2007 Vol. 25, No. 5
Display Method:
2007, 25(5): 653-662.
Abstract:
Located in the passive margin of the north of Yangtze Platform, Zheng An and Xun Yang basins in South Qingling Mountains have developed a series of Early PaleozoicMesozoic carbonate rocks containing some fine clastic rocks, which are characteristic of stable deposition, clear lithological facies, stratigraphical sequence and tracts as well as sensitive reflection to sea level change, so this area is an ideal place to study sea level change and its depositional response. On the basis of stratigraphical features and lateral change, 10 sequences have been divided as well as some depositional boundary and tracts. The evolution of sedimentary basins has close relationship with tectonic regime, regional tectonic activity, and tectonics controlled sea level change. Through the analysis on regional sequence framework and stratigraphy, we can furthermore study the history of regional tectonic activity and restore the details of sea level change to establish the lithological and chronological stratigraphical framework which is helpful for elucidating the accurate sensitive change of sea level change and describing the paleoclimate,plaeogeography and paleoenvironment as well as predicting depositional mineral resources.
Located in the passive margin of the north of Yangtze Platform, Zheng An and Xun Yang basins in South Qingling Mountains have developed a series of Early PaleozoicMesozoic carbonate rocks containing some fine clastic rocks, which are characteristic of stable deposition, clear lithological facies, stratigraphical sequence and tracts as well as sensitive reflection to sea level change, so this area is an ideal place to study sea level change and its depositional response. On the basis of stratigraphical features and lateral change, 10 sequences have been divided as well as some depositional boundary and tracts. The evolution of sedimentary basins has close relationship with tectonic regime, regional tectonic activity, and tectonics controlled sea level change. Through the analysis on regional sequence framework and stratigraphy, we can furthermore study the history of regional tectonic activity and restore the details of sea level change to establish the lithological and chronological stratigraphical framework which is helpful for elucidating the accurate sensitive change of sea level change and describing the paleoclimate,plaeogeography and paleoenvironment as well as predicting depositional mineral resources.
2007, 25(5): 671-677.
Abstract:
The geochemical researches on the upper Permian cherts of the Dalong Formation in the southwest Guangxi have been conducted. 〖JP2〗And we have the following findings: the chert is rich in the terrestrial elements (for example Al, Ti etc.), and poor in hydrothermal elements（for example Mn, Fe etc.）, with high correlation between the terrestrial elements (R>0.90) and low correlation between the hydrothermal elements (R=－0.30); The correlation between the terrestrial elements (Al, Ti, Hf, Zr, Th etc.) and ∑REE is high (R=0.70～0.83); AlFeMn diagram shows that the cherts is nonhydrothermal type. The characteristics above confirm that terrestrial debris is one of the most important provenances. Considering the truth, the high content of the siliceous biodebris in the cherts, we prove that the cherts were formed by strong bio or biochemical sedimentation, with lets of terrestrial debris and little hydrothermal and volcanic material interfused. Ce/Ce*, (La/Yb)Shale, (La/Ce)Shale, Th/U, Ceanom, ∑REE and (La/Ce)ShaleAl2O3/(Al2O3 +Fe2O3) diagram make sure that the cherts are deposited on middleouter shelf in oxic conditions. 〖JP〗
The geochemical researches on the upper Permian cherts of the Dalong Formation in the southwest Guangxi have been conducted. 〖JP2〗And we have the following findings: the chert is rich in the terrestrial elements (for example Al, Ti etc.), and poor in hydrothermal elements（for example Mn, Fe etc.）, with high correlation between the terrestrial elements (R>0.90) and low correlation between the hydrothermal elements (R=－0.30); The correlation between the terrestrial elements (Al, Ti, Hf, Zr, Th etc.) and ∑REE is high (R=0.70～0.83); AlFeMn diagram shows that the cherts is nonhydrothermal type. The characteristics above confirm that terrestrial debris is one of the most important provenances. Considering the truth, the high content of the siliceous biodebris in the cherts, we prove that the cherts were formed by strong bio or biochemical sedimentation, with lets of terrestrial debris and little hydrothermal and volcanic material interfused. Ce/Ce*, (La/Yb)Shale, (La/Ce)Shale, Th/U, Ceanom, ∑REE and (La/Ce)ShaleAl2O3/(Al2O3 +Fe2O3) diagram make sure that the cherts are deposited on middleouter shelf in oxic conditions. 〖JP〗
2007, 25(5): 684-692.
Abstract:
To yield grain size results of marine sediments reflecting variation of paleoenvironment and paleoclimate without distortion, biogenic carbonate and opal in samples should be effectively removed while terrigenous component should be undamaged during pretreatment procedure before measurement. To find the appropriate pretreatment method, marine sediments from South China Sea were treated with different dosages of hydrochloric acid (10%) or acetic acid (25%) and different dosages of NaOH and Na2CO3, then organic element analyzer, silicamolybdenum blue colorimetry and ESEM were used to evaluate the effects combined with the results of grain size measurement. The synthetic outcomes reveal that both of hydrochloric acid and acetic acid can eliminate biogenic carbonate well, however, because even a few dosage of the former can destroy terrigenous mineral component, the latter should be adopted during pretreatment procedure owing to its lower acidity; a large dosage of Na2CO3 still can't eliminate biogenic opal effectively but only a few dosage of NaOH can work well, so the latter should be used with restricted dosage to avoid destroying mineral component. According to biogenic content in marine sediments from SCS, the quantities of acetic acid (25%) and NaOH were determined and pretreatment procedure was established.
To yield grain size results of marine sediments reflecting variation of paleoenvironment and paleoclimate without distortion, biogenic carbonate and opal in samples should be effectively removed while terrigenous component should be undamaged during pretreatment procedure before measurement. To find the appropriate pretreatment method, marine sediments from South China Sea were treated with different dosages of hydrochloric acid (10%) or acetic acid (25%) and different dosages of NaOH and Na2CO3, then organic element analyzer, silicamolybdenum blue colorimetry and ESEM were used to evaluate the effects combined with the results of grain size measurement. The synthetic outcomes reveal that both of hydrochloric acid and acetic acid can eliminate biogenic carbonate well, however, because even a few dosage of the former can destroy terrigenous mineral component, the latter should be adopted during pretreatment procedure owing to its lower acidity; a large dosage of Na2CO3 still can't eliminate biogenic opal effectively but only a few dosage of NaOH can work well, so the latter should be used with restricted dosage to avoid destroying mineral component. According to biogenic content in marine sediments from SCS, the quantities of acetic acid (25%) and NaOH were determined and pretreatment procedure was established.
2007, 25(5): 701-707.
Abstract:
Inspired from anomaly low pressure in the middle and deep reservoir of Peleogene in Ji Yang Depression, "water consumption" of main mineral alteration during diagenetic stage is discussed theoretically. Preliminary research result shows that "water consumption" of mineral alteration in diagenetic stage can make formation water greatly decrease. Relevant formation must be in the stage of low pressure without supply of exterior liquid. Pressure differences between relevant formation and wall rock make hydrocarbons emplace easily to form the effective reservoir.
Inspired from anomaly low pressure in the middle and deep reservoir of Peleogene in Ji Yang Depression, "water consumption" of main mineral alteration during diagenetic stage is discussed theoretically. Preliminary research result shows that "water consumption" of mineral alteration in diagenetic stage can make formation water greatly decrease. Relevant formation must be in the stage of low pressure without supply of exterior liquid. Pressure differences between relevant formation and wall rock make hydrocarbons emplace easily to form the effective reservoir.
2007, 25(5): 716-721.
Abstract:
The first member of Qingshuihe Formation is a major pay formation of the lithologic oil reservoir in Well Shinan 31 area, of the lowamplitude structural oil reservoir in Well 44 Shinan area, and of the whole hinterland region in Junggar Basin. Researching its sequence stratigraphic characteristics is significant for the prospecting on subtle reservoir in Shinan area, even in the whole hinterland region. Based on the comprehensive analysis of cores, logs and seismic data, this paper points out that the first member of Qingshuihe Formation corresponds with the sediments of the lowstand and transgressive systems tracts of the first third class sequence in Lower Cretaceous. The sequence stratigraphy is characterized by as follows: the lowstand systems tracts, distributing limited, is consisted of the remained accommodation sediments in trench and valley, which deposited mainly pebbly sandstone of braided channel; the transgressive systems tracts develops retrograding delta and delta front slumping turbidity fan. The paper sets up a model for the hydrocarbon reservoir forming in Well Shinan 31 area and concludes that the middlewestern part of Sannan depression is the favorable prospecting region for the type of stratigraphiclithologic reservoir. Regionally, the stratigraphic traps make up of the channel pebbly sandstone and the slumping turbidite fan occurred in deltafront, and, the lithologic traps make up of the retrograding delta; the mudstone on the top of the transgressive systems tracts can be regarded as the seal; The effective passage system is matched up with the slope palaeotopography, the discordogenic fault, middleshallow fault system, and the unconformity.
The first member of Qingshuihe Formation is a major pay formation of the lithologic oil reservoir in Well Shinan 31 area, of the lowamplitude structural oil reservoir in Well 44 Shinan area, and of the whole hinterland region in Junggar Basin. Researching its sequence stratigraphic characteristics is significant for the prospecting on subtle reservoir in Shinan area, even in the whole hinterland region. Based on the comprehensive analysis of cores, logs and seismic data, this paper points out that the first member of Qingshuihe Formation corresponds with the sediments of the lowstand and transgressive systems tracts of the first third class sequence in Lower Cretaceous. The sequence stratigraphy is characterized by as follows: the lowstand systems tracts, distributing limited, is consisted of the remained accommodation sediments in trench and valley, which deposited mainly pebbly sandstone of braided channel; the transgressive systems tracts develops retrograding delta and delta front slumping turbidity fan. The paper sets up a model for the hydrocarbon reservoir forming in Well Shinan 31 area and concludes that the middlewestern part of Sannan depression is the favorable prospecting region for the type of stratigraphiclithologic reservoir. Regionally, the stratigraphic traps make up of the channel pebbly sandstone and the slumping turbidite fan occurred in deltafront, and, the lithologic traps make up of the retrograding delta; the mudstone on the top of the transgressive systems tracts can be regarded as the seal; The effective passage system is matched up with the slope palaeotopography, the discordogenic fault, middleshallow fault system, and the unconformity.
2007, 25(5): 730-736.
Abstract:
The Middle Permian Chihsia Formation of South China is featured by nodular chert, which is of implications in the reconstruction of coeval paleogeography and paleoceanography. This paper deals with mineralogical, petrologic characteristics and diagenesis of the nodular chert collected from Huangshi Hubei, Nanjing Jiangsu, and Laibin Guangxi. The nodular chert consists of mainly of microquartz, lengthfast chalcedony and megaquartz with minor lengthslow chalcedony, euhedral dolomite rhomb and sparry calcite as well as minor skeletal fragments. The microquartz, lengthfast chalcedony, lengthslow chalcedony and euhedral dolomite rhomb precipitated in the early diagenesis, the sparry calcite during burial diagenesis, and megaquartz across early and later stage. The source of silica derived from the thriving of the siliceousshell organisms, combining with evidences from the formation of nodular celestite and sepiolite in the host rock. The reliable constraints on diagenetic conditions and precipitating time relative to the diagenetic spectrum of the Chihsia carbonates for the formation of the lengthfast chalcedony and dolomite would be of farreaching implication in our understanding about their origin, and even about the origin of the bedded siliceous rocks of Permian in the investigation area.
The Middle Permian Chihsia Formation of South China is featured by nodular chert, which is of implications in the reconstruction of coeval paleogeography and paleoceanography. This paper deals with mineralogical, petrologic characteristics and diagenesis of the nodular chert collected from Huangshi Hubei, Nanjing Jiangsu, and Laibin Guangxi. The nodular chert consists of mainly of microquartz, lengthfast chalcedony and megaquartz with minor lengthslow chalcedony, euhedral dolomite rhomb and sparry calcite as well as minor skeletal fragments. The microquartz, lengthfast chalcedony, lengthslow chalcedony and euhedral dolomite rhomb precipitated in the early diagenesis, the sparry calcite during burial diagenesis, and megaquartz across early and later stage. The source of silica derived from the thriving of the siliceousshell organisms, combining with evidences from the formation of nodular celestite and sepiolite in the host rock. The reliable constraints on diagenetic conditions and precipitating time relative to the diagenetic spectrum of the Chihsia carbonates for the formation of the lengthfast chalcedony and dolomite would be of farreaching implication in our understanding about their origin, and even about the origin of the bedded siliceous rocks of Permian in the investigation area.
2007, 25(5): 745-752.
Abstract:
Elemental carbon was extracted from sediment by chemical oxidation and identified by Raman spectroscopy. The experimental results indicate that elemental carbon is defined by processing, which is a continuum from single crystal graphite to amorphous carbon. Chemical oxidation is a feasible method to extract elemental carbon from sediment and it can remove organic carbon and remain elemental carbon through controlling experimental condition and time. We think that the determination of standard sample and its concentration and unification of experimental method are very important because there are different results through different experimental conditions and methods. The unification and definition of all these carbon particulates are good for transect comparison and further research in relative field. In vertical secetion, elemental carbon was extracted by the same method and determination indicates that elemental carbon record can uncover paleoclimatic and environmental changes. In different timescale, elemental carbon has different implications for climate. At the same time, elemental carbon curve show a good change trend with other climatic indicators, which indicate elemental carbon can provide another new indicator for climatic and environmental changes.
Elemental carbon was extracted from sediment by chemical oxidation and identified by Raman spectroscopy. The experimental results indicate that elemental carbon is defined by processing, which is a continuum from single crystal graphite to amorphous carbon. Chemical oxidation is a feasible method to extract elemental carbon from sediment and it can remove organic carbon and remain elemental carbon through controlling experimental condition and time. We think that the determination of standard sample and its concentration and unification of experimental method are very important because there are different results through different experimental conditions and methods. The unification and definition of all these carbon particulates are good for transect comparison and further research in relative field. In vertical secetion, elemental carbon was extracted by the same method and determination indicates that elemental carbon record can uncover paleoclimatic and environmental changes. In different timescale, elemental carbon has different implications for climate. At the same time, elemental carbon curve show a good change trend with other climatic indicators, which indicate elemental carbon can provide another new indicator for climatic and environmental changes.
2007, 25(5): 759-766.
Abstract:
This study discusses the distribution and enrichment characteristic of redox sensitive elements defined both the seabottom surface sediments and in suspensions off the Changjiang Estuary hypoxia zone and its contiguous sea area. The distribution of RSE “enrich off the sea shore”. The results, after getting rid of the influence of “grain size effects”, terrigenous components and adsorption by organic matter, revealed that distribution of RSE still “enrich off the sea shore”. By comparison the RSE concentration between bottom layer suspension and surface sediments, the paper believes that the hypoxia zone of the bottom water induces the RSE to enrich in sediments. The authigenic precipitation mechanism and the potential energy of Mo, Cd and V is different, their different enrichment characteristics can be used as redox indicators of the hypoxia zone. So, redox sensitive elements such as Mo, Cd and V have the redox environmental significance of the Changjiang Estuary and its contiguous sea area. U are also sensitive to redox conditions of bottom sediments theoretically, the terrigenous components of U conceal the enrichment of U in hypoxia zone, and so U have no environment significance in the hypoxia zone of the research area.
This study discusses the distribution and enrichment characteristic of redox sensitive elements defined both the seabottom surface sediments and in suspensions off the Changjiang Estuary hypoxia zone and its contiguous sea area. The distribution of RSE “enrich off the sea shore”. The results, after getting rid of the influence of “grain size effects”, terrigenous components and adsorption by organic matter, revealed that distribution of RSE still “enrich off the sea shore”. By comparison the RSE concentration between bottom layer suspension and surface sediments, the paper believes that the hypoxia zone of the bottom water induces the RSE to enrich in sediments. The authigenic precipitation mechanism and the potential energy of Mo, Cd and V is different, their different enrichment characteristics can be used as redox indicators of the hypoxia zone. So, redox sensitive elements such as Mo, Cd and V have the redox environmental significance of the Changjiang Estuary and its contiguous sea area. U are also sensitive to redox conditions of bottom sediments theoretically, the terrigenous components of U conceal the enrichment of U in hypoxia zone, and so U have no environment significance in the hypoxia zone of the research area.
2007, 25(5): 774-777.
Abstract:
By the thermal simulating experiments, the authors researched the gas generation model of soluble organic matter which is dispersed in carbonate and clastic rocks. It indicates that the pyrolytic gas productivity of soluble organic matter dispersed in clastic rocks is obviously different from that of which in carbonate rocks during the hightemperature cracking. In clastic rocks, the cracked gas productivity is increase with the abundance of soluble organic matter when the abundance below 0.3% and almost constant when up 0.3%. In carbonate rocks, the cracked gas productivity is almost constant all along. There is a remarkable different between the dry coefficients of the pyrolytic gas from these two kinds of rocks. This is result from the difference of the rocks' selective adsorption to the heavy hydrocarbon.
By the thermal simulating experiments, the authors researched the gas generation model of soluble organic matter which is dispersed in carbonate and clastic rocks. It indicates that the pyrolytic gas productivity of soluble organic matter dispersed in clastic rocks is obviously different from that of which in carbonate rocks during the hightemperature cracking. In clastic rocks, the cracked gas productivity is increase with the abundance of soluble organic matter when the abundance below 0.3% and almost constant when up 0.3%. In carbonate rocks, the cracked gas productivity is almost constant all along. There is a remarkable different between the dry coefficients of the pyrolytic gas from these two kinds of rocks. This is result from the difference of the rocks' selective adsorption to the heavy hydrocarbon.
2007, 25(5): 782-786.
Abstract:
The study of evaluation criterion of carbonate oil source rocks is a basic research subject which has significant influences on exploratory decision and has important theoretical and practical value. In this paper, calculations have been performed about amount of oil generation, remained oil of unit area carbonate rocks at different geologic conditions by the parameters (strata, geohistory, and thermal history) in Tarim basin, Bohai Bay basin, and Ordos basin. According to the material balance principle, oilexpulsion amount has been worked out (oilexpulsion amount = amount of oilgeneration － amount of remained oil). We regard it as an index to present the classification evaluation of oil source rocks, figure out the corresponding organic enrichment, and establish the classification evaluation tables of carbonate oil source rocks in Tarim basin, Bohai Bay basin, and Ordos basin. Based on the simulating calculation, find that TOC industrial threshold value (TOCgy ) decreases with the increasing source rocks thickness; decreases at first and then increases with the increasing maturity and decreases with the better type of organic matter. Investigations indicate that the evaluation Standard of carbonate oil source rocks have great variance with the differences of geologic conditions. Based on the analysis, we induce the threshold values, TOC are "0.25, 0.5, 0.8, 1.5", which correspond with the classes, "non, ineffective, poor, moderate and good source rocks" of mature carbonate oil source rocks whose organic matter type is Ⅱ.
The study of evaluation criterion of carbonate oil source rocks is a basic research subject which has significant influences on exploratory decision and has important theoretical and practical value. In this paper, calculations have been performed about amount of oil generation, remained oil of unit area carbonate rocks at different geologic conditions by the parameters (strata, geohistory, and thermal history) in Tarim basin, Bohai Bay basin, and Ordos basin. According to the material balance principle, oilexpulsion amount has been worked out (oilexpulsion amount = amount of oilgeneration － amount of remained oil). We regard it as an index to present the classification evaluation of oil source rocks, figure out the corresponding organic enrichment, and establish the classification evaluation tables of carbonate oil source rocks in Tarim basin, Bohai Bay basin, and Ordos basin. Based on the simulating calculation, find that TOC industrial threshold value (TOCgy ) decreases with the increasing source rocks thickness; decreases at first and then increases with the increasing maturity and decreases with the better type of organic matter. Investigations indicate that the evaluation Standard of carbonate oil source rocks have great variance with the differences of geologic conditions. Based on the analysis, we induce the threshold values, TOC are "0.25, 0.5, 0.8, 1.5", which correspond with the classes, "non, ineffective, poor, moderate and good source rocks" of mature carbonate oil source rocks whose organic matter type is Ⅱ.
2007, 25(5): 795-799.
Abstract:
It has been performed that investigating the mixed oil in reservoirs from Niuzhuang to Bamianhe oilfield with organically geochemical method. Using mature oil in Niuzhuang oilfield from Es3 source rocks and lowmature oil in Bamianhe oilfield from Es4 source rocks as two end members, to make cross plots of gammacerane/C30hopanoid ratio and hopanoid/sterane ratio, rearranged monoaryl sterane/C27βS monoaryl sterane ratio and the content of aromatic sterene, then calculated the oil mixed rate based on the cross plots. The result indicated that the mixing ratio of oil from Es4 source rocks step up from Niuzhuang subdepression to Bamianhe oilfield, and got similar data from two cross plots. Mature oil form Es3 source rocks dominated in the centre of Niuzhuang subdepression, low mature oil from Es4 source rocks dominated in Bamianhe oilfield, and two type oil mixed in Wangjiagang oilfield.
It has been performed that investigating the mixed oil in reservoirs from Niuzhuang to Bamianhe oilfield with organically geochemical method. Using mature oil in Niuzhuang oilfield from Es3 source rocks and lowmature oil in Bamianhe oilfield from Es4 source rocks as two end members, to make cross plots of gammacerane/C30hopanoid ratio and hopanoid/sterane ratio, rearranged monoaryl sterane/C27βS monoaryl sterane ratio and the content of aromatic sterene, then calculated the oil mixed rate based on the cross plots. The result indicated that the mixing ratio of oil from Es4 source rocks step up from Niuzhuang subdepression to Bamianhe oilfield, and got similar data from two cross plots. Mature oil form Es3 source rocks dominated in the centre of Niuzhuang subdepression, low mature oil from Es4 source rocks dominated in Bamianhe oilfield, and two type oil mixed in Wangjiagang oilfield.
2007, 25(5): 808-814.
Abstract:
It is the one of the most important source rocks for the Buqu marine carbonate rocks in North Qiangtang Basin, but some issues about oil and gas geochemistry are not clear because the lowly research. The biologicsource constitution, sedimentary environment and maturity of organic matter in the Jurassic carbonate rocks in North Qiangtang Basin is studied preliminarily by means of biomarker analysis technology combined with other geochemical data. The result reveals that the hydrocarbon source rock were developed in sedimentary environment, the organic source material is mainly lowgrade hydrobios mixed with highgrade plants. The source rocks have higher maturity, and possess favorable conditions to form gas and oil.
It is the one of the most important source rocks for the Buqu marine carbonate rocks in North Qiangtang Basin, but some issues about oil and gas geochemistry are not clear because the lowly research. The biologicsource constitution, sedimentary environment and maturity of organic matter in the Jurassic carbonate rocks in North Qiangtang Basin is studied preliminarily by means of biomarker analysis technology combined with other geochemical data. The result reveals that the hydrocarbon source rock were developed in sedimentary environment, the organic source material is mainly lowgrade hydrobios mixed with highgrade plants. The source rocks have higher maturity, and possess favorable conditions to form gas and oil.
2007, 25(5): 663-670.
Abstract:
The single factor analysis which based on sedimentary dynamic mostly emphasizes the actions relating to transportation and depositional procedure, adopting one method from point to surface, from local to whole and from quantitative change to qualitative change, and the depositional regime which is based on morphology, present sedimentation and datum up and down, adopting other gradually penetrating method from surface to point and from whole to local, are different in research approach. The former is not prone to controlling the law of bulk distribution of depositional system in riftsubsidence basin, but the latter is opposite. The basic request of the method of depositional regime which includes three key technologies: palaeogeomorphology reconstruction, recognition of seismic reflection texture and waveform feature is provided with affluent and excellent seismic data. Through palaeogeomorphology reconstruction, combining the observation of present sedimentation, water depth and lithologic, the distribution law of depositional system can be ascertained. Furthermore, by researching seismic reflection texture and waveform feature, the types of sedimentary microfacies can be decided in a point. The law of plane distribution of depositional system which locates the middle part of middle submember of the 3rd member of Shahejie Formation in Gunan pothole, Zhanhua sag is studied by using the method of depositional regime. The braided rive delta front subfacies located on the south slop area is developed in the braided rive delta which progrades from south to north. The basin bottom fans located at the toe of Gunan fault are mostly distributed in the north pothole. Moreover, the basin bottom fan can be developed because the nearshore beach and bar in the shallow lake glides, too. The shallow lake subfacies with affluent nearshore beach and bar and sandsheet is mostly developed because the water depth is shallow.
The single factor analysis which based on sedimentary dynamic mostly emphasizes the actions relating to transportation and depositional procedure, adopting one method from point to surface, from local to whole and from quantitative change to qualitative change, and the depositional regime which is based on morphology, present sedimentation and datum up and down, adopting other gradually penetrating method from surface to point and from whole to local, are different in research approach. The former is not prone to controlling the law of bulk distribution of depositional system in riftsubsidence basin, but the latter is opposite. The basic request of the method of depositional regime which includes three key technologies: palaeogeomorphology reconstruction, recognition of seismic reflection texture and waveform feature is provided with affluent and excellent seismic data. Through palaeogeomorphology reconstruction, combining the observation of present sedimentation, water depth and lithologic, the distribution law of depositional system can be ascertained. Furthermore, by researching seismic reflection texture and waveform feature, the types of sedimentary microfacies can be decided in a point. The law of plane distribution of depositional system which locates the middle part of middle submember of the 3rd member of Shahejie Formation in Gunan pothole, Zhanhua sag is studied by using the method of depositional regime. The braided rive delta front subfacies located on the south slop area is developed in the braided rive delta which progrades from south to north. The basin bottom fans located at the toe of Gunan fault are mostly distributed in the north pothole. Moreover, the basin bottom fan can be developed because the nearshore beach and bar in the shallow lake glides, too. The shallow lake subfacies with affluent nearshore beach and bar and sandsheet is mostly developed because the water depth is shallow.
2007, 25(5): 678-683.
Abstract:
By comparing and analyzing the lithology, the seismic reflection fabric and the sequence development characteristics between “Didao Formation” and Dongrong Formation in Suibin depression, it is found that the lithology of the lower part of “Didao” and Dongrong Formation are sandy conglomerate and conglomerate; the middle part are mainly of fine sandstone and siltstone; the upper part sediments all includes volcanic rocks. “Didao Formation” includes coal bed, but Dongrong Formation does not. In seismic profile the amplitude and continuity of Dongrong Formation are better than “Didao Formation”.Both “Didao” and Dongrong Formation experience twice sea level changes in sequence development process and they have pertinence. It is marine sediments of Dongrong Formation in northeast of Suibin depression and in the southwest “Didao Formation” is fan delta lake sediments. So the author considers that “Didao Formation” should be included in Dongrong Formation , and it is heteropical deposits of Dongrong Formation and hereby indicates that Didao and Dongrong Formation have well source rockreservoircap combination.
By comparing and analyzing the lithology, the seismic reflection fabric and the sequence development characteristics between “Didao Formation” and Dongrong Formation in Suibin depression, it is found that the lithology of the lower part of “Didao” and Dongrong Formation are sandy conglomerate and conglomerate; the middle part are mainly of fine sandstone and siltstone; the upper part sediments all includes volcanic rocks. “Didao Formation” includes coal bed, but Dongrong Formation does not. In seismic profile the amplitude and continuity of Dongrong Formation are better than “Didao Formation”.Both “Didao” and Dongrong Formation experience twice sea level changes in sequence development process and they have pertinence. It is marine sediments of Dongrong Formation in northeast of Suibin depression and in the southwest “Didao Formation” is fan delta lake sediments. So the author considers that “Didao Formation” should be included in Dongrong Formation , and it is heteropical deposits of Dongrong Formation and hereby indicates that Didao and Dongrong Formation have well source rockreservoircap combination.
2007, 25(5): 693-700.
Abstract:
This paper presents an improved mathematical model of dissolutionprecipitation, which successfully runs in Well Tazhong 4 of the Tarim Basin. The case study of the Carboniferous Formation in the well shows that the simulation outcome of the model in clay mineral coincides with the KAr dating and approaches the data of clay mineral analyses. The case study indicates that the most sensitive parameter in whether the earlypresented kinetic model or the latest presented dissolutionprecipitation model is the activation energy, and it is a key to obtain the proper smectite and illite histories that one can calibrate the activation energy by using the data of clay mineral analyses as constraint. By adopting the optimal activation energy, one can obtain the optimal results: (a) the starting time of illite growth calculated coincides with the KAr dating, and (b) the results approach the data of clay mineral analyses. It is also found through the case study that the dissolutionprecipitation model is only applicable to the transformation in clay mineral while the kinetic model is only applicable to the transformation in illitesmectite interstratifications.
This paper presents an improved mathematical model of dissolutionprecipitation, which successfully runs in Well Tazhong 4 of the Tarim Basin. The case study of the Carboniferous Formation in the well shows that the simulation outcome of the model in clay mineral coincides with the KAr dating and approaches the data of clay mineral analyses. The case study indicates that the most sensitive parameter in whether the earlypresented kinetic model or the latest presented dissolutionprecipitation model is the activation energy, and it is a key to obtain the proper smectite and illite histories that one can calibrate the activation energy by using the data of clay mineral analyses as constraint. By adopting the optimal activation energy, one can obtain the optimal results: (a) the starting time of illite growth calculated coincides with the KAr dating, and (b) the results approach the data of clay mineral analyses. It is also found through the case study that the dissolutionprecipitation model is only applicable to the transformation in clay mineral while the kinetic model is only applicable to the transformation in illitesmectite interstratifications.
2007, 25(5): 708-715.
Abstract:
On the basis of integrating well data and seismic data, sequence boundaries of different orders are recognized. Baselevel cycles of three orders(short scale, middle scale and long scale)of every single well are recognized according to facies succession, physical character of rock, contacted manner of strata and seismic interpretations. Within dense grid wellconnecting profiles, baselevel cycles of different order are correlated in the restriction of seismic interpretations. Isochronous stratigraphic frameworks are established and single sandbody is correlated within them. Finally, the distribution and evolution of reservoir are analyzed within isochronous stratigraphic frameworks.
On the basis of integrating well data and seismic data, sequence boundaries of different orders are recognized. Baselevel cycles of three orders(short scale, middle scale and long scale)of every single well are recognized according to facies succession, physical character of rock, contacted manner of strata and seismic interpretations. Within dense grid wellconnecting profiles, baselevel cycles of different order are correlated in the restriction of seismic interpretations. Isochronous stratigraphic frameworks are established and single sandbody is correlated within them. Finally, the distribution and evolution of reservoir are analyzed within isochronous stratigraphic frameworks.
2007, 25(5): 722-729.
Abstract:
The presentlyexplored oil and gas in the central and northwestern Junggar Basin are mainly derived from CarboniferousPermian sequences. In this paper, we try to understand the basic features of petroleum fluid based on analyses on carbon, oxygen and strontium isotope composition of typical calcite veins hosted in source sequences. δ13CPDB of 25 typical calcites ranges from －21.5‰ ~ 5.2‰, and δ18OPDB(δ18OSMOW) locates between －8.1‰ and -22.3‰(22.6‰ ~ 6.9‰). On the other hand, 20 87Sr/86Sr data (0.703 896~0.706 423) are all below the average value of modern seawater (0.709 073). Combined these isotope data and their geologic background, it is suggested that the petroleum fluid in the basin is a mixture of deepsourced hot fluid and oilgaswater. It carried volcaniccharacters by dissolution on the volcano and clastic rocks during hydrocarbon generation and migration. This result indicates that the effect of deep sourced hot fluid must be given enough consideration in the future study of reservoir diagenesis and petroleum migration.
The presentlyexplored oil and gas in the central and northwestern Junggar Basin are mainly derived from CarboniferousPermian sequences. In this paper, we try to understand the basic features of petroleum fluid based on analyses on carbon, oxygen and strontium isotope composition of typical calcite veins hosted in source sequences. δ13CPDB of 25 typical calcites ranges from －21.5‰ ~ 5.2‰, and δ18OPDB(δ18OSMOW) locates between －8.1‰ and -22.3‰(22.6‰ ~ 6.9‰). On the other hand, 20 87Sr/86Sr data (0.703 896~0.706 423) are all below the average value of modern seawater (0.709 073). Combined these isotope data and their geologic background, it is suggested that the petroleum fluid in the basin is a mixture of deepsourced hot fluid and oilgaswater. It carried volcaniccharacters by dissolution on the volcano and clastic rocks during hydrocarbon generation and migration. This result indicates that the effect of deep sourced hot fluid must be given enough consideration in the future study of reservoir diagenesis and petroleum migration.
2007, 25(5): 737-744.
Abstract:
In order to investigate the organic matter liability and sedimentary environments in the China Pioneer area, Tropical East Pacific Ocean, sediment hydrolysable amino acids were analyzed using HPLC. The contents of amino acids and amino sugars were low in the study area, 0.3~0.5 mg·g-1 and 0.10~0.17 mg·g-1(dry weight), respectively. The division of functional groups of protein amino acids showed that the neutral amino acids dominated (>50 mol%), and the acidic, hydroxylic, basic, aromatic and sulfuric amino acids account for 17, 11, 9, <5 and <5 mol% respectively. The result indicates that the characteristics of the deep ocean sedimentary environment was slightly alkaline and oxidative. The degradation index (DI) and the ratio of Asp/βAla、Glu/γAba showed high decomposition state of the organic matter in the study area. And the ratio of nonprotein/protein amino acids and Glum/Gal showed that the organic matter were strongly reconstructed by microbe, indicates the possibility of the organicmicrobial mineralization of the oceanic polymetallic nodules in the study area.
In order to investigate the organic matter liability and sedimentary environments in the China Pioneer area, Tropical East Pacific Ocean, sediment hydrolysable amino acids were analyzed using HPLC. The contents of amino acids and amino sugars were low in the study area, 0.3~0.5 mg·g-1 and 0.10~0.17 mg·g-1(dry weight), respectively. The division of functional groups of protein amino acids showed that the neutral amino acids dominated (>50 mol%), and the acidic, hydroxylic, basic, aromatic and sulfuric amino acids account for 17, 11, 9, <5 and <5 mol% respectively. The result indicates that the characteristics of the deep ocean sedimentary environment was slightly alkaline and oxidative. The degradation index (DI) and the ratio of Asp/βAla、Glu/γAba showed high decomposition state of the organic matter in the study area. And the ratio of nonprotein/protein amino acids and Glum/Gal showed that the organic matter were strongly reconstructed by microbe, indicates the possibility of the organicmicrobial mineralization of the oceanic polymetallic nodules in the study area.
2007, 25(5): 753-758.
Abstract:
Multiple magnetic parameters measurement such as magnetic susceptibility, saturation remnant magnetization, anhysteresis remnant magnetization were made on 110 surface samples taken from the shelf of the East China Sea to abyssal plain of the Okinawa Trough. Based on the measured results, correlation in sediment magnetic characteristic and material provenance with different sedimentary environments were discussed. The sediment from individual sedimentary environments show distinguishable local environmental characteristics and are characterized by different magnetic properties. As the east abyssal plain of the Okinawa Trough contains some volcanic materials, it shows stronger magnetic characteristics than other sediment environments. There are no clearly correlation between CaCO3 and magnetic parameters, but magnetic feature tends to become weaker with the content of CaCO3 increase. Being a biologic index, CaCO3 possibly dilute the content of magnetic minerals of sediments to affect the magnetic characteristics of sediments.
Multiple magnetic parameters measurement such as magnetic susceptibility, saturation remnant magnetization, anhysteresis remnant magnetization were made on 110 surface samples taken from the shelf of the East China Sea to abyssal plain of the Okinawa Trough. Based on the measured results, correlation in sediment magnetic characteristic and material provenance with different sedimentary environments were discussed. The sediment from individual sedimentary environments show distinguishable local environmental characteristics and are characterized by different magnetic properties. As the east abyssal plain of the Okinawa Trough contains some volcanic materials, it shows stronger magnetic characteristics than other sediment environments. There are no clearly correlation between CaCO3 and magnetic parameters, but magnetic feature tends to become weaker with the content of CaCO3 increase. Being a biologic index, CaCO3 possibly dilute the content of magnetic minerals of sediments to affect the magnetic characteristics of sediments.
2007, 25(5): 767-773.
Abstract:
Gahai Lake lies in the conjunction area of some largescale climatic systems such as East Asian monsoon area, southwest monsoon area and westerly wind and so on. Through studies on some palaeoenvironmental proxies such as minerals, grain size and carbonate content in Core DG03, we have analyzed and discussed the characteristics of palaeoenvironment changes in Gahai Lake, where is a sensitive area for climatic change. The research results show that the main minerals in core DG03 include quartz, plagioclase, microcline, chlorite, illite, calcite, aragonite, dolomite, gypsum and halite. The core records the palaeoenvironmental change information of Gahai Lake since about 11ka BP (AMS14C age). According to change characteristics of minerals and lithology, the core is divided into three parts: Ⅰabout 11 ka～10 ka BP, the last period of lateglacial (Younger Dryas event); Ⅱ 10 ka～4 ka BP, the early and middle Holocene; Ⅲ 4 ka ～0 BP, the late Holocene. The mineral assemblages in different period indicate that the water level of Gahai Lake experiences a process of lowhighlow and accordingly salinity highlowhigh. Gahai Lake orderly experiences the reverse and forward process of lake evolution. Combining the lithology and grain size, we speculate that Gahai Lake area orderly experienced the cold and dry climate of lateglacial, the warm and dry climate of early Holocene, the warm and wet climate of middle Holocene and the gradually cold and dry climate of late Holocene. The analysis of lithology also shows that there is a complex sedimentary environment and there are some different types of terrestrial deposits in Gahai Lake and the influence of alluvialproluvial deposition is through the whole Holocene. But we believe that the complex sedimentary environments can better reveal the change characteristics of regional environment.
Gahai Lake lies in the conjunction area of some largescale climatic systems such as East Asian monsoon area, southwest monsoon area and westerly wind and so on. Through studies on some palaeoenvironmental proxies such as minerals, grain size and carbonate content in Core DG03, we have analyzed and discussed the characteristics of palaeoenvironment changes in Gahai Lake, where is a sensitive area for climatic change. The research results show that the main minerals in core DG03 include quartz, plagioclase, microcline, chlorite, illite, calcite, aragonite, dolomite, gypsum and halite. The core records the palaeoenvironmental change information of Gahai Lake since about 11ka BP (AMS14C age). According to change characteristics of minerals and lithology, the core is divided into three parts: Ⅰabout 11 ka～10 ka BP, the last period of lateglacial (Younger Dryas event); Ⅱ 10 ka～4 ka BP, the early and middle Holocene; Ⅲ 4 ka ～0 BP, the late Holocene. The mineral assemblages in different period indicate that the water level of Gahai Lake experiences a process of lowhighlow and accordingly salinity highlowhigh. Gahai Lake orderly experiences the reverse and forward process of lake evolution. Combining the lithology and grain size, we speculate that Gahai Lake area orderly experienced the cold and dry climate of lateglacial, the warm and dry climate of early Holocene, the warm and wet climate of middle Holocene and the gradually cold and dry climate of late Holocene. The analysis of lithology also shows that there is a complex sedimentary environment and there are some different types of terrestrial deposits in Gahai Lake and the influence of alluvialproluvial deposition is through the whole Holocene. But we believe that the complex sedimentary environments can better reveal the change characteristics of regional environment.
2007, 25(5): 778-781.
Abstract:
A sequential selective chemical degradation was performed for the kerogen from the Nenjiang Formation of the southern Songliao Basin by using a series of mild chemical degradations. Subsequently, GCMS analyses were carried out for different degradation products. The results show that products of alkaline hydrolysis and desulfurization mainly comprise monocarboxylic acids and nalkanes. The carbon isotope curve of nalkanes displays a “negative sloping” (i.e. gradually depleted in 13C with increasing carbon number). Monocarboxylic acids, mainly including C16 and C18 acids, have an obvious even carbonnumbered predominance. Their carbon isotope compositions are similar to those of the corresponding nalkanes with same carbon number. Monocarboxylic acids and α, ωdicarboxylic acids are the dominant products of RuO4 oxidation. Carbon isotopic composition of monocarboxylic acids fall between －28.3% and －33.7‰, and a "negative sloping" is shown in the range of light carbon number, while a “positive sloping” in high carbon number part. δ13C values of α,ωdicarboxylic acid is similar to those of monocarboxylic acids in the range of light carbon number, indicating that they have the same source. The comparison shows that the nalkanes in the extracts from sample JL30 possibly have the mixing of other sources, and their carbon isotopic compositions present the mixing characteristics.
A sequential selective chemical degradation was performed for the kerogen from the Nenjiang Formation of the southern Songliao Basin by using a series of mild chemical degradations. Subsequently, GCMS analyses were carried out for different degradation products. The results show that products of alkaline hydrolysis and desulfurization mainly comprise monocarboxylic acids and nalkanes. The carbon isotope curve of nalkanes displays a “negative sloping” (i.e. gradually depleted in 13C with increasing carbon number). Monocarboxylic acids, mainly including C16 and C18 acids, have an obvious even carbonnumbered predominance. Their carbon isotope compositions are similar to those of the corresponding nalkanes with same carbon number. Monocarboxylic acids and α, ωdicarboxylic acids are the dominant products of RuO4 oxidation. Carbon isotopic composition of monocarboxylic acids fall between －28.3% and －33.7‰, and a "negative sloping" is shown in the range of light carbon number, while a “positive sloping” in high carbon number part. δ13C values of α,ωdicarboxylic acid is similar to those of monocarboxylic acids in the range of light carbon number, indicating that they have the same source. The comparison shows that the nalkanes in the extracts from sample JL30 possibly have the mixing of other sources, and their carbon isotopic compositions present the mixing characteristics.
Discussion on the Origin of Heavy Oil and Reservoir Formation in Permian System of TurpanHami Basin
2007, 25(5): 787-794.
Abstract:
In the light of the latest heavy oil exploration progress in the Permian formation of Huoyanshan central zone, TurpanHami basin, this study on heavy oil origin and reservoir formation is carried out based on geologic and geochemical data. It is concluded that Shengbei depression is the major source area for the central heavy oil zone, biologic degradation is the major cause of the oil thickening, and the Triassic heavy oil reservoir in Well H8 was formed at the end of Xishanyao depositional stage in MidJurassic epoch. In addition, the forming mode of this kind of reservoirs “secondary influx” is described through revealing the heterogeneity of the reservoir of Upper Permian and MidJurassic system in Well Y2 and Y4
In the light of the latest heavy oil exploration progress in the Permian formation of Huoyanshan central zone, TurpanHami basin, this study on heavy oil origin and reservoir formation is carried out based on geologic and geochemical data. It is concluded that Shengbei depression is the major source area for the central heavy oil zone, biologic degradation is the major cause of the oil thickening, and the Triassic heavy oil reservoir in Well H8 was formed at the end of Xishanyao depositional stage in MidJurassic epoch. In addition, the forming mode of this kind of reservoirs “secondary influx” is described through revealing the heterogeneity of the reservoir of Upper Permian and MidJurassic system in Well Y2 and Y4
2007, 25(5): 800-807.
Abstract:
Investigation of the thermal simulation of lowevolutionary source rocks bitumen “A” of the salt lacustrine facies in Qaidam Basin indicated that the range of temperature on the hydrocarbon generating fastigium in the thermal function are 200～270℃, and the source rocks are characterized by high relative abundance of the nonhydrocarbon and asphaltene. The mature velocity of the biomarkers are different from the immature to lowmature to highmature oil, and it’s sequence is alkane>hopane>sterane. The polar compound in the nonhydrocarbon and asphaltene, which have some atom other than carbon, have some reactions after 300℃ in thermal simulation, for instance, dehydroxylation, decarboxylation, decarbonyl and the chain cleavage. The ratio of sterane C29ββ/(ββ+αα) is very high in lowevolutionary stage, indicating that there are some bacteriumgerms in this area. In low temperature range of lowevolutionary source rocks in Qaidam Basin have generated a significant volume of hydrocarbon, consequently the activation energy of source rocks would become down because the depositional organic matter have been rebuilt by the bacteriumgerms.
Investigation of the thermal simulation of lowevolutionary source rocks bitumen “A” of the salt lacustrine facies in Qaidam Basin indicated that the range of temperature on the hydrocarbon generating fastigium in the thermal function are 200～270℃, and the source rocks are characterized by high relative abundance of the nonhydrocarbon and asphaltene. The mature velocity of the biomarkers are different from the immature to lowmature to highmature oil, and it’s sequence is alkane>hopane>sterane. The polar compound in the nonhydrocarbon and asphaltene, which have some atom other than carbon, have some reactions after 300℃ in thermal simulation, for instance, dehydroxylation, decarboxylation, decarbonyl and the chain cleavage. The ratio of sterane C29ββ/(ββ+αα) is very high in lowevolutionary stage, indicating that there are some bacteriumgerms in this area. In low temperature range of lowevolutionary source rocks in Qaidam Basin have generated a significant volume of hydrocarbon, consequently the activation energy of source rocks would become down because the depositional organic matter have been rebuilt by the bacteriumgerms.
