/j.cnki.cjxb.2015.05.013
Abstract:
Combined with the depositional background of Early Cambrian Longwangmiao Formation in Sichuan Basin, the lithology, sedimentary structures, logging response, microfacies and sedimentary evolution of Longwangmiao Formation in Moxi area were analyzed. It is indicated that in Longwangmiao period, the Moxi area was located in the restricted platform, and the Longwangmiao Formation was composed of dolarenites and crystalline dolomites deposited in the restricted lagoon and grain shoal. Vertically, Longwangmiao Formation was composed of two sets of up-shallowing deposition, from restricted lagoon to the grain shoals. Grain shoal can be subdivided into shoal core, shoal margin and inter-shoal low according to the lithology, sedimentary structures, cumulative thickness of grain dolomite and the grain dolomite thickness of the single shoal. Horizontally, the sedimentary distribution of the Upper Longwangmiao Formation is similar to that of the Lower Longwangmiao Formation, but the shoal scale had been larger with the eastward migration trends. The microfacies distribution is controlled by the palaeogeography characteristic and relative sea-level. The sedimentary evolution model of Longwangmiao Formation in Moxi area has been established.
Combined with the depositional background of Early Cambrian Longwangmiao Formation in Sichuan Basin, the lithology, sedimentary structures, logging response, microfacies and sedimentary evolution of Longwangmiao Formation in Moxi area were analyzed. It is indicated that in Longwangmiao period, the Moxi area was located in the restricted platform, and the Longwangmiao Formation was composed of dolarenites and crystalline dolomites deposited in the restricted lagoon and grain shoal. Vertically, Longwangmiao Formation was composed of two sets of up-shallowing deposition, from restricted lagoon to the grain shoals. Grain shoal can be subdivided into shoal core, shoal margin and inter-shoal low according to the lithology, sedimentary structures, cumulative thickness of grain dolomite and the grain dolomite thickness of the single shoal. Horizontally, the sedimentary distribution of the Upper Longwangmiao Formation is similar to that of the Lower Longwangmiao Formation, but the shoal scale had been larger with the eastward migration trends. The microfacies distribution is controlled by the palaeogeography characteristic and relative sea-level. The sedimentary evolution model of Longwangmiao Formation in Moxi area has been established.
2015, 33(5): 983-990.
doi: 10.14027/j.cnki.cjxb.2015.05.014
Abstract:
Based on the constant speed mercury injection experiment, as well as the test data of porosity and permeability, characteristics of reservoir micro pores and throats and their influence on reservoir physical properties are analyzed in the Huangliu Formation of DF area, Yinggehai Basin. The results indicate that reservoir physical properties of the Huangliu Formation are mainly characterized by medium porosity and medium-low permeability, but with great differences in DF area. Besides, there is a relatively concentrated distribution of reservoir pore radius, while a strong inhomogeneous distribution of throat radius and the pore-throat ratio. For poor physical property reservoirs, small throats account for a higher percentage, and pore-throat ratio is also higher. On the contrary, for good physical property reservoirs, big throats account for a higher percentage, and pore-throat ratio is lower. The size of throat and its distribution are the key factors that affect the reservoir permeability, which is mainly controlled by large throats with lower percentage. Moreover, affected by sedimentation, small average throat radius of the reservoirs is the main reason for the formation of the low permeability reservoirs in the Huangliu Formation of DF area, Yinggehai Basin.
Based on the constant speed mercury injection experiment, as well as the test data of porosity and permeability, characteristics of reservoir micro pores and throats and their influence on reservoir physical properties are analyzed in the Huangliu Formation of DF area, Yinggehai Basin. The results indicate that reservoir physical properties of the Huangliu Formation are mainly characterized by medium porosity and medium-low permeability, but with great differences in DF area. Besides, there is a relatively concentrated distribution of reservoir pore radius, while a strong inhomogeneous distribution of throat radius and the pore-throat ratio. For poor physical property reservoirs, small throats account for a higher percentage, and pore-throat ratio is also higher. On the contrary, for good physical property reservoirs, big throats account for a higher percentage, and pore-throat ratio is lower. The size of throat and its distribution are the key factors that affect the reservoir permeability, which is mainly controlled by large throats with lower percentage. Moreover, affected by sedimentation, small average throat radius of the reservoirs is the main reason for the formation of the low permeability reservoirs in the Huangliu Formation of DF area, Yinggehai Basin.
2015, 33(5): 991-999.
doi: 10.14027/j.cnki.cjxb.2015.05.015
Abstract:
Carbonate cement is the product from activity of palaeo fluids, containing much profitable geological information on diagenetic environment and diagenetic fluid evolution. In this paper, integrating methods of petrology, mineralogy and geochemistry, the origin mechanism of carbonate cements are investigated in Eboliang structure belt, northern margin of Qaidam Basin. The result shows that the major carbonate cements are calcite and Fe-bearing calcite in the study area. The calcite cements are mainly discovered in Eboliang structure I, their carbon and oxygen isotope values have wide range (-13.47‰ <δ13CPDB <2.54‰,-15.93‰ <δ18OPDB <-4.74‰) and varied origin, such as organic matter decarboxylation, syngenetic or parasyngenetic, bacterial methanogenesis. However, The Fe-bearing calcite cements are maily discovered in Eboliang structure III and Yahu structure, the distribution of carbon and oxygen isotope values concentrates at -4.24‰ <δ 13CPDB <-1.99‰, -11.17‰ <δ18OPDB <-9.41‰, precipitated from sedimentary compacted water. The carbonate cements origin reveals the information on interaction between inorganic and organic fluid activity in Eboliang structure belt, which provides the important evidence for the hydrocarbon accumulation study in this area.
Carbonate cement is the product from activity of palaeo fluids, containing much profitable geological information on diagenetic environment and diagenetic fluid evolution. In this paper, integrating methods of petrology, mineralogy and geochemistry, the origin mechanism of carbonate cements are investigated in Eboliang structure belt, northern margin of Qaidam Basin. The result shows that the major carbonate cements are calcite and Fe-bearing calcite in the study area. The calcite cements are mainly discovered in Eboliang structure I, their carbon and oxygen isotope values have wide range (-13.47‰ <δ13CPDB <2.54‰,-15.93‰ <δ18OPDB <-4.74‰) and varied origin, such as organic matter decarboxylation, syngenetic or parasyngenetic, bacterial methanogenesis. However, The Fe-bearing calcite cements are maily discovered in Eboliang structure III and Yahu structure, the distribution of carbon and oxygen isotope values concentrates at -4.24‰ <δ 13CPDB <-1.99‰, -11.17‰ <δ18OPDB <-9.41‰, precipitated from sedimentary compacted water. The carbonate cements origin reveals the information on interaction between inorganic and organic fluid activity in Eboliang structure belt, which provides the important evidence for the hydrocarbon accumulation study in this area.
2015, 33(5): 1000-1012.
doi: 10.14027/j.cnki.cjxb.2015.05.016
Abstract:
Though the prospective of oil reserves of tight reservoir of Chang 4+5 reservoir of Yanchang Formation, which contains tuffaceous component, is great in Zhenbei area, Ordos Basin, but the mechanism and distribution of relatively high porosity and permeability is not clear causing the speed of oil exploration and development slowly. Diagenesis and favorable diagenetic facies of Chang 4+5 Member of Yanchang Formation are researched by casting slice, scanning electron microscope, electron probe microanalysis, cathodeluminescence, micro fluorescence, X-ray diffraction and fluorescence, fluid inclusion, high pressure mercury, and physical properties technique. The results show that the quartz overgrowths of siliceous cementation and iron dolomite of carbonate cementation caused the background of low porosity and ultra low permeability reservoir of Chang 4+5 reservoir in the study area, and the diagenetic stage has reached the "A" middle now. Chlorite film cementation and early oil accumulation effectively protected pores, and limited the mechanical compaction and cementation. The intense dissolution of feldspar components could greatly improved the porosity and caused the relatively high porosity and permeability reservoir. There are mainly divided into four kinds of diagenetic facies, including mechanical compaction facies, carbonate cementation facies, chlorite cementation facies and feldspathic solution facies. The most favorable diagenetic facies is feldspathic solution facies, which mainly distributes in the middle sandbody of the underwater distributary channel, and it is favorable for the formation of relatively high porosity and permeability reservoir, which surface porosity is more than 6.0%, porosity is more than 14.0%, permeability is more than 1.30×10-3 μm2. Comprehensive studies have shown that the combination of sedimentation and diagenesis control the distribution of relatively high porosity and permeability reservoir.
Though the prospective of oil reserves of tight reservoir of Chang 4+5 reservoir of Yanchang Formation, which contains tuffaceous component, is great in Zhenbei area, Ordos Basin, but the mechanism and distribution of relatively high porosity and permeability is not clear causing the speed of oil exploration and development slowly. Diagenesis and favorable diagenetic facies of Chang 4+5 Member of Yanchang Formation are researched by casting slice, scanning electron microscope, electron probe microanalysis, cathodeluminescence, micro fluorescence, X-ray diffraction and fluorescence, fluid inclusion, high pressure mercury, and physical properties technique. The results show that the quartz overgrowths of siliceous cementation and iron dolomite of carbonate cementation caused the background of low porosity and ultra low permeability reservoir of Chang 4+5 reservoir in the study area, and the diagenetic stage has reached the "A" middle now. Chlorite film cementation and early oil accumulation effectively protected pores, and limited the mechanical compaction and cementation. The intense dissolution of feldspar components could greatly improved the porosity and caused the relatively high porosity and permeability reservoir. There are mainly divided into four kinds of diagenetic facies, including mechanical compaction facies, carbonate cementation facies, chlorite cementation facies and feldspathic solution facies. The most favorable diagenetic facies is feldspathic solution facies, which mainly distributes in the middle sandbody of the underwater distributary channel, and it is favorable for the formation of relatively high porosity and permeability reservoir, which surface porosity is more than 6.0%, porosity is more than 14.0%, permeability is more than 1.30×10-3 μm2. Comprehensive studies have shown that the combination of sedimentation and diagenesis control the distribution of relatively high porosity and permeability reservoir.
2015, 33(5): 1013-1022.
doi: 10.14027/j.cnki.cjxb.2015.05.017
Abstract:
According to a large number of previous studies, we summarized the research progress of tight sandstone gas reservoir formation process and mechanism. Under its genetic classification, it was divided into conventional tight sandstone reservoir, deep basin tight sandstone reservoir and composite tight sandstone reservoir by its genetic classification. Their accumulation process was hydrocarbon generation → accumulation → densified → structure improved, densified → gas charge → accumulation and conventional reservoir→ densified →deep basin tight sandstone reservoir → accumulation compounded, respectively. Currently the conventional tight sandstone reservoir accumulation mechanism had been studied deeply. But the deep basin accumulation mechanism was studied at all the time. As we have known, it contained the following six general mechanism, water block, lack of buoyancy, fault block, straitigraphic-diagenetic, driving pressure differential and dynamic balance. Although among them the dynamic balance was widespread accepted, it all had deficiencies. So, considering the practical situation of geology is very important. And then we can understand and research different areas of tight sandstone gas reservoirs clearly to provide theoretical guidance for its exploration and development.
According to a large number of previous studies, we summarized the research progress of tight sandstone gas reservoir formation process and mechanism. Under its genetic classification, it was divided into conventional tight sandstone reservoir, deep basin tight sandstone reservoir and composite tight sandstone reservoir by its genetic classification. Their accumulation process was hydrocarbon generation → accumulation → densified → structure improved, densified → gas charge → accumulation and conventional reservoir→ densified →deep basin tight sandstone reservoir → accumulation compounded, respectively. Currently the conventional tight sandstone reservoir accumulation mechanism had been studied deeply. But the deep basin accumulation mechanism was studied at all the time. As we have known, it contained the following six general mechanism, water block, lack of buoyancy, fault block, straitigraphic-diagenetic, driving pressure differential and dynamic balance. Although among them the dynamic balance was widespread accepted, it all had deficiencies. So, considering the practical situation of geology is very important. And then we can understand and research different areas of tight sandstone gas reservoirs clearly to provide theoretical guidance for its exploration and development.
Oil-source Analysis for Chang-9 Subsection (Upper Triassic) of Eastern Gansu Province in Ordos Basin
2015, 33(5): 1023-1032.
doi: 10.14027/j.cnki.cjxb.2015.05.018
Abstract:
The problem of oil-source for Chang-9 subsection of eastern Gansu province in Ordos Basin is one of factors which restrict the process of exploration in the area. In order to solve it, the genesis of the crude oil from the Chang-9 is firstly studied by geochemical testing data of the crude oil. The similar geochemical characteristic of Chang-7 source rock and Chang-9 source rock results lead to that it is hard to evaluate the contribution of the two kinds of source rock to the Chang-9 reservoir. So the correlation coefficients and the category relations between the crude oil and the two kinds of source rock are calculated and analized by some sensitive biomarker parameters on the basis of Cluster Analysis Theory, at the same time the migration pathways of the crude oil are put forward in combination with geology datas. This study shows that the crude oil is mature and formed under weak oxidation-weak deoxidation environment of freshwater lakes, of which matrixes are mainly from aquatic organisms and higher plant. Furthermore, the crude oil is mostly derived from Chang-7 source rock and from the Chang-9 source rock partially. The crude oil migrates along with directon of NE-SW. It is the great ability of hydrocarbon-generation and hydrocarbon-expulsion, good migration pathway and available sandstones distribution that play a critical role in forming Chang-9 reservoir.
The problem of oil-source for Chang-9 subsection of eastern Gansu province in Ordos Basin is one of factors which restrict the process of exploration in the area. In order to solve it, the genesis of the crude oil from the Chang-9 is firstly studied by geochemical testing data of the crude oil. The similar geochemical characteristic of Chang-7 source rock and Chang-9 source rock results lead to that it is hard to evaluate the contribution of the two kinds of source rock to the Chang-9 reservoir. So the correlation coefficients and the category relations between the crude oil and the two kinds of source rock are calculated and analized by some sensitive biomarker parameters on the basis of Cluster Analysis Theory, at the same time the migration pathways of the crude oil are put forward in combination with geology datas. This study shows that the crude oil is mature and formed under weak oxidation-weak deoxidation environment of freshwater lakes, of which matrixes are mainly from aquatic organisms and higher plant. Furthermore, the crude oil is mostly derived from Chang-7 source rock and from the Chang-9 source rock partially. The crude oil migrates along with directon of NE-SW. It is the great ability of hydrocarbon-generation and hydrocarbon-expulsion, good migration pathway and available sandstones distribution that play a critical role in forming Chang-9 reservoir.
2015, 33(5): 1033-1042.
doi: 10.14027/j.cnki.cjxb.2015.05.019
Abstract:
Saturated hydrocarbons in source rock from member 8 of Yanchang Formation(Upper Triassic) in Ordos Basin were analyzed by GC-MS. Different isomers of monomethylalkanes (MMAs)( carbon number ranging from 12 to 31) have been measured on a rock sample from Well Wu 56 located in Wuqi area. MMAs, with different substituted methyl ranging from the second carbon to the middle carbon, have shorter retention time than the corresponding n-alkanes with identical carbon number.2-methylalkanes and 3-methylalkanes are the most abundant compounds among MMAs, while 4-methylalkanes and other MMAs are relatively low. The positions of the substituted methyl in the MMAs can be identified through typical fragment ions, recombination pattern for chemical bonds, and retention time by mass spectrometry. For example, it has been found that the substituted methyl positions of C22-MMAs are C2-C11.The mass spectrometry is similar to the n-alkane with the same carbon number, m/z57 or m/z 71 is their base peak. They also show a predominant M+ peak and (M-15)+peak, suggesting a branched methyl. Moreover, the relative abundance decreases as the total carbon increases. When the methyl position is exceeding the fifth carbon, in comparison with n-alkanes, their major characteristic fragment ions are such m/z126,140,154,as even CnH2n,which are important to identify MMAs. Generally, a table about the characteristic fragment ions of MMAs are concluded. As well as gas chromatographic unseparated monomethylalkane isomers were resoluted by mass spectrometric deconvolution. Finally, by using of the Kovats index and the homomorphy factors for precise retention prediction and identification of the monomethylalkanes.
Saturated hydrocarbons in source rock from member 8 of Yanchang Formation(Upper Triassic) in Ordos Basin were analyzed by GC-MS. Different isomers of monomethylalkanes (MMAs)( carbon number ranging from 12 to 31) have been measured on a rock sample from Well Wu 56 located in Wuqi area. MMAs, with different substituted methyl ranging from the second carbon to the middle carbon, have shorter retention time than the corresponding n-alkanes with identical carbon number.2-methylalkanes and 3-methylalkanes are the most abundant compounds among MMAs, while 4-methylalkanes and other MMAs are relatively low. The positions of the substituted methyl in the MMAs can be identified through typical fragment ions, recombination pattern for chemical bonds, and retention time by mass spectrometry. For example, it has been found that the substituted methyl positions of C22-MMAs are C2-C11.The mass spectrometry is similar to the n-alkane with the same carbon number, m/z57 or m/z 71 is their base peak. They also show a predominant M+ peak and (M-15)+peak, suggesting a branched methyl. Moreover, the relative abundance decreases as the total carbon increases. When the methyl position is exceeding the fifth carbon, in comparison with n-alkanes, their major characteristic fragment ions are such m/z126,140,154,as even CnH2n,which are important to identify MMAs. Generally, a table about the characteristic fragment ions of MMAs are concluded. As well as gas chromatographic unseparated monomethylalkane isomers were resoluted by mass spectrometric deconvolution. Finally, by using of the Kovats index and the homomorphy factors for precise retention prediction and identification of the monomethylalkanes.
2015, 33(5): 1043-1052.
doi: 10.14027/j.cnki.cjxb.2015.05.020
Abstract:
Different types of source rock of Houjingou profile in Songliao Basin were analyzed in details for understanding the organic geochemical characteristics and the paleoenvironmental significance in Late Cretaceous, which were collected from the upper member 1 of Nenjiang Formation to the lower member 2 of the Nenjiang Formation. The results show that the source of organic matter in the upper member 1 of Nenjiang Formation changed upwardly from hybrids of lake inherent and terrestrial plants to lake endogenous predominance; There were three models in n-alkanes, the co-existence between odd-even preference of high carbon number and even-odd preference of low carbon number, odd-even preference of high carbon number, even-odd preference of low carbon number n-alkanes, respectively; The concentrations of 24-n-propylcholestane, 24-i-sopropylcholestane and dinoflagellate-steranes were 0.09 to 8 μg/g, 0 to 2 μg/g, 0 to 0.3 μg/g, respectively, increasing as the buried depth decrease, all of these indicated marine transgression combined with variations of δ13 Corg and C/N values. For the lower member 2 of the Nenjiang Formation, the source of organic matter showed lake inherent and the preservation of organic matter were related with anoxic bottom water and microorganism activities, but the non-marine algaes were also contributed to long-chain alkanes; The concentrations of 24-n-propyl cholestane, 24-i-sopropyl cholestane and dinoflagellate-steranes were 2.8 to 12.5 μg/g, 2.4 to 8.5 μg/g, 0.1 to 0.64 μg/g, respectively. Therefore, the depositional environment of upper member 1 of Nenjiang Formation showed shore lacustrine to transition of shallow lacustrine facies with increasing of marine transgression; The lower member 2 of Nenjiang Formation was turned out to be a semi-deep lake facies to deep lacustrine facies, the concentrations variation of marine algaes C30 sterane indicated that marine transgression marched more than once according to irregular fluctuate.
Different types of source rock of Houjingou profile in Songliao Basin were analyzed in details for understanding the organic geochemical characteristics and the paleoenvironmental significance in Late Cretaceous, which were collected from the upper member 1 of Nenjiang Formation to the lower member 2 of the Nenjiang Formation. The results show that the source of organic matter in the upper member 1 of Nenjiang Formation changed upwardly from hybrids of lake inherent and terrestrial plants to lake endogenous predominance; There were three models in n-alkanes, the co-existence between odd-even preference of high carbon number and even-odd preference of low carbon number, odd-even preference of high carbon number, even-odd preference of low carbon number n-alkanes, respectively; The concentrations of 24-n-propylcholestane, 24-i-sopropylcholestane and dinoflagellate-steranes were 0.09 to 8 μg/g, 0 to 2 μg/g, 0 to 0.3 μg/g, respectively, increasing as the buried depth decrease, all of these indicated marine transgression combined with variations of δ13 Corg and C/N values. For the lower member 2 of the Nenjiang Formation, the source of organic matter showed lake inherent and the preservation of organic matter were related with anoxic bottom water and microorganism activities, but the non-marine algaes were also contributed to long-chain alkanes; The concentrations of 24-n-propyl cholestane, 24-i-sopropyl cholestane and dinoflagellate-steranes were 2.8 to 12.5 μg/g, 2.4 to 8.5 μg/g, 0.1 to 0.64 μg/g, respectively. Therefore, the depositional environment of upper member 1 of Nenjiang Formation showed shore lacustrine to transition of shallow lacustrine facies with increasing of marine transgression; The lower member 2 of Nenjiang Formation was turned out to be a semi-deep lake facies to deep lacustrine facies, the concentrations variation of marine algaes C30 sterane indicated that marine transgression marched more than once according to irregular fluctuate.
2015, 33(5): 1053-1061.
doi: 10.14027/j.cnki.cjxb.2015.05.021
Abstract:
With the extensive exploration and development for the shale hydrocarbon, researchers pay more and more attention to the research of the reservoir characteristics of the shale. This article conducts pyrolysis simulation experiment on shale samples containing three different types of kerogen. It reveals that as the increasing of maturity of organic matters, the organic pores are produced in pyrolysis hydrocarbon generation of kerogen and the dissolved pores are produced in the solution of unstable minerals increased. Both of the two kinds of pores are key to the enhancement in reservoir space of shale. The diagenesis types of shale mainly include clay mineral transformation, dissolution of unstable minerals and recrystallization. The article has described a comprehensive diagenesis evolution pattern based on pyrolysis simulation experiment combined with vitrinite reflectance. The current study shows that different kinds of kerogens have diferent evolution characters in the hydrocarbon generation. At the edge of kerogen type Ⅰ, pore is produced in "dissociative hydrocarbon generation"; whilst inside kerogen type Ⅲ, pore is produced in "paralleled removal of functional group hydrocarbon generation". The characters of kerogen type Ⅱ in hydrocarbon generation are between type Ⅰ and type Ⅲ, and it can produce organic pores both inside and at the edge of the kerogen.
With the extensive exploration and development for the shale hydrocarbon, researchers pay more and more attention to the research of the reservoir characteristics of the shale. This article conducts pyrolysis simulation experiment on shale samples containing three different types of kerogen. It reveals that as the increasing of maturity of organic matters, the organic pores are produced in pyrolysis hydrocarbon generation of kerogen and the dissolved pores are produced in the solution of unstable minerals increased. Both of the two kinds of pores are key to the enhancement in reservoir space of shale. The diagenesis types of shale mainly include clay mineral transformation, dissolution of unstable minerals and recrystallization. The article has described a comprehensive diagenesis evolution pattern based on pyrolysis simulation experiment combined with vitrinite reflectance. The current study shows that different kinds of kerogens have diferent evolution characters in the hydrocarbon generation. At the edge of kerogen type Ⅰ, pore is produced in "dissociative hydrocarbon generation"; whilst inside kerogen type Ⅲ, pore is produced in "paralleled removal of functional group hydrocarbon generation". The characters of kerogen type Ⅱ in hydrocarbon generation are between type Ⅰ and type Ⅲ, and it can produce organic pores both inside and at the edge of the kerogen.
