2005 Vol. 23, No. 4
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Display Method:
2005, 23(4): 559-565.
Abstract:
Goose Foot River is located in the south of Qionghai Lake, Sichuan, China. Huge sediment was carried into Qionghai Lake by debris flows and floods of Goose Foot River in recent 15 years. The sediment deposited in the lake and formed an underwater levee in the lake. The underwater levee is 2km in length, 200m ( along south coast)to 600m ( along north coast) in width and the average 2m in height. A channelwas found in the lake in 2003 and it was connected with the fan of river. Itwill be helpful for the research of deposition in lake and deep sea. Research on turbidity currents, especially high density turbidity currentswill have specialmeaning not only for the geomorphology of lake and deep sea, but also for the seeking the hydrocarbon in lake and deep sea.
Goose Foot River is located in the south of Qionghai Lake, Sichuan, China. Huge sediment was carried into Qionghai Lake by debris flows and floods of Goose Foot River in recent 15 years. The sediment deposited in the lake and formed an underwater levee in the lake. The underwater levee is 2km in length, 200m ( along south coast)to 600m ( along north coast) in width and the average 2m in height. A channelwas found in the lake in 2003 and it was connected with the fan of river. Itwill be helpful for the research of deposition in lake and deep sea. Research on turbidity currents, especially high density turbidity currentswill have specialmeaning not only for the geomorphology of lake and deep sea, but also for the seeking the hydrocarbon in lake and deep sea.
2005, 23(4): 574-583.
Abstract:
An intensive study has been done in the J ingan oil-field by observing five cross sections and eleven wells,analyzing 108 samp leswith thin section, cathodelumination, SEM, X-ray diffraction and related test materials. It is believed that Chang 6 oil-bearing beds underwent a series of diagenesis, such as compaction, cementation, dissolution and so on. The diagenetic phenomenona are very rich and the diagenetic characters are very obvious and complex.According to the analysis of petrology, it is found that Chang 6 oil-bearing interval is composed of middle size sand-stone and fine sub-sand. After analyzing of the whole situation, granularity is much smaller. Little of them are rock fragments feldspar sandstone. Diagenesis of Chang 6 oil-bearing interval can be divided to two stages, early and late stage. Furthermore, they can also be subdivided into two sub-phases, A and B sub-phase. The diagenetic processes that control reservoir properties include the mechanic compaction, cementation and dissolution of grains. At the early diagenesis, mechanical and chemical compaction is very strong, which reduced the primary porosity. Cementation is an important factor to reservoir, including carbonate, clay and laumontite cementation and so on. Laumontite is special mineral in OrdosBasin and is very abundant. Cementation filled the space among grains and blocked the path between grains are another factors resulting in sandstone compaction and very low permeability. But, at the same time,cements also protect grains from further compaction. At the late diagenesis phase, the dissolution of framework grains,especially the dissolution of feldspar and laumontite, is the key to form secondary porosity. They changed the porosity characteristics of sandstone; engendering new benefit storing beds consisted with secondary porosity. Feldspar is dissolved very commonly and severly. They often form dissoluble porosity among grains. Laumontite has deficient dissoluble forms and its dissolution mostly appear along rein, forming irregular size room among grains. This indicates the direction of exp loration and development for oilfield. In a word, the diagenetic study of reservoir property show that mechanical compaction and cementation is two important diagenetic controlling factors, which make oil-bearing physical property bad and porosity down in reservoir.Dissolution, particularly dissolution of laumontite and feldspar is one ofmost important diagenetic factors controlling the physical p roperty of oil2bearing interval and forming better reservoir.
An intensive study has been done in the J ingan oil-field by observing five cross sections and eleven wells,analyzing 108 samp leswith thin section, cathodelumination, SEM, X-ray diffraction and related test materials. It is believed that Chang 6 oil-bearing beds underwent a series of diagenesis, such as compaction, cementation, dissolution and so on. The diagenetic phenomenona are very rich and the diagenetic characters are very obvious and complex.According to the analysis of petrology, it is found that Chang 6 oil-bearing interval is composed of middle size sand-stone and fine sub-sand. After analyzing of the whole situation, granularity is much smaller. Little of them are rock fragments feldspar sandstone. Diagenesis of Chang 6 oil-bearing interval can be divided to two stages, early and late stage. Furthermore, they can also be subdivided into two sub-phases, A and B sub-phase. The diagenetic processes that control reservoir properties include the mechanic compaction, cementation and dissolution of grains. At the early diagenesis, mechanical and chemical compaction is very strong, which reduced the primary porosity. Cementation is an important factor to reservoir, including carbonate, clay and laumontite cementation and so on. Laumontite is special mineral in OrdosBasin and is very abundant. Cementation filled the space among grains and blocked the path between grains are another factors resulting in sandstone compaction and very low permeability. But, at the same time,cements also protect grains from further compaction. At the late diagenesis phase, the dissolution of framework grains,especially the dissolution of feldspar and laumontite, is the key to form secondary porosity. They changed the porosity characteristics of sandstone; engendering new benefit storing beds consisted with secondary porosity. Feldspar is dissolved very commonly and severly. They often form dissoluble porosity among grains. Laumontite has deficient dissoluble forms and its dissolution mostly appear along rein, forming irregular size room among grains. This indicates the direction of exp loration and development for oilfield. In a word, the diagenetic study of reservoir property show that mechanical compaction and cementation is two important diagenetic controlling factors, which make oil-bearing physical property bad and porosity down in reservoir.Dissolution, particularly dissolution of laumontite and feldspar is one ofmost important diagenetic factors controlling the physical p roperty of oil2bearing interval and forming better reservoir.
2005, 23(4): 589-595.
Abstract:
Based on a great deal of analytical data of rock andm ineral, discussed. the controlling factors on clastic rock reservoir property in the southwest area of the Qaidam basin are the sedimentary environment, lithological characteristics, buried history, unusual high fluid pressure, salt lake environmentweremain factors deciding reservoir diagenetic evolution and reservoir property. The widely developed sandstones of the shore sand platform, the delta plain and delta front are a basic condition for the development of excellent reservoirs. The content and size of the plastic grains in the reservoir clasts are important factors controlling the reservoir property. Diageneses are a crucial factor of reservoir property, in wh ich consolidation heavily a ffected reservoir property, cementation was on ly an important controlling factor influencing reservoir property in the partial area and the in fluence of dissolutionwasweak. Consolidation of reservoir is controlled by four factors,.i e., lithological haracteristics, strength of d iagenetic cementation, buried h istory, and strata flu id pressure. L ithologywas reflected by the change of the content of plastic rock clasts with grain size and different anti-pressure of reservoirwith different grain size. Development of diagenetic cements weakened consolidation of reservoir, buried history differed reservoir property and h igh fluid pressure effectively restrained consolidation.
Based on a great deal of analytical data of rock andm ineral, discussed. the controlling factors on clastic rock reservoir property in the southwest area of the Qaidam basin are the sedimentary environment, lithological characteristics, buried history, unusual high fluid pressure, salt lake environmentweremain factors deciding reservoir diagenetic evolution and reservoir property. The widely developed sandstones of the shore sand platform, the delta plain and delta front are a basic condition for the development of excellent reservoirs. The content and size of the plastic grains in the reservoir clasts are important factors controlling the reservoir property. Diageneses are a crucial factor of reservoir property, in wh ich consolidation heavily a ffected reservoir property, cementation was on ly an important controlling factor influencing reservoir property in the partial area and the in fluence of dissolutionwasweak. Consolidation of reservoir is controlled by four factors,.i e., lithological haracteristics, strength of d iagenetic cementation, buried h istory, and strata flu id pressure. L ithologywas reflected by the change of the content of plastic rock clasts with grain size and different anti-pressure of reservoirwith different grain size. Development of diagenetic cements weakened consolidation of reservoir, buried history differed reservoir property and h igh fluid pressure effectively restrained consolidation.
2005, 23(4): 604-612.
Abstract:
The question whether transgression happened in Paleogene of BohaiBayBasin has been discussed formore than 20 years, yet itwas not resolved. The scholars insisting on transgression p rovided manymarkers such asmineralogy,lithology, paleoecology and geochemistry, but these makers are not completely the same as normalmarine makers, moreover, the passageway and obviously increased makers of transgression have not been discovered, so "marine flooding" , " tsunami" and " terrestrial facies" appear, these viewpoints have coexisted for a long time. Penman considers that the question can be solved by 4 ways: ①The structural setting of BohaiBay Basin should be studied thoroughly to conclude possibility of the transgression's passageway. ②Reliability of marine makers provided should be newly considered. ③New and exclusive evidences are required. ④Similar sediment trap s in correlative strata abroad are collected to research contrastively
The question whether transgression happened in Paleogene of BohaiBayBasin has been discussed formore than 20 years, yet itwas not resolved. The scholars insisting on transgression p rovided manymarkers such asmineralogy,lithology, paleoecology and geochemistry, but these makers are not completely the same as normalmarine makers, moreover, the passageway and obviously increased makers of transgression have not been discovered, so "marine flooding" , " tsunami" and " terrestrial facies" appear, these viewpoints have coexisted for a long time. Penman considers that the question can be solved by 4 ways: ①The structural setting of BohaiBay Basin should be studied thoroughly to conclude possibility of the transgression's passageway. ②Reliability of marine makers provided should be newly considered. ③New and exclusive evidences are required. ④Similar sediment trap s in correlative strata abroad are collected to research contrastively
2005, 23(4): 620-625.
Abstract:
In the develop ing of abnormal high p ressure gas reservoir, the stress of reservoir rock will be changed by out-flow of the gas, and the rock will have elastop lastic deformation, on the contrary, the deformation influence porosity and permeability of reservoir. Therefore, it has important significance to study the porosity and permeability stress sensibility. This paper presents the reservoir stress sensibility model in theory based on the theory of rock mechanics and brings forward a buckling equation then takes it as a method to evaluate reservoir stress sensibility. This paper put theory and experiment rule together, prove the theory to be true by the experiment of reservoir stress sensibility under the simulating formation situation. The relational exp ressions between the porosity and the permeability of reservoir rock and the reservoir pressure are derived based on the theory of rock mechanics and the theory of seepage flow in porous media. And the sensibility of actual cores to the simulated formation stress is studied in laboratory. The varying laws of the porosity and the permeability of reservoir rock with confined pressure are obtained. The effect of the stress sensibility of reservoir on the development of gas reservoir is also discussed. The deformation of abnormal high pressure reservoir rock decreases the porosity and permeability of reservoir, Changes the seepage flowing ability of the reservoir, and increases the elastic energy of gas-bearing reservoir. Therefore, in the development process of the deformable gas reservoirs, the maintenance of the original pressure inside the gas reservoir is important to getting and maintaining high oytput and lasting the production time of the gas reservoir
In the develop ing of abnormal high p ressure gas reservoir, the stress of reservoir rock will be changed by out-flow of the gas, and the rock will have elastop lastic deformation, on the contrary, the deformation influence porosity and permeability of reservoir. Therefore, it has important significance to study the porosity and permeability stress sensibility. This paper presents the reservoir stress sensibility model in theory based on the theory of rock mechanics and brings forward a buckling equation then takes it as a method to evaluate reservoir stress sensibility. This paper put theory and experiment rule together, prove the theory to be true by the experiment of reservoir stress sensibility under the simulating formation situation. The relational exp ressions between the porosity and the permeability of reservoir rock and the reservoir pressure are derived based on the theory of rock mechanics and the theory of seepage flow in porous media. And the sensibility of actual cores to the simulated formation stress is studied in laboratory. The varying laws of the porosity and the permeability of reservoir rock with confined pressure are obtained. The effect of the stress sensibility of reservoir on the development of gas reservoir is also discussed. The deformation of abnormal high pressure reservoir rock decreases the porosity and permeability of reservoir, Changes the seepage flowing ability of the reservoir, and increases the elastic energy of gas-bearing reservoir. Therefore, in the development process of the deformable gas reservoirs, the maintenance of the original pressure inside the gas reservoir is important to getting and maintaining high oytput and lasting the production time of the gas reservoir
2005, 23(4): 631-638.
Abstract:
Through the comparison of the difference of sequence structure in Dongying depression and Dongpu dep ression, and the analysis of basin volume and topography of Dongying depression and Dongpu dep ression, it is considered that the paleotopography of basin, the ratio of the accommodation added to the total accommodation are nearly related to the sequence structure. During the sedimentation of the third member of Shahejie Formation, the variation rate of accommodation added and created by the third order cycle lake level fluctuation in Denying dep ression are nearly equal to the variation rate of accommodation added and created by the fourth order cycle lake level fluctuation in Dongpu depression. During the sedimentation of third member of Shahejie Formation, the basin volume ofDongying dep ression is very large and the slope is very steep, and the development of sequence is controlled by third order cycle lake level change, so the sequence is very thick. The sandbody thickness in the sequence is also big, and its distribution is very concentrative. During the sedimentation of the third member of Shahejie Formation, the basin volume ofDongpu depression is very small, the topography is very gentle, and the developmemt of sequence is controlled by fourth order cycle lake level change, so the thickness of its sequence is small, and the sandbody thickness in the sequence is small too. Its distribution is very wide and is not stable.
Through the comparison of the difference of sequence structure in Dongying depression and Dongpu dep ression, and the analysis of basin volume and topography of Dongying depression and Dongpu dep ression, it is considered that the paleotopography of basin, the ratio of the accommodation added to the total accommodation are nearly related to the sequence structure. During the sedimentation of the third member of Shahejie Formation, the variation rate of accommodation added and created by the third order cycle lake level fluctuation in Denying dep ression are nearly equal to the variation rate of accommodation added and created by the fourth order cycle lake level fluctuation in Dongpu depression. During the sedimentation of third member of Shahejie Formation, the basin volume ofDongying dep ression is very large and the slope is very steep, and the development of sequence is controlled by third order cycle lake level change, so the sequence is very thick. The sandbody thickness in the sequence is also big, and its distribution is very concentrative. During the sedimentation of the third member of Shahejie Formation, the basin volume ofDongpu depression is very small, the topography is very gentle, and the developmemt of sequence is controlled by fourth order cycle lake level change, so the thickness of its sequence is small, and the sandbody thickness in the sequence is small too. Its distribution is very wide and is not stable.
2005, 23(4): 646-656.
Abstract:
In sp ite of great economic sigificance, very little is known about the lacustrine carbonate rocks both at home and abroad. By the method of app lying sequence stratigraphy, this paper particularly analyses the sequence develop ing model, sequence gradation division and controlling factors on lacustrine carbonate rocks, and put emphasis on parasequence types, distinguishing symbol, forming mechanism and correlation model. As a result, the sequence model of lacustrine carbonate rocks is summed up as steep slope model and gentle slope model. The units of high-2resolution sequence are divided into sequence, tract system, parasequence sets, parasequence and microsequence. The parasequnce types are divided into steep slope type, gentle slope type and deep sag type, also divided into limestone-marl, shore, slipp ing and deep-water evaporate, and the controlling factor of different kinds of parasequence is different. The contrasting models of parasequence are summed up as abruptly changingmodel of steep slope and gradually changing model of gentle slope, parasequence can regularly charge under differentmodels.
In sp ite of great economic sigificance, very little is known about the lacustrine carbonate rocks both at home and abroad. By the method of app lying sequence stratigraphy, this paper particularly analyses the sequence develop ing model, sequence gradation division and controlling factors on lacustrine carbonate rocks, and put emphasis on parasequence types, distinguishing symbol, forming mechanism and correlation model. As a result, the sequence model of lacustrine carbonate rocks is summed up as steep slope model and gentle slope model. The units of high-2resolution sequence are divided into sequence, tract system, parasequence sets, parasequence and microsequence. The parasequnce types are divided into steep slope type, gentle slope type and deep sag type, also divided into limestone-marl, shore, slipp ing and deep-water evaporate, and the controlling factor of different kinds of parasequence is different. The contrasting models of parasequence are summed up as abruptly changingmodel of steep slope and gradually changing model of gentle slope, parasequence can regularly charge under differentmodels.
2005, 23(4): 664-671.
Abstract:
Pucheng oil field is located in the Dongpu dep ress, Henan p rovince. Four scales of sequence cycles are distinguished in study area, including very short term cycle, short term one, medium term one and long term cycle. The heterogeneities study indicates that base level controlled sand distribution and the reservoir heterogeneities. In the rising semi-cycle of short cycle , the p roperty are better at the bottom of the sands and becoming poorer to top, while with a totally differentway in the falling semi-cycle. At the lower position of medium and long term cycles, braided channel are well developed with a widesp read area and good property, while at the high position of the cycles, the braided channel are small and the sand sp read area are limited with poor property. In the rising semi-cycle of long-and medium-cycles, the reservoir become poorer from bottom to top, while it becomes better in the falling semi-cycle.From the bank to lacustrine center, the braided channel becomes weaker and smaller, and the reservoir architecture turns to be mainly of sheet-like sands near the front ofmiddle fan from mainly of channel sands near the middle fan,and finally of lacustrine mud at the lake center. The distribution of OO IP (original oil in place) and the residual oil are also controlled by the baselevel framework. OO IP is high at the low baselevel p lace in the framework, and high while the baselevel is at the high p lace. Sandbody at the low baselevel p lace is alwayswith good p roperty and easy to be dip loid, so it is often p laced on the important p lace in the development, and with large output. Butwith high OO IP, its remaining amount is always in large quantities. Sandbody at the high baselevel is alwayswith poor p roperty and difficult to dep loid, and be put in the secondary place in the development, so its output is little. Butwith low OO IP, its ratio of remaining oil in the reservoir is not important.
Pucheng oil field is located in the Dongpu dep ress, Henan p rovince. Four scales of sequence cycles are distinguished in study area, including very short term cycle, short term one, medium term one and long term cycle. The heterogeneities study indicates that base level controlled sand distribution and the reservoir heterogeneities. In the rising semi-cycle of short cycle , the p roperty are better at the bottom of the sands and becoming poorer to top, while with a totally differentway in the falling semi-cycle. At the lower position of medium and long term cycles, braided channel are well developed with a widesp read area and good property, while at the high position of the cycles, the braided channel are small and the sand sp read area are limited with poor property. In the rising semi-cycle of long-and medium-cycles, the reservoir become poorer from bottom to top, while it becomes better in the falling semi-cycle.From the bank to lacustrine center, the braided channel becomes weaker and smaller, and the reservoir architecture turns to be mainly of sheet-like sands near the front ofmiddle fan from mainly of channel sands near the middle fan,and finally of lacustrine mud at the lake center. The distribution of OO IP (original oil in place) and the residual oil are also controlled by the baselevel framework. OO IP is high at the low baselevel p lace in the framework, and high while the baselevel is at the high p lace. Sandbody at the low baselevel p lace is alwayswith good p roperty and easy to be dip loid, so it is often p laced on the important p lace in the development, and with large output. Butwith high OO IP, its remaining amount is always in large quantities. Sandbody at the high baselevel is alwayswith poor p roperty and difficult to dep loid, and be put in the secondary place in the development, so its output is little. Butwith low OO IP, its ratio of remaining oil in the reservoir is not important.
2005, 23(4): 677-682.
Abstract:
Environmental sedimentology emerged as the times require when human beings are facingwith some key issues of ecological destroy, environment pollution, disaster and global changes and development of environmental science and sedimentology. The development of environmental sedimentology underwent two stages and has been given more and wider attentions since mid-1990's. The concept and study target of environmental sedimentology are defined in this paper. The study content includes not only environmental problem in sedimentology study but also sedimentary one in environmental science study, and 4 main study directions are original environmental sedimentology, contamination environmental sedimentology, entironment sedimentology and global change environmental sedimentology. Environmental sedimentology, studying environment and disaster, must be important for solution of environment contamination, ecological destroy, geologic disaster and global climate change, and are becoming one of important development directions of sedimentology.
Environmental sedimentology emerged as the times require when human beings are facingwith some key issues of ecological destroy, environment pollution, disaster and global changes and development of environmental science and sedimentology. The development of environmental sedimentology underwent two stages and has been given more and wider attentions since mid-1990's. The concept and study target of environmental sedimentology are defined in this paper. The study content includes not only environmental problem in sedimentology study but also sedimentary one in environmental science study, and 4 main study directions are original environmental sedimentology, contamination environmental sedimentology, entironment sedimentology and global change environmental sedimentology. Environmental sedimentology, studying environment and disaster, must be important for solution of environment contamination, ecological destroy, geologic disaster and global climate change, and are becoming one of important development directions of sedimentology.
2005, 23(4): 696-701.
Abstract:
The grain size of samp les from sediment Core 69 in the Eastern South China Sea has been measured.Based on the fractal theory, the fractal dimension (DS) of the grain-size has been calculated. Results show that the grain - size distribution has fractal characteristics. Since late Pleistocene, the DS values of Core 69 in the Eastern South China Sea are 1.72-2.20,with an average of 1.84, Meanwhile, the DS values are different from the same core in the glacial and post glacial stage. The DS value is 1.88 and its variation is frequent during stage 1 of the oxygen isotope stratigraphy. The DS value is 1.81 and its variation is infrequent during stage 2 of the oxygen isotope stratigraphy. That is , the high value ofDS is related to the high paleotemperature but the low value of DS is related to the low paleotemperature. The fractal dimension (DS) of grain-size is considered as an important proxy describing paleoenvironment variations recorded from sediments. R /S analysis on the curves of the fractal dimension of the grain-size , paleotemperature of Uk37 values, δ18O ratios andδ13 C ratios , sea surface temperature in winter and summer, seasonal variability of sea surface temperature between winter and summer, CaCO3 content and SiO2 content yields time series fractal dimensions (DH) of 1.2855, 1.1712, 1.2659, 1.4244, 1.2719, 1.2214, 1.2979, 1.1366, 1.1609 respectively. Although these climatic data were measured in different physical units and different time scales, fractal analysis allows for a mathematical comparison of them. Among them , the time series fractal dimension of seasonal variability of sea surface temperature is close to that of the fractal dimensions of grain-size. These show that the fractal dimensions of grain-size reveal climatic variability. Based on the grain-size fractal dimensions and climatic proxy, four abrupt climate events have been revealed during the Holocene.
The grain size of samp les from sediment Core 69 in the Eastern South China Sea has been measured.Based on the fractal theory, the fractal dimension (DS) of the grain-size has been calculated. Results show that the grain - size distribution has fractal characteristics. Since late Pleistocene, the DS values of Core 69 in the Eastern South China Sea are 1.72-2.20,with an average of 1.84, Meanwhile, the DS values are different from the same core in the glacial and post glacial stage. The DS value is 1.88 and its variation is frequent during stage 1 of the oxygen isotope stratigraphy. The DS value is 1.81 and its variation is infrequent during stage 2 of the oxygen isotope stratigraphy. That is , the high value ofDS is related to the high paleotemperature but the low value of DS is related to the low paleotemperature. The fractal dimension (DS) of grain-size is considered as an important proxy describing paleoenvironment variations recorded from sediments. R /S analysis on the curves of the fractal dimension of the grain-size , paleotemperature of Uk37 values, δ18O ratios andδ13 C ratios , sea surface temperature in winter and summer, seasonal variability of sea surface temperature between winter and summer, CaCO3 content and SiO2 content yields time series fractal dimensions (DH) of 1.2855, 1.1712, 1.2659, 1.4244, 1.2719, 1.2214, 1.2979, 1.1366, 1.1609 respectively. Although these climatic data were measured in different physical units and different time scales, fractal analysis allows for a mathematical comparison of them. Among them , the time series fractal dimension of seasonal variability of sea surface temperature is close to that of the fractal dimensions of grain-size. These show that the fractal dimensions of grain-size reveal climatic variability. Based on the grain-size fractal dimensions and climatic proxy, four abrupt climate events have been revealed during the Holocene.
2005, 23(4): 709-718.
Abstract:
Concept, connotation and evaluation index of high effective gas source kitchen are discussed in the papere. High effective gas source kitchen refers to those that not only has high abundance of organic matter and good quality type of source rockswhich can generate large amount of gas under the geothermal and biology action, but also has a good coincidence with the large scale gas accumulation and pool forming in time and space, therefore, it plays an important role in the formation of large and medium gas pool. High effective gas source kitchen includes two profiles connotation, that are material basis and thermal kinetics process of gas generation. So, the evaluation index are discussed from three features as follows: the first is high intensity of gas generation ( generally larger than 20 ×108m3 /km2 ) , derived from large and medium gas field advocated by Jinxing-Dai; the second is short action time ofmain gas generation period, which is confirmed through gas generation kinetics studies of source rocks of typeⅠ, Ⅱ and Ⅲ and crude oil, and the statistic analysis ofmain gas generation time ofmain gas source rocks in China, the major gas generation period of high effective gas source kitchen is usually less than 40Ma, especially better less than 20Ma. The third is that ending time of major gas generation period is very close to present, which is important to the formation of gas accumulations in the late stage. The contributions of high effective gas source kitchen to the formation of high effective gas pool lies in high rate of gas supply resulting in high effective accumulation and migration of gas, besides little loss of natural gas etc. According to the type of source rocks and kinetics process of gas generation, three groups,including six sub-groups, of high effective gas source kitchens are classified in China.
Concept, connotation and evaluation index of high effective gas source kitchen are discussed in the papere. High effective gas source kitchen refers to those that not only has high abundance of organic matter and good quality type of source rockswhich can generate large amount of gas under the geothermal and biology action, but also has a good coincidence with the large scale gas accumulation and pool forming in time and space, therefore, it plays an important role in the formation of large and medium gas pool. High effective gas source kitchen includes two profiles connotation, that are material basis and thermal kinetics process of gas generation. So, the evaluation index are discussed from three features as follows: the first is high intensity of gas generation ( generally larger than 20 ×108m3 /km2 ) , derived from large and medium gas field advocated by Jinxing-Dai; the second is short action time ofmain gas generation period, which is confirmed through gas generation kinetics studies of source rocks of typeⅠ, Ⅱ and Ⅲ and crude oil, and the statistic analysis ofmain gas generation time ofmain gas source rocks in China, the major gas generation period of high effective gas source kitchen is usually less than 40Ma, especially better less than 20Ma. The third is that ending time of major gas generation period is very close to present, which is important to the formation of gas accumulations in the late stage. The contributions of high effective gas source kitchen to the formation of high effective gas pool lies in high rate of gas supply resulting in high effective accumulation and migration of gas, besides little loss of natural gas etc. According to the type of source rocks and kinetics process of gas generation, three groups,including six sub-groups, of high effective gas source kitchens are classified in China.
2005, 23(4): 734-739.
Abstract:
The asphalt, movable oil and gas shows are quite abundant in the Silurian reservoir in the Tazhong up lift.Hydrocarbon accumulations of the Silurian are characterized bymultip le sources of oil and gas, multip le stages of reservoir formation, multiple types of pools, and multiple occurrences of oil and gas. Vertically, hydrocarbon distributions of the Silurian are controlled by the cap beds. The asphalt and heavy oil of the Silurian are distributed under the red mudstone of the lower member of Tataaiertage Formation, while the movable oils are distributed under the gray mudstone of the second upper sub-member of Kep ingtage Formation. Hydrocarbon accumulations of the Silurian are plainly controlled by structural background, paleo-up lift of inherited development determines the migration directions of hydrocarbon, and hydrocarbon of the Tazhong area basicallymigrated from northwest to southeast. The single sand-stone body formed in tide environment is thin and its scale is small. A series of sandstone bodywere communicated by faults. The Silurian hydrocarbon accumulation of Tazhong area is characterized by no highness in abundance of hydro-carbon accumulation, coincidence of thin layerswith large distributive area, and control of several types of traps.
The asphalt, movable oil and gas shows are quite abundant in the Silurian reservoir in the Tazhong up lift.Hydrocarbon accumulations of the Silurian are characterized bymultip le sources of oil and gas, multip le stages of reservoir formation, multiple types of pools, and multiple occurrences of oil and gas. Vertically, hydrocarbon distributions of the Silurian are controlled by the cap beds. The asphalt and heavy oil of the Silurian are distributed under the red mudstone of the lower member of Tataaiertage Formation, while the movable oils are distributed under the gray mudstone of the second upper sub-member of Kep ingtage Formation. Hydrocarbon accumulations of the Silurian are plainly controlled by structural background, paleo-up lift of inherited development determines the migration directions of hydrocarbon, and hydrocarbon of the Tazhong area basicallymigrated from northwest to southeast. The single sand-stone body formed in tide environment is thin and its scale is small. A series of sandstone bodywere communicated by faults. The Silurian hydrocarbon accumulation of Tazhong area is characterized by no highness in abundance of hydro-carbon accumulation, coincidence of thin layerswith large distributive area, and control of several types of traps.
2005, 23(4): 747-752.
Abstract:
In order to find the difference of the isotopic composition of different organic compounds before and after comp lexation, the autogamy standard sample is performed by à molecular sieve adsorp tion to study the variation of the isotope compositions of n-alkanes, isoalkanes and cyclanes. Although samples were in a hot reflux for a long time at 85℃ in the experiment, and 5à molecular sieve of the adsorbed sample was acidized by hydrofluoric acid, the analyticalmethod was tested to have little influence on carbon isotopic composition of the saturated hydrocarbons before and after complexation. This paper also discussed the method to analyze the individual hydrocarbon isotopic composition from crude oil and coal rock samples. On the basis of the previouswork, the mini-sized Soxhlet extraction setwith a hot reflux device is adopted to enhance the recovery of samples and diminish the loss of light components in the tested samples.
In order to find the difference of the isotopic composition of different organic compounds before and after comp lexation, the autogamy standard sample is performed by à molecular sieve adsorp tion to study the variation of the isotope compositions of n-alkanes, isoalkanes and cyclanes. Although samples were in a hot reflux for a long time at 85℃ in the experiment, and 5à molecular sieve of the adsorbed sample was acidized by hydrofluoric acid, the analyticalmethod was tested to have little influence on carbon isotopic composition of the saturated hydrocarbons before and after complexation. This paper also discussed the method to analyze the individual hydrocarbon isotopic composition from crude oil and coal rock samples. On the basis of the previouswork, the mini-sized Soxhlet extraction setwith a hot reflux device is adopted to enhance the recovery of samples and diminish the loss of light components in the tested samples.
2005, 23(4): 566-573.
Abstract:
Based on the field surveys in 2003 and laboratory analysis of the samples which taken from Jiuduansha Shoal, the sedimentary structure, grain size distribution, assemblages of the clayminerals and the sedimentation rates are studied aswell. The sedimentation rate is determined by 210 Pb method, and the results show that the sedimentation rate of the sup ratidal zone ismuch higher than that in the inter-tidal zone. The intertidal zone of the Jiuduansha shoal are mainly micro-wave and cross bedding, and sediments are dust-color fine sand and coarse silt, this zone is affected by the wave and tidal currents, some special sedimentary structure formed, and boulder clay, ripple and erosion ridge existed, these structure formed under wave processes. Sup ratidal zone are mainly horizontal bedding, and sediments are mainly middle-fine silt, because of dominant species are Phramites australis and Scirpus mariqueter on the supratidal zone, here is the lower energy sedimentary environment, and sedimentary structure are horizontal bedding,and mean size is between 5.0-27.0Φ. Clayminerals are similar between inter-tidal zone and sup ratidal zone, claymin-eralsmainly are illite, montmorillonite, kaolinite and chlorite, but they content on sup ratidal and intertidal zone are different. The sedimentation rate on the intertidal zone are 0.735cm / a, and on the supratidal zone, the sedimentation rate are 3.342 cm / a, higher than that on the intertidal zone.
Based on the field surveys in 2003 and laboratory analysis of the samples which taken from Jiuduansha Shoal, the sedimentary structure, grain size distribution, assemblages of the clayminerals and the sedimentation rates are studied aswell. The sedimentation rate is determined by 210 Pb method, and the results show that the sedimentation rate of the sup ratidal zone ismuch higher than that in the inter-tidal zone. The intertidal zone of the Jiuduansha shoal are mainly micro-wave and cross bedding, and sediments are dust-color fine sand and coarse silt, this zone is affected by the wave and tidal currents, some special sedimentary structure formed, and boulder clay, ripple and erosion ridge existed, these structure formed under wave processes. Sup ratidal zone are mainly horizontal bedding, and sediments are mainly middle-fine silt, because of dominant species are Phramites australis and Scirpus mariqueter on the supratidal zone, here is the lower energy sedimentary environment, and sedimentary structure are horizontal bedding,and mean size is between 5.0-27.0Φ. Clayminerals are similar between inter-tidal zone and sup ratidal zone, claymin-eralsmainly are illite, montmorillonite, kaolinite and chlorite, but they content on sup ratidal and intertidal zone are different. The sedimentation rate on the intertidal zone are 0.735cm / a, and on the supratidal zone, the sedimentation rate are 3.342 cm / a, higher than that on the intertidal zone.
2005, 23(4): 584-588.
Abstract:
Decrease of debris and nonresistance minerals and increase of stable minerals such as quartz and zircon from west to east in the Huanxian region show that sediments of the Chang 6 delta system in this area was from the western regions. Three kinds of seismic facies could be recognized in the Chang 6 beds: the middle or high amp litude value-subparallel-relatively continuous reflection, the foreset reflection and the middle or low amp litude value-parallel reflection, corresponding to the deltaic plain, the deltaic front and the prodelta clay(or interdistributary clay) , respectively. Distribution characteristics of seismic facies suggest that the Huanxian Chang 6 delta system could be divided into two branches in the Hudong region: one extends easternwards from Huanxian to Fanjiachuan, another goes to Hongde in NE direction and meetswith the Anbian delta in Gengwan-Luobuyuan region. The front parts of the eastern Huanxian delta of Well Huan 4-Huan 41 are the ideal places to explore the lens and pinchout eservoirs.
Decrease of debris and nonresistance minerals and increase of stable minerals such as quartz and zircon from west to east in the Huanxian region show that sediments of the Chang 6 delta system in this area was from the western regions. Three kinds of seismic facies could be recognized in the Chang 6 beds: the middle or high amp litude value-subparallel-relatively continuous reflection, the foreset reflection and the middle or low amp litude value-parallel reflection, corresponding to the deltaic plain, the deltaic front and the prodelta clay(or interdistributary clay) , respectively. Distribution characteristics of seismic facies suggest that the Huanxian Chang 6 delta system could be divided into two branches in the Hudong region: one extends easternwards from Huanxian to Fanjiachuan, another goes to Hongde in NE direction and meetswith the Anbian delta in Gengwan-Luobuyuan region. The front parts of the eastern Huanxian delta of Well Huan 4-Huan 41 are the ideal places to explore the lens and pinchout eservoirs.
2005, 23(4): 596-603.
Abstract:
Well Zhong 1 is an important discovery well of oil and gas in Ordovician carbonate rocks located at the Northwestern Tazhong up lift. This paper p resents an updated review of the multi-period and origin of carbonate karstification, which took into account of core observation, palaeo-biological analysis, seismic section and mineralogical and petrological and geochemical of calcite cements and calcites in cleavages and cavities or vuges. The two tectonic-related truncation and sedimentary gap surfaces have been identified, which hare some extent of relationship with carbonate karstification in Caledonian, the fact that calcites in cleavages and cavities or vuges in Ordovician carbonate rockswith rather low contents of elements of Fe,Mn, Sr and Ba, and the normal value ofδ18O ( - 6. 4‰～ - 4. 5‰) andδ13 C( - 1. 4‰～0. 5‰) in comparison with that of the average value of seawater of Ordovicianare believed to occurr as a composite results of syngenesis affected by the mixed fluid at shallow buried condition and later meteoric invasion;while the calcite cements developed in Bachu,Donghe formations and Silurian sandstoneswith the ramiform structures of infiltration metasomatism related with magmatic hydrothermalism and the low value ofδ18O ( - 10. 5‰～ - 16. 1‰)andδ13 C ( - 1. 5‰～ - 9. 6‰) indicated it had undergone an intense hydrothermal buried aswell as Hercynian subaerialmeteoric diagenetic change; the low data of strontium isotop ic compositions (87 Sr /87 Sr less than 0. 7100) of filling calcites in cleavages and cavities or vuges in Kalashayi formation and Silurian and Ordovician system of Well Zhong-1 are exp lained as the results of the little effect of continental clastic sediment due to a rather short period of exposure; moreover, itmay be concluded that no similar geological condition or background of a large scale of strong ep igenic karstification exists in the Northwestern Tazhong just as occurred in the Tahei oilfield ( Shaya up lift) with Palocave systemswidely developed in forms of multiple passage caves in the Middle-Upper Ordovician carbonate
Well Zhong 1 is an important discovery well of oil and gas in Ordovician carbonate rocks located at the Northwestern Tazhong up lift. This paper p resents an updated review of the multi-period and origin of carbonate karstification, which took into account of core observation, palaeo-biological analysis, seismic section and mineralogical and petrological and geochemical of calcite cements and calcites in cleavages and cavities or vuges. The two tectonic-related truncation and sedimentary gap surfaces have been identified, which hare some extent of relationship with carbonate karstification in Caledonian, the fact that calcites in cleavages and cavities or vuges in Ordovician carbonate rockswith rather low contents of elements of Fe,Mn, Sr and Ba, and the normal value ofδ18O ( - 6. 4‰～ - 4. 5‰) andδ13 C( - 1. 4‰～0. 5‰) in comparison with that of the average value of seawater of Ordovicianare believed to occurr as a composite results of syngenesis affected by the mixed fluid at shallow buried condition and later meteoric invasion;while the calcite cements developed in Bachu,Donghe formations and Silurian sandstoneswith the ramiform structures of infiltration metasomatism related with magmatic hydrothermalism and the low value ofδ18O ( - 10. 5‰～ - 16. 1‰)andδ13 C ( - 1. 5‰～ - 9. 6‰) indicated it had undergone an intense hydrothermal buried aswell as Hercynian subaerialmeteoric diagenetic change; the low data of strontium isotop ic compositions (87 Sr /87 Sr less than 0. 7100) of filling calcites in cleavages and cavities or vuges in Kalashayi formation and Silurian and Ordovician system of Well Zhong-1 are exp lained as the results of the little effect of continental clastic sediment due to a rather short period of exposure; moreover, itmay be concluded that no similar geological condition or background of a large scale of strong ep igenic karstification exists in the Northwestern Tazhong just as occurred in the Tahei oilfield ( Shaya up lift) with Palocave systemswidely developed in forms of multiple passage caves in the Middle-Upper Ordovician carbonate
2005, 23(4): 613-619.
Abstract:
Based on analysis of geological, seismic and experimental analysis in Gaoyou dep ression, the article analyses the originalmechanism of secondary porosity. The result indicates that the analysis of secondary porositywith well logging is available. The methods include: 1) the original stage of secondary porosity can be distinguished by sonic data; 2) The secondary porosity can be collected by density porosity and neutron porosity subtracting sonic porosity. The article analyses the qualification of the method; 3) The decomposition of organic matter may bring organic acid that can p roduce a lot of secondary porosity. The organic matter in source rocks can be measured by sonic and resistivity data; 4) the abnormal high pressure can be obtained by sonic data from which the formation and p reservation of secondary porosity are analyzed. Tha above methods are tested in Gaoyou depression
Based on analysis of geological, seismic and experimental analysis in Gaoyou dep ression, the article analyses the originalmechanism of secondary porosity. The result indicates that the analysis of secondary porositywith well logging is available. The methods include: 1) the original stage of secondary porosity can be distinguished by sonic data; 2) The secondary porosity can be collected by density porosity and neutron porosity subtracting sonic porosity. The article analyses the qualification of the method; 3) The decomposition of organic matter may bring organic acid that can p roduce a lot of secondary porosity. The organic matter in source rocks can be measured by sonic and resistivity data; 4) the abnormal high pressure can be obtained by sonic data from which the formation and p reservation of secondary porosity are analyzed. Tha above methods are tested in Gaoyou depression
2005, 23(4): 626-630.
Abstract:
By using biological method, microorganisms in the Shihong tan u ranium deposit were iso lated and identified for the first time at home. Results showed that the distribution of themainm icrobe groups changed w ith the level of oxidation of the rock samples. A great deal of ae robic and anae robic bacteriaw ere ve ry active in the in termediate zone of oxidation and reduction, while in the o re zone, the speciesw asmonotonous, mainly anaerobic sulfate-reducing bacteria.In addition, the func tion ofm icroorgan isms during the formation of uranium deposit and the effect on the meta llogenic env ironment were also discussed.
By using biological method, microorganisms in the Shihong tan u ranium deposit were iso lated and identified for the first time at home. Results showed that the distribution of themainm icrobe groups changed w ith the level of oxidation of the rock samples. A great deal of ae robic and anae robic bacteriaw ere ve ry active in the in termediate zone of oxidation and reduction, while in the o re zone, the speciesw asmonotonous, mainly anaerobic sulfate-reducing bacteria.In addition, the func tion ofm icroorgan isms during the formation of uranium deposit and the effect on the meta llogenic env ironment were also discussed.
2005, 23(4): 639-645.
Abstract:
The well logging data contains plenty of geological information and is one of geological data obtained by now with the highest resolution and best continuity. The time-frequency analysis transforms the one-dimension well signals into the two-dimension domain of time-frequency, which makes the collection and distribution of its inner energy clearly revealed. Then the geological information such as the cycle of stratigraphy can be obtained utilizing the otherness of logging signals in the axis of time. According to continuouswavelet transform, the high quality time-frequency analysis is performed. With the characteristics of wavelet transform such as multi-scale, multi-resolution the sequence and parasequence are clarified. Synchronously with wavelet analysis searching the corresponding relation between various system tracts and the features of time-frequency, analyzing the sedimentary features of sequence and inner elaborate structure, the geological models of wavelet transform spectrum about TST, HST and RST are built up,which can realize the clarification of system tracts quickly and conveniently. At last, based on the wavelet transform of logging signals, the stratigraphic sequence correlation and analysis of the coalbearing strata of Permo-Carboniferous in Luxi and J iyang area have been done. The stratigraphic sequence framework of main coal-bearing strata formed in Neopaleozoic in Shandong area is established
The well logging data contains plenty of geological information and is one of geological data obtained by now with the highest resolution and best continuity. The time-frequency analysis transforms the one-dimension well signals into the two-dimension domain of time-frequency, which makes the collection and distribution of its inner energy clearly revealed. Then the geological information such as the cycle of stratigraphy can be obtained utilizing the otherness of logging signals in the axis of time. According to continuouswavelet transform, the high quality time-frequency analysis is performed. With the characteristics of wavelet transform such as multi-scale, multi-resolution the sequence and parasequence are clarified. Synchronously with wavelet analysis searching the corresponding relation between various system tracts and the features of time-frequency, analyzing the sedimentary features of sequence and inner elaborate structure, the geological models of wavelet transform spectrum about TST, HST and RST are built up,which can realize the clarification of system tracts quickly and conveniently. At last, based on the wavelet transform of logging signals, the stratigraphic sequence correlation and analysis of the coalbearing strata of Permo-Carboniferous in Luxi and J iyang area have been done. The stratigraphic sequence framework of main coal-bearing strata formed in Neopaleozoic in Shandong area is established
2005, 23(4): 657-663.
Abstract:
Based on the geological and geophysical data, this paper analyses characteristics and controls of high-frequency sequences of Lower Cretaceous Series in Wuerxun Depression. High-frequency sequences occur along the strike direction of the depression in third-order composite sequence 7 and 8, and show downlap of reflections onto the composite condensed section. Most of high-frequency sequences belong in type I, but the scopes of unconformities are very limited. There are three system tracts and parasequences stacking patterns from aggradation-progradation-retrogra-dation-progradation in high-frequency sequences. Sixteen high-frequency sequences are identified in this area. The average period and the sediment velocity of which is about 0.22～0.28 Ma and 0.57～0.76 m /kyr, respectively.This study suggests that high-frequency sequences have the greatest chance of forming under the conditions of low tectonic subsidence and high sediment supp ly during third-order base-level relative stabilizing and descending periods,and that the marginalmorphology of basin controls the geometry of high-frequency sequences
Based on the geological and geophysical data, this paper analyses characteristics and controls of high-frequency sequences of Lower Cretaceous Series in Wuerxun Depression. High-frequency sequences occur along the strike direction of the depression in third-order composite sequence 7 and 8, and show downlap of reflections onto the composite condensed section. Most of high-frequency sequences belong in type I, but the scopes of unconformities are very limited. There are three system tracts and parasequences stacking patterns from aggradation-progradation-retrogra-dation-progradation in high-frequency sequences. Sixteen high-frequency sequences are identified in this area. The average period and the sediment velocity of which is about 0.22～0.28 Ma and 0.57～0.76 m /kyr, respectively.This study suggests that high-frequency sequences have the greatest chance of forming under the conditions of low tectonic subsidence and high sediment supp ly during third-order base-level relative stabilizing and descending periods,and that the marginalmorphology of basin controls the geometry of high-frequency sequences
2005, 23(4): 672-676.
Abstract:
Resent years, high-frequence cycle charged by Milankovitch cycle as an importantmanner for stratigraphic classification, conforming age, and discussing basin evolution, is tried to used to continental rift-subsidence basin.But continental rift-subsidence basin is structure basin, fault structure theory, a lot of sedimentation and structure phenomenon which are on or under the surface show us that there is probably influence which short-period ep isodic rifting control the sedimentation of high-frequence cycle. The influence is need to eliminate before using Milankovitch cycle in continental rift-subsidence basin. In recent period, the primary research maybe be limited some sides. The first is to find out sedimentary response of short-period ep isodic settlementwithin deposit of high-frequence cycle; the second is to research sedimentary feature, lateral change and contrast of tectonic high-frequence cycle with different sedimentary location and source distance; the third is to study accurate index and contrast of paleoclimate and paleo- water depth in lacustrine high-frequence cycle. These sides are very important before to pick-up Milankovitch sedimentary cycle accurately.
Resent years, high-frequence cycle charged by Milankovitch cycle as an importantmanner for stratigraphic classification, conforming age, and discussing basin evolution, is tried to used to continental rift-subsidence basin.But continental rift-subsidence basin is structure basin, fault structure theory, a lot of sedimentation and structure phenomenon which are on or under the surface show us that there is probably influence which short-period ep isodic rifting control the sedimentation of high-frequence cycle. The influence is need to eliminate before using Milankovitch cycle in continental rift-subsidence basin. In recent period, the primary research maybe be limited some sides. The first is to find out sedimentary response of short-period ep isodic settlementwithin deposit of high-frequence cycle; the second is to research sedimentary feature, lateral change and contrast of tectonic high-frequence cycle with different sedimentary location and source distance; the third is to study accurate index and contrast of paleoclimate and paleo- water depth in lacustrine high-frequence cycle. These sides are very important before to pick-up Milankovitch sedimentary cycle accurately.
2005, 23(4): 690-695.
Abstract:
Chinese loess, the Quaternary aeolian deposits in another term, covers a nationwide area from the east China coast to the northwest inland desert. Studies show that the origin of clayminerals bears relation to the formation and evolution of loess. To understand and exp lain the differences of loess under different climatic conditions, this paper constructs a NWW-SEE cross-section which consists of five rep resentative loess profiles (sites) in central Gansu (Lanzhou) , northern Shaanxi (Luochuan) , central Shaanxi (Baoji) , northern Henan (Jiyuan) and the lower reaches of the Yangtze river ( Zhenjiang) , respectively. Samples taken from Lanzhou loess and Zhenjiang loess, and also from the present dust-storm deposits were analyzed by using X-ray diffraction system. Preliminary conclusions can been drawn as follows: In both loess and the dust-storm deposits, a number of clay minerals were examined through X-ray diffraction. They are illite, chlorite, vermiculite, kaolinite, smectite group and mixed layerminerals. In Lanzhou loess illite and chlorite are dominant, but in Zhenjiang loess the clay mineral assemblage is illite-vermiculite type. Comparing with other loess profiles ranging between Lanzhou and Zhenjiang, it is found that the claymineral assemblage changes gradually from northwest to southeast. Along with the latitude getting lower, the content of chlorite decreases, while the content of vermiculite increases. This imp lies that clay mineral assemblage must have close reference to the climate.The dry and cold climate favors for the formation of chlorite, the warm and humid climate benefits for vermiculite.Furthermore, the content of vermiculite and its interstratified minerals can also be a proxy ofweathering intensity. To conclude, the claymineral assemblage of loess can be used to trace the source ofmothermaterial and understand the post-depositional climate conditions
Chinese loess, the Quaternary aeolian deposits in another term, covers a nationwide area from the east China coast to the northwest inland desert. Studies show that the origin of clayminerals bears relation to the formation and evolution of loess. To understand and exp lain the differences of loess under different climatic conditions, this paper constructs a NWW-SEE cross-section which consists of five rep resentative loess profiles (sites) in central Gansu (Lanzhou) , northern Shaanxi (Luochuan) , central Shaanxi (Baoji) , northern Henan (Jiyuan) and the lower reaches of the Yangtze river ( Zhenjiang) , respectively. Samples taken from Lanzhou loess and Zhenjiang loess, and also from the present dust-storm deposits were analyzed by using X-ray diffraction system. Preliminary conclusions can been drawn as follows: In both loess and the dust-storm deposits, a number of clay minerals were examined through X-ray diffraction. They are illite, chlorite, vermiculite, kaolinite, smectite group and mixed layerminerals. In Lanzhou loess illite and chlorite are dominant, but in Zhenjiang loess the clay mineral assemblage is illite-vermiculite type. Comparing with other loess profiles ranging between Lanzhou and Zhenjiang, it is found that the claymineral assemblage changes gradually from northwest to southeast. Along with the latitude getting lower, the content of chlorite decreases, while the content of vermiculite increases. This imp lies that clay mineral assemblage must have close reference to the climate.The dry and cold climate favors for the formation of chlorite, the warm and humid climate benefits for vermiculite.Furthermore, the content of vermiculite and its interstratified minerals can also be a proxy ofweathering intensity. To conclude, the claymineral assemblage of loess can be used to trace the source ofmothermaterial and understand the post-depositional climate conditions
2005, 23(4): 702-708.
Abstract:
Chinese loess-paleosol sequence has provided the most detailed terrestrial records of climate changes in Quaternary. The aeolian sand and dust has been taken as an important proxy of expansion and contraction of the desert during geological period. The signals of the desert evolution were well p reserved in the aeolian deposits on the margin of the desert, which are effective to reconstruct the desert expansion and contraction. According to the dominantwind direction, generally NW-SE, we systematically studies 24 sections ofMalan loess in the west of Chinese Loess Plateau during the Last Glacial period. Detailed granular analyses show the properties of temporal and spatial of theMalan loess, and reducing of the percentage of the sand from northwest to southeast. Our study indicates that the proxies such asD [ 4, 3 ] , the fraction > 40μm (%) , the fraction > 63μm (% ) , and theMode are more sensitive than any other proxy. A new linear correlation model of sand percentage and distance are established, which shows different pattern to the east of the Chinese Loess Plateau.
Chinese loess-paleosol sequence has provided the most detailed terrestrial records of climate changes in Quaternary. The aeolian sand and dust has been taken as an important proxy of expansion and contraction of the desert during geological period. The signals of the desert evolution were well p reserved in the aeolian deposits on the margin of the desert, which are effective to reconstruct the desert expansion and contraction. According to the dominantwind direction, generally NW-SE, we systematically studies 24 sections ofMalan loess in the west of Chinese Loess Plateau during the Last Glacial period. Detailed granular analyses show the properties of temporal and spatial of theMalan loess, and reducing of the percentage of the sand from northwest to southeast. Our study indicates that the proxies such asD [ 4, 3 ] , the fraction > 40μm (%) , the fraction > 63μm (% ) , and theMode are more sensitive than any other proxy. A new linear correlation model of sand percentage and distance are established, which shows different pattern to the east of the Chinese Loess Plateau.
2005, 23(4): 719-725.
Abstract:
The oil recharge event defined by the K2Ar dating of the authigenic illite proved to be episodic indicated by the following two factors. First, the recharge time is clustered in the following four periods, 60Ma, 58Ma, 45Ma、and 45-32Ma. Second, the first 3 stages of oil recharge are widely sp read in the whole west slope zone of the Songliao basin. The oil-recharge event happened in two different places far away from each other (35km linearly) linked by the hydrocarbon migration pathway systems. According to the oil recharge time, the minimum hydrocarbon migration velocity is estimated to be greater than 4. 5km /Ma, which cannot be exp lained bywater dynamics and density difference between formation water and hydrocarbon. The velocity driven by the late two factors are estimated to be less than 2km /Ma, far less than the actual hydrocarbon migration velocity. Thismeans that there exist other factors that driven the hydrocarbon to migrate westward. It is suggested here that the hydrocarbon migration and concentration wasmainly controlled by the tectonic comp ression during the Paleogene. First, tectonic comp ression has p romoted the initialmigration of the hydrocarbon by strengthening the overp ressure generated in the mudrock and driven the hydrocarbon out of the microfissures generated during the basin extension. Second, the ep isodic movement of the tectonic comp ression will result in the ep isodic movement of the formation fluid, which will drive the hydrocarbon migration and concentration ep isodically. This is whatwe found in the west slope zone of the Songliao basin. Finally, tectonic compression in an E-W direction has generated many anticlines in the basin, which is the most important trap in the Songliao basin.Tectonic compression has changed the characters of the faults that striking NNE,NE,which resulted in the forming of many fault-sealed oil reservoirs in the study area.
The oil recharge event defined by the K2Ar dating of the authigenic illite proved to be episodic indicated by the following two factors. First, the recharge time is clustered in the following four periods, 60Ma, 58Ma, 45Ma、and 45-32Ma. Second, the first 3 stages of oil recharge are widely sp read in the whole west slope zone of the Songliao basin. The oil-recharge event happened in two different places far away from each other (35km linearly) linked by the hydrocarbon migration pathway systems. According to the oil recharge time, the minimum hydrocarbon migration velocity is estimated to be greater than 4. 5km /Ma, which cannot be exp lained bywater dynamics and density difference between formation water and hydrocarbon. The velocity driven by the late two factors are estimated to be less than 2km /Ma, far less than the actual hydrocarbon migration velocity. Thismeans that there exist other factors that driven the hydrocarbon to migrate westward. It is suggested here that the hydrocarbon migration and concentration wasmainly controlled by the tectonic comp ression during the Paleogene. First, tectonic comp ression has p romoted the initialmigration of the hydrocarbon by strengthening the overp ressure generated in the mudrock and driven the hydrocarbon out of the microfissures generated during the basin extension. Second, the ep isodic movement of the tectonic comp ression will result in the ep isodic movement of the formation fluid, which will drive the hydrocarbon migration and concentration ep isodically. This is whatwe found in the west slope zone of the Songliao basin. Finally, tectonic compression in an E-W direction has generated many anticlines in the basin, which is the most important trap in the Songliao basin.Tectonic compression has changed the characters of the faults that striking NNE,NE,which resulted in the forming of many fault-sealed oil reservoirs in the study area.
2005, 23(4): 740-746.
Abstract:
Rare earth element (REE) abundance of Ordovician, Triassic and Jurassic mudstone in the Tabei up lift,Tarim basin has been analysed. All the mudstones show the characteristics of high LREE content, uniform HREE and negative Eu anomaly. The ratios such as ΣLREE /ΣHREE, LaN /YbN , (La /Yb) UCC , Eu /Eu3 and Ce /Ce3, however, are obviously different among them, and thus reflecting the different sources and environments when they were formed. The mudstones formed in different ages display variable degrees of REE differentiation and negative Eu anomaly. The Ordovician mudstones have high ratios of ΣLREE /ΣHREE and LaN /YbN (12.1 and 19.8) and significant negative Eu anomaly ( Eu /Eu3= 0.59). The Triassic mudstones, however, show unusual low ratios of ΣLREE /ΣHREE and LaN /YbN (5.9 and 7.7) and small negative Eu anomaly ( Eu /Eu3= 0.78). The Jurassic mudstones are similar to the Ordovician samp les except less negative Eu anomaly ( Eu /Eu 3= 0.72). Similarly, UCC - normalizedm REE patterns of samples also show significant changeswithin different ages. In general, the Ordovician and Jurassic mudstones show slight enrichment of LREE relative to UCC, whereas the Triassic ones show strong LREE depletion.These characteristics indicate that the Ordovician mudstoneswere formed under a relatively stable sedimentary environ- ment. The sources should be the upper continental crust with high maturity. During Permian - Triassic times, the north of the Tarim basin was tectonic and volcanic, which provide abundant volcanic materials. It stepped into the stable sinking period in Jurssic. The REE difference amongmudstones has indicating significance for studying the formation and evolution of the Tarim basin and surrounding orogenic belt
Rare earth element (REE) abundance of Ordovician, Triassic and Jurassic mudstone in the Tabei up lift,Tarim basin has been analysed. All the mudstones show the characteristics of high LREE content, uniform HREE and negative Eu anomaly. The ratios such as ΣLREE /ΣHREE, LaN /YbN , (La /Yb) UCC , Eu /Eu3 and Ce /Ce3, however, are obviously different among them, and thus reflecting the different sources and environments when they were formed. The mudstones formed in different ages display variable degrees of REE differentiation and negative Eu anomaly. The Ordovician mudstones have high ratios of ΣLREE /ΣHREE and LaN /YbN (12.1 and 19.8) and significant negative Eu anomaly ( Eu /Eu3= 0.59). The Triassic mudstones, however, show unusual low ratios of ΣLREE /ΣHREE and LaN /YbN (5.9 and 7.7) and small negative Eu anomaly ( Eu /Eu3= 0.78). The Jurassic mudstones are similar to the Ordovician samp les except less negative Eu anomaly ( Eu /Eu 3= 0.72). Similarly, UCC - normalizedm REE patterns of samples also show significant changeswithin different ages. In general, the Ordovician and Jurassic mudstones show slight enrichment of LREE relative to UCC, whereas the Triassic ones show strong LREE depletion.These characteristics indicate that the Ordovician mudstoneswere formed under a relatively stable sedimentary environ- ment. The sources should be the upper continental crust with high maturity. During Permian - Triassic times, the north of the Tarim basin was tectonic and volcanic, which provide abundant volcanic materials. It stepped into the stable sinking period in Jurssic. The REE difference amongmudstones has indicating significance for studying the formation and evolution of the Tarim basin and surrounding orogenic belt
