2013 Vol. 31, No. 2
Display Method:
2013, 31(2): 193-209.
Abstract:
Based on reconstruction and restoration of geotectonicpaleogeographic position and tectonic lithofacies, the Paleozoic sedimentary basin of ZhashuiShanyangShangxian in Shaanxi Province could be the apartpull basin on the north passive margin of the Qinling subplate block. This apartpull basin might have been developed on the residue oceanic basin on the north passive margin of the Yangtze plate, and undergone transformation of arcorogeny and residue oceanic basin during the SilurianDevonian age. Furthermore, this basin might be superimposed by deepsourced, alkaline hydrothermal fluid during the Late Devonian Period, resulted in lithofacies zones of ankeritealbite breccia and inversion of the basin. Finally, it had been advanced into a remainsea basin to be shrinking and closed during the Carboniferous Period. Transformation and coupling process of orogenysedimentary basinisland structure may be records form the arcland type orogeny to landland type orogeny. Obvious regional mineralization zonation in this basin may be possibly related to poly diagenesismineralization. Firstly, a variety of hydrothermal sedimentary lithofacies are well established in the basin which disclosed that hydrothermal diagenesismineralization at the large scale took place in the basin. On the one hand, this could be that hydrothermal fluids from the orogeny belt migrated at the large scale into the basin enclosed by paleolandblock and orogeny during the transformation and coupling process of orogenysedimentary basinisland structure. On the other hand, thirdand fourthorder basins controlled by NEand EWtrending synfaults offered sedimentary capacity for the hydrothermal mineralization. Mapping of sublithofacies and microlithofacies may help to delineate their distribution of topologic structure. Secondly, lithofacies zones of ankeritealbite breccia in the remainsea basin closely related to veintype of AuNiCoCu deposits at the higher grades were formed by cryptoexplosion of deepsourced, alkaline hydrothermal fluids. The fluids might be driven by mainly verticalupping force during landland type collision at the southnorthdirection shrinking of lithosphere. Finally, Carlinlike gold deposits are hosted in the upper part of basinbase structure layer and lithofacies of hydrothermal turbidity at the basin were controlled by the late brittleductile shear zone in the area.
Based on reconstruction and restoration of geotectonicpaleogeographic position and tectonic lithofacies, the Paleozoic sedimentary basin of ZhashuiShanyangShangxian in Shaanxi Province could be the apartpull basin on the north passive margin of the Qinling subplate block. This apartpull basin might have been developed on the residue oceanic basin on the north passive margin of the Yangtze plate, and undergone transformation of arcorogeny and residue oceanic basin during the SilurianDevonian age. Furthermore, this basin might be superimposed by deepsourced, alkaline hydrothermal fluid during the Late Devonian Period, resulted in lithofacies zones of ankeritealbite breccia and inversion of the basin. Finally, it had been advanced into a remainsea basin to be shrinking and closed during the Carboniferous Period. Transformation and coupling process of orogenysedimentary basinisland structure may be records form the arcland type orogeny to landland type orogeny. Obvious regional mineralization zonation in this basin may be possibly related to poly diagenesismineralization. Firstly, a variety of hydrothermal sedimentary lithofacies are well established in the basin which disclosed that hydrothermal diagenesismineralization at the large scale took place in the basin. On the one hand, this could be that hydrothermal fluids from the orogeny belt migrated at the large scale into the basin enclosed by paleolandblock and orogeny during the transformation and coupling process of orogenysedimentary basinisland structure. On the other hand, thirdand fourthorder basins controlled by NEand EWtrending synfaults offered sedimentary capacity for the hydrothermal mineralization. Mapping of sublithofacies and microlithofacies may help to delineate their distribution of topologic structure. Secondly, lithofacies zones of ankeritealbite breccia in the remainsea basin closely related to veintype of AuNiCoCu deposits at the higher grades were formed by cryptoexplosion of deepsourced, alkaline hydrothermal fluids. The fluids might be driven by mainly verticalupping force during landland type collision at the southnorthdirection shrinking of lithosphere. Finally, Carlinlike gold deposits are hosted in the upper part of basinbase structure layer and lithofacies of hydrothermal turbidity at the basin were controlled by the late brittleductile shear zone in the area.
2013, 31(2): 220-236.
Abstract:
The surface sediments on Shi Island of Xisha Islands are aeolian sediments, which have been formed during late Pleistocene, and they are undergoing early diagenesis. Through the detailed observation of outcrops, sections and SEM, combing with the analysis of stable isotope of carbon and oxygen, major elements and trace elements, we found the aeolian seddiments had been consolidated mainly in meteoric diagenetic environment, and the evaporation diagenesis might play an important role during the early consolidation of the aeolian sediments. Under the influence of meteoric diagenesis, part of clasts have been leached and experienced neomorphism. And the newly producted microspar low magnesium calcite (410 m) cements usually pectinally inlayed on the surface of grains or pores in form of graininess, and became main cements. However, the content of calcsparite cements, which usually taken as the marker products of vadose and phreatic diagenesis, were generally less than the microspar cements in the most of rocks. The sea water mainly influenced and altered the former meteoric diagenesis, could raise the content of Sr and Mg, while only the surface of aeolianite had been affected. And the sea water diagenesis had a little influence about the δ13C and δ18O of the aeolian carbonatite. However, the formation of calcrete and rhizoliths, which were mainly developed in the paleosols, might have been affected by biochemical process. But the biochemical process had little sense for the whole diagenesis of the aeolian sediments. The meteoric diagenesis could decline the δ13C and δ18O of the aeolian sediments, and leach the Sr2+ and Mg2+ by the neomorphism. For the pedogenesis, the palaeosols are relative abundant in Al (aluminium), Fe (ferrum), Mn (manganese), Y (yttrium) and Cr (chromium) than the aeolian calcarenite. Nevertheless, the concentration of Y (yttrium) and Cr (chromium) showed little relationship with pedogenesis, and we induced that they might come from travel fatigue or volcanic ash during the relatively long term exposure.
The surface sediments on Shi Island of Xisha Islands are aeolian sediments, which have been formed during late Pleistocene, and they are undergoing early diagenesis. Through the detailed observation of outcrops, sections and SEM, combing with the analysis of stable isotope of carbon and oxygen, major elements and trace elements, we found the aeolian seddiments had been consolidated mainly in meteoric diagenetic environment, and the evaporation diagenesis might play an important role during the early consolidation of the aeolian sediments. Under the influence of meteoric diagenesis, part of clasts have been leached and experienced neomorphism. And the newly producted microspar low magnesium calcite (410 m) cements usually pectinally inlayed on the surface of grains or pores in form of graininess, and became main cements. However, the content of calcsparite cements, which usually taken as the marker products of vadose and phreatic diagenesis, were generally less than the microspar cements in the most of rocks. The sea water mainly influenced and altered the former meteoric diagenesis, could raise the content of Sr and Mg, while only the surface of aeolianite had been affected. And the sea water diagenesis had a little influence about the δ13C and δ18O of the aeolian carbonatite. However, the formation of calcrete and rhizoliths, which were mainly developed in the paleosols, might have been affected by biochemical process. But the biochemical process had little sense for the whole diagenesis of the aeolian sediments. The meteoric diagenesis could decline the δ13C and δ18O of the aeolian sediments, and leach the Sr2+ and Mg2+ by the neomorphism. For the pedogenesis, the palaeosols are relative abundant in Al (aluminium), Fe (ferrum), Mn (manganese), Y (yttrium) and Cr (chromium) than the aeolian calcarenite. Nevertheless, the concentration of Y (yttrium) and Cr (chromium) showed little relationship with pedogenesis, and we induced that they might come from travel fatigue or volcanic ash during the relatively long term exposure.
2013, 31(2): 248-258.
Abstract:
Depositional succession of the Lower Cretaceous XiagouZhonggou Formations is widely distributed in Hanxia of the northern Qilian Mountain, and mainly composed of conglomerates, sandstones, calcareous siltstone, mudstone or shale. Gravels within conglomerates are poorly sorted and subrounded. Sandstones are characterized of poor or medium compositional maturities. Depositional succession lithological associations and facies indicate that both the Xiagou and Zhonggou Formations consist of lacustrine, fan delta or fluvial facies as well as gravity flow deposits. Lacustrine is mainly in the bottom of the Xiagou Formation and the Zhonggou Formation. Fan delta facies is dominantly in the middle and upper parts of the Xiagou Formation. Fluvial facies is common in the Zhonggou Formation. Correlation and synthesized analysis of stratigraphy, depositional facies and lithological associations in Hanxia and its adjacent areas(Changma basin and the western Jiuquan basin) illustrate that the Xiagou and Zhonggou Formations in Changma to the southwest of Hanxia, are interpreted as deposits of shallow lacustrine and meandering river facies, and then Hongliuxia to the north of Hanxia was shallow lacustrine environment, Xinminpu(to the northeast of Hanxia), however, is mainly and meandering river facies. Based on the huge stratigraphic thickness in Hanxia than the mentioned three areas else and deepening shallow lacustrine depositional subfacies as well, was regarded as a depocenter of the Jiuxi basin of midlate Early Cretaceous. Paleocurrent reconstruction show northeastwards in the Xiagou Formation and westward in the Zhonggou Formation. A dispositional model of the Lower Cretaceous Xiagou and Zhonggou Formations is synthesized finally.
Depositional succession of the Lower Cretaceous XiagouZhonggou Formations is widely distributed in Hanxia of the northern Qilian Mountain, and mainly composed of conglomerates, sandstones, calcareous siltstone, mudstone or shale. Gravels within conglomerates are poorly sorted and subrounded. Sandstones are characterized of poor or medium compositional maturities. Depositional succession lithological associations and facies indicate that both the Xiagou and Zhonggou Formations consist of lacustrine, fan delta or fluvial facies as well as gravity flow deposits. Lacustrine is mainly in the bottom of the Xiagou Formation and the Zhonggou Formation. Fan delta facies is dominantly in the middle and upper parts of the Xiagou Formation. Fluvial facies is common in the Zhonggou Formation. Correlation and synthesized analysis of stratigraphy, depositional facies and lithological associations in Hanxia and its adjacent areas(Changma basin and the western Jiuquan basin) illustrate that the Xiagou and Zhonggou Formations in Changma to the southwest of Hanxia, are interpreted as deposits of shallow lacustrine and meandering river facies, and then Hongliuxia to the north of Hanxia was shallow lacustrine environment, Xinminpu(to the northeast of Hanxia), however, is mainly and meandering river facies. Based on the huge stratigraphic thickness in Hanxia than the mentioned three areas else and deepening shallow lacustrine depositional subfacies as well, was regarded as a depocenter of the Jiuxi basin of midlate Early Cretaceous. Paleocurrent reconstruction show northeastwards in the Xiagou Formation and westward in the Zhonggou Formation. A dispositional model of the Lower Cretaceous Xiagou and Zhonggou Formations is synthesized finally.
2013, 31(2): 269-281.
Abstract:
Lagar Formation was developed in Lhasa Block which located between Himalaya belt south and Qiangtang Block north. It represents the glaciomarine deposits related to the Late CarboniferousEarly Permian Gondwana glaciation. However, its litho/sedimentary facies have never been clearly understood. In this paper, the litho/sedimentary facies of the Lagar Formation were analyzed based on the ZhakangMujiucuo section in Xainza County, central Tibet. The lithology of Lagar can be distinguished into five types of rocks assemblage. Assemblage Ⅰ could be supposed to subaqueous ice fan which compose of pebbly coarse grained sandstonesandy shoulder (diamictite), and fine pebbly sandstone gradually. Assemblage Ⅱ is composed of finegrained sandstone developed bimodal crossbedding and muds, and could be regarded as channel and interchannel. Having no bedding, extremely poor sorted, and developed complex components of grave, the rocks of Assemblage Ⅲ was supposed by "tillites". The mainly lithology of Assemblage Ⅳ is dark or grey green silts or calsiltstone, interbeded thick pebbly coarsegrained sandstone and finegrained sandstone. The remarkable character of Assemblage Ⅳ is developed soft sediment deformation in grey green finegrained sandstone, and this should to attribute to sediment gravity flows. Being developed coarse grave and pebbly sandstone in the dark siltstone, the Assemblage Ⅴ also can be attributed to channel extending so far. Assemblage Ⅵ composed of shale laminated finegrained quartz sandstone which is well roundness and sorted should be supposed by coast and shallow sea. According to above, depositional environment of Lagar Formation is proximal glaciomarine environment which identification factor lies in whether the depositional site is proximal or distal to a grounded ice margin (or grounding line of an ice shelf or tongue). Whether ice sheet can be form ice wall near coast tide water depend on the thermal regime of ice sheet and stability of inner ice sheet. The thermal condition at an ice base can be divided into thawed (and thawing) zones where basal ice slides over the substrate producing basal meltwaters that are integrated into a well developed drainage network, and frozen and freezing zones where no free meltwaters available. Ice shelves are also inherently unstable and during times of decreasing mass balance or rising sea level may rapidly disintegrate and revert to a grounded tidewater ice margin that terminates as a steep ice wall in shallower water along the basin margin. According to present literature and depositional models, Early Permian sedimentary facies belts of Indian Gondwana to Tethyan Himalaya show continental tillitesglaciofluvialproximal glaciomarinedistal icerafted debris successively from south to north. And it is said that Lhasa and South Qiangtang block also has been considered distal or superdistal glaciomarine environment. Sedimentation rates in marine environments around thawed/thawing ice margins are much higher than around cold zones. The factors influenced the glacier thermal regime relate to global warming, drift to low latitude and warm currents influence. Global climate became warm with Sakmarian' deglaciation. But at the same time, Lhasa block has been in tectonic activities similar to adjacent Tengchong block and Sibumasu block where rifting from north margin of Austria.
Lagar Formation was developed in Lhasa Block which located between Himalaya belt south and Qiangtang Block north. It represents the glaciomarine deposits related to the Late CarboniferousEarly Permian Gondwana glaciation. However, its litho/sedimentary facies have never been clearly understood. In this paper, the litho/sedimentary facies of the Lagar Formation were analyzed based on the ZhakangMujiucuo section in Xainza County, central Tibet. The lithology of Lagar can be distinguished into five types of rocks assemblage. Assemblage Ⅰ could be supposed to subaqueous ice fan which compose of pebbly coarse grained sandstonesandy shoulder (diamictite), and fine pebbly sandstone gradually. Assemblage Ⅱ is composed of finegrained sandstone developed bimodal crossbedding and muds, and could be regarded as channel and interchannel. Having no bedding, extremely poor sorted, and developed complex components of grave, the rocks of Assemblage Ⅲ was supposed by "tillites". The mainly lithology of Assemblage Ⅳ is dark or grey green silts or calsiltstone, interbeded thick pebbly coarsegrained sandstone and finegrained sandstone. The remarkable character of Assemblage Ⅳ is developed soft sediment deformation in grey green finegrained sandstone, and this should to attribute to sediment gravity flows. Being developed coarse grave and pebbly sandstone in the dark siltstone, the Assemblage Ⅴ also can be attributed to channel extending so far. Assemblage Ⅵ composed of shale laminated finegrained quartz sandstone which is well roundness and sorted should be supposed by coast and shallow sea. According to above, depositional environment of Lagar Formation is proximal glaciomarine environment which identification factor lies in whether the depositional site is proximal or distal to a grounded ice margin (or grounding line of an ice shelf or tongue). Whether ice sheet can be form ice wall near coast tide water depend on the thermal regime of ice sheet and stability of inner ice sheet. The thermal condition at an ice base can be divided into thawed (and thawing) zones where basal ice slides over the substrate producing basal meltwaters that are integrated into a well developed drainage network, and frozen and freezing zones where no free meltwaters available. Ice shelves are also inherently unstable and during times of decreasing mass balance or rising sea level may rapidly disintegrate and revert to a grounded tidewater ice margin that terminates as a steep ice wall in shallower water along the basin margin. According to present literature and depositional models, Early Permian sedimentary facies belts of Indian Gondwana to Tethyan Himalaya show continental tillitesglaciofluvialproximal glaciomarinedistal icerafted debris successively from south to north. And it is said that Lhasa and South Qiangtang block also has been considered distal or superdistal glaciomarine environment. Sedimentation rates in marine environments around thawed/thawing ice margins are much higher than around cold zones. The factors influenced the glacier thermal regime relate to global warming, drift to low latitude and warm currents influence. Global climate became warm with Sakmarian' deglaciation. But at the same time, Lhasa block has been in tectonic activities similar to adjacent Tengchong block and Sibumasu block where rifting from north margin of Austria.
2013, 31(2): 291-301.
Abstract:
Based on the study of highresolution sequence stratigrapghy and sedimentology, isochronic stratigraphy framework of high accuracy in fifthlevel has been established, and tested by the analysis of maximum entropy spectrum, a case study of the 1st member of Qingshankou formation in Dabusu area of west slope, south Songliao basin. Using cores, logging and seismic responses, sedimentary characteristics and differences with delta front deposits were concluded. With the analysis of single wells, connective wells amd RMS, the position of slope break belt and distribution law of turbidte deposites were verified. The turbidite deposits in this area belong to the origin of distantmild slope slumping of mouth bars in delta front subfacies, and were also attributed to linearsource and mudsand rich type. The sedimentary law of thinlayer, finegrain turbidites certificated that ①slumps were mostly located in the falling period of baselevel cycles, near the sequence boundary, thick thickness, superimposed or interlayed with turbidite channels vertically, and thickening upwards. ②turbidite channels were usually near the sequence boundary, thick thickness, and conducted as mainbodies of boxing logs in the rising period. But turbidite channels were usually near the flooding surface, thin thickness, conducted as flanks of aciculatefinger logs in the falling period of baselevel cycle. The thickness of turbidite channels was thinner with the rising of base level, and was thicker with the falling of base level. ③turbidite sand sheets were mainly distributed in deeper and near maximum flooding surfaces, thin thickness, superimposed or interlayed with lacustrine muds, turbidite channel flanks or slumps vertically.Exloration practices indicated that highoil reserves can be found in thinlayer, finegrain turbidites of this area.
Based on the study of highresolution sequence stratigrapghy and sedimentology, isochronic stratigraphy framework of high accuracy in fifthlevel has been established, and tested by the analysis of maximum entropy spectrum, a case study of the 1st member of Qingshankou formation in Dabusu area of west slope, south Songliao basin. Using cores, logging and seismic responses, sedimentary characteristics and differences with delta front deposits were concluded. With the analysis of single wells, connective wells amd RMS, the position of slope break belt and distribution law of turbidte deposites were verified. The turbidite deposits in this area belong to the origin of distantmild slope slumping of mouth bars in delta front subfacies, and were also attributed to linearsource and mudsand rich type. The sedimentary law of thinlayer, finegrain turbidites certificated that ①slumps were mostly located in the falling period of baselevel cycles, near the sequence boundary, thick thickness, superimposed or interlayed with turbidite channels vertically, and thickening upwards. ②turbidite channels were usually near the sequence boundary, thick thickness, and conducted as mainbodies of boxing logs in the rising period. But turbidite channels were usually near the flooding surface, thin thickness, conducted as flanks of aciculatefinger logs in the falling period of baselevel cycle. The thickness of turbidite channels was thinner with the rising of base level, and was thicker with the falling of base level. ③turbidite sand sheets were mainly distributed in deeper and near maximum flooding surfaces, thin thickness, superimposed or interlayed with lacustrine muds, turbidite channel flanks or slumps vertically.Exloration practices indicated that highoil reserves can be found in thinlayer, finegrain turbidites of this area.
2013, 31(2): 315-324.
Abstract:
In order to understand the processes and mechanisms of sediment erosion and accretion caused by typhoon event, in situ measurements of water level, tidal current speed and direction were carried out using Acoustic Doppler Velocimeter (ADV, Vector by Nortek), Electromagnetic Current Meter (EMCM, AM HR by ALEC), and miniature pressure sensor (MkV/D by ALEC) at two sites over coastal wetlands in Luoyuan Bay, during the period when typhoon "FUNGWONG" was impacting region. Observed results showed that the water inundation time increased about 2 h in the tidal cycle during the typhoon landing, and the mean value of current speed varied slightly, but the fluctuation of current speed during a short time significantly increased, then the bottom shear stress also increased obviously, which brought about seabed erosion. After the typhoon landed, the current speed fluctuation decreased significantly, and the bottom shear stress also decreased obviously, then the suspended sediment settled on the seabed heavily, which resulted in seabed accretion. The sediment erosion and accretion during the typhoon event over embayment coastal wetlands was controlled by the variations of bottom shear stress.
In order to understand the processes and mechanisms of sediment erosion and accretion caused by typhoon event, in situ measurements of water level, tidal current speed and direction were carried out using Acoustic Doppler Velocimeter (ADV, Vector by Nortek), Electromagnetic Current Meter (EMCM, AM HR by ALEC), and miniature pressure sensor (MkV/D by ALEC) at two sites over coastal wetlands in Luoyuan Bay, during the period when typhoon "FUNGWONG" was impacting region. Observed results showed that the water inundation time increased about 2 h in the tidal cycle during the typhoon landing, and the mean value of current speed varied slightly, but the fluctuation of current speed during a short time significantly increased, then the bottom shear stress also increased obviously, which brought about seabed erosion. After the typhoon landed, the current speed fluctuation decreased significantly, and the bottom shear stress also decreased obviously, then the suspended sediment settled on the seabed heavily, which resulted in seabed accretion. The sediment erosion and accretion during the typhoon event over embayment coastal wetlands was controlled by the variations of bottom shear stress.
2013, 31(2): 331-339.
Abstract:
The continental shelf mud areas over the East China Sea were formed from the midHolocene, and are regarded as important places to study regional responses to global climate change due to their high sedimentation rate, which provide continual and rich record of environmental information. In this paper, the Minolta CM2002 spectrophotometer was used to measure the color reflectance data of sediments in Core MZ11, which was taken from the Yangtze River mud area. Based on the factor analysis using 400~700 nm color reflectance dada, the parameters such as F1, F2, brightness, redness and yellowness were summarized. By contrast with these curves, the results show that factor 1 and brightness show similar fluctuation patterns, while factor 2 and yellowness show complete contrary trend, so we can draw a conclusion that brightness and yellowness are the main factor to control the color composition of the sediment in core MZ11. The mud area near the Yangtze River estuary was believed to have been formed by finegrained sediments from the Yangtze River, which was influenced by the Eastern Asian Monsoon obviously, so by comparing with the historic record of the climate and the sediment brightness, we found the brightness could be a good proxy to monitor paleoclimatic changes in the study area and a time series analysis of the factor F1 and brightness indicate that relative high values in the past 100 yr occurred in 1887a, 1897a, 1904a, 1915a, 1936a, 1945a, 1953a, 1965a, 1977a, 1987a and 1992a, which may correlate with the abnormally strong summer monsoon events, suggesting that the tropical ocean had a major effect on the East Asian summer monsoon. Periodicities of 28 yr and 2 yr are observed in the color reflectance records coinciding with those known for solar cycles in the past 100 yr might be resulted from changes in solar activity.
The continental shelf mud areas over the East China Sea were formed from the midHolocene, and are regarded as important places to study regional responses to global climate change due to their high sedimentation rate, which provide continual and rich record of environmental information. In this paper, the Minolta CM2002 spectrophotometer was used to measure the color reflectance data of sediments in Core MZ11, which was taken from the Yangtze River mud area. Based on the factor analysis using 400~700 nm color reflectance dada, the parameters such as F1, F2, brightness, redness and yellowness were summarized. By contrast with these curves, the results show that factor 1 and brightness show similar fluctuation patterns, while factor 2 and yellowness show complete contrary trend, so we can draw a conclusion that brightness and yellowness are the main factor to control the color composition of the sediment in core MZ11. The mud area near the Yangtze River estuary was believed to have been formed by finegrained sediments from the Yangtze River, which was influenced by the Eastern Asian Monsoon obviously, so by comparing with the historic record of the climate and the sediment brightness, we found the brightness could be a good proxy to monitor paleoclimatic changes in the study area and a time series analysis of the factor F1 and brightness indicate that relative high values in the past 100 yr occurred in 1887a, 1897a, 1904a, 1915a, 1936a, 1945a, 1953a, 1965a, 1977a, 1987a and 1992a, which may correlate with the abnormally strong summer monsoon events, suggesting that the tropical ocean had a major effect on the East Asian summer monsoon. Periodicities of 28 yr and 2 yr are observed in the color reflectance records coinciding with those known for solar cycles in the past 100 yr might be resulted from changes in solar activity.
2013, 31(2): 340-349.
Abstract:
Based on core observation, analysis of electrofacies, sedimentary facies section and sand body distribution, the eighth member of Shihezi Formation of Block Su120 in Sulige gas field pertains to shallow braided river delta subfacies. However, the development degrees of different distributary channel sand bodies are different.He81upper section develops low degree,which shows the meandering riverlike shape and pertains to the style of poorly braided distributary channel;He81lower section,He82lower section and He82upper section develop high degree,which shows the banded shape and pertains to the style of greatly braided distributary channel. By comparing these two styles, the sedimentary models of braided river deltas with different braidshaped level are established. Meanwhile, by superimposing the center line of distributary channel sand bodies of the eighth member of Shihezi Formation in this area, the inheritance and migration rules of the development of distributary channel sand bodies are obtained. The inheritance presents that the amount and location of distributary channels of different sections almost remain the same. The migration presents that distributary channels always migrate towards either side, including 3 kinds of lateral migration, namely, eastward, westward, back and forth.
Based on core observation, analysis of electrofacies, sedimentary facies section and sand body distribution, the eighth member of Shihezi Formation of Block Su120 in Sulige gas field pertains to shallow braided river delta subfacies. However, the development degrees of different distributary channel sand bodies are different.He81upper section develops low degree,which shows the meandering riverlike shape and pertains to the style of poorly braided distributary channel;He81lower section,He82lower section and He82upper section develop high degree,which shows the banded shape and pertains to the style of greatly braided distributary channel. By comparing these two styles, the sedimentary models of braided river deltas with different braidshaped level are established. Meanwhile, by superimposing the center line of distributary channel sand bodies of the eighth member of Shihezi Formation in this area, the inheritance and migration rules of the development of distributary channel sand bodies are obtained. The inheritance presents that the amount and location of distributary channels of different sections almost remain the same. The migration presents that distributary channels always migrate towards either side, including 3 kinds of lateral migration, namely, eastward, westward, back and forth.
2013, 31(2): 358-367.
Abstract:
Huhehu depression is a half graben rift which is downfaulting along the eastern boundary and overlapping along the western boundary. Huhehu depression is a half graben with the form of eastfaulting and westoverlapping. The structural slopebreak zone which is widely developed in depression period plays a key role in the sand bodies and the accumulation of hydrocarbon. The study in this area is significant for further exploration. According to the fracture developing characteristics and their assemblage styles in plane and profile, many syndepositional fracture assemblage styles are identified in the depression. The fracture system mainly includes the forms of parallel faulted step, brush, fork, breaking of contact, and so on, which built up the complicate structural palaeogeomorphy in lake basin and its fracture slopebreak system, and which strictly controlled the deposition of sand bodies and their pilingup patterns in the depression. In accordance with the distribution of the fracture slopebreak zone, this paper presents the control effects of three structural slopebreak zonesfaultcontrolling steep slope, faultedstep gentle slope and depression margin for sediment infilling and sedimentary system.Based on the exploration practice, the paper discusses the relation between accumulation of hydrocarbon and the sand bodies which were controlled by syndepositional fracture slopebreak zone. It points out that the fracture slopebreak zone of depression margin is the most favorable exploration area.
Huhehu depression is a half graben rift which is downfaulting along the eastern boundary and overlapping along the western boundary. Huhehu depression is a half graben with the form of eastfaulting and westoverlapping. The structural slopebreak zone which is widely developed in depression period plays a key role in the sand bodies and the accumulation of hydrocarbon. The study in this area is significant for further exploration. According to the fracture developing characteristics and their assemblage styles in plane and profile, many syndepositional fracture assemblage styles are identified in the depression. The fracture system mainly includes the forms of parallel faulted step, brush, fork, breaking of contact, and so on, which built up the complicate structural palaeogeomorphy in lake basin and its fracture slopebreak system, and which strictly controlled the deposition of sand bodies and their pilingup patterns in the depression. In accordance with the distribution of the fracture slopebreak zone, this paper presents the control effects of three structural slopebreak zonesfaultcontrolling steep slope, faultedstep gentle slope and depression margin for sediment infilling and sedimentary system.Based on the exploration practice, the paper discusses the relation between accumulation of hydrocarbon and the sand bodies which were controlled by syndepositional fracture slopebreak zone. It points out that the fracture slopebreak zone of depression margin is the most favorable exploration area.
2013, 31(2): 374-383.
Abstract:
The oil sources in the Yanchang Formation of the Ordos Basin has always been controversial, especially in the reservoir Chang8 to Chang10.According to the crude oil of Chang6 to Chang10 of Yanchang Formation in Wubao area, the article discusses the physical properties, the group composition, the biomarkers, and the oiloil and oilsource correlation in terms of their geneses and the origin of petroleum in respective reservoirs so as to provide the geological basis for the area's petroleum exploration and prediction. The result shows that the group composition of Chang6 to Chang10 is characterized by the highest content of the saturated hydrocarbon, which follows the aromatics, and non hydrocarbons are the lowest. Chang6 to Chang10 are all mature crude oil, revealing the hybrid origin of the lower hydrobionts and the higher plants, however, the crude oil in Chang6 is distinctively different from that in Chang7 to Chang10 in terms of its group composition. The crude oil in Chang6 is the early migration result of hydrocarbons in the source rock of Chang7 to Chang10, whose maturity is the lowest, while the crude oil in Chang7 to Chang10 is migration result of hydrocarbon generating peaks, whose maturity is superior. And the oil and source correlation demonstrates that Zhangjiatan shale, at the bottom of the Chang7, contribute to the oil pools in Chang6 and Chang7, in addition, the effective source rocks on the top and middle of Chang7 and Chang6 make difference. The oil pools in Chang8, mixed geneses crude oil, are mainly the down migration result of the lower source rocks in Chang7, secondly Chang8 and Lijiapan source rocks on the top of Chang9 do. The oil pools in Chang9 are formed by the downward flow of Lijiapan shale, but the petroleum in Chang10 is accumulated may by the downward migration of the effective source rocks of Chang92. The thermal maturity should be the most responsible for the differences between crude oil group compositions which are far away from the dominant source rocks.
The oil sources in the Yanchang Formation of the Ordos Basin has always been controversial, especially in the reservoir Chang8 to Chang10.According to the crude oil of Chang6 to Chang10 of Yanchang Formation in Wubao area, the article discusses the physical properties, the group composition, the biomarkers, and the oiloil and oilsource correlation in terms of their geneses and the origin of petroleum in respective reservoirs so as to provide the geological basis for the area's petroleum exploration and prediction. The result shows that the group composition of Chang6 to Chang10 is characterized by the highest content of the saturated hydrocarbon, which follows the aromatics, and non hydrocarbons are the lowest. Chang6 to Chang10 are all mature crude oil, revealing the hybrid origin of the lower hydrobionts and the higher plants, however, the crude oil in Chang6 is distinctively different from that in Chang7 to Chang10 in terms of its group composition. The crude oil in Chang6 is the early migration result of hydrocarbons in the source rock of Chang7 to Chang10, whose maturity is the lowest, while the crude oil in Chang7 to Chang10 is migration result of hydrocarbon generating peaks, whose maturity is superior. And the oil and source correlation demonstrates that Zhangjiatan shale, at the bottom of the Chang7, contribute to the oil pools in Chang6 and Chang7, in addition, the effective source rocks on the top and middle of Chang7 and Chang6 make difference. The oil pools in Chang8, mixed geneses crude oil, are mainly the down migration result of the lower source rocks in Chang7, secondly Chang8 and Lijiapan source rocks on the top of Chang9 do. The oil pools in Chang9 are formed by the downward flow of Lijiapan shale, but the petroleum in Chang10 is accumulated may by the downward migration of the effective source rocks of Chang92. The thermal maturity should be the most responsible for the differences between crude oil group compositions which are far away from the dominant source rocks.
2013, 31(2): 210-219.
Abstract:
Through geological profile and trunk route survey, the characteristics of sedimentary facies of Huangmaqing Formation in Luzong basin and its peripheral regions has been studied. Through testing of samples, the contents characteristics of Cu, Pb, Zn, Au, Ag and some other metal elements at the upper Huangmaqing Formation has been analysed. Further more, the accumulation beds of Cu and its mechanism of concentration has been tentatively discussed. Sedimentary sequence of Huangmaqing Formation in Luzong basin and its peripheral regions is typical river delta which includes front delta delta front subfacies. The Lower Huangmaqing Formation rich in marine fossil bivalve contains dark grey and purplish clay, silty clay, and a little micritic dolomite, calcareous clayey siltstone, whose sedimentary subfacies is front delta. The sedimentary subfacies of Upper Huangmaqing Formation containing mudstone and sandstone is delta front which developed mainly distal bar, rivermouth bar, interdistributary bay, distributary channel, natural levee microfacies. On the whole, it is coarseningupward sequence of regression deltaic. The background content of Cu calculated by 84 samples from Upper Huangmaqing Formation is 79.39×10 6. However, content of Cu of various rocks is obviously different, with that of silty mudstone 8 times significantly higher than sandstone. Further analysis manifests that the concentration of Cu in silty mudstone attributes to these grayish greendark gray silty mudstone and muddy siltstone deposited in reducing environments, thus its content of Cu is 10 times higher than the background values of Huangmaqing formation. Thus, Cu bearing stratiform of Huangmaqing Formation is silty mudstone and muddy siltstone covered with reduced colour of grayish greendark gray silty which deposited in interdistributary bay of delta front. The abundant organic matters and weak hydrodynamic forces of interdistributary bay is in favour of sedimentataion of organic matters carried by running water of distributary channel. The organic matters can obsorb Cu2+, Fe2+. At the same time, H2S generated by bacterial degradation of the organic matters to form the reductive environments where Cu2+, Fe2+contained in the fluid and gel deposited. Thus reducing materials such as chalcocite, bornite, chalcopyrite, pyrite have been generated and the Cu is concentrated. The mudstone and silty mudstone of Upper Huangmaqing Formation developed in interdistributary bay, thus mudstone content can reflect its development. The lithofacies paleogeography graph is plotted by ratio of rocks (contour map of mudstone/sandstone). By ratio of mudstone/sandstone of the section, the four areas of mudstone <10, 10~20, 20~30, >30 are determined through interpolation method which use contour value 10%, 20%, 30%. The four areas reflect the plane development of interdistributary bay microfacies and also the Cubearing stratiform. The lithofacies paleogeography graph manifests the Cubearing stratiform of Huangmaqing Formation is well developed to the east of YijinqiaoShiji in southcentral basin.
Through geological profile and trunk route survey, the characteristics of sedimentary facies of Huangmaqing Formation in Luzong basin and its peripheral regions has been studied. Through testing of samples, the contents characteristics of Cu, Pb, Zn, Au, Ag and some other metal elements at the upper Huangmaqing Formation has been analysed. Further more, the accumulation beds of Cu and its mechanism of concentration has been tentatively discussed. Sedimentary sequence of Huangmaqing Formation in Luzong basin and its peripheral regions is typical river delta which includes front delta delta front subfacies. The Lower Huangmaqing Formation rich in marine fossil bivalve contains dark grey and purplish clay, silty clay, and a little micritic dolomite, calcareous clayey siltstone, whose sedimentary subfacies is front delta. The sedimentary subfacies of Upper Huangmaqing Formation containing mudstone and sandstone is delta front which developed mainly distal bar, rivermouth bar, interdistributary bay, distributary channel, natural levee microfacies. On the whole, it is coarseningupward sequence of regression deltaic. The background content of Cu calculated by 84 samples from Upper Huangmaqing Formation is 79.39×10 6. However, content of Cu of various rocks is obviously different, with that of silty mudstone 8 times significantly higher than sandstone. Further analysis manifests that the concentration of Cu in silty mudstone attributes to these grayish greendark gray silty mudstone and muddy siltstone deposited in reducing environments, thus its content of Cu is 10 times higher than the background values of Huangmaqing formation. Thus, Cu bearing stratiform of Huangmaqing Formation is silty mudstone and muddy siltstone covered with reduced colour of grayish greendark gray silty which deposited in interdistributary bay of delta front. The abundant organic matters and weak hydrodynamic forces of interdistributary bay is in favour of sedimentataion of organic matters carried by running water of distributary channel. The organic matters can obsorb Cu2+, Fe2+. At the same time, H2S generated by bacterial degradation of the organic matters to form the reductive environments where Cu2+, Fe2+contained in the fluid and gel deposited. Thus reducing materials such as chalcocite, bornite, chalcopyrite, pyrite have been generated and the Cu is concentrated. The mudstone and silty mudstone of Upper Huangmaqing Formation developed in interdistributary bay, thus mudstone content can reflect its development. The lithofacies paleogeography graph is plotted by ratio of rocks (contour map of mudstone/sandstone). By ratio of mudstone/sandstone of the section, the four areas of mudstone <10, 10~20, 20~30, >30 are determined through interpolation method which use contour value 10%, 20%, 30%. The four areas reflect the plane development of interdistributary bay microfacies and also the Cubearing stratiform. The lithofacies paleogeography graph manifests the Cubearing stratiform of Huangmaqing Formation is well developed to the east of YijinqiaoShiji in southcentral basin.
2013, 31(2): 237-247.
Abstract:
Sedimentary process, Xrays fluorescence analysis of sandstone and mudstone, and reservoir characteristics analysing were used in measuring the strata of Kapushaliang outcrop in Kuqa foreland basin. An evolution of sedimentary process is obviously in dry climate. Intermittent braided river deposits in Upper Jurassic Kalazha Formation. Turbidite fans develope in lacustrine deep water of Lower Yageliemu Formation, and shallow water lake mudstone and lacustrine bars deposit in Upper Yageliemu Formation. The dry and cold paleoclimate occurs in early period of Yageliemu Formation. At the same time, some sedimentary structures for examples the groove cast, flute cast, gravity markers, and Bouma sequences deposit in turbidite fan channels. The black lacustrine mudstone developes in the upper Yageliemu Formation, the paleoclimate changes from warm to cold. The quartz percentage of turbidite fan channel is higher than lacustrine bar. The value of tuibidite fan channel is from 62% to 70%, and the value of lacustrine bar is from 55% to 58%. There are some solution opening in sandstones of tuibidite fan channel and lacustrine bar, but the solution value of lacustrine bar is higher than turbidite fan channel. The discovery of turbidite fan in Kapushaliang outcrop of Yageliemu Formation is important for foreland basin research in Kuqa, and instructs lacustrine deep water region development in the western Kuqa depression.
Sedimentary process, Xrays fluorescence analysis of sandstone and mudstone, and reservoir characteristics analysing were used in measuring the strata of Kapushaliang outcrop in Kuqa foreland basin. An evolution of sedimentary process is obviously in dry climate. Intermittent braided river deposits in Upper Jurassic Kalazha Formation. Turbidite fans develope in lacustrine deep water of Lower Yageliemu Formation, and shallow water lake mudstone and lacustrine bars deposit in Upper Yageliemu Formation. The dry and cold paleoclimate occurs in early period of Yageliemu Formation. At the same time, some sedimentary structures for examples the groove cast, flute cast, gravity markers, and Bouma sequences deposit in turbidite fan channels. The black lacustrine mudstone developes in the upper Yageliemu Formation, the paleoclimate changes from warm to cold. The quartz percentage of turbidite fan channel is higher than lacustrine bar. The value of tuibidite fan channel is from 62% to 70%, and the value of lacustrine bar is from 55% to 58%. There are some solution opening in sandstones of tuibidite fan channel and lacustrine bar, but the solution value of lacustrine bar is higher than turbidite fan channel. The discovery of turbidite fan in Kapushaliang outcrop of Yageliemu Formation is important for foreland basin research in Kuqa, and instructs lacustrine deep water region development in the western Kuqa depression.
2013, 31(2): 259-268.
Abstract:
Many types of oncoids, which have great significance for sedimentary environment research, are well developed in Paleogene Guanzhuang Formation in Pingyi Basin. Based on previous studies, the morphometry, structure, fossil, texture and the characteristics of geochemistry of the oncolites in host area were analyzed by means of field inspection, microscope observation and geochemical test. In order to study the characteristics and environmental significance of lacustrine oncolites in Paleogene Guanzhuang Formation in Pingyi Basin, the following aspects are described in this paper: (1) The general geological conditions of the host area. (2) The research on the sedimentary environment and growing pattern of the oncoids in host area in Guanzhuang Formation. (3) The characteristics of the oncoids and oncolites in host area. (4) The classification the oncoids in Paleogene Guanzhuang Formation in Pingyi Basin. Based this study, the oncoids were divided into Type A and Type B, and the most fundamental difference between them lies in sedimentary environments where they originated. Type A originated in the higher energy water than Type B, and Type A developed in quiet and clean water while Type B growed in the turbid water. According to above study, the oncolites developed in a close, dry and hot lake, which was on the stage of transgression.
Many types of oncoids, which have great significance for sedimentary environment research, are well developed in Paleogene Guanzhuang Formation in Pingyi Basin. Based on previous studies, the morphometry, structure, fossil, texture and the characteristics of geochemistry of the oncolites in host area were analyzed by means of field inspection, microscope observation and geochemical test. In order to study the characteristics and environmental significance of lacustrine oncolites in Paleogene Guanzhuang Formation in Pingyi Basin, the following aspects are described in this paper: (1) The general geological conditions of the host area. (2) The research on the sedimentary environment and growing pattern of the oncoids in host area in Guanzhuang Formation. (3) The characteristics of the oncoids and oncolites in host area. (4) The classification the oncoids in Paleogene Guanzhuang Formation in Pingyi Basin. Based this study, the oncoids were divided into Type A and Type B, and the most fundamental difference between them lies in sedimentary environments where they originated. Type A originated in the higher energy water than Type B, and Type A developed in quiet and clean water while Type B growed in the turbid water. According to above study, the oncolites developed in a close, dry and hot lake, which was on the stage of transgression.
2013, 31(2): 282-290.
Abstract:
Based on the outcrop investigation and core borings identification, we systematically studied the cycle of development, the sedimentary and distribution characteristics of NeogeneQuaternary gravel layers of Kuqa Depression in Tarim Basin, to solve the problems of velocity changes and engineering decision. We analysed the thicknes, lithology, structures, tectonic and gravel composition of different outcrops and rock debris, and we also correlate gravel layers of all period. We believe that there were four periods which developed thick gravel layers, and the sedimentary origins of gravel layers could be alluvial fan, fan delta and fluvial plain. All gravels had four provenance systems, in which there developed different gravel composition. The gravel layers of Kuqa depression continuously developed in different periods vertically, and had different facies which changed fast laterally. The tectonic evolution, tectonic style, and the northsouth faults were the main factors which influenced the sedimentary characteristics, distribution of the gravel layers.
Based on the outcrop investigation and core borings identification, we systematically studied the cycle of development, the sedimentary and distribution characteristics of NeogeneQuaternary gravel layers of Kuqa Depression in Tarim Basin, to solve the problems of velocity changes and engineering decision. We analysed the thicknes, lithology, structures, tectonic and gravel composition of different outcrops and rock debris, and we also correlate gravel layers of all period. We believe that there were four periods which developed thick gravel layers, and the sedimentary origins of gravel layers could be alluvial fan, fan delta and fluvial plain. All gravels had four provenance systems, in which there developed different gravel composition. The gravel layers of Kuqa depression continuously developed in different periods vertically, and had different facies which changed fast laterally. The tectonic evolution, tectonic style, and the northsouth faults were the main factors which influenced the sedimentary characteristics, distribution of the gravel layers.
2013, 31(2): 302-314.
Abstract:
In the past thirty years，microbial dolomite model provides a new insight into longstanding “Dolomite Problem”. Many experiments and cases demonstrated that the metabolic activities of microorganisms (sulfatereducing bacteria, methanogenic Archaea, and moderately halophilic aerobic bacteria, etc.) played a key role in mediating the dolomite lowtemperature precipitation. The characteristic microtexture, micromorphology and specific carbonate isotopes are the major distinguishing remarks of the microbial dolomite. However，there have stillcontroversies on the scale of microbial dolomite, its mediation mechanism, whether there exist putative "nanobacteria" fossils, and whether the modern microbial dolomite model can be reliable criteria to ancient analogues. Ancient lascustrine dolostones widespread in China which show a diversity of mechanisms, offer good opputinities to better understand these intensive issues in comparison with the modern counterparts.
In the past thirty years，microbial dolomite model provides a new insight into longstanding “Dolomite Problem”. Many experiments and cases demonstrated that the metabolic activities of microorganisms (sulfatereducing bacteria, methanogenic Archaea, and moderately halophilic aerobic bacteria, etc.) played a key role in mediating the dolomite lowtemperature precipitation. The characteristic microtexture, micromorphology and specific carbonate isotopes are the major distinguishing remarks of the microbial dolomite. However，there have stillcontroversies on the scale of microbial dolomite, its mediation mechanism, whether there exist putative "nanobacteria" fossils, and whether the modern microbial dolomite model can be reliable criteria to ancient analogues. Ancient lascustrine dolostones widespread in China which show a diversity of mechanisms, offer good opputinities to better understand these intensive issues in comparison with the modern counterparts.
2013, 31(2): 325-330.
Abstract:
Located within and outside the Taiwan Canyon in the northeastern South China Sea, with the water depths of 3 280 m and 3 378 m separately, two sediment cores HD133 and HD77 are carefully investigated through analysis of grain size, paleontology and calcium carbonate content. In combination with the sea level history during the LGM (Last Glacial Maximum), the sedimentary elements and responses are discussed. Based on sediment grain size and carbonate content, the two cores can be subdivided into three sediment layers. The layer 2 is consisted of medium to fine grained thickbedded sands which is interpreted to be terrigenous gravity flow deposits, evidenced by the abundant shallow water benthic foraminifera, the carbonate content reaching 60% and the internal chaos of AMS14C isotope dating. Layers 1 and 3 are dominated by silt mud with silt interbeds, with few shallow water benthic foraminifera and carbonate content less than 10%, indicating a decrease of sediment gravity flows. The controlling factors for the deepwater sands within these two sediment cores are as the following: temporally, terrigenous sediments are directly delivered into the deepwater settings, forming sandrich deposits layer 2; spatially, submarine canyons are the conduits for terrigenous gravity flow, making the deposition occur firstly within the canyon. Thus, HD133 is richer in sand than HD77.
Located within and outside the Taiwan Canyon in the northeastern South China Sea, with the water depths of 3 280 m and 3 378 m separately, two sediment cores HD133 and HD77 are carefully investigated through analysis of grain size, paleontology and calcium carbonate content. In combination with the sea level history during the LGM (Last Glacial Maximum), the sedimentary elements and responses are discussed. Based on sediment grain size and carbonate content, the two cores can be subdivided into three sediment layers. The layer 2 is consisted of medium to fine grained thickbedded sands which is interpreted to be terrigenous gravity flow deposits, evidenced by the abundant shallow water benthic foraminifera, the carbonate content reaching 60% and the internal chaos of AMS14C isotope dating. Layers 1 and 3 are dominated by silt mud with silt interbeds, with few shallow water benthic foraminifera and carbonate content less than 10%, indicating a decrease of sediment gravity flows. The controlling factors for the deepwater sands within these two sediment cores are as the following: temporally, terrigenous sediments are directly delivered into the deepwater settings, forming sandrich deposits layer 2; spatially, submarine canyons are the conduits for terrigenous gravity flow, making the deposition occur firstly within the canyon. Thus, HD133 is richer in sand than HD77.
2013, 31(2): 350-357.
Abstract:
Reservoir rocks of Tenggeer Formation in Shanghe area of Baiyinchagan Sag, mainly consists of arkose , lithic arkose and feldspathic litharenite. The main interstitial matter is carbonate, basically comprised by calcite and dolomite. Cementation type is pore cementation. The primary intergranular pores are the main reservoir spaces.The pore structure is characterized by small pore throat radius,poor connection and poor sorting.The reservoir porosity and permeability has a good positive correlation and the reservoir permeability is mainly controlled by the pore abundance. The primary controlling factors of reservoirs in this area are sedimentary environment,burial depth and diagenesis.Sedimentary facies, clastic particle's physical property and differences of diagenetic minerals significantly controlled the physical properties of reservoirs. The component of diagenetic minerals are influenced by the sedimentary facies and the lithology at provenance. The 1 6001 900 m well section shows abnormal lower value of physical properties with the plastic minerals such as debris and feldspar significantly increased. Burial depth in this area also have some control effect on physical properties. Generally, reservoir physical properties becomes poor with the increasing of burial depth. In addition, diagenesis have exerted great effects on the proporties of reservoir rocks. The most destructive diagenesis is compaction, it is one of major affecting factors for poor reservoir physical properties in the study area. Compaction and cementation are the main pore destroyers, which reduce the pore space and block pore throat. Dissolution play a constructive role in forming secondary solution pores, it obviously improved the reservoir properties. In 2 0002 200 m range, it developed a dissolution zone. In this zone, the reservoir physical properties become better. Transitional area of fan delta plain and fan delta front is the favorable zone in the study area. The transitional zone is a balance area with the joint influence of depositional facies, burial depth and diagenesis. This balance area tends to have the features of proximal provenance and multiple origins with rapidly deposited sediments, where compaction is the dominate diagenesis. The reservoir physical properties in this balance area is controlled by many factors, and its favorable physical properties is the contribution of their comprehensive effects.
Reservoir rocks of Tenggeer Formation in Shanghe area of Baiyinchagan Sag, mainly consists of arkose , lithic arkose and feldspathic litharenite. The main interstitial matter is carbonate, basically comprised by calcite and dolomite. Cementation type is pore cementation. The primary intergranular pores are the main reservoir spaces.The pore structure is characterized by small pore throat radius,poor connection and poor sorting.The reservoir porosity and permeability has a good positive correlation and the reservoir permeability is mainly controlled by the pore abundance. The primary controlling factors of reservoirs in this area are sedimentary environment,burial depth and diagenesis.Sedimentary facies, clastic particle's physical property and differences of diagenetic minerals significantly controlled the physical properties of reservoirs. The component of diagenetic minerals are influenced by the sedimentary facies and the lithology at provenance. The 1 6001 900 m well section shows abnormal lower value of physical properties with the plastic minerals such as debris and feldspar significantly increased. Burial depth in this area also have some control effect on physical properties. Generally, reservoir physical properties becomes poor with the increasing of burial depth. In addition, diagenesis have exerted great effects on the proporties of reservoir rocks. The most destructive diagenesis is compaction, it is one of major affecting factors for poor reservoir physical properties in the study area. Compaction and cementation are the main pore destroyers, which reduce the pore space and block pore throat. Dissolution play a constructive role in forming secondary solution pores, it obviously improved the reservoir properties. In 2 0002 200 m range, it developed a dissolution zone. In this zone, the reservoir physical properties become better. Transitional area of fan delta plain and fan delta front is the favorable zone in the study area. The transitional zone is a balance area with the joint influence of depositional facies, burial depth and diagenesis. This balance area tends to have the features of proximal provenance and multiple origins with rapidly deposited sediments, where compaction is the dominate diagenesis. The reservoir physical properties in this balance area is controlled by many factors, and its favorable physical properties is the contribution of their comprehensive effects.
2013, 31(2): 366-373.
Abstract:
Based on fine horizon calibration of the third member of Shahejie formation in Liaozhong Depression, seismic stratigraphic interpretation is completed by seismic modeling. According to the definition and criterion of identification of highquality hydrocarbon source rocks, mainly for dark mudstone with rich organic matter of semideepdeep lacustrine facies, features of seismic facies such as low frequency, continuation and strong reflection is identified. Based on the analysis of seismic facies and sedimentary facies, seismicsedimentary facies models are established and distribution of highquality hydrocarbon source rocks of Shahejie Formation in Liaozhong Depression is predicted. The results show that highquality hydrocarbon source rocks is mainly distributed in the north sag of Liaozhong Depression，the range decreases gradually from north to south. In the north, highquality hydrocarbon source rocks is well developed, but in the central area and south, It is only developed in the middle and lower part of the third member of Shahejie Formation,respectively.
Based on fine horizon calibration of the third member of Shahejie formation in Liaozhong Depression, seismic stratigraphic interpretation is completed by seismic modeling. According to the definition and criterion of identification of highquality hydrocarbon source rocks, mainly for dark mudstone with rich organic matter of semideepdeep lacustrine facies, features of seismic facies such as low frequency, continuation and strong reflection is identified. Based on the analysis of seismic facies and sedimentary facies, seismicsedimentary facies models are established and distribution of highquality hydrocarbon source rocks of Shahejie Formation in Liaozhong Depression is predicted. The results show that highquality hydrocarbon source rocks is mainly distributed in the north sag of Liaozhong Depression，the range decreases gradually from north to south. In the north, highquality hydrocarbon source rocks is well developed, but in the central area and south, It is only developed in the middle and lower part of the third member of Shahejie Formation,respectively.
