2007 Vol. 25, No. 2
Display Method:
2007, 25(2): 161-168.
Abstract:
Based on the analysis of sequence type and developing models of the lower Tertiary of Raoyang depression, the controlling factors of every types of sequence are analyzed according to its configuration. It is considered that at the circumstance that the supply rate of sediments is stable, the configuration of rift sequence ,the initial and closing time of the developing of its system tracts are determined by the subsidence rate and the time of highest rate of subsidence of the basin basement. The style of parasequence set are controlled by the ratio of sediment supply to the accommodation, local highest rate of sediment supply can produce progradational parasequence set. The change of climate is also a controlling factor of the development of sequence. In aridity period, lake level change and the configuration of sequence are controlled by climate.
Based on the analysis of sequence type and developing models of the lower Tertiary of Raoyang depression, the controlling factors of every types of sequence are analyzed according to its configuration. It is considered that at the circumstance that the supply rate of sediments is stable, the configuration of rift sequence ,the initial and closing time of the developing of its system tracts are determined by the subsidence rate and the time of highest rate of subsidence of the basin basement. The style of parasequence set are controlled by the ratio of sediment supply to the accommodation, local highest rate of sediment supply can produce progradational parasequence set. The change of climate is also a controlling factor of the development of sequence. In aridity period, lake level change and the configuration of sequence are controlled by climate.
Carboniferous Phylloid Algal Reefs in Ziyun County , Guizhou (South China): Evidence of Algal Blooms
2007, 25(2): 177-182.
Abstract:
Late Carboniferous phylloid algal reefs developed on the carbonate platform margin in Ziyun County, Guizhou (South China). Phylloid algal reefs are morphologically diverse, including isolated small patches, complex superposed bodies, and largesized reefs. The constructional role of algal was decisive in contributing to build frameworks. Three growth stages with distinct parts were recognized by our investigations: (1) the reef base consisting of a bioclastic shoal, (2) the reef core, when phylloid algae proliferated and contributed to reef growth, and (3) the reef cover indicating the termination of phylloid algal growth. In one of the studied case, five phases of algal blooms were recognized during the growth of a largesized phylloid algal reef, as indicated by clearly marked intervals separating these phases of algal proliferation.〖JP〗
Late Carboniferous phylloid algal reefs developed on the carbonate platform margin in Ziyun County, Guizhou (South China). Phylloid algal reefs are morphologically diverse, including isolated small patches, complex superposed bodies, and largesized reefs. The constructional role of algal was decisive in contributing to build frameworks. Three growth stages with distinct parts were recognized by our investigations: (1) the reef base consisting of a bioclastic shoal, (2) the reef core, when phylloid algae proliferated and contributed to reef growth, and (3) the reef cover indicating the termination of phylloid algal growth. In one of the studied case, five phases of algal blooms were recognized during the growth of a largesized phylloid algal reef, as indicated by clearly marked intervals separating these phases of algal proliferation.〖JP〗
2007, 25(2): 192-200.
Abstract:
The Upper Shuaiba Member(USH) is the main force pay bed in the Daleel oil field. Based on the data of geology, seicmic and paleobiology, the lithofacies assemblage and sedimentary environment in the USH were studied. Intershoal lows subfacies (where the water depth is 1050m) and shallow shoal subfacies( where the water depth is not more than 10m) were extinguished in the layer D, and storm deposit was found in the layer E1, in which intershoal lows subfacies also developed. The feature of the sedimentary subfacies and the sedimentary condition were summarized and studied, and the sedimentary model was set up in the paper that the intershoal lows on carbonate rocks were developed under the background of broad land in shallow sea, where storm events usually occurred in the lower Cretaceous in the area.
The Upper Shuaiba Member(USH) is the main force pay bed in the Daleel oil field. Based on the data of geology, seicmic and paleobiology, the lithofacies assemblage and sedimentary environment in the USH were studied. Intershoal lows subfacies (where the water depth is 1050m) and shallow shoal subfacies( where the water depth is not more than 10m) were extinguished in the layer D, and storm deposit was found in the layer E1, in which intershoal lows subfacies also developed. The feature of the sedimentary subfacies and the sedimentary condition were summarized and studied, and the sedimentary model was set up in the paper that the intershoal lows on carbonate rocks were developed under the background of broad land in shallow sea, where storm events usually occurred in the lower Cretaceous in the area.
2007, 25(2): 207-213.
Abstract:
To discuss the problem that the analysis of interior architectural structures of underground fluvial reservoirs is difficult, and the heterogeneity is serious. Based on cores, outcrop, drilling and well log data, this paper analyzes the fluvial characteristics of the 3 Sand Sets in the 2 member of Shahejie Formation(S32) in 2 District, Shengtuo Oilfield(TDSO), and recognizes all kinds of hierarchical bounding surfaces, lithofacies and architectural elements in the sandbody according to Miall's suggestion. Then the paper analyzes well logs of the architectural elements, and extracts characteristic parameters, to establish quantitative fuzzy digital model and develop a set of effective software to discriminate the types of architectural elements, and the results coincide very well with the interpretation of the geological specialist. Finally, geological models are established by using this software in Shengtuo Oilfield, and this method provides scientific foundation for enhancing oil recovery in mature oilfield.
To discuss the problem that the analysis of interior architectural structures of underground fluvial reservoirs is difficult, and the heterogeneity is serious. Based on cores, outcrop, drilling and well log data, this paper analyzes the fluvial characteristics of the 3 Sand Sets in the 2 member of Shahejie Formation(S32) in 2 District, Shengtuo Oilfield(TDSO), and recognizes all kinds of hierarchical bounding surfaces, lithofacies and architectural elements in the sandbody according to Miall's suggestion. Then the paper analyzes well logs of the architectural elements, and extracts characteristic parameters, to establish quantitative fuzzy digital model and develop a set of effective software to discriminate the types of architectural elements, and the results coincide very well with the interpretation of the geological specialist. Finally, geological models are established by using this software in Shengtuo Oilfield, and this method provides scientific foundation for enhancing oil recovery in mature oilfield.
2007, 25(2): 224-229.
Abstract:
The microanisotropy characteristics of the oil and gas reservoirs are one of the important contents in reservoir geology. Based on the authentic sandstone micromodel experiment, the microanisotropy characteristic of Chang 3 reservoirs of Zhenbei area in Ordos Basin was analyzed. Chang 3 reservoirs belong to tight sandstone. The authentic sandstone micromodel experiment audiovisually display the intense microanisotropy of Chang 3 reservoirs in this area. The sandstone pore structure and diagenesis are main factors influencing Chang 3 reservoirs microanisotropy. The dissolution resulted in the intense microanistropy of Chang 3 low permeable sandstone, but this sandstone formed high permeable zone of Chang 3 reservoirs in this area.
The microanisotropy characteristics of the oil and gas reservoirs are one of the important contents in reservoir geology. Based on the authentic sandstone micromodel experiment, the microanisotropy characteristic of Chang 3 reservoirs of Zhenbei area in Ordos Basin was analyzed. Chang 3 reservoirs belong to tight sandstone. The authentic sandstone micromodel experiment audiovisually display the intense microanisotropy of Chang 3 reservoirs in this area. The sandstone pore structure and diagenesis are main factors influencing Chang 3 reservoirs microanisotropy. The dissolution resulted in the intense microanistropy of Chang 3 low permeable sandstone, but this sandstone formed high permeable zone of Chang 3 reservoirs in this area.
2007, 25(2): 239-245.
Abstract:
Thick chert series occur from the Upper Emsian through Frasnian strata in the Nanning area, South China. These siliceous deposits are characterized by black to dark grey, thinbedded chert intercalated with light grey tuffaceous beds, which tend to be brownish yellow in the upper portion of the Frasnian. The bedded chert has very high SiO2contents (usually ＞90％) and relatively high contents of TFe2O3（total iron）(avg. 3.32%). By contrast, the contents of other major elements, i.e. Al2O3, TiO2, MgO and MnO are extremely low (avg. 0.71％, 0.04％, 0.10％ and 0.02％, respectively). Some major element ratios of Fe/Ti, (Fe+Mn)/Ti and Al/(Al+Fe+Mn) are 92.12 and 0.25 in average, respectively. Trace element ratios of Ti/V and U/Th are 4.57 and 4.09 in average, of which the U/Th ratio reached a maximum in the early Frasnian. These geochemical features suggest a hydrothermal influence upon the precipitation of the bedded chert, and a strongest hydrothermal activity in the Early Frasnian. The hydrothermal activity was likely a reflection of deepseated basement faulting. In this case, the strongest hydrothermal venting in the early Frasnian point towards a strongest extension process of the rift basin, reconciling the scenario of temporal distributions of chert and lithofacies in Devonian in South China.
Thick chert series occur from the Upper Emsian through Frasnian strata in the Nanning area, South China. These siliceous deposits are characterized by black to dark grey, thinbedded chert intercalated with light grey tuffaceous beds, which tend to be brownish yellow in the upper portion of the Frasnian. The bedded chert has very high SiO2contents (usually ＞90％) and relatively high contents of TFe2O3（total iron）(avg. 3.32%). By contrast, the contents of other major elements, i.e. Al2O3, TiO2, MgO and MnO are extremely low (avg. 0.71％, 0.04％, 0.10％ and 0.02％, respectively). Some major element ratios of Fe/Ti, (Fe+Mn)/Ti and Al/(Al+Fe+Mn) are 92.12 and 0.25 in average, respectively. Trace element ratios of Ti/V and U/Th are 4.57 and 4.09 in average, of which the U/Th ratio reached a maximum in the early Frasnian. These geochemical features suggest a hydrothermal influence upon the precipitation of the bedded chert, and a strongest hydrothermal activity in the Early Frasnian. The hydrothermal activity was likely a reflection of deepseated basement faulting. In this case, the strongest hydrothermal venting in the early Frasnian point towards a strongest extension process of the rift basin, reconciling the scenario of temporal distributions of chert and lithofacies in Devonian in South China.
2007, 25(2): 253-260.
Abstract:
Taking fractured reservoir of Budate Group in the buried hill of Sudeerte structural zone, Hailaer basin as an example, this paper discusses classification methods for development period of fractures. Based on the core observation and description, the stable isotopic analysis, fluid inclusion homogenization temperature of infilled components in fractures and acoustic emission technology, and combined with regional structural evolution history, the development period of fractures is researched. The result indicates about three stages of structural break occur in Budate Group. The fractures activity in stageⅠrelates to NantunDamoguaihe movement. The fractures are filled by
mainly caleite, of which the forming temperature is between 72 and 76 degrees. In this stage, hydrocarbon inclusions are found but their maturity is low. The fractures of stageⅡare the result of regional extension movement of Yimin phase. StageⅡis subdivided into two stages. In the first stage, fractures are filled by calcite, of which the forming temperature is between 117 and 132 degrees. In the second stage, fractures are filled by microcrystallineaplite quartz, which forming temperature is between 120 and 154 degrees. Relatively, the hydrocarbon maturity of stageⅡboosts up in evidence. The fractures of stage Ⅲ come into being in violent uplift movement of Yimin telophase. The fillings of fractures are microcrystallineaplite calcite and quartz, of which the forming temperature is between 89 and 110 degrees. The hydrocarbon maturity weakens. It is significant for rebuilding evolution history fractures to classify the development period of fractures
Taking fractured reservoir of Budate Group in the buried hill of Sudeerte structural zone, Hailaer basin as an example, this paper discusses classification methods for development period of fractures. Based on the core observation and description, the stable isotopic analysis, fluid inclusion homogenization temperature of infilled components in fractures and acoustic emission technology, and combined with regional structural evolution history, the development period of fractures is researched. The result indicates about three stages of structural break occur in Budate Group. The fractures activity in stageⅠrelates to NantunDamoguaihe movement. The fractures are filled by
mainly caleite, of which the forming temperature is between 72 and 76 degrees. In this stage, hydrocarbon inclusions are found but their maturity is low. The fractures of stageⅡare the result of regional extension movement of Yimin phase. StageⅡis subdivided into two stages. In the first stage, fractures are filled by calcite, of which the forming temperature is between 117 and 132 degrees. In the second stage, fractures are filled by microcrystallineaplite quartz, which forming temperature is between 120 and 154 degrees. Relatively, the hydrocarbon maturity of stageⅡboosts up in evidence. The fractures of stage Ⅲ come into being in violent uplift movement of Yimin telophase. The fillings of fractures are microcrystallineaplite calcite and quartz, of which the forming temperature is between 89 and 110 degrees. The hydrocarbon maturity weakens. It is significant for rebuilding evolution history fractures to classify the development period of fractures
2007, 25(2): 261-266.
Abstract:
The grain size analysis of sediments from 1981 flood and possible paleoflood in Zhongba Site, the Three Gorges reservoir, Changejiang river shows that their average diameters, sorting coefficients, skew coefficients and kurtosis coefficients are all in the same style, and they bear similar frequency curve of grain size with one crest and similar probability cumulative curve with an obvious pattern of three segments. So it is reasonable to infer that the culture interruption layers are paleoflood deposits. The study on the sedimentary environment based on the AMS14C dating and the age judged by cultural relics reveals that most paleoflood sediments occurred during the warm and wet period, but the paleofloods of the Zhou Dynasty and the middle Song Dynasty occurred during the cold period, possibly, due to the climate hypocirculation of our country and the particular topography of the place. After the Qing Danasty, the average diameters of grain size became much bigger, which suggests the local environment was degradation. The wider range of diameters of grain size and kurtosis coefficients after the Qing Dynasty, especially in modern age indicates that human activities have made the local ecosystem fragile and the climate volatile.
The grain size analysis of sediments from 1981 flood and possible paleoflood in Zhongba Site, the Three Gorges reservoir, Changejiang river shows that their average diameters, sorting coefficients, skew coefficients and kurtosis coefficients are all in the same style, and they bear similar frequency curve of grain size with one crest and similar probability cumulative curve with an obvious pattern of three segments. So it is reasonable to infer that the culture interruption layers are paleoflood deposits. The study on the sedimentary environment based on the AMS14C dating and the age judged by cultural relics reveals that most paleoflood sediments occurred during the warm and wet period, but the paleofloods of the Zhou Dynasty and the middle Song Dynasty occurred during the cold period, possibly, due to the climate hypocirculation of our country and the particular topography of the place. After the Qing Danasty, the average diameters of grain size became much bigger, which suggests the local environment was degradation. The wider range of diameters of grain size and kurtosis coefficients after the Qing Dynasty, especially in modern age indicates that human activities have made the local ecosystem fragile and the climate volatile.
2007, 25(2): 274-282.
Abstract:
Based on the grain size analysis, carbonate, magnetic susceptibility measurements on the shell bar section at Qarhan Lake in Qaidam Basin, the translation and sedimentation processes of the materials have been discussed and the lake level change history is reconstructed. The results suggest that from 38.2 to 35.5 ka C14 BP be the period of lake formation, the grain size recorded a quick lake level rise event at 35.5ka BP; from 35.533.3ka BP the grainsize indicates that the lake level was low; from 33.3 to 27.1 ka BP, the fine grainsize, higher carbonate content and low magnetic susceptibility demonstrate a high lake level period. During this time, there are three times (28.327.1 ka BP,30.329.7 ka BP and 32.132.3 ka BP) during them lake level decreased. The lake level reached it maximum between 29.7 and 28.3ka BP with a finest grainsize. Between 27.1 and 18.1ka BP, the lake level started to decrease, and from 18.1ka BP, the lake retreated abruptly with a very strong increase of the evaporation, resulted in the salt formation. After that the lake shrank further and never reached this level again.
Based on the grain size analysis, carbonate, magnetic susceptibility measurements on the shell bar section at Qarhan Lake in Qaidam Basin, the translation and sedimentation processes of the materials have been discussed and the lake level change history is reconstructed. The results suggest that from 38.2 to 35.5 ka C14 BP be the period of lake formation, the grain size recorded a quick lake level rise event at 35.5ka BP; from 35.533.3ka BP the grainsize indicates that the lake level was low; from 33.3 to 27.1 ka BP, the fine grainsize, higher carbonate content and low magnetic susceptibility demonstrate a high lake level period. During this time, there are three times (28.327.1 ka BP,30.329.7 ka BP and 32.132.3 ka BP) during them lake level decreased. The lake level reached it maximum between 29.7 and 28.3ka BP with a finest grainsize. Between 27.1 and 18.1ka BP, the lake level started to decrease, and from 18.1ka BP, the lake retreated abruptly with a very strong increase of the evaporation, resulted in the salt formation. After that the lake shrank further and never reached this level again.
2007, 25(2): 293-297.
Abstract:
The evolutionary history from the Jurassic passive continental margin to the Cretaceous foreland basin of the northern Indian plate where are located in the northern Himalayas of the southern Tibet. The huge transgressregressive cycle has been developed during the Jurassic. The Himalayan Tethysan oceanfloor spreading velocity is obviously sped up at late Jurassic, from about 0.32㎝/a of the early and middle Jurassic up to 1.24㎝/a of the late Jurassic. The Cretaceous Himalayan foreland basin evolution is divided into the two stages that included the early deepwater flysch basin and the late marine molasse basin in the southern Tibet. The upward rapid deepening sandmuddy flysch formation and black shale formation and islandarc volcanic rocks are developed in the early foreland (early Cretaceous), the upward shallowing and coarsening marine molasse formation in the late foreland (late CretaceousEocene). The Himalayan Tethysan in the southern Tibet was finally closed at about 4038Ma of the midlate Eocene.
The evolutionary history from the Jurassic passive continental margin to the Cretaceous foreland basin of the northern Indian plate where are located in the northern Himalayas of the southern Tibet. The huge transgressregressive cycle has been developed during the Jurassic. The Himalayan Tethysan oceanfloor spreading velocity is obviously sped up at late Jurassic, from about 0.32㎝/a of the early and middle Jurassic up to 1.24㎝/a of the late Jurassic. The Cretaceous Himalayan foreland basin evolution is divided into the two stages that included the early deepwater flysch basin and the late marine molasse basin in the southern Tibet. The upward rapid deepening sandmuddy flysch formation and black shale formation and islandarc volcanic rocks are developed in the early foreland (early Cretaceous), the upward shallowing and coarsening marine molasse formation in the late foreland (late CretaceousEocene). The Himalayan Tethysan in the southern Tibet was finally closed at about 4038Ma of the midlate Eocene.
2007, 25(2): 298-306.
Abstract:
A coal sample was separately heated with kaolinite, CaCO3, Fe3O4, FeS , S and without any minerals at 250℃ to 600℃ in closed hydrous pyrolysis systems for 72 h. The results show that inorganic minerals have considerable affects on oil and gas generating processes. When coal was heated with kaolinite, the coal sample has higher bitumen "A" productivity than that of without kaolin at the highest bitumen "A" producing temperature, and this highest bitumen "A" producing temperature was moved from 400℃ (pure coal ) to 350℃ when kaolin was involved. The coal sample get its highest bitumen “A” producing at 400℃ when it was heated with and without CaCO3, but when coal was heated with CaCO3, it produce more bitumen “A” than that of without CaCO3 at 400℃. More bitumen “A” was produced at 250℃ and 300℃ and less of bitumen “A” was produced at 400℃ when the coal was heated with Fe3O4 than that of without Fe3O4. Similarly to kaolinite, Fe3O4 also make the coal moving its highest bitumen “A” producing temperature from 400℃(pure coal ) to 350℃.When coal was heated with FeS, the coal sample produce more bitumen “A” at all heating temperatures than that of without FeS, and the highest bitumen “A” producing temperature was also moved to 350℃(coal+FeS) instead of 400℃ (pure coal ).The coal produced less bitumen “A” at 350℃ and 400℃ and produced much more bitumen “A” 450℃ when it was heated with element S than that of without S. All the above observations indicate that inorganic minerals have both catalysis or delay affects on the oil generating process when the coal sample was heated with minerals.
The coal has its highest gas productivity at 550℃ when it was heated with and without minerals. Comparatively, coal produced more gas when it was separately heated with kaolinite, CaCO3 and S and produced relatively less gas products when it was separately heated with Fe3O4 and FeS than that of without any minerals at high temperatures (from 400℃ to 600℃) .
The laboratory studies previously have shown that the activation energies for thermal cracking of macr-organic molecules to light hydrocarbons are much higher than that in nature. These observations have led geologists believe that there must have some catalysts in nature which could lower the activation energies for oil and gas generating reactions and make oil and gas generating reactions happened or make them accelerated that not occurred or occurred slowly because of higher activation energies.
This study indicates that thermal reaction is a very important factor during the oil and gas generating processes, but mineral catalysis or delay affects also play important roles in those processes. So, we should pay more attention on mineral catalysis/delay affects as well as thermal reactions on oil and gas exploration.
A coal sample was separately heated with kaolinite, CaCO3, Fe3O4, FeS , S and without any minerals at 250℃ to 600℃ in closed hydrous pyrolysis systems for 72 h. The results show that inorganic minerals have considerable affects on oil and gas generating processes. When coal was heated with kaolinite, the coal sample has higher bitumen "A" productivity than that of without kaolin at the highest bitumen "A" producing temperature, and this highest bitumen "A" producing temperature was moved from 400℃ (pure coal ) to 350℃ when kaolin was involved. The coal sample get its highest bitumen “A” producing at 400℃ when it was heated with and without CaCO3, but when coal was heated with CaCO3, it produce more bitumen “A” than that of without CaCO3 at 400℃. More bitumen “A” was produced at 250℃ and 300℃ and less of bitumen “A” was produced at 400℃ when the coal was heated with Fe3O4 than that of without Fe3O4. Similarly to kaolinite, Fe3O4 also make the coal moving its highest bitumen “A” producing temperature from 400℃(pure coal ) to 350℃.When coal was heated with FeS, the coal sample produce more bitumen “A” at all heating temperatures than that of without FeS, and the highest bitumen “A” producing temperature was also moved to 350℃(coal+FeS) instead of 400℃ (pure coal ).The coal produced less bitumen “A” at 350℃ and 400℃ and produced much more bitumen “A” 450℃ when it was heated with element S than that of without S. All the above observations indicate that inorganic minerals have both catalysis or delay affects on the oil generating process when the coal sample was heated with minerals.
The coal has its highest gas productivity at 550℃ when it was heated with and without minerals. Comparatively, coal produced more gas when it was separately heated with kaolinite, CaCO3 and S and produced relatively less gas products when it was separately heated with Fe3O4 and FeS than that of without any minerals at high temperatures (from 400℃ to 600℃) .
The laboratory studies previously have shown that the activation energies for thermal cracking of macr-organic molecules to light hydrocarbons are much higher than that in nature. These observations have led geologists believe that there must have some catalysts in nature which could lower the activation energies for oil and gas generating reactions and make oil and gas generating reactions happened or make them accelerated that not occurred or occurred slowly because of higher activation energies.
This study indicates that thermal reaction is a very important factor during the oil and gas generating processes, but mineral catalysis or delay affects also play important roles in those processes. So, we should pay more attention on mineral catalysis/delay affects as well as thermal reactions on oil and gas exploration.
2007, 25(2): 314-318.
Abstract:
Using experiment and formula method, this study calculated mixing proportion of thermogenic gases and secondary biogenic gases, and evaluated resources significance of secondary biogenic gases in Huainan coalfield. The result showed that mixing proportion is accordant by two different methods. The content of secondary biogenic gases is large in coalbed gases. the distribution range is from 43% to 79％. Moreover, the research results of domestic and oversea show that the generation of secondary biogenic gases increases gas content of coalbed. Therefore, the contribution of secondary biogenic gases is great for coalbed gases resources in Huainan coalfield.
Using experiment and formula method, this study calculated mixing proportion of thermogenic gases and secondary biogenic gases, and evaluated resources significance of secondary biogenic gases in Huainan coalfield. The result showed that mixing proportion is accordant by two different methods. The content of secondary biogenic gases is large in coalbed gases. the distribution range is from 43% to 79％. Moreover, the research results of domestic and oversea show that the generation of secondary biogenic gases increases gas content of coalbed. Therefore, the contribution of secondary biogenic gases is great for coalbed gases resources in Huainan coalfield.
2007, 25(2): 169-176.
Abstract:
Based on comprehensive geological analysis of log data and seismic data, integrated with outcrop observation and experimental analysis, stratigraphic cyclicity reflecting lake level change of Triassic Period in the studied area is very clear. According to the dividing criterion of sequence, seven type Ⅰsequence boundaries could be identified, and six type Ⅰsequences are divided correspondingly. Generally, Lowstand Systems Tracts (LST) are well developed, and they constitute the main reservoir sandstone bodies of the studied area. Whereas, the sandstones of highstand System Tracts (HST) and Transgressive Systems Tracts (TST) are eroded, or sometimes lost. The distribution of reservoir is strictly controlled by sequence framework. The genetic types of sandstone bodies have sublacustrinefan deposit during early stage of LST, fluvial deposit in eroded valley and shore lake deposit during later stage of LST, and delta deposit, beach and dam deposition of shore lake during HST. The study of regional basin framework has demonstrated that the studied area lied on foreupfold and backedge basin edge of Kuche foreland system during Triassic Period. So the relative change of lacustrine level result in prominent stratigraphic cyclicity which control sandstone body type and distribution.
Based on comprehensive geological analysis of log data and seismic data, integrated with outcrop observation and experimental analysis, stratigraphic cyclicity reflecting lake level change of Triassic Period in the studied area is very clear. According to the dividing criterion of sequence, seven type Ⅰsequence boundaries could be identified, and six type Ⅰsequences are divided correspondingly. Generally, Lowstand Systems Tracts (LST) are well developed, and they constitute the main reservoir sandstone bodies of the studied area. Whereas, the sandstones of highstand System Tracts (HST) and Transgressive Systems Tracts (TST) are eroded, or sometimes lost. The distribution of reservoir is strictly controlled by sequence framework. The genetic types of sandstone bodies have sublacustrinefan deposit during early stage of LST, fluvial deposit in eroded valley and shore lake deposit during later stage of LST, and delta deposit, beach and dam deposition of shore lake during HST. The study of regional basin framework has demonstrated that the studied area lied on foreupfold and backedge basin edge of Kuche foreland system during Triassic Period. So the relative change of lacustrine level result in prominent stratigraphic cyclicity which control sandstone body type and distribution.
2007, 25(2): 183-191.
Abstract:
Sedimentary facies controls plane distribution of reservoir and diagenesis controls its vertical zonation. Establishing detailed diagenesis pattern according to distinctive geology background and microfacies types is crucial for reservoir evaluation. In this paper, according to the analyses of sedimentary facies distribution and vertical sequence, by using rock thin sections, scanning electron microscope (SEM), cathodoluminescence, Xdiffraction, paleogeotemperature for the 42 sandstone samples of Shahejie Formation, it is summarized that there are 2 types of diagenesispore evolutions model ,i.e. main gravityflow channel sandbodies，and flankdistal sandbodies of gravityflow channel, which indicating that the center part of the main gravityflow channel sandbodies is potential exploration targets.
Sedimentary facies controls plane distribution of reservoir and diagenesis controls its vertical zonation. Establishing detailed diagenesis pattern according to distinctive geology background and microfacies types is crucial for reservoir evaluation. In this paper, according to the analyses of sedimentary facies distribution and vertical sequence, by using rock thin sections, scanning electron microscope (SEM), cathodoluminescence, Xdiffraction, paleogeotemperature for the 42 sandstone samples of Shahejie Formation, it is summarized that there are 2 types of diagenesispore evolutions model ,i.e. main gravityflow channel sandbodies，and flankdistal sandbodies of gravityflow channel, which indicating that the center part of the main gravityflow channel sandbodies is potential exploration targets.
2007, 25(2): 201-206.
Abstract:
Lower Cretaceous of Suibin depression includes Didao , Chengzihe, Muleng and Dongshan Formations.The geochemical compositions of sandstones and mudstones in Suibin depression, Sanjiang basin reveal the tectonic settings in the different epochs. Didao Formation mainly represents active continental margin but the rocks of Chengzihe and Muleng indicate the transition from continental island to active continental margin. Dongshan Formation expresses active continental margin. Combined with ancient direction of waterflow, the characteristic of the facies of sedimentary rocks and lithic fragments, it is referred that the provenance of Didao Formation located in the south of the Suibin depression and the provenance of Chengzihe , Muling and Dongshan Formations in the southeast of the Suibin depression. The primary materials of sedimentary rocks should come from the upper crust. This provides strong geochemical evidence for realizing the evolution of basins of eastern Heilongjian province correctly.
Lower Cretaceous of Suibin depression includes Didao , Chengzihe, Muleng and Dongshan Formations.The geochemical compositions of sandstones and mudstones in Suibin depression, Sanjiang basin reveal the tectonic settings in the different epochs. Didao Formation mainly represents active continental margin but the rocks of Chengzihe and Muleng indicate the transition from continental island to active continental margin. Dongshan Formation expresses active continental margin. Combined with ancient direction of waterflow, the characteristic of the facies of sedimentary rocks and lithic fragments, it is referred that the provenance of Didao Formation located in the south of the Suibin depression and the provenance of Chengzihe , Muling and Dongshan Formations in the southeast of the Suibin depression. The primary materials of sedimentary rocks should come from the upper crust. This provides strong geochemical evidence for realizing the evolution of basins of eastern Heilongjian province correctly.
2007, 25(2): 214-223.
Abstract:
As a result of karstification in early Hercynian and Caledonian, karst reservoirs are the main kind of Ordovician carbonate reservoirs in Tahe oilfield. Karst reservoirs in Hercynian develop mostly in the area where Carboniferous strata directly overlay the midlower Ordovician, and the karst reservoirs in the area covered by upper Ordovician were formed in Caledonian. The Ordovician strata had experienced uplift and erosion, which is proven by bottom onlap and top erosion truncation of the Ordovician reflected wave group in seismic section, lack of conodont fossil belt and sequence stratigraphic correlation in Silurian. So, there were geologic conditions for Caledonian karst formation in Tahe oilfield. In addition, the existence of karst cave has been proven by Sr isotope characteristics. In area covered by upper Ordovician, karst reservoirs mainly develop in the depth less than 300 m under Caledonian unconformity surface. In these karst reservoirs, the height of karst caves is between 0 and 30 m, maximum of 75 m, which shows that the karst caves were distinctly formed by midCaledonian karstification. Based on the domination of Caledonian faults on the development of Caledonian karst reservoirs, this paper predicts the development area of Caledonian karst reservoirs.
As a result of karstification in early Hercynian and Caledonian, karst reservoirs are the main kind of Ordovician carbonate reservoirs in Tahe oilfield. Karst reservoirs in Hercynian develop mostly in the area where Carboniferous strata directly overlay the midlower Ordovician, and the karst reservoirs in the area covered by upper Ordovician were formed in Caledonian. The Ordovician strata had experienced uplift and erosion, which is proven by bottom onlap and top erosion truncation of the Ordovician reflected wave group in seismic section, lack of conodont fossil belt and sequence stratigraphic correlation in Silurian. So, there were geologic conditions for Caledonian karst formation in Tahe oilfield. In addition, the existence of karst cave has been proven by Sr isotope characteristics. In area covered by upper Ordovician, karst reservoirs mainly develop in the depth less than 300 m under Caledonian unconformity surface. In these karst reservoirs, the height of karst caves is between 0 and 30 m, maximum of 75 m, which shows that the karst caves were distinctly formed by midCaledonian karstification. Based on the domination of Caledonian faults on the development of Caledonian karst reservoirs, this paper predicts the development area of Caledonian karst reservoirs.
2007, 25(2): 230-238.
Abstract:
Based on the ratios of Ni/Co, V/Co, Mg/Mn, Mn/Sr, Ba/Mn, Fe/K, Mg/Ca, Ba/Sr, Al/Mg and Al/Na, the provenance of the sandbodies of the upper part of the fourth member of the Shahejie Formation in W58 area, Dongying depression was studied by distribution pattern, provenance index and Qtype cluster. During the period of the upper part of the fourth member of the Shahejie Formation, the south and north provenance systems coexist in W58 area. The deposits in W58 well and its north area were provided by the north provenance system, and the deposits in WX583 and W126 wells and their south area were provided by the south provenance system, and the deposits in the vicinity of N114X1 well have the characteristics both of the south and north provenance. This study shows that the direction of the provenance can be determined more accurately by the use of characteristic elements ratios because the influences of hydrodynamic force and diagenesis can be effectively avoided.
Based on the ratios of Ni/Co, V/Co, Mg/Mn, Mn/Sr, Ba/Mn, Fe/K, Mg/Ca, Ba/Sr, Al/Mg and Al/Na, the provenance of the sandbodies of the upper part of the fourth member of the Shahejie Formation in W58 area, Dongying depression was studied by distribution pattern, provenance index and Qtype cluster. During the period of the upper part of the fourth member of the Shahejie Formation, the south and north provenance systems coexist in W58 area. The deposits in W58 well and its north area were provided by the north provenance system, and the deposits in WX583 and W126 wells and their south area were provided by the south provenance system, and the deposits in the vicinity of N114X1 well have the characteristics both of the south and north provenance. This study shows that the direction of the provenance can be determined more accurately by the use of characteristic elements ratios because the influences of hydrodynamic force and diagenesis can be effectively avoided.
2007, 25(2): 246-252.
Abstract:
Many earthquakerelated seismites were discovered in the Chang 6Chang 8 of the Yanchang Formation, Upper Triassic, southern Ordos Basin. Having surveyed the cores of wells, many typical deformation structures were discovered, such as synsedimentary micro fractures, stone veins, vibration liquefaction, deformation structure, earthquake breccia and loadcasts and ballsand pillows types, etc. The complete vertical sequence of seismite of Well Ta 17, which include shattered rock bed, laddershaped faulted bed, vibration liquefaction deformation structure bed, liquefied sandstone vein bed, rubble bed and homogenized bed. The discovery of seismite can be used to interpret the tectonic evolvement of the basin. In Late Triassic, with the closing of Qinling and the sea slot of Southern Qilian, the southnorth thrust band appeared strong activity. It was the direct inducing factors of the seimodeposition in Yanchang Formation.and provided the evidence for the turbidite of Chang 6Chang 8 of the Yanchang Formation, southwestern Ordos Basin, and the outsider trigger mechanism of the turbidite is earthquake activity.
Many earthquakerelated seismites were discovered in the Chang 6Chang 8 of the Yanchang Formation, Upper Triassic, southern Ordos Basin. Having surveyed the cores of wells, many typical deformation structures were discovered, such as synsedimentary micro fractures, stone veins, vibration liquefaction, deformation structure, earthquake breccia and loadcasts and ballsand pillows types, etc. The complete vertical sequence of seismite of Well Ta 17, which include shattered rock bed, laddershaped faulted bed, vibration liquefaction deformation structure bed, liquefied sandstone vein bed, rubble bed and homogenized bed. The discovery of seismite can be used to interpret the tectonic evolvement of the basin. In Late Triassic, with the closing of Qinling and the sea slot of Southern Qilian, the southnorth thrust band appeared strong activity. It was the direct inducing factors of the seimodeposition in Yanchang Formation.and provided the evidence for the turbidite of Chang 6Chang 8 of the Yanchang Formation, southwestern Ordos Basin, and the outsider trigger mechanism of the turbidite is earthquake activity.
2007, 25(2): 267-273.
Abstract:
This study discussed the monthly variations of magnetic properties of surface intertidal sediments along the northern bank of the Hangzhou Bay and their response to sedimentation dynamics. Fortynine surface sediment samples were collected at a fixed sampling site in the middle tidal flat from September 2004 to August 2005. The results indicate that magnetic properties of surface sediments vary significantly with month. From late December of 2004 to early May of 2005, the values of SIRM, χARM, χfd%, χARM/χ and χARM/SIRM in surface sediments are relatively higher, suggesting higher concentration of ferrimagnetic minerals with finer grain size. Samples with such magnetic properties occur in the period of tidal flat accretion with a finer sediment particle size composition. For samples from the remaining months, the above magnetic parameters have lower values, corresponding to a period of tidal flat erosion with a coarse particle size composition. Therefore, magnetic properties of surface sediments can reflect the changes in sedimentation dynamics during the process of tidal flat accretionerosion cycle.
This study discussed the monthly variations of magnetic properties of surface intertidal sediments along the northern bank of the Hangzhou Bay and their response to sedimentation dynamics. Fortynine surface sediment samples were collected at a fixed sampling site in the middle tidal flat from September 2004 to August 2005. The results indicate that magnetic properties of surface sediments vary significantly with month. From late December of 2004 to early May of 2005, the values of SIRM, χARM, χfd%, χARM/χ and χARM/SIRM in surface sediments are relatively higher, suggesting higher concentration of ferrimagnetic minerals with finer grain size. Samples with such magnetic properties occur in the period of tidal flat accretion with a finer sediment particle size composition. For samples from the remaining months, the above magnetic parameters have lower values, corresponding to a period of tidal flat erosion with a coarse particle size composition. Therefore, magnetic properties of surface sediments can reflect the changes in sedimentation dynamics during the process of tidal flat accretionerosion cycle.
2007, 25(2): 283-292.
Abstract:
The northern Bogdashan is located in the south of the Junggar Basin and in the north of Tian Shan. Paleocurrents analysis reveals that paleocurrent direction had three important abrupt transformations from the Neopaleozoic to the Cenozoic. Before the Late Carboniferous, the paleocurrent directions were from north to south. During the Permian, the paleocurrent directions were from west to east or form northwest to southeast. From the Triassic Period to the Jurassic, the paleocurrent directions were from north to south. From the Cretaceous to the Cenozoic, the paleocurrent directions was form south to north. The northern Bogodashan may be divided four tectonic evolution stages form the Neopaleozoic to the Cenozoic by integrated analysis paleocurrent，provenance and sidimentary environment. The transition phase of paleocurrent directions was not only the boundary of each stages of basin tectonic evolution but also important sedimentary record of orogenic belt evolution around the area. Furthermore, the transition time of the paleocurrent directions may restricts when structural belt around Bogodashan had uplifted. At the end of the late Carboniferous, the north western Junggar Basin had be intensity uplift and subsequently sediments fluxes into the basin form west to east. At begin of the Triassic Period, the northern jungar basin was uplifted and it provided clastic sediments for basin from the Triassic to the Jurassic. At the end of the Jurassic, the Bogodashan began to be uplifted and provided clastic sediments for besides of the Bogodashan. Why had the orogenic belt be uplifted clockwise around of the Junggar Basin? It would be researched further.
The northern Bogdashan is located in the south of the Junggar Basin and in the north of Tian Shan. Paleocurrents analysis reveals that paleocurrent direction had three important abrupt transformations from the Neopaleozoic to the Cenozoic. Before the Late Carboniferous, the paleocurrent directions were from north to south. During the Permian, the paleocurrent directions were from west to east or form northwest to southeast. From the Triassic Period to the Jurassic, the paleocurrent directions were from north to south. From the Cretaceous to the Cenozoic, the paleocurrent directions was form south to north. The northern Bogodashan may be divided four tectonic evolution stages form the Neopaleozoic to the Cenozoic by integrated analysis paleocurrent，provenance and sidimentary environment. The transition phase of paleocurrent directions was not only the boundary of each stages of basin tectonic evolution but also important sedimentary record of orogenic belt evolution around the area. Furthermore, the transition time of the paleocurrent directions may restricts when structural belt around Bogodashan had uplifted. At the end of the late Carboniferous, the north western Junggar Basin had be intensity uplift and subsequently sediments fluxes into the basin form west to east. At begin of the Triassic Period, the northern jungar basin was uplifted and it provided clastic sediments for basin from the Triassic to the Jurassic. At the end of the Jurassic, the Bogodashan began to be uplifted and provided clastic sediments for besides of the Bogodashan. Why had the orogenic belt be uplifted clockwise around of the Junggar Basin? It would be researched further.
2007, 25(2): 307-313.
Abstract:
The data of source rock and oil samples reveal three distribution patterns of nalkanes in the second group of the Funing Formation in Jinhu Sag of Subei basin, eastern China. The three patterns are, respectively, the oddtoeven predominance，the eventoodd predominance, the even and odd carbon number predominance coexisting in whole carbon number. In papers, the characteristics of a nalkane coexisting even and odd carbon number predominance and its origin are investigated only. The shortchain nalkanes and longchain nalkanes are characterized by a pronounced odd carbon predominance, with the dominant carbon number of nC15, nC17 and with nC25, nC27, nC29，nC31. And the midchain nalkanes are dominated by even carbon predominance, with the dominant carbon number of nC20 and nC22.A number of biomarkers support sediments deposited in an anoxic, hypersaline lacustrine setting. These include the phytane preference, high gammacerane and the presence of βcarotene and C24tetracyclic terpane. The biomarkers are not homosphere, which shows that salinity and redox is not constant in lake. The nalkanes are mainly derived from algae in lake and macrophytes on land or around edges of the lake. The nalkane distribution patterns of the source rocks and oils studied are believed not to be dependent of the redox in depositional environments and the salinity of water body, but to be associated with original organic matter composition.
The data of source rock and oil samples reveal three distribution patterns of nalkanes in the second group of the Funing Formation in Jinhu Sag of Subei basin, eastern China. The three patterns are, respectively, the oddtoeven predominance，the eventoodd predominance, the even and odd carbon number predominance coexisting in whole carbon number. In papers, the characteristics of a nalkane coexisting even and odd carbon number predominance and its origin are investigated only. The shortchain nalkanes and longchain nalkanes are characterized by a pronounced odd carbon predominance, with the dominant carbon number of nC15, nC17 and with nC25, nC27, nC29，nC31. And the midchain nalkanes are dominated by even carbon predominance, with the dominant carbon number of nC20 and nC22.A number of biomarkers support sediments deposited in an anoxic, hypersaline lacustrine setting. These include the phytane preference, high gammacerane and the presence of βcarotene and C24tetracyclic terpane. The biomarkers are not homosphere, which shows that salinity and redox is not constant in lake. The nalkanes are mainly derived from algae in lake and macrophytes on land or around edges of the lake. The nalkane distribution patterns of the source rocks and oils studied are believed not to be dependent of the redox in depositional environments and the salinity of water body, but to be associated with original organic matter composition.
2007, 25(2): 319-324.
Abstract:
Maturity and types of crude oil depend on maturity of source rock. It is adopted R0, C2920S/20S+20R and C29ββ/ββ+αα define the maturity of source rock, and C2920S/20S+20R, C29ββ/ββ+αα as well as vitrinite reflectance of crude oil reduction (RC) to define maturity of crude oil in west Qaidam basin. In the light of studies there are two types of crude oil for lowmaturity and maturity in west Qaidam basin, original lowmaturity crude oil migrate to deep structural trap of Mangya depression and its margin, part of lowmaturity crude oil remove to shallow structural trap because of affection of late movement, late maturity crude oil accumulates in the deep structural trap. Therefore, exploration of primary reservoir of lowmaturity and maturity crude oil, in the west Qaidam basin, should surround
deep structural trap of Mangya and Gasi sag, and shallow structural trap of Xiaolianshan sag and its margin.
Maturity and types of crude oil depend on maturity of source rock. It is adopted R0, C2920S/20S+20R and C29ββ/ββ+αα define the maturity of source rock, and C2920S/20S+20R, C29ββ/ββ+αα as well as vitrinite reflectance of crude oil reduction (RC) to define maturity of crude oil in west Qaidam basin. In the light of studies there are two types of crude oil for lowmaturity and maturity in west Qaidam basin, original lowmaturity crude oil migrate to deep structural trap of Mangya depression and its margin, part of lowmaturity crude oil remove to shallow structural trap because of affection of late movement, late maturity crude oil accumulates in the deep structural trap. Therefore, exploration of primary reservoir of lowmaturity and maturity crude oil, in the west Qaidam basin, should surround
deep structural trap of Mangya and Gasi sag, and shallow structural trap of Xiaolianshan sag and its margin.
