2007 Vol. 25, No. 1
Display Method:
2007, 25(1): 1-9.
Abstract:
Based on the identification of continental sequence on seismic section and welllogging curve and the characteristics of rocks′ combination and paleontology, the strata of Eogene in Raoyang Depression are divided into three secondorder sequences and ten thirdorder sequences. Thirdorder sequencesⅠ,Ⅱ,Ⅲ,Ⅳ,Ⅴ,Ⅵ,Ⅶ are rift lacustrine basin sequence, and can be divided into three system tracts, that is low stand system tracts, lacustrine transgressive system tracts and high stand system tracts. Thirdorder sequencesⅧ, Ⅸ, Ⅹare fluvial sequence, which can be divided into base level rising system tract and base level falling system tract. Based on the identification and correlation of sequence stratigraphic units, sequence stratigraphy models are established. A primary research on relationship between sequence stratigraphic model has been done.
Based on the identification of continental sequence on seismic section and welllogging curve and the characteristics of rocks′ combination and paleontology, the strata of Eogene in Raoyang Depression are divided into three secondorder sequences and ten thirdorder sequences. Thirdorder sequencesⅠ,Ⅱ,Ⅲ,Ⅳ,Ⅴ,Ⅵ,Ⅶ are rift lacustrine basin sequence, and can be divided into three system tracts, that is low stand system tracts, lacustrine transgressive system tracts and high stand system tracts. Thirdorder sequencesⅧ, Ⅸ, Ⅹare fluvial sequence, which can be divided into base level rising system tract and base level falling system tract. Based on the identification and correlation of sequence stratigraphic units, sequence stratigraphy models are established. A primary research on relationship between sequence stratigraphic model has been done.
2007, 25(1): 21-28.
Abstract:
The sequence in Yuyang Formation of lateCretaceous in southwest of Jianghan Basin is controlled by arid climate. Due to the evolution of climate, the flood period and interflood period alternately occur. In shortterm cycle, the sandstone of channel microfacies and sandflat microfacies deposits in flood period and the mudstone of mudflat microfacies deposits in interflood period. In midterm cycle, there appear several assemblages of shortterm sequence cycle. The main flood period usually lasts quite a long time with a large scale, so there deposits a set of thick grey sandstone of channel microfacies and mudstone of distal microfacies with interlayers of laminar red mudstone of mudflat microfacies .Moreover, there is a set of sandflat, mixedflat and mudflat microfacies in the main interflood period. Different from the two cycles above, in longterm cycle, it has a trend that the scales of the channel decrease in main flood period while the thicknesses of red mudflat increase in interflood period. All these characters in mid& longterm sequence cycle suggest the climate has a tendency to become more and more arid. In terms of the characters of sequences and microfacies in arid climate evolution, the authors build up a set of highresolution stratigraphic sequence and make the stratigraphic correlation.
The sequence in Yuyang Formation of lateCretaceous in southwest of Jianghan Basin is controlled by arid climate. Due to the evolution of climate, the flood period and interflood period alternately occur. In shortterm cycle, the sandstone of channel microfacies and sandflat microfacies deposits in flood period and the mudstone of mudflat microfacies deposits in interflood period. In midterm cycle, there appear several assemblages of shortterm sequence cycle. The main flood period usually lasts quite a long time with a large scale, so there deposits a set of thick grey sandstone of channel microfacies and mudstone of distal microfacies with interlayers of laminar red mudstone of mudflat microfacies .Moreover, there is a set of sandflat, mixedflat and mudflat microfacies in the main interflood period. Different from the two cycles above, in longterm cycle, it has a trend that the scales of the channel decrease in main flood period while the thicknesses of red mudflat increase in interflood period. All these characters in mid& longterm sequence cycle suggest the climate has a tendency to become more and more arid. In terms of the characters of sequences and microfacies in arid climate evolution, the authors build up a set of highresolution stratigraphic sequence and make the stratigraphic correlation.
2007, 25(1): 39-47.
Abstract:
A correlation between sandbodies and analysis of their spatial distribution within an isochronous stratigraphic correlation framework, which is established, based on identification of mediumterm and shortterm saselevel cycles in Lower Shihezi Formation in Daniudi gas field, according to the highresolution sequence stratigraphy concept. Flow units are subdivided into A, B, C and D types in a downgrade order in terms of porosity, permeability and gas saturation parameters, which are obtained from analyzing the datum cycles and hierarchy of the flow units. In addition, types of barriers separating flow units, vertical superimposition and lateral separation patterns of sma
llsized flow units are analyzed and the relationship between the flow units and baselevel cycle is discussed. It is believed that: ①the vertical superimposition and lateral separation of sandbodies and flow units are directly controlled by various grades of baselevel cycles and A/S values; ②The baselevel cycles have directly controls over types, location, scale and lateral connection of vertical superimposition and lateral separation patterns of small –sized flow units; ③In the longterm LSC2 cycle, the types of flow units in a medium-term cycle tend to upgrade with increased accommodations and A/S values; ④In mediumterm and shortterm baselevel cycles, as accommodations and A/S values increase, flow units have deteriorated development and types, with less vertical thickness, shortened lateral extending distance and poor connections.
A correlation between sandbodies and analysis of their spatial distribution within an isochronous stratigraphic correlation framework, which is established, based on identification of mediumterm and shortterm saselevel cycles in Lower Shihezi Formation in Daniudi gas field, according to the highresolution sequence stratigraphy concept. Flow units are subdivided into A, B, C and D types in a downgrade order in terms of porosity, permeability and gas saturation parameters, which are obtained from analyzing the datum cycles and hierarchy of the flow units. In addition, types of barriers separating flow units, vertical superimposition and lateral separation patterns of sma
llsized flow units are analyzed and the relationship between the flow units and baselevel cycle is discussed. It is believed that: ①the vertical superimposition and lateral separation of sandbodies and flow units are directly controlled by various grades of baselevel cycles and A/S values; ②The baselevel cycles have directly controls over types, location, scale and lateral connection of vertical superimposition and lateral separation patterns of small –sized flow units; ③In the longterm LSC2 cycle, the types of flow units in a medium-term cycle tend to upgrade with increased accommodations and A/S values; ④In mediumterm and shortterm baselevel cycles, as accommodations and A/S values increase, flow units have deteriorated development and types, with less vertical thickness, shortened lateral extending distance and poor connections.
2007, 25(1): 53-58.
Abstract:
On the basis of a careful analysis of sedimentary facies from outcrop sections, cores, test data, drilling and well loggings, delta, lake, and sublacustrine fan facies are mainly developed in the Chang 6 Member, Yangchang Formation, Upper Triassic in Fuxian Exploration Area of Ordos Basin. Ten microfacies types of sandbody have been distinguished in these sedimentary facies, for example distributary channel, rivermouth bar, distal bar, gravityflow channel, and distal turbidite sandbodies. Their reservoirs range from 2.20% to 14.90% in the porosity and vary from 0.01×10-3μm2 to 6.50×10-3μm2 in the permeability. These sandbodies are mostly the reservoir type of low porosity and permeability. They are resulted from postdepositional compaction, cementation and filling. The loss ratio of porosity from the compaction is 18%～19％, and those from cementation and filling is equally about 9%. An average of ultimate porosity is equally about 10% today. Four basic types of intraformational heterogeneity are recognized by the vertical pattern of grain size, porosity, permeability and other reservoir parameters and logging response. These types of intraformational heterogeneity are porosity and permeability pooring upward, porosity and permeability improving upward, compound, and complex types. The former three types of intraformational heterogeneity are determined by sandbody microfacies, depositional hydrodynamics, sediment grainsize, depositional sequence. The complex type of intrafomational heterogeneity is largely related to the diagenetic reworking, including differential cementation and differential buried dissolution.
On the basis of a careful analysis of sedimentary facies from outcrop sections, cores, test data, drilling and well loggings, delta, lake, and sublacustrine fan facies are mainly developed in the Chang 6 Member, Yangchang Formation, Upper Triassic in Fuxian Exploration Area of Ordos Basin. Ten microfacies types of sandbody have been distinguished in these sedimentary facies, for example distributary channel, rivermouth bar, distal bar, gravityflow channel, and distal turbidite sandbodies. Their reservoirs range from 2.20% to 14.90% in the porosity and vary from 0.01×10-3μm2 to 6.50×10-3μm2 in the permeability. These sandbodies are mostly the reservoir type of low porosity and permeability. They are resulted from postdepositional compaction, cementation and filling. The loss ratio of porosity from the compaction is 18%～19％, and those from cementation and filling is equally about 9%. An average of ultimate porosity is equally about 10% today. Four basic types of intraformational heterogeneity are recognized by the vertical pattern of grain size, porosity, permeability and other reservoir parameters and logging response. These types of intraformational heterogeneity are porosity and permeability pooring upward, porosity and permeability improving upward, compound, and complex types. The former three types of intraformational heterogeneity are determined by sandbody microfacies, depositional hydrodynamics, sediment grainsize, depositional sequence. The complex type of intrafomational heterogeneity is largely related to the diagenetic reworking, including differential cementation and differential buried dissolution.
2007, 25(1): 65-74.
Abstract:
In the exploration practice, it is found that the inadequate knowledge about the Mesozoic proto-type basin in the western Qaidam basin slowed the oil and gas exploration in this area. Based on analyzing the paleocurrents, combining the Mesozoic outcrops and seismic interpretation data, the Mesozoic prototype of the western Qaidam basin is recovered in this paper. There developed an intermountain depression between the old Alabasitao mountain and the Kunlun mountain, which trending is EW. The evolution of the depression includes two stages: the EarlyMiddle Jurassic and the Late JurassicCretaceous, corresponding developed two prototype basins. The EarlyMiddle Jurassic basin is fault basin type and the Late JurassicCretaceous depression type. During the EarlyMiddle Jurassic, the Altyn Tagh was not uplifted. The deposition was coal bearing formation. The depocenter was in the present Altyn Tagh region. The northwest edge of the depression crossed the Altyn Tagh and conjoined with the Southeast Tarim basin, the northeast edge was ended in the Alabasitao region, and the south was restricted along the HongliuquanMeigouHeishishanYueyashan. During the LateCretaceous, the Altyn Tagh uplifted rapidly and became a province. The deposition was coarse clastic formation. The subsidence and sedimentation area migrated gradually towards inside basin because of the uplift of the Altyn Mountain. The south edge of the depression was along the AlaerHongliuquanHonggouziYue3jing.
In the exploration practice, it is found that the inadequate knowledge about the Mesozoic proto-type basin in the western Qaidam basin slowed the oil and gas exploration in this area. Based on analyzing the paleocurrents, combining the Mesozoic outcrops and seismic interpretation data, the Mesozoic prototype of the western Qaidam basin is recovered in this paper. There developed an intermountain depression between the old Alabasitao mountain and the Kunlun mountain, which trending is EW. The evolution of the depression includes two stages: the EarlyMiddle Jurassic and the Late JurassicCretaceous, corresponding developed two prototype basins. The EarlyMiddle Jurassic basin is fault basin type and the Late JurassicCretaceous depression type. During the EarlyMiddle Jurassic, the Altyn Tagh was not uplifted. The deposition was coal bearing formation. The depocenter was in the present Altyn Tagh region. The northwest edge of the depression crossed the Altyn Tagh and conjoined with the Southeast Tarim basin, the northeast edge was ended in the Alabasitao region, and the south was restricted along the HongliuquanMeigouHeishishanYueyashan. During the LateCretaceous, the Altyn Tagh uplifted rapidly and became a province. The deposition was coarse clastic formation. The subsidence and sedimentation area migrated gradually towards inside basin because of the uplift of the Altyn Mountain. The south edge of the depression was along the AlaerHongliuquanHonggouziYue3jing.
2007, 25(1): 82-89.
Abstract:
Shallow oscillating lacustrine deposit is a special kind of shallow lake, while the lake topography is smooth, lake surface is wide, and water body is very shallow. Lake plane which mainly influenced by climate rise or fall in vibrating type. Deposit mainly is mostly alternative red mudstone and grey mudstone, indicating oxidizing and reducing environment. Shallow oscillating lacustrine deposit extensively developed in the late period of Guantao Formation (Ng1+2 sand sets) in Gudao Oilfield. Deposit features show that high frequency alternative mostly red and grey mudstone, sedimentary structure generally occur in shallow lakes and creature structure growing, water plane rise to decline depositional cycle obviously. Through taking the observation of core hole, describing and analyzing lab test results, five microfacies(water channel, sand flat, mixed flat, mud flat and marsh) can be distinguished and established the high water period and low flow period sedimentary model of Ng1+2 sand sets in Gudao Oilfield.
Shallow oscillating lacustrine deposit is a special kind of shallow lake, while the lake topography is smooth, lake surface is wide, and water body is very shallow. Lake plane which mainly influenced by climate rise or fall in vibrating type. Deposit mainly is mostly alternative red mudstone and grey mudstone, indicating oxidizing and reducing environment. Shallow oscillating lacustrine deposit extensively developed in the late period of Guantao Formation (Ng1+2 sand sets) in Gudao Oilfield. Deposit features show that high frequency alternative mostly red and grey mudstone, sedimentary structure generally occur in shallow lakes and creature structure growing, water plane rise to decline depositional cycle obviously. Through taking the observation of core hole, describing and analyzing lab test results, five microfacies(water channel, sand flat, mixed flat, mud flat and marsh) can be distinguished and established the high water period and low flow period sedimentary model of Ng1+2 sand sets in Gudao Oilfield.
2007, 25(1): 99-109.
Abstract:
Reservoir rocks of the intermediate section of Member 3 of Shahejie Formation of Paleogene in Niuzhuang Subsag, Shandong Province, mainly consists of feldspathic litharenite and litharenite arkose with low compositional maturity and textural maturity. Diagenesis of the sandstones includes compaction, cementation, replacement and dissolution. Compaction includes five occurehces, they are brittle cracking of rigid grains, lined and concavoconvex intergranular contacts, apparently directional arrangement of framework grains, compressional deformation of plastic grains or intercalation of rigid grains in deformational grains, pseudomatrixization of compressional deformed ductile detrital grains. Cements are argilla, carbonates, authigenic clay minerals, quartz and feldspars. Replacement includes quartz replaced feldspars, carbonate cements replaced quartz, feldspars and lithic fragments, and carbonates cements replaced each other. Dissolution of grains mainly are quartz, feldspars and lithic fragments, and of cements of carbonate minerals. The research result shows that the diagenesis of reservoir rock is in Asubstage of telodiagenesis. The main factors which affect the diagenesis of the reservoir include rock composition, sedimentary environment and property of pore fluid. The influences of diagenesis on the reservoir physical properties are mainly the change of porosity and permeability. Compaction and cementation of the reservoir rocks makes the primary pores and permeability decreased quickly, which is the main causes of the poor physical properties; but dissolution of the reservoir rocks is the main factor of the development of the secondary pores, which can improve the physical properties of the reservoir sandstones.
Reservoir rocks of the intermediate section of Member 3 of Shahejie Formation of Paleogene in Niuzhuang Subsag, Shandong Province, mainly consists of feldspathic litharenite and litharenite arkose with low compositional maturity and textural maturity. Diagenesis of the sandstones includes compaction, cementation, replacement and dissolution. Compaction includes five occurehces, they are brittle cracking of rigid grains, lined and concavoconvex intergranular contacts, apparently directional arrangement of framework grains, compressional deformation of plastic grains or intercalation of rigid grains in deformational grains, pseudomatrixization of compressional deformed ductile detrital grains. Cements are argilla, carbonates, authigenic clay minerals, quartz and feldspars. Replacement includes quartz replaced feldspars, carbonate cements replaced quartz, feldspars and lithic fragments, and carbonates cements replaced each other. Dissolution of grains mainly are quartz, feldspars and lithic fragments, and of cements of carbonate minerals. The research result shows that the diagenesis of reservoir rock is in Asubstage of telodiagenesis. The main factors which affect the diagenesis of the reservoir include rock composition, sedimentary environment and property of pore fluid. The influences of diagenesis on the reservoir physical properties are mainly the change of porosity and permeability. Compaction and cementation of the reservoir rocks makes the primary pores and permeability decreased quickly, which is the main causes of the poor physical properties; but dissolution of the reservoir rocks is the main factor of the development of the secondary pores, which can improve the physical properties of the reservoir sandstones.
2007, 25(1): 110-115.
Abstract:
The reservoir of Ansai oilfield was low porosity and low permeability reservoir. The characteristic of the reservoir and microfacies of Chang6 reservoir in H area of Ansai oilfield was analyzed, and the characteristic of the six microfacies include underwater channel, riverside, interfluve, debouch bar, underwater lateral levee, and sheet sand in the area were analyzed in detail. The facies model and reservoir model of the study area were built up by using lots of indicators. The results of the modeling show that ,under the control of facies model, the reservoir model can show the facts underground better, and the model is fit for the work for developing the remaining oil.
The reservoir of Ansai oilfield was low porosity and low permeability reservoir. The characteristic of the reservoir and microfacies of Chang6 reservoir in H area of Ansai oilfield was analyzed, and the characteristic of the six microfacies include underwater channel, riverside, interfluve, debouch bar, underwater lateral levee, and sheet sand in the area were analyzed in detail. The facies model and reservoir model of the study area were built up by using lots of indicators. The results of the modeling show that ,under the control of facies model, the reservoir model can show the facts underground better, and the model is fit for the work for developing the remaining oil.
2007, 25(1): 124-130.
Abstract:
The extraction methods of Quaternary pollen and spores are the bases and precondition in Quaternary Palynology. Northern China is in particular physical geography environment. In Quaternary there are many different types of sediments in northern China. And at all times extraction methods of Quaternary pollen and spores from different type of sediments are the difficulties and highlights in North China. In this paper we choose 74 sediment samples which are from different types of sediment (Loesspaleosol sequence sediment samples, lake sediment samples, Aeolian sand samples, peat and bog samples, Archaeological samples and surface samples). Through our investigations in the laboratory, we have some conclusion about the extraction methods of Quaternary pollen and spores from different type of sediments. To the Loesspaleosol sequence sediment samples the HF treatment and sievinganalysis methods are effective, to be attention is the HF and HCl treatment are needed to be treated more times, and very time of treatment is need to wash to neutral. To lake sediments the HF treatment method is effective, but in North China there are many lakes in the arid area to these samples from arid lakes after HF treatment we should take another step which is heavy liquid methods. To Aeolian sand samples the HF treatment method and heavy liquid method are also effective. To peat and bog samples the heavy liquid method is effective, but some samples of the peat and bog after heavy liquid method we need use the sievinganalysis method to reduce impurity. To the archaeological samples, the first step is heavy liquid method and after that it is better to use the HF treatment method. To surface samples acidalkalifree analysis is the best choice. In the end we discussed the use of the dispersant and HNO3 and the using sequence of acid and alkali.
The extraction methods of Quaternary pollen and spores are the bases and precondition in Quaternary Palynology. Northern China is in particular physical geography environment. In Quaternary there are many different types of sediments in northern China. And at all times extraction methods of Quaternary pollen and spores from different type of sediments are the difficulties and highlights in North China. In this paper we choose 74 sediment samples which are from different types of sediment (Loesspaleosol sequence sediment samples, lake sediment samples, Aeolian sand samples, peat and bog samples, Archaeological samples and surface samples). Through our investigations in the laboratory, we have some conclusion about the extraction methods of Quaternary pollen and spores from different type of sediments. To the Loesspaleosol sequence sediment samples the HF treatment and sievinganalysis methods are effective, to be attention is the HF and HCl treatment are needed to be treated more times, and very time of treatment is need to wash to neutral. To lake sediments the HF treatment method is effective, but in North China there are many lakes in the arid area to these samples from arid lakes after HF treatment we should take another step which is heavy liquid methods. To Aeolian sand samples the HF treatment method and heavy liquid method are also effective. To peat and bog samples the heavy liquid method is effective, but some samples of the peat and bog after heavy liquid method we need use the sievinganalysis method to reduce impurity. To the archaeological samples, the first step is heavy liquid method and after that it is better to use the HF treatment method. To surface samples acidalkalifree analysis is the best choice. In the end we discussed the use of the dispersant and HNO3 and the using sequence of acid and alkali.
2007, 25(1): 131-138.
Abstract:
An oxygenisotope record of a thoriumuraniumdated stalagmite from Tian’e Cave at Shennongjia reflects variation of the East Asian monsoon during the period from 76 to 58 kaB. P. The highresolution (40yr)δ18O record displays a centennialscale variability of the monsoonal precipitation during MIS4. Comparison between stalagmite SW12, Tian’e Cave, stalagmite MSL, Hulu Cave and NGRIP ice core shows that moisture intensity of Tian'e Cave DO18 event reaches that during MIS3, with an amplitude similar to the counterpart in polar record. The initiation timing of DO18 event, Tian'e Cave is consistent with that in Hulu Cave within the dating error, and further confirmed the age of polar DO18 event. Such a strong peak reveals a period of strengthened summer monsoon under a decrease in global temperature during MIS4. Before 70 kaB.P., DO19 event in ice core is older than the counterpart in Asian monsoon at least by 950 years, which is far beyond 230Th dating error of about 700 years. During 69.3～64.4 kaB.P. (DO19′18), centennial oscillations in ice core are an analogy to those of stalagmite SW12, suggesting an interaction of tropical sea and North Atlantic thermohaline.
An oxygenisotope record of a thoriumuraniumdated stalagmite from Tian’e Cave at Shennongjia reflects variation of the East Asian monsoon during the period from 76 to 58 kaB. P. The highresolution (40yr)δ18O record displays a centennialscale variability of the monsoonal precipitation during MIS4. Comparison between stalagmite SW12, Tian’e Cave, stalagmite MSL, Hulu Cave and NGRIP ice core shows that moisture intensity of Tian'e Cave DO18 event reaches that during MIS3, with an amplitude similar to the counterpart in polar record. The initiation timing of DO18 event, Tian'e Cave is consistent with that in Hulu Cave within the dating error, and further confirmed the age of polar DO18 event. Such a strong peak reveals a period of strengthened summer monsoon under a decrease in global temperature during MIS4. Before 70 kaB.P., DO19 event in ice core is older than the counterpart in Asian monsoon at least by 950 years, which is far beyond 230Th dating error of about 700 years. During 69.3～64.4 kaB.P. (DO19′18), centennial oscillations in ice core are an analogy to those of stalagmite SW12, suggesting an interaction of tropical sea and North Atlantic thermohaline.
2007, 25(1): 147-153.
Abstract:
The organic laminae (laminar algal) in the argillaceous limestone and dolomitic mudstone of lower Cretaceous are abundant in Jiuquan basin, but it′s heterogeneity is obvious that mainly shows that the difference of laminar algal contents are very large between the same formation and different areas and same well and different depth. The distribution and yield of laminar algal are all controlled by sedimentary facies and its change. The laminar algal are mainly composite by planktonic algae and it′s pyrolysis products, and most of the algal are the Granoreticella of Chlorophyta . There has a positive correlation between the content of laminar algal and the hydrocarbon generating potentiality of source rock. Most of the found oil in Jiuxi depression is mainly generated from the laminar algal argillaceous limestone of Xiagou Formation of lower Cretaceous, which means that laminar algal is a very important hydrocarbon generating material; it has closed relationship with oilgas in Jiuquan basin. Not only the lacustrine carbonate with abundant organic laminae is good source rock, but also favorable in the fracture initiation and hydrocarbon drainage during the course of hydrocarbon generating and drainage because of the bedded enrichment of hydrocarbon generating materials.
The organic laminae (laminar algal) in the argillaceous limestone and dolomitic mudstone of lower Cretaceous are abundant in Jiuquan basin, but it′s heterogeneity is obvious that mainly shows that the difference of laminar algal contents are very large between the same formation and different areas and same well and different depth. The distribution and yield of laminar algal are all controlled by sedimentary facies and its change. The laminar algal are mainly composite by planktonic algae and it′s pyrolysis products, and most of the algal are the Granoreticella of Chlorophyta . There has a positive correlation between the content of laminar algal and the hydrocarbon generating potentiality of source rock. Most of the found oil in Jiuxi depression is mainly generated from the laminar algal argillaceous limestone of Xiagou Formation of lower Cretaceous, which means that laminar algal is a very important hydrocarbon generating material; it has closed relationship with oilgas in Jiuquan basin. Not only the lacustrine carbonate with abundant organic laminae is good source rock, but also favorable in the fracture initiation and hydrocarbon drainage during the course of hydrocarbon generating and drainage because of the bedded enrichment of hydrocarbon generating materials.
2007, 25(1): 10-20.
Abstract:
According to the law of Milankovitch Cycles in the perpendicularity,the depositional sequences which lay on the verge of the NeoTethys Ocean,north Himalaya continent can be divided into three sequences with typeⅡand eighteen sequences with typeⅢ from Jurassic Period to Early Cretaceous.Lowstand System Tracts of Early and Metaphse Jurassic Period was undergrown,of which Transgressive Systems Tract and Highstand Systems Tract made up .And then Late Jurassic Period,it shaped huge incised valley,sea level had sunk deeply, Early Jurassic Period changed into Shelf Systems Tract.Therefore, it is established that the stratigraphic framework of Jurassic Period and Early Cretaceous.Based on the 1∶〖KG-*2〗250,000 and the 1∶〖KG-*2〗50,000 regional geological survey mapping,the essential sequences of Lithostratigraphic unit will change the static description into the dynamic law survey of basal sequences,which elucidates the relationship of essential sequence law and sequence stratum.
According to the law of Milankovitch Cycles in the perpendicularity,the depositional sequences which lay on the verge of the NeoTethys Ocean,north Himalaya continent can be divided into three sequences with typeⅡand eighteen sequences with typeⅢ from Jurassic Period to Early Cretaceous.Lowstand System Tracts of Early and Metaphse Jurassic Period was undergrown,of which Transgressive Systems Tract and Highstand Systems Tract made up .And then Late Jurassic Period,it shaped huge incised valley,sea level had sunk deeply, Early Jurassic Period changed into Shelf Systems Tract.Therefore, it is established that the stratigraphic framework of Jurassic Period and Early Cretaceous.Based on the 1∶〖KG-*2〗250,000 and the 1∶〖KG-*2〗50,000 regional geological survey mapping,the essential sequences of Lithostratigraphic unit will change the static description into the dynamic law survey of basal sequences,which elucidates the relationship of essential sequence law and sequence stratum.
2007, 25(1): 29-38.
Abstract:
Qingshankou and Yaojia Formation developed delta and lacustrine facies along the long axis of the basin during the period of depression. Qingshankou Formation consists of littoral lake, shallow lake and semideep lake facies. Yaojia Formation consists of delta plain, delta front and prodelta facies. Base on analyses of drilling cores, from the top of Quantou Formation to the top of Yaojia Formation can be divided into 6 sequences, and corresponding to 7 sequence boundaries. One of the sequence boundaries is supersequence boundary. Sequence boundary is characterized by paleosol, erosional surface, calcareous nodules, and truncation. Generally, oolitic limestone, bioclastic limestone, worm boring and pyrite develop above the sequence boundary.
Qingshankou and Yaojia Formation developed delta and lacustrine facies along the long axis of the basin during the period of depression. Qingshankou Formation consists of littoral lake, shallow lake and semideep lake facies. Yaojia Formation consists of delta plain, delta front and prodelta facies. Base on analyses of drilling cores, from the top of Quantou Formation to the top of Yaojia Formation can be divided into 6 sequences, and corresponding to 7 sequence boundaries. One of the sequence boundaries is supersequence boundary. Sequence boundary is characterized by paleosol, erosional surface, calcareous nodules, and truncation. Generally, oolitic limestone, bioclastic limestone, worm boring and pyrite develop above the sequence boundary.
2007, 25(1): 48-52.
Abstract:
According to the idea of analytical hierarchy process, using structure element analytical method combining outcrop studies, for anatomizing
inlayer short lap, to study in detail Shengli oil field fluvial facies sand body internal building structure, the complete set reservoir bed can be divided in to single sand bed at highly asymmetrical longitudinal direction and described to microfacies and single sand body at flat. As a result, geometry, connectivity and reservoir heterogeneity of single sand body can be described predictably, genetic type be estimated accurately and character of sand body internal building structure be revealed ,as well as, the study adapted the requirement of adjusting exploitation and tertiary oil recovery of laterhigh watercut period oil field.
According to the idea of analytical hierarchy process, using structure element analytical method combining outcrop studies, for anatomizing
inlayer short lap, to study in detail Shengli oil field fluvial facies sand body internal building structure, the complete set reservoir bed can be divided in to single sand bed at highly asymmetrical longitudinal direction and described to microfacies and single sand body at flat. As a result, geometry, connectivity and reservoir heterogeneity of single sand body can be described predictably, genetic type be estimated accurately and character of sand body internal building structure be revealed ,as well as, the study adapted the requirement of adjusting exploitation and tertiary oil recovery of laterhigh watercut period oil field.
2007, 25(1): 59-64.
Abstract:
Based on the geological history evolution of Bogda, in this paper the process of basin formation, hydrocarbon generation and petroleum accumulation of Bogda region are discussed. According to the obvious multiphases and segmentations in spatial and temporal evolution, it can be divided into 3 phases: ① from late Devonian to early Permian west Bogda was in intracontinental rifting stage while east Bogda was folded into uplift by inversion in late Carboniferous after experiencing the rifting from Devonian to Carboniferous; Be continued on page 98)②from late Permian to Jurassic west Bogda was in postrifting stage, east Bogda showed the rudiment of mountain with further uplifting, southern margin was in weak pressureflexure subsidence stage；③from late Jurassic to Quaternary west Bogda rifting was folded into the mountains by inversion, northern and southern margins were evolved into forelands, east Bogda experienced further uplifting. The evolution of basin formation, hydrocarbon generation and petroleum accumulation of Bogda region suggests: lacustrine source rock developed in west Bogda during postrifting (P2), which experienced deep burial history(TJ), later uplifting from rifting by inversion destroyed former reservoir, farsourced petroleum accumulating is favorable before incipient uplifting; southern margin of east Bogda experienced multiphases' pressureflexural subsidences, multiinterbedded mudstone and coal hydrocarbon of lakeswamp facies developed(P2J2), former Jurrasic rise controls farsourced oil and gas accumulation of upper Permian petroleum system, the faultrelated folds traps by orogeny since late Jurassic control vertical oil and gas accumulation in Jurassic source rock.
Based on the geological history evolution of Bogda, in this paper the process of basin formation, hydrocarbon generation and petroleum accumulation of Bogda region are discussed. According to the obvious multiphases and segmentations in spatial and temporal evolution, it can be divided into 3 phases: ① from late Devonian to early Permian west Bogda was in intracontinental rifting stage while east Bogda was folded into uplift by inversion in late Carboniferous after experiencing the rifting from Devonian to Carboniferous; Be continued on page 98)②from late Permian to Jurassic west Bogda was in postrifting stage, east Bogda showed the rudiment of mountain with further uplifting, southern margin was in weak pressureflexure subsidence stage；③from late Jurassic to Quaternary west Bogda rifting was folded into the mountains by inversion, northern and southern margins were evolved into forelands, east Bogda experienced further uplifting. The evolution of basin formation, hydrocarbon generation and petroleum accumulation of Bogda region suggests: lacustrine source rock developed in west Bogda during postrifting (P2), which experienced deep burial history(TJ), later uplifting from rifting by inversion destroyed former reservoir, farsourced petroleum accumulating is favorable before incipient uplifting; southern margin of east Bogda experienced multiphases' pressureflexural subsidences, multiinterbedded mudstone and coal hydrocarbon of lakeswamp facies developed(P2J2), former Jurrasic rise controls farsourced oil and gas accumulation of upper Permian petroleum system, the faultrelated folds traps by orogeny since late Jurassic control vertical oil and gas accumulation in Jurassic source rock.
2007, 25(1): 75-81.
Abstract:
The origin of dolostones discussed by means of thin sections staining, trace elements analyzing and isotopes testing, which existed together with lucutrine dark mudstone of Lucaogou Formation, middle Permian, Santanghu Basin. The Lucaogou dolostones were composed of lamellar algal dolostone and patchy dolostone. The characteristics of trace elements and stable isotopes indicated that the dolostones formed in the sedimentary environment with higher salinity, higher Ma/Ca ratio and strong reducibility. By analyzing the source of magnesium ion of Lucaogou dolostones, two types of origin were proposed. Lamellar algal dolostone was formed in quasicontemporaneous phase, and patchy dolostone formed with leaching dolomitization of volcanic material in burial diagenetic phase.
The origin of dolostones discussed by means of thin sections staining, trace elements analyzing and isotopes testing, which existed together with lucutrine dark mudstone of Lucaogou Formation, middle Permian, Santanghu Basin. The Lucaogou dolostones were composed of lamellar algal dolostone and patchy dolostone. The characteristics of trace elements and stable isotopes indicated that the dolostones formed in the sedimentary environment with higher salinity, higher Ma/Ca ratio and strong reducibility. By analyzing the source of magnesium ion of Lucaogou dolostones, two types of origin were proposed. Lamellar algal dolostone was formed in quasicontemporaneous phase, and patchy dolostone formed with leaching dolomitization of volcanic material in burial diagenetic phase.
2007, 25(1): 90-98.
Abstract:
Su6 area is the main gasproducing district in Sulige gas field. There is a lot of debate among institutes and scholars on the type and characteristic of sedimentary facies in the 8th member of the Middle Permian Lower Shihezi Formation which is the main gasproducing strata. According to comprehensive studies of well logs, cores and previous study, the authors conclude that the kind of depositional system is river in the 8th member of Lower Shihezi Formation and it could be further classified into two kinds as the braidedriver in the lower part and the meanderingriver in the upper part. Based on the deliberate analysis of microfacies, the authors set up the gentlegradient braided river sedimentary model and the multichannel and lowsinuosity meandering river sedimentary model, and think that the most favorable reservoir is overriding sand bodies of channel bar and point bar and channel bed sand bodies is subfavorable reservoir. The establishment of the sedimentary facies type and sedimentary model gives a good method to favorable facies belts prediction, reservoir evaluation and exploitation in Sulige gas field including the whole Su6 area.
Su6 area is the main gasproducing district in Sulige gas field. There is a lot of debate among institutes and scholars on the type and characteristic of sedimentary facies in the 8th member of the Middle Permian Lower Shihezi Formation which is the main gasproducing strata. According to comprehensive studies of well logs, cores and previous study, the authors conclude that the kind of depositional system is river in the 8th member of Lower Shihezi Formation and it could be further classified into two kinds as the braidedriver in the lower part and the meanderingriver in the upper part. Based on the deliberate analysis of microfacies, the authors set up the gentlegradient braided river sedimentary model and the multichannel and lowsinuosity meandering river sedimentary model, and think that the most favorable reservoir is overriding sand bodies of channel bar and point bar and channel bed sand bodies is subfavorable reservoir. The establishment of the sedimentary facies type and sedimentary model gives a good method to favorable facies belts prediction, reservoir evaluation and exploitation in Sulige gas field including the whole Su6 area.
2007, 25(1): 116-123.
Abstract:
The researches on the paleoclimatology and paleoenvironment recorded by the red clay have made much progress in the region of China's loess plateau during the past decade. The earliest red clay in the western part of the loess plateau is about 22 Ma old. While in the eastern region to Liupanshan Mountain, the bottom part of the red clay sequences is no more than 9 Ma. Red clay was regarded as the result of aeolian sedimentation which is similar to the loesspaleosol sequences. Red clay records have important significance in the studies on Asian environmental evolution in the Era of Cenozoic, especially on the fields of inland desertification and the impacts of the Tibetan Uplifting. But no aeolian sediments older than the early time of Pleistocene has found in East China.
On the basis of field investigation in the northern suburb of Nanjing, East China, the section of Lingyan Hill was discovered and the loesslike sediment layer was covered by basalt layers with the age of 12.17Ma. Field investigation and sampling was carried out and the whole sedimentary section was about 19 meters high not including the covered basalt layers. Under the basalt layer was the loesslike sediments. A general analysis about the loesslike sediments was carried out on the proxies of grain size, magnetic susceptibility, quartz SEM and geochemical elements. According to the sedimentary characteristics of the sediments and the laboratory analysis results, the 4metre thickness loess like deposits in the section of Lingyan Hill was regarded as the aeolian sediments with the age of more than 12 Ma, which is the earliest aeolian deposits in East China. The deposit is the result of climatic event in the midMiocene, which was corresponding with the 1513Ma rapidly strong deposition of aeolian sediments in the Qin'an section in Loess Plateau and the enlargement of ice sheet in Antarctic after 15Ma.
The researches on the paleoclimatology and paleoenvironment recorded by the red clay have made much progress in the region of China's loess plateau during the past decade. The earliest red clay in the western part of the loess plateau is about 22 Ma old. While in the eastern region to Liupanshan Mountain, the bottom part of the red clay sequences is no more than 9 Ma. Red clay was regarded as the result of aeolian sedimentation which is similar to the loesspaleosol sequences. Red clay records have important significance in the studies on Asian environmental evolution in the Era of Cenozoic, especially on the fields of inland desertification and the impacts of the Tibetan Uplifting. But no aeolian sediments older than the early time of Pleistocene has found in East China.
On the basis of field investigation in the northern suburb of Nanjing, East China, the section of Lingyan Hill was discovered and the loesslike sediment layer was covered by basalt layers with the age of 12.17Ma. Field investigation and sampling was carried out and the whole sedimentary section was about 19 meters high not including the covered basalt layers. Under the basalt layer was the loesslike sediments. A general analysis about the loesslike sediments was carried out on the proxies of grain size, magnetic susceptibility, quartz SEM and geochemical elements. According to the sedimentary characteristics of the sediments and the laboratory analysis results, the 4metre thickness loess like deposits in the section of Lingyan Hill was regarded as the aeolian sediments with the age of more than 12 Ma, which is the earliest aeolian deposits in East China. The deposit is the result of climatic event in the midMiocene, which was corresponding with the 1513Ma rapidly strong deposition of aeolian sediments in the Qin'an section in Loess Plateau and the enlargement of ice sheet in Antarctic after 15Ma.
2007, 25(1): 139-146.
Abstract:
Source rock is very important for deepwater. Because there is no well piercing the Eocene strata, regional correlation method is applied to identify the source rock and define its distribution in Baiyun Depression, including the correlation of subsidence rate, sedimentary facies, seismic facies and seismic velocity lithology with the adjacent areas. The condensed section in the Paleogene strata of Baiyun Depression has three features: ① parasequences moved forward the shore; ② the supply of terrigenous detrital material was not enough; ③ semideep lacustrine fine sediment developed well. The seismic reflection characters are well corresponding to the favored source rock. The seismic facies of mediumweak amplitude, mediumlow frequency and mediumhigh continuity of lake progressive system tracts of Enping and Wenchang Formation in Baiyun Depression is the area of favored source rock. A forecast model is built up for the degree of organic maturity of source beds with single well and the mudstone porosity which can be got easily from the seismic information. This model is then applied to evaluate the thermal evolution degree of the source beds in Baiyun depression preliminarily. Based on the research of Baiyun depression, this paper represents a Methodology of evaluation on source rocks of deep water. This methodology includes five aspects: (1) analysis of sequence stratigraphy to determine the main formation of source rocks, (2) analysis of seismic reflectance signature to determine the occurring position of source rocks, (3) prediction of vitrinite reflectance based on mudstone velocity to determine the maturation of source rocks, (4) prediction of types of organic facies based on the conversion from sedimentary facies to organic facies, (5) comprehensive evaluation to select optimum hydrocarbongenerating sag.
Source rock is very important for deepwater. Because there is no well piercing the Eocene strata, regional correlation method is applied to identify the source rock and define its distribution in Baiyun Depression, including the correlation of subsidence rate, sedimentary facies, seismic facies and seismic velocity lithology with the adjacent areas. The condensed section in the Paleogene strata of Baiyun Depression has three features: ① parasequences moved forward the shore; ② the supply of terrigenous detrital material was not enough; ③ semideep lacustrine fine sediment developed well. The seismic reflection characters are well corresponding to the favored source rock. The seismic facies of mediumweak amplitude, mediumlow frequency and mediumhigh continuity of lake progressive system tracts of Enping and Wenchang Formation in Baiyun Depression is the area of favored source rock. A forecast model is built up for the degree of organic maturity of source beds with single well and the mudstone porosity which can be got easily from the seismic information. This model is then applied to evaluate the thermal evolution degree of the source beds in Baiyun depression preliminarily. Based on the research of Baiyun depression, this paper represents a Methodology of evaluation on source rocks of deep water. This methodology includes five aspects: (1) analysis of sequence stratigraphy to determine the main formation of source rocks, (2) analysis of seismic reflectance signature to determine the occurring position of source rocks, (3) prediction of vitrinite reflectance based on mudstone velocity to determine the maturation of source rocks, (4) prediction of types of organic facies based on the conversion from sedimentary facies to organic facies, (5) comprehensive evaluation to select optimum hydrocarbongenerating sag.
2007, 25(1): 154-160.
Abstract:
The Shihongtan uranium deposit in TurpanHami basin is an interlayer oxidized zone type sandstone uranium deposit, which occurs in the coalbearing detrital rocks of braided meandering stream facies in the Middle Jurassic Xishanyao Formation. There is a great deal of organic matter in the orehosting bed. There is distinct content of organic carbon, soluble organic matter, acidolysis hydrocarbon in various geochemistry belt rocks, and the maximum content in the ore belt. Organics carbon mothermaterial type is sapropelic humus, organic matter is under mature stage. Acidolysis hydrocarbon is coalgas type. Uranium content in rock is positively correlative to soluble organics and acidolysis hydrocarbon by statistical count. The paper analyzed the role of organic matter in sandstone type uranium metallogenetic process, and concluded that the material decomposed under oxygenic condition is advantageous to uranium dissolution and migration in groundwater, material decomposed and polymerized under oxygendeficient condition forms reducing and adsorption geochemistry barrier for uranium precipitation, play an important role in uranium metallogenetic process.
The Shihongtan uranium deposit in TurpanHami basin is an interlayer oxidized zone type sandstone uranium deposit, which occurs in the coalbearing detrital rocks of braided meandering stream facies in the Middle Jurassic Xishanyao Formation. There is a great deal of organic matter in the orehosting bed. There is distinct content of organic carbon, soluble organic matter, acidolysis hydrocarbon in various geochemistry belt rocks, and the maximum content in the ore belt. Organics carbon mothermaterial type is sapropelic humus, organic matter is under mature stage. Acidolysis hydrocarbon is coalgas type. Uranium content in rock is positively correlative to soluble organics and acidolysis hydrocarbon by statistical count. The paper analyzed the role of organic matter in sandstone type uranium metallogenetic process, and concluded that the material decomposed under oxygenic condition is advantageous to uranium dissolution and migration in groundwater, material decomposed and polymerized under oxygendeficient condition forms reducing and adsorption geochemistry barrier for uranium precipitation, play an important role in uranium metallogenetic process.
