2001 Vol. 19, No. 2
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Display Method:
2001, 19(2): 169-176.
Abstract:
The polymetallic nodule deposit is a kind of submarine mineral resources.Except for its two dimension distrihution, heing covered by the thick overlying waters, basic theory and method of submarine mineral resources evaluation, as well as its procedure of exploration and exploitation are similar to those of the land mineral resources.However it should be thought to select mathematical function and to construct theoretical model based on plymetallic nodule deposit. The foundational theory and method of polymetallic nodule resources evaluation has been briefly introduced.The principle and the advantage of the resources evaluation methods such as multivariate statistical method(including cluster analysis,factor analysis and trend surface analysis),geostatistics(Kriging)and neural network analysis(back-propogation method) are respectively described in detail.The application examples and calculation results are given out in the forms of tables or figures according to the theory and method.The software of"Evaluation System of Polvmetallic Nodule Resources"has been developed by authors for realizing the computerized mobile analysis of cutoff indexes( grade and abundance)-resource amounts-deposit area and its program structure is shown in the paper.
The polymetallic nodule deposit is a kind of submarine mineral resources.Except for its two dimension distrihution, heing covered by the thick overlying waters, basic theory and method of submarine mineral resources evaluation, as well as its procedure of exploration and exploitation are similar to those of the land mineral resources.However it should be thought to select mathematical function and to construct theoretical model based on plymetallic nodule deposit. The foundational theory and method of polymetallic nodule resources evaluation has been briefly introduced.The principle and the advantage of the resources evaluation methods such as multivariate statistical method(including cluster analysis,factor analysis and trend surface analysis),geostatistics(Kriging)and neural network analysis(back-propogation method) are respectively described in detail.The application examples and calculation results are given out in the forms of tables or figures according to the theory and method.The software of"Evaluation System of Polvmetallic Nodule Resources"has been developed by authors for realizing the computerized mobile analysis of cutoff indexes( grade and abundance)-resource amounts-deposit area and its program structure is shown in the paper.
2001, 19(2): 182-185.
Abstract:
The Tertiary‘Rcd Clay' deposit in Chincsc Loess Plateau has attracted considerable research interests in recent wars as it may provide the information of palcoclimatc in Northern China. The evidences from sedimentology, geochemistry, gcomorphology and field survcv indicate that the‘Rcd Clay' may he of colain origin the same as the overlying loess.Howcver, it is controversial on which wind svstcm transported the deposit. In this paper the grain size of hulk samples and chcmicallv isolated quartzes from‘Rcd Clay' of the late Pliocene are investigated.The samples were taken from six locations spanning 550 km from the north to the south in the Loess Plateau.The results show that the mean sizes of both hulk and quartz samples decease southwards so does the coarse-faction content(>42μm % and>30μm%).Moreover the‘Rcd Clay' samples include a great deal of particles more than 20μm,which was proved to he transported onlv by suhacrial wind.These therefore suggest that it is mainly the northern suhacrial wind rather than the supernal wind that transported the dust of‘Rcd Clay'.The spatial distribution of‘Rcd Clav' is comparable to that of overlying colian locss} which proves the‘Rcd Clay' may he formed in a little hit dry environment but it is not so dry as to the environment the loess deposited.
The Tertiary‘Rcd Clay' deposit in Chincsc Loess Plateau has attracted considerable research interests in recent wars as it may provide the information of palcoclimatc in Northern China. The evidences from sedimentology, geochemistry, gcomorphology and field survcv indicate that the‘Rcd Clay' may he of colain origin the same as the overlying loess.Howcver, it is controversial on which wind svstcm transported the deposit. In this paper the grain size of hulk samples and chcmicallv isolated quartzes from‘Rcd Clay' of the late Pliocene are investigated.The samples were taken from six locations spanning 550 km from the north to the south in the Loess Plateau.The results show that the mean sizes of both hulk and quartz samples decease southwards so does the coarse-faction content(>42μm % and>30μm%).Moreover the‘Rcd Clay' samples include a great deal of particles more than 20μm,which was proved to he transported onlv by suhacrial wind.These therefore suggest that it is mainly the northern suhacrial wind rather than the supernal wind that transported the dust of‘Rcd Clay'.The spatial distribution of‘Rcd Clav' is comparable to that of overlying colian locss} which proves the‘Rcd Clay' may he formed in a little hit dry environment but it is not so dry as to the environment the loess deposited.
2001, 19(2): 192-198.
Abstract:
The Bav of Bengal is of a deep-sea environment.Samples of 4 cores(MD77181,MD77183,MD77190 and MD81349 )from this area were studied in detail.As a result it is found that the carbonate content in this area was high during the intcrglacial interval and low during the glacial interval, and thus, shows the dilution cvclcs of“Atlantic Type. The analysis of the carbonate dissolution of the 4 cores mentioned above shows the dissolution was intense in this area. Core MD77190 is nearly 3800m in depth.The preservation situation of planktonic foraminifcrs indicates a distinct crolion of the shell.The foraminifcral dissolution index( FDX) curve shows that in core MD77190 located place the dissolution extent is high.FDX are mostly above 5.The dissolution extent is the lowest in oxygen isotope stage 2.The dissolution extent is high in oxygen isotope stages 1,5 and the early stage 4.Core MD81349 is located in the 90y Sca Mountain and about 2 500 m in depth.The FDX curve shows that in the MD81349 core located place the dissolution extent is relatively low and no big change. The mass accumulation rates(MAR) of planktonic foraminifcrs and CaC03 change are entirely in accordance with each other in core MD77190, both reach their highest in oxygen isotope stage 2.The MARs of both planktonic foraminifcrs and CaC03 in oxygen isotope stage 5 are lower than that in oxygen isotope stages 1,2 and 3,and reach their lowest in oxygen isotope stage 4.The MAR curves of CaC03 and coarse fractiom>160μm from cores MD77181 and MD77183 show that the MARs of CaC03 and coarse fraction are both the highest in oxygen isotope stage 2, the lowest in oxygen isotope stage 4 and 5.This indicates a low dissolution extent or a high productivity or both in oxygen isotope stage 2 and a high dissolution extent in oxygen isotope stages 4 and 5 in the studied area. To sum up, the dissolution in the studied area is relatively weak in oxygen isotope stage 2, but became intensified in oxygen isotope stages 4 and 5. In the studied area the accumulated amount of CaC03 is low and the dissolution extent is high in oxygen isotope stages 4 and 5.The dissolution extent is low, and the accumulate amounts of CaC03 and planktonic foraminifcrs are both relatively high in oxygen isotope stage 2.This accords with the fact that CaC03 dissolution extent reaches its peak in the late oxygen isotope stage 5 through 4 in Indian and Pacific oceans.The fact that the CaC03 cycle in the Bav of Bengal was expressed as of the Atlantic type dilution cycle due to the dilution effect of terrestrial material is actually the result of the combined effects of the Atlantic type dilution and the Pacific type dissolution.
The Bav of Bengal is of a deep-sea environment.Samples of 4 cores(MD77181,MD77183,MD77190 and MD81349 )from this area were studied in detail.As a result it is found that the carbonate content in this area was high during the intcrglacial interval and low during the glacial interval, and thus, shows the dilution cvclcs of“Atlantic Type. The analysis of the carbonate dissolution of the 4 cores mentioned above shows the dissolution was intense in this area. Core MD77190 is nearly 3800m in depth.The preservation situation of planktonic foraminifcrs indicates a distinct crolion of the shell.The foraminifcral dissolution index( FDX) curve shows that in core MD77190 located place the dissolution extent is high.FDX are mostly above 5.The dissolution extent is the lowest in oxygen isotope stage 2.The dissolution extent is high in oxygen isotope stages 1,5 and the early stage 4.Core MD81349 is located in the 90y Sca Mountain and about 2 500 m in depth.The FDX curve shows that in the MD81349 core located place the dissolution extent is relatively low and no big change. The mass accumulation rates(MAR) of planktonic foraminifcrs and CaC03 change are entirely in accordance with each other in core MD77190, both reach their highest in oxygen isotope stage 2.The MARs of both planktonic foraminifcrs and CaC03 in oxygen isotope stage 5 are lower than that in oxygen isotope stages 1,2 and 3,and reach their lowest in oxygen isotope stage 4.The MAR curves of CaC03 and coarse fractiom>160μm from cores MD77181 and MD77183 show that the MARs of CaC03 and coarse fraction are both the highest in oxygen isotope stage 2, the lowest in oxygen isotope stage 4 and 5.This indicates a low dissolution extent or a high productivity or both in oxygen isotope stage 2 and a high dissolution extent in oxygen isotope stages 4 and 5 in the studied area. To sum up, the dissolution in the studied area is relatively weak in oxygen isotope stage 2, but became intensified in oxygen isotope stages 4 and 5. In the studied area the accumulated amount of CaC03 is low and the dissolution extent is high in oxygen isotope stages 4 and 5.The dissolution extent is low, and the accumulate amounts of CaC03 and planktonic foraminifcrs are both relatively high in oxygen isotope stage 2.This accords with the fact that CaC03 dissolution extent reaches its peak in the late oxygen isotope stage 5 through 4 in Indian and Pacific oceans.The fact that the CaC03 cycle in the Bav of Bengal was expressed as of the Atlantic type dilution cycle due to the dilution effect of terrestrial material is actually the result of the combined effects of the Atlantic type dilution and the Pacific type dissolution.
2001, 19(2): 207-213.
Abstract:
Most of lacustrinc carbonate rocks of Mesozoic-Cenozoic era consist of limestone mainly.However in some lake basins such as the Nan-Xiang hasi, it mainly deposited dolomite with a net accumulative thickness of 900 meters.Whilt the entire dolomite sedimentarv, sequence can he more than 2100 meters which formed a set of good oil-generation source rocks, and a small and rich Nan-Yang oil field iashccn found there.This paper descrihes, taking the Bivang depression as an example the genetic conditions of the thick lacustrinc dolomite of stable sedimentary fac ics: 1.A hot palcoclimatc which is semi-wet to wet;2.A water body of carbonate type which contains plenty of K+,Na+,HC03- and C03-but less. Ca2+ and S042- ions; 3.A medium of palcowatcr with a pH value of ≥ 9, and a low water salinity of generally 3‰-10‰, which belongs to the range of slight salty<0.5‰-5‰>to semi-salty<5‰-30‰>,or even higher salinity although the deposition of dolomite may not he so strict on the palcosalinitv: 4.A stable shallow lake and deep lake condition of a broad lake basin: 5.The biological and chemical effect may he strong so that the contents of C032-and HC03-,as well as the pH value will he increased while the content of 042- decreased.
Most of lacustrinc carbonate rocks of Mesozoic-Cenozoic era consist of limestone mainly.However in some lake basins such as the Nan-Xiang hasi, it mainly deposited dolomite with a net accumulative thickness of 900 meters.Whilt the entire dolomite sedimentarv, sequence can he more than 2100 meters which formed a set of good oil-generation source rocks, and a small and rich Nan-Yang oil field iashccn found there.This paper descrihes, taking the Bivang depression as an example the genetic conditions of the thick lacustrinc dolomite of stable sedimentary fac ics: 1.A hot palcoclimatc which is semi-wet to wet;2.A water body of carbonate type which contains plenty of K+,Na+,HC03- and C03-but less. Ca2+ and S042- ions; 3.A medium of palcowatcr with a pH value of ≥ 9, and a low water salinity of generally 3‰-10‰, which belongs to the range of slight salty<0.5‰-5‰>to semi-salty<5‰-30‰>,or even higher salinity although the deposition of dolomite may not he so strict on the palcosalinitv: 4.A stable shallow lake and deep lake condition of a broad lake basin: 5.The biological and chemical effect may he strong so that the contents of C032-and HC03-,as well as the pH value will he increased while the content of 042- decreased.
2001, 19(2): 219-223.
Abstract:
The tectonic movement of Jivang Suh-basin in Earlv TerLiarv is mainly characterized by faulting-depressing. The deposiLional svstem, which were dominated by proximal gravity flow is developed along the steep slope of Jivang Suh-hasin, and its development and distribution are controlled by the types of steep slopes.In Lhis paper based on Lhe depositional characterisLics, depositional models of sleep slope sedimentation are concluded as 3 Lypes-sLeep slope on Lhe depositional eroded faulL, slope model interim steep slope and continuous steep slope.The common deposiLional characteristics on sleep slopes are LhaL Lhe nearshore suhaqueous fan is widely developed and it's developed degree has close relation to the fault throw and active time.The deposltlonal types on stpep siopes ace contcolled by the activities and developlng characheteristics of faultsn and different deposiLional types have developed in different deposition systems and vertical evolution successions.The evolution law of deposition on steep slope is that: alluvial fan→fandelta→delta, nearshore suhaqueous fan→suhlacusLrine fan.
The tectonic movement of Jivang Suh-basin in Earlv TerLiarv is mainly characterized by faulting-depressing. The deposiLional svstem, which were dominated by proximal gravity flow is developed along the steep slope of Jivang Suh-hasin, and its development and distribution are controlled by the types of steep slopes.In Lhis paper based on Lhe depositional characterisLics, depositional models of sleep slope sedimentation are concluded as 3 Lypes-sLeep slope on Lhe depositional eroded faulL, slope model interim steep slope and continuous steep slope.The common deposiLional characteristics on sleep slopes are LhaL Lhe nearshore suhaqueous fan is widely developed and it's developed degree has close relation to the fault throw and active time.The deposltlonal types on stpep siopes ace contcolled by the activities and developlng characheteristics of faultsn and different deposiLional types have developed in different deposition systems and vertical evolution successions.The evolution law of deposition on steep slope is that: alluvial fan→fandelta→delta, nearshore suhaqueous fan→suhlacusLrine fan.
2001, 19(2): 232-238.
Abstract:
The Lianhua reservoir of Shahejie group( geology period E1)in Gaosheng Oil field located in Liaohe granen faulting hasi, is rich in heavy crude oil, with the burial depth being 1 450-1 700 m. The reservoirs have been under development for 22 years.The company has made great profit from the reservoir development by means of steam-flooding technology but some problems have been found in the reservoir with the technology application, because the difficulty in reservoir development is increasing with the frequency of applying the technology.Bv the end of 1998 the average steam flooding for every well has been four times but the more steam-flooding the less satisfactory the efforts to increase the production. Therefore a more comprehensive study of the types content and the horizontal and vertical distribution characteristics of the clay minerals in the reservoir is of most important consequence to the design of the heavy crude oil development reservoir protection reservoir evaluation and enhanced oil recovery(EOR) etc.The clay minerals in Lianhua reservoir are systematically studied by means of X-ray diffraction scan electronic microscope and heat simulation experiments. The Lianhua reservoir is a sediment by gravity flow, with the rock types being gravel, sandstone, and mudstone, and the sedimentary depth being 50-600 m.Lianhua reservoir has excellent physical property, with the porosity being 20 %-26 % and the permeability being 1-4μm2. The studies show that the major clay minerals in Lianhua reservoir are montmorillonite( 60%-85%),illite(8 %-20 %),kaolinite(5%-25%),and chlorite(<5%).The montmorillonite content decreases with the increase of the burial depth but the kaolinite and illite content are just the opposite because the porosity fluid in sandstone and gravels more easily circulative than that in mudstone, and the montmorillonite in sandstone can more easily convert into other claw. For the study of the relationship between oil saturation and clay types the rock is divided into two groups according to the oil saturation degree: the oil-saturated and non-saturated.The statistical result shows that the clay minerals content and clay types have nothing to do with the oil saturation percentage. The types contents and distributions of clay minerals are mainly controlled by rock types and sedimentary fades.In general the absolute content of the montmorillonite increases with decrease of the sedimentary rock grains.The montmorillonite in gravel and sandstone has a relatively lower content than that in mudstone, but there is no much difference between the gravel and sandstone in their contents of montmorillonite.The relative content of montmorillonite in gravel and sandstone is 53.88%-85.99 %,with an average of 67.94 %,while the content in mudstone is 69.54%-86.59 %,with an aver- age of 79.02 %.The relative contents of kaolinite distribution decrease in the sequence of gravel sandstone and mudstone. But that of the illitc is just the opposite.Lianhua reservoir is a turhiditv current deposit in lake facics.Sandstone and gravel are mainly distributed in groove and branch groove facics, mudstonc and alcurolitc in deep lake,groove front margin and intcrlavcr branch groove facics.During the evolving process of the facics from the main groove to branch groove to the groove front margin, to the intcrlavcr branch groove, and finally to deep lake, the absolute content of clay minerals and the relative content of montmorillonitc in Lianhua reservoir increases with the decline of the primary hydraulics. Bv heat simulation experiments and a comparative study of the distribution characteristics of clay minerals before and after the steam flooding,it is found that the montmorillonitc in the reservoir can increase because of kaolinitc's reaction to carbonate grains.But because the heavy crude oil carries the montmorillonitc grains out, there finally is an approximately 1%deduction of the absolute amount of montmorillonitc in the reservoir after steam flooding.Because the steam flooding can destroy the clay microstructure to a large degree, some clay minerals disperse and migrate to increase the microheterogeneity parameters of reservoir. According to the types, contents and distributions of the sensitive minerals, the main mechanism of formation damage during steam flooding is particle migration and swelling of montmorillonitc.Steam has a strong effect to the microstructure of the clay minerals.
The Lianhua reservoir of Shahejie group( geology period E1)in Gaosheng Oil field located in Liaohe granen faulting hasi, is rich in heavy crude oil, with the burial depth being 1 450-1 700 m. The reservoirs have been under development for 22 years.The company has made great profit from the reservoir development by means of steam-flooding technology but some problems have been found in the reservoir with the technology application, because the difficulty in reservoir development is increasing with the frequency of applying the technology.Bv the end of 1998 the average steam flooding for every well has been four times but the more steam-flooding the less satisfactory the efforts to increase the production. Therefore a more comprehensive study of the types content and the horizontal and vertical distribution characteristics of the clay minerals in the reservoir is of most important consequence to the design of the heavy crude oil development reservoir protection reservoir evaluation and enhanced oil recovery(EOR) etc.The clay minerals in Lianhua reservoir are systematically studied by means of X-ray diffraction scan electronic microscope and heat simulation experiments. The Lianhua reservoir is a sediment by gravity flow, with the rock types being gravel, sandstone, and mudstone, and the sedimentary depth being 50-600 m.Lianhua reservoir has excellent physical property, with the porosity being 20 %-26 % and the permeability being 1-4μm2. The studies show that the major clay minerals in Lianhua reservoir are montmorillonite( 60%-85%),illite(8 %-20 %),kaolinite(5%-25%),and chlorite(<5%).The montmorillonite content decreases with the increase of the burial depth but the kaolinite and illite content are just the opposite because the porosity fluid in sandstone and gravels more easily circulative than that in mudstone, and the montmorillonite in sandstone can more easily convert into other claw. For the study of the relationship between oil saturation and clay types the rock is divided into two groups according to the oil saturation degree: the oil-saturated and non-saturated.The statistical result shows that the clay minerals content and clay types have nothing to do with the oil saturation percentage. The types contents and distributions of clay minerals are mainly controlled by rock types and sedimentary fades.In general the absolute content of the montmorillonite increases with decrease of the sedimentary rock grains.The montmorillonite in gravel and sandstone has a relatively lower content than that in mudstone, but there is no much difference between the gravel and sandstone in their contents of montmorillonite.The relative content of montmorillonite in gravel and sandstone is 53.88%-85.99 %,with an average of 67.94 %,while the content in mudstone is 69.54%-86.59 %,with an aver- age of 79.02 %.The relative contents of kaolinite distribution decrease in the sequence of gravel sandstone and mudstone. But that of the illitc is just the opposite.Lianhua reservoir is a turhiditv current deposit in lake facics.Sandstone and gravel are mainly distributed in groove and branch groove facics, mudstonc and alcurolitc in deep lake,groove front margin and intcrlavcr branch groove facics.During the evolving process of the facics from the main groove to branch groove to the groove front margin, to the intcrlavcr branch groove, and finally to deep lake, the absolute content of clay minerals and the relative content of montmorillonitc in Lianhua reservoir increases with the decline of the primary hydraulics. Bv heat simulation experiments and a comparative study of the distribution characteristics of clay minerals before and after the steam flooding,it is found that the montmorillonitc in the reservoir can increase because of kaolinitc's reaction to carbonate grains.But because the heavy crude oil carries the montmorillonitc grains out, there finally is an approximately 1%deduction of the absolute amount of montmorillonitc in the reservoir after steam flooding.Because the steam flooding can destroy the clay microstructure to a large degree, some clay minerals disperse and migrate to increase the microheterogeneity parameters of reservoir. According to the types, contents and distributions of the sensitive minerals, the main mechanism of formation damage during steam flooding is particle migration and swelling of montmorillonitc.Steam has a strong effect to the microstructure of the clay minerals.
2001, 19(2): 245-248,270.
Abstract:
Combining wavelet analysis with Milankovitch cycle by logging data we accurately determine the continuous age of strata and chronostratigraphic framework of Lower Silurian in Tarim Basin is found then sedimentary rate of research seclion is calculated. Two high-frequency wave processing are performed by sliding window and wavelet analysis which control and influence the scdimcntarv evolution of hasin, and the identification of which provides the possihilitv to combining wave processing with sequence stratigraphy and with reservoir and cap rock and improves the accuracy of each research relative to wave analysis. On the basis of comparison and analysis of all data from wells, lithology and sequence, the figure of comprehensive analysis of high-frequency wave is discoverd, which includes the information about curves of sedimentary rate sedimentary circumstances,sequence and soon.Furthermore we discovered the relations among high-frequency waves sequence and changes of sea level,between high-frequency wave and reservoir as well as caprock.
Combining wavelet analysis with Milankovitch cycle by logging data we accurately determine the continuous age of strata and chronostratigraphic framework of Lower Silurian in Tarim Basin is found then sedimentary rate of research seclion is calculated. Two high-frequency wave processing are performed by sliding window and wavelet analysis which control and influence the scdimcntarv evolution of hasin, and the identification of which provides the possihilitv to combining wave processing with sequence stratigraphy and with reservoir and cap rock and improves the accuracy of each research relative to wave analysis. On the basis of comparison and analysis of all data from wells, lithology and sequence, the figure of comprehensive analysis of high-frequency wave is discoverd, which includes the information about curves of sedimentary rate sedimentary circumstances,sequence and soon.Furthermore we discovered the relations among high-frequency waves sequence and changes of sea level,between high-frequency wave and reservoir as well as caprock.
2001, 19(2): 256-262.
Abstract:
Mesozoi。-Neozoic terrigenous sequence of Bivang fault-depression in Nanxiang Basin is treated as a case to study influential factors of terrigenous sequence formation and development. Basement structural suhsidence, sedimentary source recharge, palaeoclimate transformation and lacustrine level change are the four factors which are very important to control terrigenous sequence development in fault-depressed lacustrince basin.In Bivang fault-depressed lacustrince hasi, regional tectonism brought about the formation of basin-fill sequence and tectonic sequence and pulsation of basin boundary faults led to the development of sequence sets/sequence.And the rate of source recharge and accommodation variation determined stacking styles of terrigenous sequence units.Palaeclimate influenced the development of terrigenous sequence by the change of sedimentary source and lacustrine level, and its cyclical transformation determined the formation and evolution of high Erequenev sequence.Lacustrine level change which is an important subject to study terrigenous sequence in fault-depressed lacustrince hasin, directly controlled the terrigenous sequence geometrical characteristics.There is a specific dialectical causality between the four factors which are basic to control terrigenous sequence development.
Mesozoi。-Neozoic terrigenous sequence of Bivang fault-depression in Nanxiang Basin is treated as a case to study influential factors of terrigenous sequence formation and development. Basement structural suhsidence, sedimentary source recharge, palaeoclimate transformation and lacustrine level change are the four factors which are very important to control terrigenous sequence development in fault-depressed lacustrince basin.In Bivang fault-depressed lacustrince hasi, regional tectonism brought about the formation of basin-fill sequence and tectonic sequence and pulsation of basin boundary faults led to the development of sequence sets/sequence.And the rate of source recharge and accommodation variation determined stacking styles of terrigenous sequence units.Palaeclimate influenced the development of terrigenous sequence by the change of sedimentary source and lacustrine level, and its cyclical transformation determined the formation and evolution of high Erequenev sequence.Lacustrine level change which is an important subject to study terrigenous sequence in fault-depressed lacustrince hasin, directly controlled the terrigenous sequence geometrical characteristics.There is a specific dialectical causality between the four factors which are basic to control terrigenous sequence development.
2001, 19(2): 271-272.
Abstract:
A high vacuum purification line with lower leakage and lower background level had been established.The contamination of atmospheric argon to the samples was eliminated.The author determined the40/36Ar ratios of the samples analyzed previously using new method. Precise sup>40/36Ar ratio is obtained by this system.The sup>40/36Ar ratio observed by the new method is significantly higher than the previously determined ones, and the discrepancy was related to the Ar content of nature gas.Separating Ar from Kr and Xe is basically successful by temperature-modulated cold finger Kr and Xe isotopic compositions then can he measured.
A high vacuum purification line with lower leakage and lower background level had been established.The contamination of atmospheric argon to the samples was eliminated.The author determined the40/36Ar ratios of the samples analyzed previously using new method. Precise sup>40/36Ar ratio is obtained by this system.The sup>40/36Ar ratio observed by the new method is significantly higher than the previously determined ones, and the discrepancy was related to the Ar content of nature gas.Separating Ar from Kr and Xe is basically successful by temperature-modulated cold finger Kr and Xe isotopic compositions then can he measured.
2001, 19(2): 293-298.
Abstract:
The Jivang depression is one of the suhhasins of the Bohai Gulf Rift Basin in the eastern China.About 65 oil fields have been discovered in this depression over the past 30 wars and the oil mainly derived from three types of finch laminated lacustrinc rocks of Shahcjic Formation （Eoccnc-Oligoccnc）.Thcsc source rocks are organic-rich laminated shale calcarcous laminated shale and calcareous laminated mudstonc.High resolution studies have been carried out on these petroleum source rocks by scanning electron microscopcC（SEM),hackscattcrcd electron imagcry（ BSEI)and energy dispcrsivc spectrometry(EDS).The results show that these source rocks are all laminated sedimentary rocks, and organic matters are very abundant in it, but they have the different sediment composition. Organic-rich laminated shale is composed of organic matter lamination and clay mineral lamination: The clay-rich laminac range in thickness from 15 to 100μm and are predominantly composed of illite, (80 %).In addition they have subsidiary components which comprise ankcritc( 5-10%),pyrite ( 1-3%),quartz (l-2%)and fcldspar( 1%-2%)along with trace amounts of apatite( 0.03%).In contrast, the organic-rich laminae are thinner than the clay-rich laminae, ranging from 6-50 μm and are predominantly composed of amorphous organic mattcr( 20%-70 %),as well as organic matter these laminae also contain dctrital clay(predominantly illite),silt-sized quartz, fcldspar( 1%-2%),and pyritc( 1%-3%).Displacivc calcite layers were also present.The calcite in these layers consits of low-Mg, non-fcrroan calcite.In addition to the characteristic "beef" texture of this calcite these layers also contain pyrite framhoids, dctrital quartz and ankcritc.Calcareous laminated shale is composed of organic matter lamination and coccolith or coarse calcite lamination:The coccolith laminae laminae is composed almost wholly of one species, Rcticulofcncstra hohaicnsis and the coarse grained calcite laminc are composed of coarse calcitc( 10-20 μm) and also contain coccolths.within the coccolith laminae the size of coccolith ranges from 2 to 5 μm,and it has a good preservation.within the coarse calcite laminae the coarse calcite are sparrv calcite characteristically by its overgrowth and the coccolths have a poor preservation characteristics such as dissolution.This indicated that the coccolith-hearing coarse calcite laminae may he rvstallizcd from the dissolution of coccolth laminac.Organic matter laminae is mainly composed of the lath of amorphous organic matter and contain trace amounts of dctrital clay.The thickness of organic-rich laminae range from 15 to 50 μm and the thickness of the calcite laminae range from 40 to 130 μm. Another important phenomenon is that there are dinoflagcllatcs laminae in the organic-rich laminae.These dlnoflagcllatcs laminae are also composed of one species Fcramo( Fig.3). Calcareous laminated mudstonc is composed of finely grain calcite lamination and organic-rich clay mineral lamination.The clay-rich laminae range in thickness from 50-250 μm and are predominantly composed of illite(70%)and organic matter(organic matter may he formed by suhlaminac in clay-rich laminae ).They also contain fine grained calcitc( 5 %) and silt-sized dctrital quartz( 3 %).In contrast the carbonate-rich laminae are predominantly composed of micrrn sized and fine grained calcite which form layers 30-100 μm in thickness.The dinoflagcllatcs laminae is also discovered in the organic-hearing clay-rich laminae( Fig.6).
The Jivang depression is one of the suhhasins of the Bohai Gulf Rift Basin in the eastern China.About 65 oil fields have been discovered in this depression over the past 30 wars and the oil mainly derived from three types of finch laminated lacustrinc rocks of Shahcjic Formation （Eoccnc-Oligoccnc）.Thcsc source rocks are organic-rich laminated shale calcarcous laminated shale and calcareous laminated mudstonc.High resolution studies have been carried out on these petroleum source rocks by scanning electron microscopcC（SEM),hackscattcrcd electron imagcry（ BSEI)and energy dispcrsivc spectrometry(EDS).The results show that these source rocks are all laminated sedimentary rocks, and organic matters are very abundant in it, but they have the different sediment composition. Organic-rich laminated shale is composed of organic matter lamination and clay mineral lamination: The clay-rich laminac range in thickness from 15 to 100μm and are predominantly composed of illite, (80 %).In addition they have subsidiary components which comprise ankcritc( 5-10%),pyrite ( 1-3%),quartz (l-2%)and fcldspar( 1%-2%)along with trace amounts of apatite( 0.03%).In contrast, the organic-rich laminae are thinner than the clay-rich laminae, ranging from 6-50 μm and are predominantly composed of amorphous organic mattcr( 20%-70 %),as well as organic matter these laminae also contain dctrital clay(predominantly illite),silt-sized quartz, fcldspar( 1%-2%),and pyritc( 1%-3%).Displacivc calcite layers were also present.The calcite in these layers consits of low-Mg, non-fcrroan calcite.In addition to the characteristic "beef" texture of this calcite these layers also contain pyrite framhoids, dctrital quartz and ankcritc.Calcareous laminated shale is composed of organic matter lamination and coccolith or coarse calcite lamination:The coccolith laminae laminae is composed almost wholly of one species, Rcticulofcncstra hohaicnsis and the coarse grained calcite laminc are composed of coarse calcitc( 10-20 μm) and also contain coccolths.within the coccolith laminae the size of coccolith ranges from 2 to 5 μm,and it has a good preservation.within the coarse calcite laminae the coarse calcite are sparrv calcite characteristically by its overgrowth and the coccolths have a poor preservation characteristics such as dissolution.This indicated that the coccolith-hearing coarse calcite laminae may he rvstallizcd from the dissolution of coccolth laminac.Organic matter laminae is mainly composed of the lath of amorphous organic matter and contain trace amounts of dctrital clay.The thickness of organic-rich laminae range from 15 to 50 μm and the thickness of the calcite laminae range from 40 to 130 μm. Another important phenomenon is that there are dinoflagcllatcs laminae in the organic-rich laminae.These dlnoflagcllatcs laminae are also composed of one species Fcramo( Fig.3). Calcareous laminated mudstonc is composed of finely grain calcite lamination and organic-rich clay mineral lamination.The clay-rich laminae range in thickness from 50-250 μm and are predominantly composed of illite(70%)and organic matter(organic matter may he formed by suhlaminac in clay-rich laminae ).They also contain fine grained calcitc( 5 %) and silt-sized dctrital quartz( 3 %).In contrast the carbonate-rich laminae are predominantly composed of micrrn sized and fine grained calcite which form layers 30-100 μm in thickness.The dinoflagcllatcs laminae is also discovered in the organic-hearing clay-rich laminae( Fig.6).
2001, 19(2): 309-314.
Abstract:
Using the wide angle x-rav scattering( WAXS ) and radial distribution function(RDF),the structure of pianlinitc occuring in China has been discussed.It is shown that pianlinitc is mainly composed of amorphous phase with less amount of order phase.The structural units constructing pianlinitc are tetrahedron[M04]( M=Si, Al)and octahetron[ AlO6 ](O=O,OH).The connecting of neighbour tctrahcdran with common vertex angle forms M-O lavcr( M=Al, Si),and the conncction of neighbour octahcdran with common edge or plane forms Al-0 layer. The structure of pianlinitc is formed from the such kind layers.Its structure change with temperatures is mainly caused by that of the correlation or order between structural units, and its structure in neighbour range is nearly unchanged.Pianlinitc is a clay rock with the structure different from that of the metakaolinites.
Using the wide angle x-rav scattering( WAXS ) and radial distribution function(RDF),the structure of pianlinitc occuring in China has been discussed.It is shown that pianlinitc is mainly composed of amorphous phase with less amount of order phase.The structural units constructing pianlinitc are tetrahedron[M04]( M=Si, Al)and octahetron[ AlO6 ](O=O,OH).The connecting of neighbour tctrahcdran with common vertex angle forms M-O lavcr( M=Al, Si),and the conncction of neighbour octahcdran with common edge or plane forms Al-0 layer. The structure of pianlinitc is formed from the such kind layers.Its structure change with temperatures is mainly caused by that of the correlation or order between structural units, and its structure in neighbour range is nearly unchanged.Pianlinitc is a clay rock with the structure different from that of the metakaolinites.
2001, 19(2): 177-181,206.
Abstract:
Qinghai-Tibet Plateau is a unigue and speciai region on environmental change,the famous wetland of Zorge Plateau is in northeast Oinghai-Tlbetan Piateau and covers 4 605. 28 sguare kilometers. In the wetland,peat was wideiy piled in the wide valleys and abundant information about environmental change was contained in it,which is very valuabie for investigating the globally environmental change. Erecting a correct time reference frame of Holocene is the precondition to make use of great environmental information. Existed time reference frame of Holocene was established based on the 14C data,and it is iimited and has Shortcomings.So,it is necessary to look for a method that is more reliable and can emend result of 14C age.Authors discovered peat varve structure in peat layers of Zorge Piateau wetiand,which couid be used as a new method combinig 14C for determining Holocene age.And it is posible that the resolution come up to standard of year. The paper,which is based on age dates that were made just from mine Ⅱ of Hongyuan Peat Site,found an age tabie of Holocene peat deposition. The tabie is a more complete system and has higher believabie and higher resolution. In addition,the age dates of some important peatland in Zorge Plateau except the region of Hongyaun were published systematically,and then the age seguence of peat in Zorge Plateau was presented in the paper. These results indicated that the Latest mire mud of the Zorge Plateau formed in above 12 000 yrBP and the deposition of peat started in 11 500 yrBP. It was alse closed of a vlolently falling temperature,Younge Dryas ,appeared in 11 500 ~ 12111yrBP. The Holocene megathermal was formed from 9 500 yrBP to 2 000 yrBP,which is a period of faster peat deposition. Before 9 500 yrBP and after 2 000 yrBP of Holocene,peat deposition siowed. The slowest period of peat deposition has appeared in modern times. Under the effect of difference of environment,peat age of deposition has big difference in the plateau.Generally,the high mountainous regions are later than the wide valley,and the latter was dominant in middle Holocene.
Qinghai-Tibet Plateau is a unigue and speciai region on environmental change,the famous wetland of Zorge Plateau is in northeast Oinghai-Tlbetan Piateau and covers 4 605. 28 sguare kilometers. In the wetland,peat was wideiy piled in the wide valleys and abundant information about environmental change was contained in it,which is very valuabie for investigating the globally environmental change. Erecting a correct time reference frame of Holocene is the precondition to make use of great environmental information. Existed time reference frame of Holocene was established based on the 14C data,and it is iimited and has Shortcomings.So,it is necessary to look for a method that is more reliable and can emend result of 14C age.Authors discovered peat varve structure in peat layers of Zorge Piateau wetiand,which couid be used as a new method combinig 14C for determining Holocene age.And it is posible that the resolution come up to standard of year. The paper,which is based on age dates that were made just from mine Ⅱ of Hongyuan Peat Site,found an age tabie of Holocene peat deposition. The tabie is a more complete system and has higher believabie and higher resolution. In addition,the age dates of some important peatland in Zorge Plateau except the region of Hongyaun were published systematically,and then the age seguence of peat in Zorge Plateau was presented in the paper. These results indicated that the Latest mire mud of the Zorge Plateau formed in above 12 000 yrBP and the deposition of peat started in 11 500 yrBP. It was alse closed of a vlolently falling temperature,Younge Dryas ,appeared in 11 500 ~ 12111yrBP. The Holocene megathermal was formed from 9 500 yrBP to 2 000 yrBP,which is a period of faster peat deposition. Before 9 500 yrBP and after 2 000 yrBP of Holocene,peat deposition siowed. The slowest period of peat deposition has appeared in modern times. Under the effect of difference of environment,peat age of deposition has big difference in the plateau.Generally,the high mountainous regions are later than the wide valley,and the latter was dominant in middle Holocene.
2001, 19(2): 186-191.
Abstract:
The differences of the pollen assemblages of three sites in Shivang River basin, an internal river system in the arid area of Northwest China are so sharp that they can' t he explained by climatic change.The early to mid-Holocene pollen assemhlage of Sanjiaocheng section located at the end of Shivang River basin is dominated by the conifer. The surface samples of a site closed by the Sanjiaocheng Section has over 90% of xeromophte in the pollen assemblages.The pollen in the lower part of Hongshui River Secton is mainly xeric herb.In the upper part of the same section however conifer is dominant. Based on the analyses of sedimentary facies, depositional environments and the transportion characteristics of modern pollen we proposed that the obvious difference of pollen assemblages in the catchment are caused by the differences of depositional environments.As the Sanjiaocheng Section is near to the inlet of Shivang River to the paleo-lake with a semi-enclosed environmenu the sediments including pollen transported by water from the upper reaches would settle down there.The pollen assemhlage, therefore represents the vegetation of the upper reaches of the drainage.the Hongshui River Section is located near the end of the Hongshui River a tributary of Shivang River. The lower part of the section is alluvial sediments indicating an open flowing environment where only a small portion of the pollen carried by water can he kept in the sediments.There is no environmental significance in this pollen assemblage and it can' t he used to explain the vegetation.The upper part of the section is lacustrine sediments suggesting an enclosed environment similar to that in Sanjiaocheng Section.The pollen assemblage also reflects the vegetation in the uplands.The prevailing xeromophte in the surface sample near the Sanjiaocheng section implies the local desert vegetation because there is no water to the lowest reaches of the Shivang River as several reservoirs were built for irrigation in the upper and middle reaches.We have to he very careful when reconstructing or explaining palaeoenvironment with pollen assemblages only.Sedimentary fades and environment should also he given enough consideration as it is useful in judging the origin of pollen in the sediments.
The differences of the pollen assemblages of three sites in Shivang River basin, an internal river system in the arid area of Northwest China are so sharp that they can' t he explained by climatic change.The early to mid-Holocene pollen assemhlage of Sanjiaocheng section located at the end of Shivang River basin is dominated by the conifer. The surface samples of a site closed by the Sanjiaocheng Section has over 90% of xeromophte in the pollen assemblages.The pollen in the lower part of Hongshui River Secton is mainly xeric herb.In the upper part of the same section however conifer is dominant. Based on the analyses of sedimentary facies, depositional environments and the transportion characteristics of modern pollen we proposed that the obvious difference of pollen assemblages in the catchment are caused by the differences of depositional environments.As the Sanjiaocheng Section is near to the inlet of Shivang River to the paleo-lake with a semi-enclosed environmenu the sediments including pollen transported by water from the upper reaches would settle down there.The pollen assemhlage, therefore represents the vegetation of the upper reaches of the drainage.the Hongshui River Section is located near the end of the Hongshui River a tributary of Shivang River. The lower part of the section is alluvial sediments indicating an open flowing environment where only a small portion of the pollen carried by water can he kept in the sediments.There is no environmental significance in this pollen assemblage and it can' t he used to explain the vegetation.The upper part of the section is lacustrine sediments suggesting an enclosed environment similar to that in Sanjiaocheng Section.The pollen assemblage also reflects the vegetation in the uplands.The prevailing xeromophte in the surface sample near the Sanjiaocheng section implies the local desert vegetation because there is no water to the lowest reaches of the Shivang River as several reservoirs were built for irrigation in the upper and middle reaches.We have to he very careful when reconstructing or explaining palaeoenvironment with pollen assemblages only.Sedimentary fades and environment should also he given enough consideration as it is useful in judging the origin of pollen in the sediments.
2001, 19(2): 199-206.
Abstract:
Jomda interare basin is located in the north part of Three-River area,eastern Tihet, and today covered by Triassic with about 10 000 m in thickness.Marine sediments predominated, and were characterized by the largely thick turhiditv rocks and arc volcanic rocks of cal。-alkalic suites that resulted from frequent volcanic events.The basin analvscs were on the bases of two sides:(1)utility of sequence stratigraphy, based on outcrop profiles, 10 three-order boundaries and sequcnccs were recognized by research of fine sediment facics and its models.Isochronous grillwork for Triassic sequence stratigraphy were established.The recognized marks of boundaries were built by the distinguished kcv sequence boundaries and geometric or superposed patterns of system traces and compared isochron of sedimentary and volcanic events.10 sequcncc stratigraphic boundaries were discriminated with marks of tectonic and strata including 6 Ⅰ-type and 4 Ⅱ-type boundaries.10 sequences were divided,.including 6 Ⅰ-type and 4 Ⅱ-type.These sequences developed during 37 Ma, the estimated average time of a sequence is 3-7Ma, with generally 1-2 Ma, the longest about lOMa. (2) Analvses of subsidence, the rebuilt of tectonic subsidence curves suggested that there were clearly two uplifts(at 250 Ma and 235 Ma) and two sinks.The estimated sedimentary rates were among 87-537 m/Ma. It is inferred that relations among tectonic suhsidence, water depth and high-frequency sedimentary velocities represented characteristics of depositional process in the arc area.It is concluded that evolution of Jomda basin were classificated into 6 depositional accumulation stages.The 6 stages were respectably: ①sedimentation of first shallow shelfs② formation of carbonate platforms ③development of the volcanic-terrigeous auhmarine fans④advancement of the volcanic-terrigeous shelfs③evolution of carbonate ramp and ⑥advancement of the terrigeous shelf to delta. It is pointed out that interarc basin of Jomda experienced processes of both early extensive deepness and late compressed shallowness.
Jomda interare basin is located in the north part of Three-River area,eastern Tihet, and today covered by Triassic with about 10 000 m in thickness.Marine sediments predominated, and were characterized by the largely thick turhiditv rocks and arc volcanic rocks of cal。-alkalic suites that resulted from frequent volcanic events.The basin analvscs were on the bases of two sides:(1)utility of sequence stratigraphy, based on outcrop profiles, 10 three-order boundaries and sequcnccs were recognized by research of fine sediment facics and its models.Isochronous grillwork for Triassic sequence stratigraphy were established.The recognized marks of boundaries were built by the distinguished kcv sequence boundaries and geometric or superposed patterns of system traces and compared isochron of sedimentary and volcanic events.10 sequcncc stratigraphic boundaries were discriminated with marks of tectonic and strata including 6 Ⅰ-type and 4 Ⅱ-type boundaries.10 sequences were divided,.including 6 Ⅰ-type and 4 Ⅱ-type.These sequences developed during 37 Ma, the estimated average time of a sequence is 3-7Ma, with generally 1-2 Ma, the longest about lOMa. (2) Analvses of subsidence, the rebuilt of tectonic subsidence curves suggested that there were clearly two uplifts(at 250 Ma and 235 Ma) and two sinks.The estimated sedimentary rates were among 87-537 m/Ma. It is inferred that relations among tectonic suhsidence, water depth and high-frequency sedimentary velocities represented characteristics of depositional process in the arc area.It is concluded that evolution of Jomda basin were classificated into 6 depositional accumulation stages.The 6 stages were respectably: ①sedimentation of first shallow shelfs② formation of carbonate platforms ③development of the volcanic-terrigeous auhmarine fans④advancement of the volcanic-terrigeous shelfs③evolution of carbonate ramp and ⑥advancement of the terrigeous shelf to delta. It is pointed out that interarc basin of Jomda experienced processes of both early extensive deepness and late compressed shallowness.
2001, 19(2): 214-218.
Abstract:
Based on the analysis and some typical data of petroleum basins in China and world it discusses some important exprcssion forms and major research methods of thermal fluid flow and tion and hydrocarbon generation in this paper. According to the major emphasized its enhancement to organic-matter maturacontrolling factor passage of fluid migrations,to thermal fluid flow it divides thermal fluid flow into four types:(1)lithologic-type(2) conformity-type(3 ) fault-type and (4) compound-type.Finally it also discusses the significance of thermal fluid flow to pool-forming dynamics:(1) provides a new explanation way to abnormal vitrinitc reflectance, which can enlarge the fields of hydrocarbon exploration and development: (2)provides some important evidences to and(3)providcs means to study diagnosis research of hvdrocarhon migration which support to choose exploration targets:and porosity evolution of reservoir rocks which can he used to predict the dcvclopmcnt units of deep reservoirs.
Based on the analysis and some typical data of petroleum basins in China and world it discusses some important exprcssion forms and major research methods of thermal fluid flow and tion and hydrocarbon generation in this paper. According to the major emphasized its enhancement to organic-matter maturacontrolling factor passage of fluid migrations,to thermal fluid flow it divides thermal fluid flow into four types:(1)lithologic-type(2) conformity-type(3 ) fault-type and (4) compound-type.Finally it also discusses the significance of thermal fluid flow to pool-forming dynamics:(1) provides a new explanation way to abnormal vitrinitc reflectance, which can enlarge the fields of hydrocarbon exploration and development: (2)provides some important evidences to and(3)providcs means to study diagnosis research of hvdrocarhon migration which support to choose exploration targets:and porosity evolution of reservoir rocks which can he used to predict the dcvclopmcnt units of deep reservoirs.
2001, 19(2): 224-231.
Abstract:
Spatio-temporal variation of subsurface porosity and permeability is controlled by various factors during sedimentation and diagcncsis.The dcpositional environments and the types of sediment basin control the original composition before hurial, texture and porosity of sediments.The sedimentary factors to control the porosity and permeability are mainly sedimentary facics, stratigraphy sequences and so on.The process of sedimentation was much shorter than the diagcncsis, and relatively easy to study.Recently, some traditional mechanism of secondary porosity formation for subsurface sediment is challenged by new theories.The formation of secondary porosity from the aluminium-silicate solution by organic acid is the most important mechanism.However it will result in the increase of pH value precipitation of carbonate and kaolinitc.The dissolulion by carbonic water to form the secondary porosity in subsurface is also limited.Ncw mechanism such as dissolution of sediment by the meteoric water by the deep cooling formation water proves effective and hydrolysis of the silicates is also accepted universally.In addition, the precipitation and material sources of some diagcnctic authigcnic minerals related to the secondary porosity also have new mode.These are several essentials to understand the formation of secondary porosity and estimate the porosity and the permeability of the reservoir. For the carbonate rocks the oil/gas reservoir related to the palco-carst nearby the unconformitv have got more attention. During the deep burial diagenesis, the temperature and prcssure control the difference of the habit of dissolution and precipitation for different carbonate minerals leading to the differcncc of porosity and permeability distribution in subsurface carbonate rocks, which is very important for prediction of carhonate reservoir.
Spatio-temporal variation of subsurface porosity and permeability is controlled by various factors during sedimentation and diagcncsis.The dcpositional environments and the types of sediment basin control the original composition before hurial, texture and porosity of sediments.The sedimentary factors to control the porosity and permeability are mainly sedimentary facics, stratigraphy sequences and so on.The process of sedimentation was much shorter than the diagcncsis, and relatively easy to study.Recently, some traditional mechanism of secondary porosity formation for subsurface sediment is challenged by new theories.The formation of secondary porosity from the aluminium-silicate solution by organic acid is the most important mechanism.However it will result in the increase of pH value precipitation of carbonate and kaolinitc.The dissolulion by carbonic water to form the secondary porosity in subsurface is also limited.Ncw mechanism such as dissolution of sediment by the meteoric water by the deep cooling formation water proves effective and hydrolysis of the silicates is also accepted universally.In addition, the precipitation and material sources of some diagcnctic authigcnic minerals related to the secondary porosity also have new mode.These are several essentials to understand the formation of secondary porosity and estimate the porosity and the permeability of the reservoir. For the carbonate rocks the oil/gas reservoir related to the palco-carst nearby the unconformitv have got more attention. During the deep burial diagenesis, the temperature and prcssure control the difference of the habit of dissolution and precipitation for different carbonate minerals leading to the differcncc of porosity and permeability distribution in subsurface carbonate rocks, which is very important for prediction of carhonate reservoir.
2001, 19(2): 239-244.
Abstract:
Carbonate ccmcntation is the main diagcnctic process except for compaction in shallow-burial(shallower than 700 metcrs) Ncogcnc-Quatcrnarv fluvial sandstoncs of northern Tarim Basin.High-resolution electric borcholc images provide valuable information on the gcomctrv and occurrence of carbonate concretions in these sandstoncs. Carbonate concretions in the sandstoncs are characterized with white high-resistive features in both static and dynamic images.The shape of these concretions is round clliptoid or irregular. They may occur as isolate patches scattered in poorcemented sandstones, or appear in group as spiccato or continuous carbonate-cemented laminae intcrbcddcd with poor-cemcntcd sandstone laminae. Strong selectivity of carbonate ccmcntation at different scales is observed on the images of these sandstoncs.On scale of sandstone beds, carbonate concretions preferentially developed at the upper and/or lower parts, where ion materials needed for carbonate cement precipitation are believed to be more easily available from adjacent clay sediments.On scale of beddings,carbonate concretions usually aligned parallel to bedding surfaces.In most cases, they intcrbcddcd with poor-ccmcnted sandstone laminae as spiccato or continuous carbonate-cemented laminae which may be resulted from the texture and hence permeability differences between laminae.On laminae scale, carbonate cements selectively precipitate around some nuclei then enlarge outwards as cemented patches.when the patches grow closer or merge together spiccato or continuous cemented laminae form. fragments, which are the The selectivity of ccmcntation some relation to the,listrihution of elastic carbonate common gram components in these sandstones. Based on interpertation of electric images,this paper concluded a growth of early-diagenetic carbonate cements in these sandstoncs.They were developed following the sequences from the top and/or the middle of the sandstone beds, from high-permeable laminae to low-permeable laminae, and from some local nuclei to their vicinity.
Carbonate ccmcntation is the main diagcnctic process except for compaction in shallow-burial(shallower than 700 metcrs) Ncogcnc-Quatcrnarv fluvial sandstoncs of northern Tarim Basin.High-resolution electric borcholc images provide valuable information on the gcomctrv and occurrence of carbonate concretions in these sandstoncs. Carbonate concretions in the sandstoncs are characterized with white high-resistive features in both static and dynamic images.The shape of these concretions is round clliptoid or irregular. They may occur as isolate patches scattered in poorcemented sandstones, or appear in group as spiccato or continuous carbonate-cemented laminae intcrbcddcd with poor-cemcntcd sandstone laminae. Strong selectivity of carbonate ccmcntation at different scales is observed on the images of these sandstoncs.On scale of sandstone beds, carbonate concretions preferentially developed at the upper and/or lower parts, where ion materials needed for carbonate cement precipitation are believed to be more easily available from adjacent clay sediments.On scale of beddings,carbonate concretions usually aligned parallel to bedding surfaces.In most cases, they intcrbcddcd with poor-ccmcnted sandstone laminae as spiccato or continuous carbonate-cemented laminae which may be resulted from the texture and hence permeability differences between laminae.On laminae scale, carbonate cements selectively precipitate around some nuclei then enlarge outwards as cemented patches.when the patches grow closer or merge together spiccato or continuous cemented laminae form. fragments, which are the The selectivity of ccmcntation some relation to the,listrihution of elastic carbonate common gram components in these sandstones. Based on interpertation of electric images,this paper concluded a growth of early-diagenetic carbonate cements in these sandstoncs.They were developed following the sequences from the top and/or the middle of the sandstone beds, from high-permeable laminae to low-permeable laminae, and from some local nuclei to their vicinity.
2001, 19(2): 249-255.
Abstract:
By applying the thcorv and technology of the high-resolution sequence stratigraphy to the sequence analysis of tcrrigcnous hasin, one of the kcv techniques is to distinguish and divide the different genesis interfaces and the different grades of the base-level cycle.In this paper taking a few basins which have different tectonic characteristics as cases, the authors have recognized six types of interfaces which are controlled by different factors, and have different genetic features, developmcnt scales and identification marks.According to the genetic features and the differences among the interfaces, six-grade division schemes of base-level cycle are proposed which are huge base level cycle and super-long-time long time middle time short time super-short-time base-level cvclc, and division criterions of different base-level cycles arc established.The authors have also discussed the time interval of different base level cycle and considered that the preceding three low frcqucncc and long period cycles are mainly controlled by tectonic factors and the following three high frcqucncc and short period cycles are mainly controlled by the astronomic factor. At the same time the implications of different grade base-level cycles dcaltwith the exploration and development of oil and gas field are discussed respectively.
By applying the thcorv and technology of the high-resolution sequence stratigraphy to the sequence analysis of tcrrigcnous hasin, one of the kcv techniques is to distinguish and divide the different genesis interfaces and the different grades of the base-level cycle.In this paper taking a few basins which have different tectonic characteristics as cases, the authors have recognized six types of interfaces which are controlled by different factors, and have different genetic features, developmcnt scales and identification marks.According to the genetic features and the differences among the interfaces, six-grade division schemes of base-level cycle are proposed which are huge base level cycle and super-long-time long time middle time short time super-short-time base-level cvclc, and division criterions of different base-level cycles arc established.The authors have also discussed the time interval of different base level cycle and considered that the preceding three low frcqucncc and long period cycles are mainly controlled by tectonic factors and the following three high frcqucncc and short period cycles are mainly controlled by the astronomic factor. At the same time the implications of different grade base-level cycles dcaltwith the exploration and development of oil and gas field are discussed respectively.
2001, 19(2): 263-270.
Abstract:
Fourteen sequence boundaries showing onlap or erosional truncation are recognized in the seismic sections of the Juras- sic Turpan-Hami basin. The two major boundaries(at the top and bottom of the Jurassic deposits ) are regional unconformities extending hevond the basin.Three intermediate ones(between 3re and 4th section of Xishanvao Fm. Qikeai Fm.and Sanjianfeng Fm.and I}alaza Fm.and Qigu Fm.)are unconformities spaning most of the basin.The remaining nine sequence houndcries are local unconformities.The Jurassic sedimentary strata in Turpan-Hami basin is a basin-fill sequence(1st order)including four tectonic sequences( 2nd order) and thirteen depositional sequences( 3rd order).The four tectonic sequences are bound with the four evolutionary stages( stable suhsidence, short-time contraction expansion and uplift desiccation)of the lake basin. According to classic sequence stratigraphy,there are two types of sequences and sequence boundaries in passive continental margins with a shelf and slope.The types of depositional sequences in terrestrial hasin, however are not the same as those from a passive continental margin.Four types of sequence houndaries, type A, B, C, and D ) are identified in the basin.A type A boundary is formed at the desiccation stage of the lake basin caused by strong tectonic uplift.The sequence above the type A boundary is here termed as,fluvial sequervce,in which the major systems tract is a lowstand deposit composed of alluvial fan and fluvial fades.A type B houndary where base-level falls below the previous shore-slope break and then rises rapidly occurs as the stage of basin expansion caused by rapid tectonic subsidence.The corresponding sequence without the lowstand systems tract is here termed as submerged sequence.A type C houndary where base-level also falls below the previous shore-slope break and fluvial incision occurs is similar to the type 1 boundary identified by Vail et alb 1977).The lowstand systems tract with deposits of basin-floor fan and incised valley overlies type C boundary.Therefore type C sequence is called as similar type 1 sequence.A type D houndary where base-level falls but shore-slope is not exposed is similar to type 2 houndarv identified by Vail et a1( 1977).The corresponding sequence without the lowstand systems tract is here termed as similar type 2sequeuce.The difference between these boundary types is the nature of transgression above the boundary for type B and D.which both lack a lowstand systems tract.There is a gradual transgression in type D compared with a rapid and abrupt one in type B.In other words.the sedimentary fades above the type B boundary are distinct from those below the boundary and record a rapid change in base level compared with a gradual one in type D. Four types of sequence models in this paper have demonstrated the difference between marine fades sequences and non-marine fades sequences.The type A boundary&fluvial sequence and type B boundary&submerged sequence are indicative of two extreme conditions of desiccation and rapid subsidence of the lake hasin, and are totally different from marine fades sequences.We suggest several reasons for the variety of non-marine fades sequences of the lake basin: a smaller scale multiple sediment input provenances, relative short distance from sediment source.and differences in local tectonic achmtv. There is a relationship between the sequence stratigraphy and the hvdrocarhon shows in well TC2 of Turpan-Hami basin. Hvdrocarhon shows are often adjacent to sequence boundaries in Kalaza Fm. and Qigu Fm.because both formations lack oil source rocks or/and source rocks are not at the depth of the oil window. Hvdrocarhons originating from underlying formations thas migrate through fractures occur along the sequence boundaries.which usually have higher pcrmcahilitv.However. hvdrocathon shows in the Qiketai, Sanjianfeng, and Xishanvao formations are different from the overlying formations hecause they contain good source rocks buried to the oil window. In some fore-delta sandstone bodies adjacent to the source rocks there are pools formed by stratigraphic traps and structural-stratigraphic combination traps in addition to the sequence bounilaries.
Fourteen sequence boundaries showing onlap or erosional truncation are recognized in the seismic sections of the Juras- sic Turpan-Hami basin. The two major boundaries(at the top and bottom of the Jurassic deposits ) are regional unconformities extending hevond the basin.Three intermediate ones(between 3re and 4th section of Xishanvao Fm. Qikeai Fm.and Sanjianfeng Fm.and I}alaza Fm.and Qigu Fm.)are unconformities spaning most of the basin.The remaining nine sequence houndcries are local unconformities.The Jurassic sedimentary strata in Turpan-Hami basin is a basin-fill sequence(1st order)including four tectonic sequences( 2nd order) and thirteen depositional sequences( 3rd order).The four tectonic sequences are bound with the four evolutionary stages( stable suhsidence, short-time contraction expansion and uplift desiccation)of the lake basin. According to classic sequence stratigraphy,there are two types of sequences and sequence boundaries in passive continental margins with a shelf and slope.The types of depositional sequences in terrestrial hasin, however are not the same as those from a passive continental margin.Four types of sequence houndaries, type A, B, C, and D ) are identified in the basin.A type A boundary is formed at the desiccation stage of the lake basin caused by strong tectonic uplift.The sequence above the type A boundary is here termed as,fluvial sequervce,in which the major systems tract is a lowstand deposit composed of alluvial fan and fluvial fades.A type B houndary where base-level falls below the previous shore-slope break and then rises rapidly occurs as the stage of basin expansion caused by rapid tectonic subsidence.The corresponding sequence without the lowstand systems tract is here termed as submerged sequence.A type C houndary where base-level also falls below the previous shore-slope break and fluvial incision occurs is similar to the type 1 boundary identified by Vail et alb 1977).The lowstand systems tract with deposits of basin-floor fan and incised valley overlies type C boundary.Therefore type C sequence is called as similar type 1 sequence.A type D houndary where base-level falls but shore-slope is not exposed is similar to type 2 houndarv identified by Vail et a1( 1977).The corresponding sequence without the lowstand systems tract is here termed as similar type 2sequeuce.The difference between these boundary types is the nature of transgression above the boundary for type B and D.which both lack a lowstand systems tract.There is a gradual transgression in type D compared with a rapid and abrupt one in type B.In other words.the sedimentary fades above the type B boundary are distinct from those below the boundary and record a rapid change in base level compared with a gradual one in type D. Four types of sequence models in this paper have demonstrated the difference between marine fades sequences and non-marine fades sequences.The type A boundary&fluvial sequence and type B boundary&submerged sequence are indicative of two extreme conditions of desiccation and rapid subsidence of the lake hasin, and are totally different from marine fades sequences.We suggest several reasons for the variety of non-marine fades sequences of the lake basin: a smaller scale multiple sediment input provenances, relative short distance from sediment source.and differences in local tectonic achmtv. There is a relationship between the sequence stratigraphy and the hvdrocarhon shows in well TC2 of Turpan-Hami basin. Hvdrocarhon shows are often adjacent to sequence boundaries in Kalaza Fm. and Qigu Fm.because both formations lack oil source rocks or/and source rocks are not at the depth of the oil window. Hvdrocarhons originating from underlying formations thas migrate through fractures occur along the sequence boundaries.which usually have higher pcrmcahilitv.However. hvdrocathon shows in the Qiketai, Sanjianfeng, and Xishanvao formations are different from the overlying formations hecause they contain good source rocks buried to the oil window. In some fore-delta sandstone bodies adjacent to the source rocks there are pools formed by stratigraphic traps and structural-stratigraphic combination traps in addition to the sequence bounilaries.
2001, 19(2): 287-292.
Abstract:
Abundant hiomarkcrs, including n-alkancs, isoprcnoid, stcrancs and tcrpancs, have been detected by GC-MS from the middle Jurassic oil shalcs in the Shuanghu area northern Tibet plateau.N-alkancs contain carbon number nC12-nC35 with a rclativclv wide range,nC15,nC16 or nC17 as the highest peak.Examination of the relative abundance show a dominancc of low carbon molecular components in the n-alkanc.Pr/Ph ratio in oil shalcs range from 0.77 to 1.59, and it fluetuatcs in the vertical section.The upper and lower part of the oil shalcs have slight predominance of pristanc, whereas phytune dominates in the middle part of the oil shale sequence.C30-hopanc is the most abundant in the hopanc series.According to the rclativclv abundance, pcntacvclic tritcrpanc>tricvclic tcrpanc>quartcvclic tcrpanc.Stcranc ∑C27/C29 ratio ranges from 0.79 to 1.20} and ∑(C27+C28)>∑C29.The carbon number distribution of the stcrancs show a slight predominance of C27 components over C29 in the lower part of the oil shalcs and a slight dominance of C29 component over C27 in the upper part of the oil shalcs sequence.C27-diastcranc/ C27-stcranc ratio range from 0.51 to 3.63,which also fluctuate in the vertical section.It indicates organic matter of algacl origin with proper ratio contribution from terrestrial sources.The organic matter in the oil shalcs is mature.Different Pr/Ph and C27-diastcrancs/C27-stcrancs proved cspcciallv useful in asscssing variation in dcpositional environment and recognizing preservation potential of the organic matter.
Abundant hiomarkcrs, including n-alkancs, isoprcnoid, stcrancs and tcrpancs, have been detected by GC-MS from the middle Jurassic oil shalcs in the Shuanghu area northern Tibet plateau.N-alkancs contain carbon number nC12-nC35 with a rclativclv wide range,nC15,nC16 or nC17 as the highest peak.Examination of the relative abundance show a dominancc of low carbon molecular components in the n-alkanc.Pr/Ph ratio in oil shalcs range from 0.77 to 1.59, and it fluetuatcs in the vertical section.The upper and lower part of the oil shalcs have slight predominance of pristanc, whereas phytune dominates in the middle part of the oil shale sequence.C30-hopanc is the most abundant in the hopanc series.According to the rclativclv abundance, pcntacvclic tritcrpanc>tricvclic tcrpanc>quartcvclic tcrpanc.Stcranc ∑C27/C29 ratio ranges from 0.79 to 1.20} and ∑(C27+C28)>∑C29.The carbon number distribution of the stcrancs show a slight predominance of C27 components over C29 in the lower part of the oil shalcs and a slight dominance of C29 component over C27 in the upper part of the oil shalcs sequence.C27-diastcranc/ C27-stcranc ratio range from 0.51 to 3.63,which also fluctuate in the vertical section.It indicates organic matter of algacl origin with proper ratio contribution from terrestrial sources.The organic matter in the oil shalcs is mature.Different Pr/Ph and C27-diastcrancs/C27-stcrancs proved cspcciallv useful in asscssing variation in dcpositional environment and recognizing preservation potential of the organic matter.
2001, 19(2): 306-308.
Abstract:
Paleomagnetic data from Ruche Formation(Pliocene)in Kuche Depression indicate that mean dlp angles possess the smallest values in mudstone and progressively increase from muddy siltstone to sandstone and siltstone.The corresponding paleolatitudes bet higher in the same sequences.In order to research this phenomenon we conduct an experiment with 48 specimens and find that decrease in magnetic dip ankle is linearly related to volume variation resulting from compaction.
Paleomagnetic data from Ruche Formation(Pliocene)in Kuche Depression indicate that mean dlp angles possess the smallest values in mudstone and progressively increase from muddy siltstone to sandstone and siltstone.The corresponding paleolatitudes bet higher in the same sequences.In order to research this phenomenon we conduct an experiment with 48 specimens and find that decrease in magnetic dip ankle is linearly related to volume variation resulting from compaction.
2001, 19(2): 315-319.
Abstract:
The area of East China Sea and its vicinity includes East China Sca Shelf Okinawa Trough Rvukvu Island Rvukvu Trench and the west part of Philippine Sca.This is the famous zone of collision and suhduction between an ocean block and a continental block.It is famous and attractive not only for its complex tectonic content but also for its abundant oil and gas resources. Since 1960s, the Institute of Oceanology, Chinese Acadcmv of Sciences has conducted many geology and gcophysics explorations in the area of East China Sea and its vicinity such as seismic reflection explorations scisic refraction ex- plorations, heatflow measurements sea floor temperature measurements and samplings.Rcccnt vears, scientists all over the world pay attention to the gas hydrate study in this area. This paper gives a brief introduction to what is gas hydrate and its steady state under a given temperature-pressure condition.All the geological and geophysical data obtained in the cxplorations mentioned above has been carefully studied in the view of gas hydrate.Based on this data the pressure and temperaturc was calculated along a profile which is perpendicular to the tectonic direction of Rvukvu T-A-Ba system down to several kilometers from the sea floor. Steady temperature-pressure condition of the gas hydrate is also analyzed along this profile.The paper points out that the possible areas that the gas hydrate can he steadily exit mainly are the west slope of the East China Sea, the west part of Okinawa Trough the cast slope of Rvukvu Trench and Philippine basin.The paper points out that it can not say that there are area in the East China Sca basin that the hydrate gas can steadily exist.
The area of East China Sea and its vicinity includes East China Sca Shelf Okinawa Trough Rvukvu Island Rvukvu Trench and the west part of Philippine Sca.This is the famous zone of collision and suhduction between an ocean block and a continental block.It is famous and attractive not only for its complex tectonic content but also for its abundant oil and gas resources. Since 1960s, the Institute of Oceanology, Chinese Acadcmv of Sciences has conducted many geology and gcophysics explorations in the area of East China Sea and its vicinity such as seismic reflection explorations scisic refraction ex- plorations, heatflow measurements sea floor temperature measurements and samplings.Rcccnt vears, scientists all over the world pay attention to the gas hydrate study in this area. This paper gives a brief introduction to what is gas hydrate and its steady state under a given temperature-pressure condition.All the geological and geophysical data obtained in the cxplorations mentioned above has been carefully studied in the view of gas hydrate.Based on this data the pressure and temperaturc was calculated along a profile which is perpendicular to the tectonic direction of Rvukvu T-A-Ba system down to several kilometers from the sea floor. Steady temperature-pressure condition of the gas hydrate is also analyzed along this profile.The paper points out that the possible areas that the gas hydrate can he steadily exit mainly are the west slope of the East China Sea, the west part of Okinawa Trough the cast slope of Rvukvu Trench and Philippine basin.The paper points out that it can not say that there are area in the East China Sca basin that the hydrate gas can steadily exist.
