2010 Vol. 28, No. 6
Display Method:
2010, 28(6): 1047-1053.
Abstract:
Segment activity of Xi'nanzhuang fault in Nanpu Sag was studied by using fault fall. On the base of this, controlling of fault on sedimentary Process was researched. Xi'nanzhuang fault was divided into three parts, the eastern part was developed firstly, the western part and the middle part was strongly activated at the middle and later period. Furthermore, the western part controlled development of Nanpu5 tectonic belt, rollover anticline was formed in there; While linkage of the middle and eastern part was the developed part of Laoyemiao tectonic belt, it was a transverse fold of which axis was vertical to Xi'nanzhuang fault. It was formed for bilateral strong subsidence. Sedimentary source of Nanpu5 tectonic belt came from pitching end of the western part into the center of western part along down wall; Laoyemiao tectonic belt was correlated with inherited sedimentary source entrance, depositional systems entered the center of sag along hinge of transverse fold.
Segment activity of Xi'nanzhuang fault in Nanpu Sag was studied by using fault fall. On the base of this, controlling of fault on sedimentary Process was researched. Xi'nanzhuang fault was divided into three parts, the eastern part was developed firstly, the western part and the middle part was strongly activated at the middle and later period. Furthermore, the western part controlled development of Nanpu5 tectonic belt, rollover anticline was formed in there; While linkage of the middle and eastern part was the developed part of Laoyemiao tectonic belt, it was a transverse fold of which axis was vertical to Xi'nanzhuang fault. It was formed for bilateral strong subsidence. Sedimentary source of Nanpu5 tectonic belt came from pitching end of the western part into the center of western part along down wall; Laoyemiao tectonic belt was correlated with inherited sedimentary source entrance, depositional systems entered the center of sag along hinge of transverse fold.
2010, 28(6): 1066-1075.
Abstract:
Compared with China's inland, sedimentary environments of the Cenozoic in China offshore basins have the diversity. In different sedimentary basins, there are three kinds of sedimentary environments include continental, paralic and marine facies. Each basin has undergone changes in different sedimentary environments generally. Through studying the China offshore basins controlled by plate tectonic movement, analyzing the basin structure in the evolution of plate movement, combined with the evidence related to sedimentary environment, we could verify the relationship between sedimentary environment and sedimentary system in China offshore basins.
As China offshore was caught in the middle of Eurasian Plate, Pacific Plate and Indian Ocean Plate, its formation and evolution were controlled by these three plates. Western Pacific is a north to south of the trencharcbasin system. Generally bounded by the Taiwan Strait, the East China Sea Basin is a convergent margin with the evolution of conversion or passive continental margin due to the continuing westward subduction by the Pacific Plate or the Philippines Plate. The South China Sea is a passive margin with the evolution of active or convergent margin due to the continuing eastward subduction of South Ocean Shell. So there would have different basins as the evolution of different mechanisms. In this paper, the Cenozoic in China offshore basins were divided into three types including rift basins on internal plate, convergent basins on plate margin and scatter basins on plate margin. Convergent basins on plate margin can be subdivided into rift and depression. Scatter basins on plate margin can be divided into rift, depression and slip.
Different types of sedimentary basins could reflect the evolution of different sedimentary environments. In the main developmental stages of Cenozoic basin, the sedimentary environment of rift on internal plate is relatively simple. It was dominated by continental deposits. The sedimentary environment of plate margin is relatively complex as it near the ocean. Due to the continuing subduction to the Eurasian plate by the Pacific plate and Philippine plate, the convergent basins on plate margin have the characteristics of convergence with the evolution of continental to marine facies. As the continuous expansion of the South China Sea basin, the scatter basins on plate margin have the characteristics of scatter with the evolution of marine to continental facies.
In different basin structure and sedimentary environment, there are different types of sedimentary system. The rift basin has the sedimentary system with accumulation of nearsource. The depression basin has the sedimentary system with accumulation of farsource. As far from the sea, these basins on internal plate which mainly have continental sedimentary system were less affected by the transgression. Those basins near from the sea on plate margin which mainly have paralic or marine sedimentary system were more affected by the transgression. In these basins on plate margin，the convergent basins on plate margin have shallow water body, small slope break and small delta. They were more influenced by the tidal water and paralic strata were well developed. The scatter basins on plate margin have deeper water body, large slope break, large delta and marine strata.
Compared with China's inland, sedimentary environments of the Cenozoic in China offshore basins have the diversity. In different sedimentary basins, there are three kinds of sedimentary environments include continental, paralic and marine facies. Each basin has undergone changes in different sedimentary environments generally. Through studying the China offshore basins controlled by plate tectonic movement, analyzing the basin structure in the evolution of plate movement, combined with the evidence related to sedimentary environment, we could verify the relationship between sedimentary environment and sedimentary system in China offshore basins.
As China offshore was caught in the middle of Eurasian Plate, Pacific Plate and Indian Ocean Plate, its formation and evolution were controlled by these three plates. Western Pacific is a north to south of the trencharcbasin system. Generally bounded by the Taiwan Strait, the East China Sea Basin is a convergent margin with the evolution of conversion or passive continental margin due to the continuing westward subduction by the Pacific Plate or the Philippines Plate. The South China Sea is a passive margin with the evolution of active or convergent margin due to the continuing eastward subduction of South Ocean Shell. So there would have different basins as the evolution of different mechanisms. In this paper, the Cenozoic in China offshore basins were divided into three types including rift basins on internal plate, convergent basins on plate margin and scatter basins on plate margin. Convergent basins on plate margin can be subdivided into rift and depression. Scatter basins on plate margin can be divided into rift, depression and slip.
Different types of sedimentary basins could reflect the evolution of different sedimentary environments. In the main developmental stages of Cenozoic basin, the sedimentary environment of rift on internal plate is relatively simple. It was dominated by continental deposits. The sedimentary environment of plate margin is relatively complex as it near the ocean. Due to the continuing subduction to the Eurasian plate by the Pacific plate and Philippine plate, the convergent basins on plate margin have the characteristics of convergence with the evolution of continental to marine facies. As the continuous expansion of the South China Sea basin, the scatter basins on plate margin have the characteristics of scatter with the evolution of marine to continental facies.
In different basin structure and sedimentary environment, there are different types of sedimentary system. The rift basin has the sedimentary system with accumulation of nearsource. The depression basin has the sedimentary system with accumulation of farsource. As far from the sea, these basins on internal plate which mainly have continental sedimentary system were less affected by the transgression. Those basins near from the sea on plate margin which mainly have paralic or marine sedimentary system were more affected by the transgression. In these basins on plate margin，the convergent basins on plate margin have shallow water body, small slope break and small delta. They were more influenced by the tidal water and paralic strata were well developed. The scatter basins on plate margin have deeper water body, large slope break, large delta and marine strata.
2010, 28(6): 1081-1089.
Abstract:
Thick sandbody are widely and stably developed at the depositional period of Chang6 and Chang7 oil bearing formation in late Triassic in the centre of Ordos basin. The thickness surpass one hundred metres uninterruptedly in some areas. The large scale sand belt, formed in deep lake, stretches along the facies boundary and isolates itself from delta front sandbody in the southwest sedimentary system, while the sand belt or lobes encircle the delta front in the northeast sedimentary system. The thick sandbody was resulted from gravity flow and deep water tractive current and can be divided into five types, i.e. slump, sandy debrite, turbidite, delta sandbody and underflow transforming sandbody. Among them, deposition of gravity flow is the dominant sedimentary type; However, thick sanbody in Baibao area and its north area belong to delta deposition and sandy debrite, with deposition of gravity flow. The stable distribution of thick sandbody is controlled by the factors as supply rate of sediment, bottom shape of basin and tectonic activity.
Thick sandbody are widely and stably developed at the depositional period of Chang6 and Chang7 oil bearing formation in late Triassic in the centre of Ordos basin. The thickness surpass one hundred metres uninterruptedly in some areas. The large scale sand belt, formed in deep lake, stretches along the facies boundary and isolates itself from delta front sandbody in the southwest sedimentary system, while the sand belt or lobes encircle the delta front in the northeast sedimentary system. The thick sandbody was resulted from gravity flow and deep water tractive current and can be divided into five types, i.e. slump, sandy debrite, turbidite, delta sandbody and underflow transforming sandbody. Among them, deposition of gravity flow is the dominant sedimentary type; However, thick sanbody in Baibao area and its north area belong to delta deposition and sandy debrite, with deposition of gravity flow. The stable distribution of thick sandbody is controlled by the factors as supply rate of sediment, bottom shape of basin and tectonic activity.
2010, 28(6): 1098-1107.
Abstract:
The Silikou chert in Northern Guangxi Province was deposited in a terminal Ediacaran to early Cambrian (about 550～540 Ma) deep ocean basin. It has high SiO2 concentration (average 93.8%). Al2O3 content ranges from 0.17% to 4.92% and increases from the lower to the upper section which is more than 2%. Al/(Al+Fe+Mn) and Fe/Ti ratios for most of the chert are more than 0.42 and less than 16.3, respectively. Al2O3/( Al2O3+Fe2O3) ratios for most of the chert exceeds 0.4 and the ratios are 0.8～0.9 for chert in the upper section. Y/Ho ratios (26.4～36.9) are high (more than 32) for chert in the lower and middle section, and are similar to that of the upper crust (27) for chert in the upper section. It has no positive Eu anomalies (average 1.0) for the chert samples. REE concentrations for chert in the lower section (15.9×106～27.1×106) are low relative to PAAS, which are similar to that of the seawater but hydrothermal fluids or jasper related to seafloorhydrothermal sulfide deposits. Although REE patterns for chert in the middle section become flat since the increase of terrigenous detrital input, they have low REE concentrations (26.2×106～49.4×106) and seawater characteristics. REE concentrations for chert in the upper section range from 40.5×106 to 59×106 and they have flat REE patterns that are similar to PAAS, yet REE concentrations are just 1/4～1/3 of the PAAS. The major and rare earth elements characteristics of the Silikou chert suggest hydrothermal fluids and terrigenous detrital input were not main sources of the silica. In fact, huge amounts of dissolved silica derived from chemical weathering due to high CO2 concentration in the atmosphere and degradation of organic matter were the basic cause for the basinal chert in South China.
The Silikou chert in Northern Guangxi Province was deposited in a terminal Ediacaran to early Cambrian (about 550～540 Ma) deep ocean basin. It has high SiO2 concentration (average 93.8%). Al2O3 content ranges from 0.17% to 4.92% and increases from the lower to the upper section which is more than 2%. Al/(Al+Fe+Mn) and Fe/Ti ratios for most of the chert are more than 0.42 and less than 16.3, respectively. Al2O3/( Al2O3+Fe2O3) ratios for most of the chert exceeds 0.4 and the ratios are 0.8～0.9 for chert in the upper section. Y/Ho ratios (26.4～36.9) are high (more than 32) for chert in the lower and middle section, and are similar to that of the upper crust (27) for chert in the upper section. It has no positive Eu anomalies (average 1.0) for the chert samples. REE concentrations for chert in the lower section (15.9×106～27.1×106) are low relative to PAAS, which are similar to that of the seawater but hydrothermal fluids or jasper related to seafloorhydrothermal sulfide deposits. Although REE patterns for chert in the middle section become flat since the increase of terrigenous detrital input, they have low REE concentrations (26.2×106～49.4×106) and seawater characteristics. REE concentrations for chert in the upper section range from 40.5×106 to 59×106 and they have flat REE patterns that are similar to PAAS, yet REE concentrations are just 1/4～1/3 of the PAAS. The major and rare earth elements characteristics of the Silikou chert suggest hydrothermal fluids and terrigenous detrital input were not main sources of the silica. In fact, huge amounts of dissolved silica derived from chemical weathering due to high CO2 concentration in the atmosphere and degradation of organic matter were the basic cause for the basinal chert in South China.
2010, 28(6): 1117-1128.
Abstract:
Synthesizing methods of clastic constituments, heavy mineral, and sedimentation, we analyzed Dainan Formation provenance of Majiazui in Gaoyou Sag, Subei Basin. Igneous rock is the main lithology of Majiazui source rocks, followed successively by metamorphics and sedimentary rock; distribution range of neutral and acidic igneous rocks is wider than that of basic igneous rock; and medium to low is the dominating grade of metamorphics; while plutonite here is rare. According to sandstone types, types and contents of clastic constituents, percentage of sandstones, thickness of layers, distribution of sedimentary facies, stability factors of heavy minerals, heavy mineral combination, ZTR index and index of heavy mineral, we believe that during the depositional period of Dainan Formation, provenance differed between different blocks. Sediments of Ma 8 block mainly from Lingtang low bulge and partly came from Tongyang uplift; that of Ma 31 block was only from Lingtang low bulge and paleorivers transferred; while sediments of Ma 33 block came from Tongyang uplift.
Synthesizing methods of clastic constituments, heavy mineral, and sedimentation, we analyzed Dainan Formation provenance of Majiazui in Gaoyou Sag, Subei Basin. Igneous rock is the main lithology of Majiazui source rocks, followed successively by metamorphics and sedimentary rock; distribution range of neutral and acidic igneous rocks is wider than that of basic igneous rock; and medium to low is the dominating grade of metamorphics; while plutonite here is rare. According to sandstone types, types and contents of clastic constituents, percentage of sandstones, thickness of layers, distribution of sedimentary facies, stability factors of heavy minerals, heavy mineral combination, ZTR index and index of heavy mineral, we believe that during the depositional period of Dainan Formation, provenance differed between different blocks. Sediments of Ma 8 block mainly from Lingtang low bulge and partly came from Tongyang uplift; that of Ma 31 block was only from Lingtang low bulge and paleorivers transferred; while sediments of Ma 33 block came from Tongyang uplift.
2010, 28(6): 1135-1144.
Abstract:
Through the analysis of core, cast thin slice and wireline logging data, a typical retrograding sequence alluvial fan is found in Baikouquan Formation of Wuerhe Oilfield which is located in the Junggar Basin. Midfan intrafacies is developed in the lowermiddle part of affuvial fan and endfan intrafacies is developed in the upper part which remark the sedimentary environment that A/S (the ratio of available accommodation and sediment flux rate) increased under a transgression of the lake water body at early Trias. Microfacies include braided channel filling, sieve deposit, mudrock flow deposit and sheet deposit. Integrated with regional structure style, well testing data and production rate, braided channel filling in midfan intrafacies is the most favorable facies which controls hydrocarbon's accumulation and reservoir boundary. After the study, more appraisal wells were designed and drilled according to the distribution of favorable facies, and considerable hydrocarbon output in Baikouquan formation proved the accuracy of the conclusions. The laws summarized in this study will play an important role in the development of the reservoir for other oilfields.
Through the analysis of core, cast thin slice and wireline logging data, a typical retrograding sequence alluvial fan is found in Baikouquan Formation of Wuerhe Oilfield which is located in the Junggar Basin. Midfan intrafacies is developed in the lowermiddle part of affuvial fan and endfan intrafacies is developed in the upper part which remark the sedimentary environment that A/S (the ratio of available accommodation and sediment flux rate) increased under a transgression of the lake water body at early Trias. Microfacies include braided channel filling, sieve deposit, mudrock flow deposit and sheet deposit. Integrated with regional structure style, well testing data and production rate, braided channel filling in midfan intrafacies is the most favorable facies which controls hydrocarbon's accumulation and reservoir boundary. After the study, more appraisal wells were designed and drilled according to the distribution of favorable facies, and considerable hydrocarbon output in Baikouquan formation proved the accuracy of the conclusions. The laws summarized in this study will play an important role in the development of the reservoir for other oilfields.
2010, 28(6): 1153-1164.
Abstract:
Majiagou Formation of the middle part of Ordos Basin belong to epeiric sea carbonatites and evaporates. Majiagou Formation have Ma1 Ma6 Member(from bottom to top), Ma1, Ma3, Ma5 Members are micritefine powder dolomite, gyprock and saline. Ma2, Ma4, Ma6 Members are mainly micrite limestone or wackestone. Caledonian event uplift North China Platform since last stage of Middle Ordovician. The top of Majiagou Formation in Ordos Basin udergo weather worn in 1300 million endurance. Weathered crust dolomite reservoir of the top of Ma5 Member are produced by dissolution of ancient karst. Ma5 member divided into Ma510, Ma59…Ma51 from bottom to top. The producing pay allocation in Ma51－4〗submember which are top of weather crust. Ma514 submember have thick 80~110 m, are dolomite, argillaceous dolomite, minor gypseous dolomite andtuffaceous mudstone. The reservoir rock of Ma514 submember are mainly corrosion pore and hole dolomite, valid reservoir are grand total 2~10 m, which initial rock are gypseous micritefine powder dolomite.
Ma 51－4 submember of Jinbian Gas Field in Ordos Basin belong to evaporated carbonate tidal flat facies,which divided into three subfacies: supratital zone, intertital zone,infratital zone, and 18 microfacies. The microfacies that are favour of developing reservoirs are supratidal zone dolomite which have anhydrite noddle and upper part intertidal zone dolomite which have anhydrite crystal. Ma514 Submember had undergone various diageneses. Penecontemporaneous dolomitization and gypsification that settled material base of reservoirs. Epidiagenesis selective dissolution of gypseous dolomite constructs the ambit of reservoirs. anhydrite noddle and crystal in dolomite selectively dissolved by meteoric fresh water and create pore and hole. Dissolved pore and hole what partly fill by one or some mineral form reservoirs. Early stage dissolution pore and hole are reconstructed by burial period dissolution, fill mineral sort and amount that determine the preservation condition of dissolution pore and the feature of reservoirs.
Call in “minus cement porosity”, it directly reflects sedimentary that control reservoir Ma514 Submember. Combining of research microfacies and diagenesis facies, use concise numerical symbol that express semiquantitatively sedimentary microfacies and diagenesis facies. Used that in compilation microfacies chart and diagenesis partition chart, beneficial area for reservoir is so clearly. That method acquire approved effect on the evaluation and forecasing reservoir of Jingbian Gas Field.
Majiagou Formation of the middle part of Ordos Basin belong to epeiric sea carbonatites and evaporates. Majiagou Formation have Ma1 Ma6 Member(from bottom to top), Ma1, Ma3, Ma5 Members are micritefine powder dolomite, gyprock and saline. Ma2, Ma4, Ma6 Members are mainly micrite limestone or wackestone. Caledonian event uplift North China Platform since last stage of Middle Ordovician. The top of Majiagou Formation in Ordos Basin udergo weather worn in 1300 million endurance. Weathered crust dolomite reservoir of the top of Ma5 Member are produced by dissolution of ancient karst. Ma5 member divided into Ma510, Ma59…Ma51 from bottom to top. The producing pay allocation in Ma51－4〗submember which are top of weather crust. Ma514 submember have thick 80~110 m, are dolomite, argillaceous dolomite, minor gypseous dolomite andtuffaceous mudstone. The reservoir rock of Ma514 submember are mainly corrosion pore and hole dolomite, valid reservoir are grand total 2~10 m, which initial rock are gypseous micritefine powder dolomite.
Ma 51－4 submember of Jinbian Gas Field in Ordos Basin belong to evaporated carbonate tidal flat facies,which divided into three subfacies: supratital zone, intertital zone,infratital zone, and 18 microfacies. The microfacies that are favour of developing reservoirs are supratidal zone dolomite which have anhydrite noddle and upper part intertidal zone dolomite which have anhydrite crystal. Ma514 Submember had undergone various diageneses. Penecontemporaneous dolomitization and gypsification that settled material base of reservoirs. Epidiagenesis selective dissolution of gypseous dolomite constructs the ambit of reservoirs. anhydrite noddle and crystal in dolomite selectively dissolved by meteoric fresh water and create pore and hole. Dissolved pore and hole what partly fill by one or some mineral form reservoirs. Early stage dissolution pore and hole are reconstructed by burial period dissolution, fill mineral sort and amount that determine the preservation condition of dissolution pore and the feature of reservoirs.
Call in “minus cement porosity”, it directly reflects sedimentary that control reservoir Ma514 Submember. Combining of research microfacies and diagenesis facies, use concise numerical symbol that express semiquantitatively sedimentary microfacies and diagenesis facies. Used that in compilation microfacies chart and diagenesis partition chart, beneficial area for reservoir is so clearly. That method acquire approved effect on the evaluation and forecasing reservoir of Jingbian Gas Field.
2010, 28(6): 1175-1181.
Abstract:
Bamianshan is an unusual large fluorite deposit discovered in recent years. This paper studies the geologic background of mineralization, geological feature of orebody, ore characters, characters of petrochemistry composition, REE characters of rocks and ores, and SmNd isotope of Bamianshan fluorite deposit. It shows that Bamianshan fluorite deposit is an unusual large fluorite deposit which was formed mostly by sedimentation and later hydrothermal reformation. Based on the analysis data and combined with characters of orehosted rocks and orebody, it is predicted that the sedimentary rocks of Cambrain System as its source bed, which supplied necessary materials of Bamianshan fluorite deposit. Magmatism in later stage altered some orebodies in different extent and
formed partial deep lean vein ore bodies in structure belt.
Bamianshan is an unusual large fluorite deposit discovered in recent years. This paper studies the geologic background of mineralization, geological feature of orebody, ore characters, characters of petrochemistry composition, REE characters of rocks and ores, and SmNd isotope of Bamianshan fluorite deposit. It shows that Bamianshan fluorite deposit is an unusual large fluorite deposit which was formed mostly by sedimentation and later hydrothermal reformation. Based on the analysis data and combined with characters of orehosted rocks and orebody, it is predicted that the sedimentary rocks of Cambrain System as its source bed, which supplied necessary materials of Bamianshan fluorite deposit. Magmatism in later stage altered some orebodies in different extent and
formed partial deep lean vein ore bodies in structure belt.
2010, 28(6): 1182-1189.
Abstract:
The rare earth elements (REE) of 72 sediment samples taken from Core NT2 in the South Yellow Sea near Jiangsu coast were measured with ICPMS in order to study the variation of sediment source since the middlelate period of middle Pleistocene. The correlation plot indicates that the REE composition was less influenced by sediment grain size and chemical weathering, therefore, was primarily controlled by provenance rocks. The discrimination plot of REE parameter suggests that provenance of sediment in this core is mainly the Yangtze River and Yellow River. Of the core, the sediments between 0~5.50 m, 5.50~19.30 m in upper Core NT2 mainly belong to Yangtze River source; the sediments between 19.30~27.00 m in middle Core NT2 are mainly from Yellow River, and the sediments between 27.00~54.60 m are mainly from Yangtze River; the sediments between 54.60~70.31 m in lower Core NT2 are mainly from Yellow River. The results demonstrate that the Yellow River has an obvious effect on sedimentation of the South Yellow Sea shelf from during the middlelate period of middle Pleistocene and the Yangtze River has been playing a main role to the South Yellow Sea since early period of Late Pleistocene.
The rare earth elements (REE) of 72 sediment samples taken from Core NT2 in the South Yellow Sea near Jiangsu coast were measured with ICPMS in order to study the variation of sediment source since the middlelate period of middle Pleistocene. The correlation plot indicates that the REE composition was less influenced by sediment grain size and chemical weathering, therefore, was primarily controlled by provenance rocks. The discrimination plot of REE parameter suggests that provenance of sediment in this core is mainly the Yangtze River and Yellow River. Of the core, the sediments between 0~5.50 m, 5.50~19.30 m in upper Core NT2 mainly belong to Yangtze River source; the sediments between 19.30~27.00 m in middle Core NT2 are mainly from Yellow River, and the sediments between 27.00~54.60 m are mainly from Yangtze River; the sediments between 54.60~70.31 m in lower Core NT2 are mainly from Yellow River. The results demonstrate that the Yellow River has an obvious effect on sedimentation of the South Yellow Sea shelf from during the middlelate period of middle Pleistocene and the Yangtze River has been playing a main role to the South Yellow Sea since early period of Late Pleistocene.
2010, 28(6): 1198-1205.
Abstract:
Lithology, AMS14C dating, grainsize, major and trace element analysis were carried out for Core S20, which was retrieved from the continental shelf in the northern South China Sea (SCS). Sediment provenance and evolution history of Asian monsoon were discussed in this paper. Since 4400 a BP, the lithology of Core S20 is homogenous, the hydrodynamic conditions in the study area is relatively stable. The silicate material in the source area experienced significant weathering processes. ACNK plot and low CIA (chemical index of alteration) value indicated a lower degree of chemical weathering. The river in the eastern Hainan Island and Pearl River is the two most likely sources of the study area. Because of inadequate research on the former, this study could not quantitatively estimate their possible contributions. The variations of CIA, Al2O3/Na2O, CaO*/TiO2 and Na2O/TiO2 value mainly reflect the degree of weathering of the source area. Gradually weakened weathering between 4 400~1 600 a BP and strengthened from 1600 a BP to nowadays well corresponded to the absolutedated oxygen isotope record from Dongge stalagmite, southern China, indicating that the core sediments in the study area containing a wealth of information on the evolution of Asian monsoon. The degree of chemical weathering of sediments in the northern SCS is mainly controlled by the variation of orbitallyinduced Northern Hemisphere summer insolation. More research work with high resolution is necessary for extracting information on sediment provenance and monsoon evolution in the Northern SCS shelf.
Lithology, AMS14C dating, grainsize, major and trace element analysis were carried out for Core S20, which was retrieved from the continental shelf in the northern South China Sea (SCS). Sediment provenance and evolution history of Asian monsoon were discussed in this paper. Since 4400 a BP, the lithology of Core S20 is homogenous, the hydrodynamic conditions in the study area is relatively stable. The silicate material in the source area experienced significant weathering processes. ACNK plot and low CIA (chemical index of alteration) value indicated a lower degree of chemical weathering. The river in the eastern Hainan Island and Pearl River is the two most likely sources of the study area. Because of inadequate research on the former, this study could not quantitatively estimate their possible contributions. The variations of CIA, Al2O3/Na2O, CaO*/TiO2 and Na2O/TiO2 value mainly reflect the degree of weathering of the source area. Gradually weakened weathering between 4 400~1 600 a BP and strengthened from 1600 a BP to nowadays well corresponded to the absolutedated oxygen isotope record from Dongge stalagmite, southern China, indicating that the core sediments in the study area containing a wealth of information on the evolution of Asian monsoon. The degree of chemical weathering of sediments in the northern SCS is mainly controlled by the variation of orbitallyinduced Northern Hemisphere summer insolation. More research work with high resolution is necessary for extracting information on sediment provenance and monsoon evolution in the Northern SCS shelf.
2010, 28(6): 1213-1228.
Abstract:
Qaidam Basin is a tectonically controlled depression on the northern margin of the Tibetan Plateau. In 2008, a long core was drilled in Qahansilatu subbasin in the western Qaidam Basin. The sediment layers in the upper 400 m alternate between evaporative mineral layers and carbonaceous clay layers. The detailed mineralogical investigation focused on evaporative minerals including halite, gypsum, mirabilite, thenardite, glauberite, eugsterite, bloedite, barite, cesanite, shortite, thermonatrite, gaylussite, nahcolite and inderborite. Gypsum and halite make up the majority of the evaporative minerals. Environmentally induced variations in the mineralogy and crystal habit of the sulfates have been extensively investigated. Gypsum has prismatic and pyramid habits, such as disc pyramid, stubby prismatic, slender prismatic. Visible isolated gypsum and aggregates (rosette/radial and twins) are mostly scattered in carbonaceous clay layers, suggesting secondary gypsum well developed. Gypsum may be a precursor mineral of glauberite, and thenardite is the precursor of bloedite. As a metastable and rare mineral, eugsterite does not appear in other Tibetan areas. It forms at the expense of pre existing gypsum or thenardite in the core at an experimental temperature of higher than room temperature. The presence of eugsterite indicates a warm and/or hot climate at its deposition time. Mineralogical variations have been explained by the brine evolution of NaCl, NaCaSO4, NaSO4, NaSO4Cl, NaCaSO4Cl, CaSO4, and NaMgSO4. For instance, NaMgSO4 type corresponds to the bloedite, while NaCaSO4Cl type to the assemblage of halite, gypsum and glauberite. The evaporative minerals and carbonaceous clay layers alternation indicates the shift between dry and wet climate. According to the thickness, eighteen evaporative stages and/or dry climate stages were identified from 0.97 Ma to about 0.03 Ma. The two early dry climate stages are identified at 0.96~0.97 Ma and 0.87 Ma. The other sixteen evaporative stages occurred from 0.78 Ma to about 0.03 Ma. The evaporaterich stages suggested that evaporation was high and groundwater inflow was sufficient at the subbasin.
Qaidam Basin is a tectonically controlled depression on the northern margin of the Tibetan Plateau. In 2008, a long core was drilled in Qahansilatu subbasin in the western Qaidam Basin. The sediment layers in the upper 400 m alternate between evaporative mineral layers and carbonaceous clay layers. The detailed mineralogical investigation focused on evaporative minerals including halite, gypsum, mirabilite, thenardite, glauberite, eugsterite, bloedite, barite, cesanite, shortite, thermonatrite, gaylussite, nahcolite and inderborite. Gypsum and halite make up the majority of the evaporative minerals. Environmentally induced variations in the mineralogy and crystal habit of the sulfates have been extensively investigated. Gypsum has prismatic and pyramid habits, such as disc pyramid, stubby prismatic, slender prismatic. Visible isolated gypsum and aggregates (rosette/radial and twins) are mostly scattered in carbonaceous clay layers, suggesting secondary gypsum well developed. Gypsum may be a precursor mineral of glauberite, and thenardite is the precursor of bloedite. As a metastable and rare mineral, eugsterite does not appear in other Tibetan areas. It forms at the expense of pre existing gypsum or thenardite in the core at an experimental temperature of higher than room temperature. The presence of eugsterite indicates a warm and/or hot climate at its deposition time. Mineralogical variations have been explained by the brine evolution of NaCl, NaCaSO4, NaSO4, NaSO4Cl, NaCaSO4Cl, CaSO4, and NaMgSO4. For instance, NaMgSO4 type corresponds to the bloedite, while NaCaSO4Cl type to the assemblage of halite, gypsum and glauberite. The evaporative minerals and carbonaceous clay layers alternation indicates the shift between dry and wet climate. According to the thickness, eighteen evaporative stages and/or dry climate stages were identified from 0.97 Ma to about 0.03 Ma. The two early dry climate stages are identified at 0.96~0.97 Ma and 0.87 Ma. The other sixteen evaporative stages occurred from 0.78 Ma to about 0.03 Ma. The evaporaterich stages suggested that evaporation was high and groundwater inflow was sufficient at the subbasin.
2010, 28(6): 1229-1237.
Abstract:
In previous achievements, depositional system, paleogeomorphology, geological evolutionary and sedimentary characteristics of Ordos basin has been quite clearly recognized. However, the research precision and depth in local area still has certain limitation. As geological data's supplement and corroborative evidence of Ordos basin, the research on precise depiction of geological features, sedimentary characteristics as well as their matching relationship with practical production in local area, undoubtedly, has its necessity and inevitability.
Most of the previous researches on petroleum geology in the eastern Gansu were focused on Triassic, and the research on Jurassic is few, scatter, and lacking of integration and systematicness. The petroleum exploration history on Jurassic went through three stages: most of the achievements are mainly on regional geological surveying, researches on Jurassic are few(before 1970s); Several oil fields of Jurassic, such as Maling, Yuancheng, were successively founded in study area, and Fuxian Formation, Yan′an Formation of Jurassic become the major explorative horizon(form 1970 to 2000); New oil reservoirs of Y10,Y9 and Y8 member of Yan′an Formation are founded continuously in local regional (from 2000 to now). In the past few years, exploration practice indicated that Y10 and Y9 members are the main oilbearing layer of Yan′an Formation, owning great resource potential. Paleogeomorphic form is the basic factor of Y8Y10 oil reservoir.
In view of petroleum accumulation of Jurassic controlled by paleogeomorphic forms, this paper will rebuild the paleogeomorphic formwork of preJurassic, and first make up the 3D simulation restored maps, which are based on geological analysis(such as sedimentary background, tectonic setting), changing tendency of sand layer thickness and formation thickness of each members(especially the formation thickness of Y10 Formation), calculating key parameters(such as ancient landform evaluation difference, slope gradient, paleocurrent direction), combining with seismic data and so on, adopting remnant thicknesscompensation cast and synthesis method of sedimentary geology.
First, according to the stratum development features, five paleogeomorphic units are divided: erosion valley, paleoupland, paleoslope, paleoterrace, interchannel mound. There are three paleouplands, four ancient rivers, six interchannel mounds and one platform in eastern Gansu area. Between paleouplands and ancient rivers, there are slopes and terraces from high to low in order, which are strictly controlled sedimentary facies and compactiondrape tectonic of Fuxian formation and lower Yan'an formation.
Second, according to spatial distribution of oil reservoir already founded and combined with analysis of paleogeomorphic features and reservoir forming conditions, six paleogeomorphic reservoir models are summed up in the study area: edge of deep dissection valleydelta front, edge of deep dissection valleydelta plain, ancient valleydelta plain, paleoterracedelta plain, paleouplanddelta plain, and interchannel mounddelta plain combination models. Exploration practices shows that formation conditions are very complicated, which is controlled by many factors, and paleogeomorphic features is only one of the important factors.
In previous achievements, depositional system, paleogeomorphology, geological evolutionary and sedimentary characteristics of Ordos basin has been quite clearly recognized. However, the research precision and depth in local area still has certain limitation. As geological data's supplement and corroborative evidence of Ordos basin, the research on precise depiction of geological features, sedimentary characteristics as well as their matching relationship with practical production in local area, undoubtedly, has its necessity and inevitability.
Most of the previous researches on petroleum geology in the eastern Gansu were focused on Triassic, and the research on Jurassic is few, scatter, and lacking of integration and systematicness. The petroleum exploration history on Jurassic went through three stages: most of the achievements are mainly on regional geological surveying, researches on Jurassic are few(before 1970s); Several oil fields of Jurassic, such as Maling, Yuancheng, were successively founded in study area, and Fuxian Formation, Yan′an Formation of Jurassic become the major explorative horizon(form 1970 to 2000); New oil reservoirs of Y10,Y9 and Y8 member of Yan′an Formation are founded continuously in local regional (from 2000 to now). In the past few years, exploration practice indicated that Y10 and Y9 members are the main oilbearing layer of Yan′an Formation, owning great resource potential. Paleogeomorphic form is the basic factor of Y8Y10 oil reservoir.
In view of petroleum accumulation of Jurassic controlled by paleogeomorphic forms, this paper will rebuild the paleogeomorphic formwork of preJurassic, and first make up the 3D simulation restored maps, which are based on geological analysis(such as sedimentary background, tectonic setting), changing tendency of sand layer thickness and formation thickness of each members(especially the formation thickness of Y10 Formation), calculating key parameters(such as ancient landform evaluation difference, slope gradient, paleocurrent direction), combining with seismic data and so on, adopting remnant thicknesscompensation cast and synthesis method of sedimentary geology.
First, according to the stratum development features, five paleogeomorphic units are divided: erosion valley, paleoupland, paleoslope, paleoterrace, interchannel mound. There are three paleouplands, four ancient rivers, six interchannel mounds and one platform in eastern Gansu area. Between paleouplands and ancient rivers, there are slopes and terraces from high to low in order, which are strictly controlled sedimentary facies and compactiondrape tectonic of Fuxian formation and lower Yan'an formation.
Second, according to spatial distribution of oil reservoir already founded and combined with analysis of paleogeomorphic features and reservoir forming conditions, six paleogeomorphic reservoir models are summed up in the study area: edge of deep dissection valleydelta front, edge of deep dissection valleydelta plain, ancient valleydelta plain, paleoterracedelta plain, paleouplanddelta plain, and interchannel mounddelta plain combination models. Exploration practices shows that formation conditions are very complicated, which is controlled by many factors, and paleogeomorphic features is only one of the important factors.
2010, 28(6): 1244-1249.
Abstract:
Researched the distributing characteristics of biomarkers of lowevolution source rocks in TurpanHami basin, the organic matter has been transformed by microorganism. The result shows: The bacterium microorganism acting on deposit organic matter relative strength, there is a “quasistepwise” sequence to describe the general order of susceptibility of various biomarker compound classes to biodegradation, that is nalkanes > acyclic isoprenoids> hopanes >steranes> aromatic hydrocarbon, C29ββ/(ββ+αα) and 9MP/ΣMP are sensitive parameters to the reforming of bacteriummicroorganism effect on organic matter. The biomarkerparameters of the same source rock appear: OEP2>OEP1(perhaps OEP1＜1,show even carbon number predominance), hopane C31αβ22S/22(S+R)＞steraneC29αα20S/20(S+R), sterane C29αββ/(αββ+ααα)＞C29αα20S/20(S+R) etc. abnormal combination characteristics of the biomarkers, suggests the source rock had experienced stronger bacterium–microorganism degradation process, and these ratios can be used to scale the extent of biodegradation,
as well as be further served as meaningful basis to judge whether the biogenic hydrocarbon (gas and oil) generated from the source rocks in the area. The characteristic of source rock organic matter would be changed by the reforming of bacterium microorganism in the study area, these changes will enable decreasing the activation energy of hydrocarbon generated, and they are favorable for lowmature gas(oil) generation.
Researched the distributing characteristics of biomarkers of lowevolution source rocks in TurpanHami basin, the organic matter has been transformed by microorganism. The result shows: The bacterium microorganism acting on deposit organic matter relative strength, there is a “quasistepwise” sequence to describe the general order of susceptibility of various biomarker compound classes to biodegradation, that is nalkanes > acyclic isoprenoids> hopanes >steranes> aromatic hydrocarbon, C29ββ/(ββ+αα) and 9MP/ΣMP are sensitive parameters to the reforming of bacteriummicroorganism effect on organic matter. The biomarkerparameters of the same source rock appear: OEP2>OEP1(perhaps OEP1＜1,show even carbon number predominance), hopane C31αβ22S/22(S+R)＞steraneC29αα20S/20(S+R), sterane C29αββ/(αββ+ααα)＞C29αα20S/20(S+R) etc. abnormal combination characteristics of the biomarkers, suggests the source rock had experienced stronger bacterium–microorganism degradation process, and these ratios can be used to scale the extent of biodegradation,
as well as be further served as meaningful basis to judge whether the biogenic hydrocarbon (gas and oil) generated from the source rocks in the area. The characteristic of source rock organic matter would be changed by the reforming of bacterium microorganism in the study area, these changes will enable decreasing the activation energy of hydrocarbon generated, and they are favorable for lowmature gas(oil) generation.
2010, 28(6): 1054-1065.
Abstract:
Sediment of evaporite with gigantic thickness had been developed in Kuqa Basin from Paleogene to Neogene period, and the main stratum were composed of Kumugeliemu group, Suweiyi group(Paleogene), and Jidike group(Neogene). Going with transformation of the water of saline lake changing from fresh water, saline water, to brine, and then to saline water, fresh water, accordingly, the sediment changes from clastic rock, gypsum, to saline rock, and then to gypsum, clastic rock, so the sediment of evaporate and clastic rock is alternated each other, and the sediment rhythm or gyration come into being. Based on some datum of drill holes, 5 sedimentary cycles of evaporite are given. Ⅰ1 andⅠ2 sediment cycles have been developed in Kumugeliemu period. Ⅰ1 sediment cycle, which mainly developed in early Kumugeliemu period, has been fulled of folium saline rock, gypsum, limestone or dolomite, clastic rock, not only is the sediment scope mainly attached center to Tubei1, Dabei2 and Xiqiu2 drilling holes, but also attached borderline to Kela2 drilling hole in north of basin and Yangta 2 drilling hole in the south of basin, and extended from northwest to southeast. Ⅰ2 sediment cycles have been developed in late Kumugeliemu period, has been fulled of gigantic and thick saline rock and gypsum, and the sediment scope han been extended based on early sediment scope. Ⅰ3 sediment cycles has been mainly developed in Suweiyi period, and influenced on the early Himalayan tectonic movement, the floor in northwest of basin was uplifted, so the sediment area was split into two parts which moved not only from north to south but also from west to east. The main sediment is clastic rock and gypsum contained clastic rock, and the evaporite sediment moved from north, middle, to south of Kuqa basin in the west, in the east of basin it moved from west to east. The gigantic thickness sediment of evaporite in Kumugeliemu period (Ⅰ1、Ⅰ2 sediment cycles) reflects comparatively quiet tectonic setting after Yanshan movement; and the sediment of evaporate has been changed obviously on lithology and scope in (Ⅰ3 sediment cycles) in Suweiyi period, so unsteadily tectonic setting has been reflected in early Himalayan tectonic phase. Sediment of evaporite with gigantic thickness (Ⅰ4 sediment cycles) had been mainly developed in east of basin in Jidike period, and a few in south of basin, comparing sediment of evaporate in west of basin in Kumugeliemu period, the thickness of saline rock is attenuation but the gypsum is opposite, which reflects the long time of salty lake and the short time of saline lake. The movement from west to east of the sediment area reflects the early Himalayan tectonic movement was still continuing In spite of its decline. The sediment of evaporate （Ⅰ5 sediment cycles） has been breaken down in Jidike period, and it han been changed into continental sedimentation, so the setting of the mountain uplifted, denuded, cumulated fleetly, was indicated by piedmont deposits, and the middle Himalayan tectonic movement period were coming. So it is a good corresponding relation on sediment of evaporite in Kuqa Basin and Himalayan tectonic movement, and it is a reflection of geology event made by largescale tectonic movement in small areas.
Sediment of evaporite with gigantic thickness had been developed in Kuqa Basin from Paleogene to Neogene period, and the main stratum were composed of Kumugeliemu group, Suweiyi group(Paleogene), and Jidike group(Neogene). Going with transformation of the water of saline lake changing from fresh water, saline water, to brine, and then to saline water, fresh water, accordingly, the sediment changes from clastic rock, gypsum, to saline rock, and then to gypsum, clastic rock, so the sediment of evaporate and clastic rock is alternated each other, and the sediment rhythm or gyration come into being. Based on some datum of drill holes, 5 sedimentary cycles of evaporite are given. Ⅰ1 andⅠ2 sediment cycles have been developed in Kumugeliemu period. Ⅰ1 sediment cycle, which mainly developed in early Kumugeliemu period, has been fulled of folium saline rock, gypsum, limestone or dolomite, clastic rock, not only is the sediment scope mainly attached center to Tubei1, Dabei2 and Xiqiu2 drilling holes, but also attached borderline to Kela2 drilling hole in north of basin and Yangta 2 drilling hole in the south of basin, and extended from northwest to southeast. Ⅰ2 sediment cycles have been developed in late Kumugeliemu period, has been fulled of gigantic and thick saline rock and gypsum, and the sediment scope han been extended based on early sediment scope. Ⅰ3 sediment cycles has been mainly developed in Suweiyi period, and influenced on the early Himalayan tectonic movement, the floor in northwest of basin was uplifted, so the sediment area was split into two parts which moved not only from north to south but also from west to east. The main sediment is clastic rock and gypsum contained clastic rock, and the evaporite sediment moved from north, middle, to south of Kuqa basin in the west, in the east of basin it moved from west to east. The gigantic thickness sediment of evaporite in Kumugeliemu period (Ⅰ1、Ⅰ2 sediment cycles) reflects comparatively quiet tectonic setting after Yanshan movement; and the sediment of evaporate has been changed obviously on lithology and scope in (Ⅰ3 sediment cycles) in Suweiyi period, so unsteadily tectonic setting has been reflected in early Himalayan tectonic phase. Sediment of evaporite with gigantic thickness (Ⅰ4 sediment cycles) had been mainly developed in east of basin in Jidike period, and a few in south of basin, comparing sediment of evaporate in west of basin in Kumugeliemu period, the thickness of saline rock is attenuation but the gypsum is opposite, which reflects the long time of salty lake and the short time of saline lake. The movement from west to east of the sediment area reflects the early Himalayan tectonic movement was still continuing In spite of its decline. The sediment of evaporate （Ⅰ5 sediment cycles） has been breaken down in Jidike period, and it han been changed into continental sedimentation, so the setting of the mountain uplifted, denuded, cumulated fleetly, was indicated by piedmont deposits, and the middle Himalayan tectonic movement period were coming. So it is a good corresponding relation on sediment of evaporite in Kuqa Basin and Himalayan tectonic movement, and it is a reflection of geology event made by largescale tectonic movement in small areas.
2010, 28(6): 1076-1080.
Abstract:
In the littoral and neritic sedimentary environment, there is a special kind of gravityflow deposition, known as mud flow gully. Mudflow gully filled with mudstone mainly positive rhythm, the thickness of the middle, often incised the sand body below it. Vertically, the mud flow gully was often underlain by shoreface or offshore sandbar and beach sand and overlain mostly by offshore mudstone deposition. Mud flow gully mainly formed at the topography transition area of shore and offshore, due to the tectonic events which resulted in slumping of plastic, low diagenetic consolidation finegrained sediment and forming a gully shape similar to incised valley. Finally, in the gentle terrain, those mud flows began to afflux and generate contiguous cluster distribution characteristics. According to the size of incising sand body, mud flow gully can be classified into “deep”, “middle” and “shallow” three types. In which, “deep gully” performanced for the “deep and wide”, mainly developed in the terrain slopebreak area and incised the sand body deeply; while “shallow gully” presented “shallow and narrow”, appeared mainly in the upper area of flat terrain with a lower level of a weak cut; meanwhile, “middle gully” cutting degree was between deep and shallow depth. Mud flow gully was the lateral seepage barrier for reservoir sand bodies, and usually, shallow gullies were often found in the center of sand body, deep gullies were located in the edge of the sand body and middle gullies were between such two. Influenced by the mud flow gullies, sand bars were isolated and at the same time, because of the impact of intercalation mudstone, sand body’s lateral and vertical continuity and connectivity became worse.
In the littoral and neritic sedimentary environment, there is a special kind of gravityflow deposition, known as mud flow gully. Mudflow gully filled with mudstone mainly positive rhythm, the thickness of the middle, often incised the sand body below it. Vertically, the mud flow gully was often underlain by shoreface or offshore sandbar and beach sand and overlain mostly by offshore mudstone deposition. Mud flow gully mainly formed at the topography transition area of shore and offshore, due to the tectonic events which resulted in slumping of plastic, low diagenetic consolidation finegrained sediment and forming a gully shape similar to incised valley. Finally, in the gentle terrain, those mud flows began to afflux and generate contiguous cluster distribution characteristics. According to the size of incising sand body, mud flow gully can be classified into “deep”, “middle” and “shallow” three types. In which, “deep gully” performanced for the “deep and wide”, mainly developed in the terrain slopebreak area and incised the sand body deeply; while “shallow gully” presented “shallow and narrow”, appeared mainly in the upper area of flat terrain with a lower level of a weak cut; meanwhile, “middle gully” cutting degree was between deep and shallow depth. Mud flow gully was the lateral seepage barrier for reservoir sand bodies, and usually, shallow gullies were often found in the center of sand body, deep gullies were located in the edge of the sand body and middle gullies were between such two. Influenced by the mud flow gullies, sand bars were isolated and at the same time, because of the impact of intercalation mudstone, sand body’s lateral and vertical continuity and connectivity became worse.
New Evidence on the Sedimentary Framework of the Early Ordovician in Central Tarim and Adjacent Area
2010, 28(6): 1090-1097.
Abstract:
The previous viewpoint considered that,the early Tarim basin was an “unified carbonate platform”, its slope was developed along the GuchengLunnan area.Based on sedimentologic and seismic stratigraphic data from the lowermiddle Ordovician, deepwater slope and basinal facies were recognized along the MJ1TZ29 section, so that the Tazhong and its adjacent areas could have already been isolated from the “unified carbonate platform” and seprated into three platforms of TazhongBachu, Gucheng and Tangnan, which was also faced with TaBei area across a trough. The highenergy reefshore bodies bandingly developed among the edge of each isolated platform as a band, which were mainly composed of midhigh energy grain banks. Inwards, it becomes the deposition of platform,developing the subphases of intraplatform banks, intraplatform depression and interabeach seas and soon. Outwards it becomes deeperwater deposition area of slopetrough. Under this circumstance,the new regional depositional pattern of the Tazhong and adjacent areas has been established.This new pattern has great theoretical and realistic significance for the establishment of new favourable exploration zones.It also greatly increases the strategic position for the petroleum exploration in lower Ordovician of research area.
The previous viewpoint considered that,the early Tarim basin was an “unified carbonate platform”, its slope was developed along the GuchengLunnan area.Based on sedimentologic and seismic stratigraphic data from the lowermiddle Ordovician, deepwater slope and basinal facies were recognized along the MJ1TZ29 section, so that the Tazhong and its adjacent areas could have already been isolated from the “unified carbonate platform” and seprated into three platforms of TazhongBachu, Gucheng and Tangnan, which was also faced with TaBei area across a trough. The highenergy reefshore bodies bandingly developed among the edge of each isolated platform as a band, which were mainly composed of midhigh energy grain banks. Inwards, it becomes the deposition of platform,developing the subphases of intraplatform banks, intraplatform depression and interabeach seas and soon. Outwards it becomes deeperwater deposition area of slopetrough. Under this circumstance,the new regional depositional pattern of the Tazhong and adjacent areas has been established.This new pattern has great theoretical and realistic significance for the establishment of new favourable exploration zones.It also greatly increases the strategic position for the petroleum exploration in lower Ordovician of research area.
2010, 28(6): 1108-1116.
Abstract:
Sedimentary rocks of lower Cretaceous widely distribute in volcaniccovered area in Zhejiang and Fujiang provinces, southeast China, and its sedimentary environment that whether it has been influenced by marine water is still controversial. Though carefully observation in outcrops, we have systematically sampled dark sedimentary rocks, including Bantou Formation (K1b) in Fujian province, Shouchang Formation (K1s) and Guantou Formation (K1g) in Zhejiang province. Under microscope, besides high plant, marine fossils such as red algae and brown algae, were found in these samples. Organic geochemistry features, such as lower γ/ C30 hopanoid values (range from 0.11 to 0.18, 0.14 on average) and C30 rearrangement hopanoid, are furthermore to approve the marine influence. Combining with geological background, it is presupposed that it is mainly influenced by paleoPacific.
Sedimentary rocks of lower Cretaceous widely distribute in volcaniccovered area in Zhejiang and Fujiang provinces, southeast China, and its sedimentary environment that whether it has been influenced by marine water is still controversial. Though carefully observation in outcrops, we have systematically sampled dark sedimentary rocks, including Bantou Formation (K1b) in Fujian province, Shouchang Formation (K1s) and Guantou Formation (K1g) in Zhejiang province. Under microscope, besides high plant, marine fossils such as red algae and brown algae, were found in these samples. Organic geochemistry features, such as lower γ/ C30 hopanoid values (range from 0.11 to 0.18, 0.14 on average) and C30 rearrangement hopanoid, are furthermore to approve the marine influence. Combining with geological background, it is presupposed that it is mainly influenced by paleoPacific.
2010, 28(6): 1129-1134.
Abstract:
The northwestern, western, southern and southeastern depositional margin of the Ordos basin is tectonic slopebreak controlled by tectonic movement occurred at the end of the Triassic, where alluvial, fandeltaic and braideddeltaic sedimentary suite developed. While the eastern and northeastern margin belong to depositional slopebreak because of its gently uplifting during the late Triassic, which resulted in the meanderingdeltaic sedimentary system. Two types of slopes including slopeshapedfront and platformfront can be recognized in the Jiyuan area, northwestern Ordos Basin, based upon analysis on feature of the basin margin, types of depositional facies and sediments, thickness of the strata, spatial assemblage and distribution of the sandstone bodies, and changes of the sandstone grain size, combined with seismic interpretation for topographic form of the Chang 4+5Chang 7 lake basin. Research result shows that sandstones at the slopeshapedfront are of greater thickness with relatively developed secondary dissolution pores and higher permeability values in delta front setting where sandstones tend to be of low porosity and very low permeability. Thus, sandstones at the slopeshapedfront with the better reservoir potential in Jiyuan area are optimistic regions for hydrocarbon accumulation. This study will provide a new idea and a fresh approach to explore and search for hidden oil pools at a delta depositional system in depression basins.
The northwestern, western, southern and southeastern depositional margin of the Ordos basin is tectonic slopebreak controlled by tectonic movement occurred at the end of the Triassic, where alluvial, fandeltaic and braideddeltaic sedimentary suite developed. While the eastern and northeastern margin belong to depositional slopebreak because of its gently uplifting during the late Triassic, which resulted in the meanderingdeltaic sedimentary system. Two types of slopes including slopeshapedfront and platformfront can be recognized in the Jiyuan area, northwestern Ordos Basin, based upon analysis on feature of the basin margin, types of depositional facies and sediments, thickness of the strata, spatial assemblage and distribution of the sandstone bodies, and changes of the sandstone grain size, combined with seismic interpretation for topographic form of the Chang 4+5Chang 7 lake basin. Research result shows that sandstones at the slopeshapedfront are of greater thickness with relatively developed secondary dissolution pores and higher permeability values in delta front setting where sandstones tend to be of low porosity and very low permeability. Thus, sandstones at the slopeshapedfront with the better reservoir potential in Jiyuan area are optimistic regions for hydrocarbon accumulation. This study will provide a new idea and a fresh approach to explore and search for hidden oil pools at a delta depositional system in depression basins.
2010, 28(6): 1145-1152.
Abstract:
The Jialingjiang Formation of Lower Triassic in Sichuan basin is composed of carbonate platform sedimentary system and carbonateterrigenous clastic sedimentary system, and including four major sedimentary facies such as carbonateterrigenous clastic tidal, restricted platform, open platform and evaporite platform. In the end of Feixianguan stage of Early Triassic, there was a largescale regression and regional exposure and erosion in the Upper Yangtze maritime space, and until early Jialingjiang stage the Upper Yangtze maritime space undergoed extensive transgression and accepted the deposition again. Therefore, at the bottom of Jialingjiang Formation of Lower Triassic developed partial exposure unconformity surface and inner of the Jialingjiang Formation mainly developed lithologylithofacies transformational sequence interface. According to the tracing and recognition of sequence interface and through the sequence stratigraphy division of typical singlewell and the sequence stratigraphy comparison of well tie, the Jialingjiang Formation of Lower Triassic in Sichuan basin can be devided into 3 thirdorder sequences. The sequence 1 which is located in the lower part of Jialingjiang Formation belongs to the type Ⅰ sequence, the sequence 2 and 3 in the middle and supreme part belongs to the type Ⅱ sequence. Based on the sequence stratigraphy division and sedimentary facies analysis, we first systematic compiled the sequencelithofacies paleographic map of each system tract with the system tract as unit and analysed the characteristic of sequencelithofacies paleographic of Jialingjiang Formation in the study area. It shows that from west to east in Sichuan Basin with a clear differentiation in the plane , in the vertical facies belt with a clear evolution. Open platform facies are dominated and oolitic shoal reservoirs are the most developed ones in the east and middle part of Sichuan basin during the trassgrassive system tracts, restricted and evaporite platform facies are dominated and dolomite reservoirs are the most developed ones in the north and northeast part of Sichuan basin during the highstand system tracts. It can be divided into three types oil prospect zone in Sichuan basin Primarily based on reservoir distribution, united of generating rock, reservoircapping rock composition and forming conditions. The most favorable oil prospect zone is located in northeast Sichuan basin,because granule shoal reservoirs and dolomite reservoirs are the most favorable developed and it is also the karst slope distributed area. The more favorable oil prospect zone is from Hechuan in central of Sichuan to Gaoxun in south of Sichuan. This district developed the granule shoal reservoirs and dolomite reservoirs and we have found several accumulation of gas in Jialingjiang Formation, so it's the more favorable oil and gas prospect zone in Sichuan Basin.
The Jialingjiang Formation of Lower Triassic in Sichuan basin is composed of carbonate platform sedimentary system and carbonateterrigenous clastic sedimentary system, and including four major sedimentary facies such as carbonateterrigenous clastic tidal, restricted platform, open platform and evaporite platform. In the end of Feixianguan stage of Early Triassic, there was a largescale regression and regional exposure and erosion in the Upper Yangtze maritime space, and until early Jialingjiang stage the Upper Yangtze maritime space undergoed extensive transgression and accepted the deposition again. Therefore, at the bottom of Jialingjiang Formation of Lower Triassic developed partial exposure unconformity surface and inner of the Jialingjiang Formation mainly developed lithologylithofacies transformational sequence interface. According to the tracing and recognition of sequence interface and through the sequence stratigraphy division of typical singlewell and the sequence stratigraphy comparison of well tie, the Jialingjiang Formation of Lower Triassic in Sichuan basin can be devided into 3 thirdorder sequences. The sequence 1 which is located in the lower part of Jialingjiang Formation belongs to the type Ⅰ sequence, the sequence 2 and 3 in the middle and supreme part belongs to the type Ⅱ sequence. Based on the sequence stratigraphy division and sedimentary facies analysis, we first systematic compiled the sequencelithofacies paleographic map of each system tract with the system tract as unit and analysed the characteristic of sequencelithofacies paleographic of Jialingjiang Formation in the study area. It shows that from west to east in Sichuan Basin with a clear differentiation in the plane , in the vertical facies belt with a clear evolution. Open platform facies are dominated and oolitic shoal reservoirs are the most developed ones in the east and middle part of Sichuan basin during the trassgrassive system tracts, restricted and evaporite platform facies are dominated and dolomite reservoirs are the most developed ones in the north and northeast part of Sichuan basin during the highstand system tracts. It can be divided into three types oil prospect zone in Sichuan basin Primarily based on reservoir distribution, united of generating rock, reservoircapping rock composition and forming conditions. The most favorable oil prospect zone is located in northeast Sichuan basin,because granule shoal reservoirs and dolomite reservoirs are the most favorable developed and it is also the karst slope distributed area. The more favorable oil prospect zone is from Hechuan in central of Sichuan to Gaoxun in south of Sichuan. This district developed the granule shoal reservoirs and dolomite reservoirs and we have found several accumulation of gas in Jialingjiang Formation, so it's the more favorable oil and gas prospect zone in Sichuan Basin.
2010, 28(6): 1165-1174.
Abstract:
T1f3 reservoir in Tongnanba area obtain industrial gasflow in recent years, reservoir pressure are high, reservoir lithology mainly is grainstone and mud microcrystalline limestone, physical properties is bad. Reservoir space mainly are oolimolds, dissolve inside grainmold hole and dissolve pore.There are big changes in transverse, and significant different in longitudinal. Generally, reservoir development poor in tongnanba area. In this article, the author deeply discussed the reservoir forming mechanism of T1f3 reservoir in tongnanba area through the analysis of the diagenesis types and it`s influence to the porosity evolution, diagenetic evolution sequence, and contrast to which in Puguang gas field. Accoroding to the research there are three factors which controll the forming of T1f3 reservoir. Firstly: Dolomitization is very weak because of the limitation of the sedimentary and diagenetic environment, so the dolomite reservoir do not develop, which lead to the poor reservoir develop; Secondly:Primary pore disappeared basicly, dissolution become the key factor to the forming of T1f3 reservoir, synsedimentary dissolution are dominant among dissolution in all stages; Thirdly:There are not TSR reaction in T1f3reservoir because of the hydrocarbon injection did not happen during the middledeep burial stage. So the destructive diagenesis enhancement relatively can not influence resevroir quality.
T1f3 reservoir in Tongnanba area obtain industrial gasflow in recent years, reservoir pressure are high, reservoir lithology mainly is grainstone and mud microcrystalline limestone, physical properties is bad. Reservoir space mainly are oolimolds, dissolve inside grainmold hole and dissolve pore.There are big changes in transverse, and significant different in longitudinal. Generally, reservoir development poor in tongnanba area. In this article, the author deeply discussed the reservoir forming mechanism of T1f3 reservoir in tongnanba area through the analysis of the diagenesis types and it`s influence to the porosity evolution, diagenetic evolution sequence, and contrast to which in Puguang gas field. Accoroding to the research there are three factors which controll the forming of T1f3 reservoir. Firstly: Dolomitization is very weak because of the limitation of the sedimentary and diagenetic environment, so the dolomite reservoir do not develop, which lead to the poor reservoir develop; Secondly:Primary pore disappeared basicly, dissolution become the key factor to the forming of T1f3 reservoir, synsedimentary dissolution are dominant among dissolution in all stages; Thirdly:There are not TSR reaction in T1f3reservoir because of the hydrocarbon injection did not happen during the middledeep burial stage. So the destructive diagenesis enhancement relatively can not influence resevroir quality.
2010, 28(6): 1190-1197.
Abstract:
The Linxia Basin is a key place to study the paleoclimate change and the Tibetan Plateau uplift for its special place at the Asian monsoon margin and the northeastern Tibetan Plateau. Variations of the magnetic susceptibility and rockmagnetic characteristics from the Heilinding sediments in the Linxia Basin revealed a huge change occurred at the about 8.6 Ma based on a ideal palaeomagnetic dating (11.85.0 Ma). During 11.88.6 Ma, the value of the magnetic susceptibility was stably low (0.586.9/10 8m3kg1). After 8.6 Ma, it became very high(0.7510.6/108m3kg1) for the soft mineral magnetic properties. We argued such change was mainly caused by the change of the material origin driven by the uplift of the Tibetan Plateau. The magnetic susceptibility in the lake sediments is different from the loesspaleosol layers in the explanation of the environment and climate change.
The Linxia Basin is a key place to study the paleoclimate change and the Tibetan Plateau uplift for its special place at the Asian monsoon margin and the northeastern Tibetan Plateau. Variations of the magnetic susceptibility and rockmagnetic characteristics from the Heilinding sediments in the Linxia Basin revealed a huge change occurred at the about 8.6 Ma based on a ideal palaeomagnetic dating (11.85.0 Ma). During 11.88.6 Ma, the value of the magnetic susceptibility was stably low (0.586.9/10 8m3kg1). After 8.6 Ma, it became very high(0.7510.6/108m3kg1) for the soft mineral magnetic properties. We argued such change was mainly caused by the change of the material origin driven by the uplift of the Tibetan Plateau. The magnetic susceptibility in the lake sediments is different from the loesspaleosol layers in the explanation of the environment and climate change.
2010, 28(6): 1206-1212.
Abstract:
Based on the sporepollen analysis of the core HZS, in Handan region, Hebei Province. The results show that the Handan region's climate since the Late Pleistocene evolution of the form of both the characteristics of the global synchronization, but also the characteristics of the region alone.The evolutional stages of palaeoclimate and palaeovegetation are recognized in the following:（1）During the Late Pleistocene, the climatic changes were from warm and humid(130~75 kaBP)→ cool and dry(75~55 kaBP)→warm and humid(40~30 kaBP)→cool and dry(30~10 kaBP), the vegetation evolutions were sylvosteppe →grassland →sylvosteppe →grassland.（2）The evolution of Holocene climate has experienced slightly cold and moderately dry(10~8 kaBP)→ warm and humid(8~3 kaBP)→slightly worm and moderately dry(3~0 kaBP) process, the vegetation evolutions were sparse sylvosteppe→ sylvosteppe→ sparse sylvosteppe. （3）Occurred in 25 kaBP around, 16 kaBP around, and 1110 kaBP cold events may be Heinrich events 3, 1 and Younger Dryas event in eastern China monsoon region's response.
Based on the sporepollen analysis of the core HZS, in Handan region, Hebei Province. The results show that the Handan region's climate since the Late Pleistocene evolution of the form of both the characteristics of the global synchronization, but also the characteristics of the region alone.The evolutional stages of palaeoclimate and palaeovegetation are recognized in the following:（1）During the Late Pleistocene, the climatic changes were from warm and humid(130~75 kaBP)→ cool and dry(75~55 kaBP)→warm and humid(40~30 kaBP)→cool and dry(30~10 kaBP), the vegetation evolutions were sylvosteppe →grassland →sylvosteppe →grassland.（2）The evolution of Holocene climate has experienced slightly cold and moderately dry(10~8 kaBP)→ warm and humid(8~3 kaBP)→slightly worm and moderately dry(3~0 kaBP) process, the vegetation evolutions were sparse sylvosteppe→ sylvosteppe→ sparse sylvosteppe. （3）Occurred in 25 kaBP around, 16 kaBP around, and 1110 kaBP cold events may be Heinrich events 3, 1 and Younger Dryas event in eastern China monsoon region's response.
2010, 28(6): 1238-1243.
Abstract:
The sedimentary environments and the original inputs of source rocks close related with the nature of the organic matter, in different layers and different regions of Taibei Depression, TurpanHami Basin, due to the differences of the depositional environments and the original inputs of Jurassic coalbearing source rocks, result in differences of the geochemical index. The analysis of geochemical indicators of source rocks showing that Pr/Ph and C29ααα20R relative content are important indicators of redox environment and the salinity of water. At the same time, we found that the main indicators of the type of source rocks are aromatic hydrocarbon and asphaltene contents in the group composition of soluble organic matter, the ratio of saturated hydrocarbon and aromatic hydrocarbon ,also the ratio of nonhydrocarbon and asphaltene. Pr/Ph, gammacerane index are secondary indicators of classification of source rocks. The Jurassic coalbearing source rocks can be classfied into three categories by the above index in Taibei Depression.
The sedimentary environments and the original inputs of source rocks close related with the nature of the organic matter, in different layers and different regions of Taibei Depression, TurpanHami Basin, due to the differences of the depositional environments and the original inputs of Jurassic coalbearing source rocks, result in differences of the geochemical index. The analysis of geochemical indicators of source rocks showing that Pr/Ph and C29ααα20R relative content are important indicators of redox environment and the salinity of water. At the same time, we found that the main indicators of the type of source rocks are aromatic hydrocarbon and asphaltene contents in the group composition of soluble organic matter, the ratio of saturated hydrocarbon and aromatic hydrocarbon ,also the ratio of nonhydrocarbon and asphaltene. Pr/Ph, gammacerane index are secondary indicators of classification of source rocks. The Jurassic coalbearing source rocks can be classfied into three categories by the above index in Taibei Depression.
2010, 28(6): 1250-1253.
Abstract:
In order to study on the evolution of hydrocarbongeneration by organic acid salt, pyrolysis experiment is taken on organic acid salt at a series of temperature point270℃, 320℃,360℃, 400℃ and 430℃. The experimental result indicates that organic acid salt can be largely produced into ketone compounds. The threshold temperature of largerquantity yield is between 320℃ and 360℃ and the peak production rate at 360℃, where the conversion rate of the organic acid salt reaches 39%. But beyond the 400℃ the production rate rapidly declines. This result suggests that magnesium salt converses into ketone at the lower temperature or same as that of hydrocarbongeneration. But this type of compounds is sensitive to thermal, so it is difficult to preserve at higher temperature. Therefore, as the index of estimating hydrocarbon generation by organic acid salt, the index of ketone is generally only suitable for the middlelow maturity hydrocarbon source rocks.
In order to study on the evolution of hydrocarbongeneration by organic acid salt, pyrolysis experiment is taken on organic acid salt at a series of temperature point270℃, 320℃,360℃, 400℃ and 430℃. The experimental result indicates that organic acid salt can be largely produced into ketone compounds. The threshold temperature of largerquantity yield is between 320℃ and 360℃ and the peak production rate at 360℃, where the conversion rate of the organic acid salt reaches 39%. But beyond the 400℃ the production rate rapidly declines. This result suggests that magnesium salt converses into ketone at the lower temperature or same as that of hydrocarbongeneration. But this type of compounds is sensitive to thermal, so it is difficult to preserve at higher temperature. Therefore, as the index of estimating hydrocarbon generation by organic acid salt, the index of ketone is generally only suitable for the middlelow maturity hydrocarbon source rocks.
