2004 Vol. 22, No. 3
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Display Method:
2004, 22(3): 373-379.
Abstract:
Fluvial facies stratum is one of important reservoirs in Meso-Cenozoic continental basin in China. Sequence stratigraphy conventional sequence stratigraphy interpretation techniques based on seismic stratigraphy in passive continental margin is generally considered difficult to be applied to fluvial facies due to the sequence complexity and multiple mixed facies. The paper studies sequence architecture of fluvial strata by using high-resolution sequence stratigraphy based on base-level cycle recognition. Geological-seismic response models of fluvial reservoirs have been established, which are also illustrated by an example in Guantao Formation, Upper Tertiary, Offshore area in Shengli Oilfield.
Fluvial facies stratum is one of important reservoirs in Meso-Cenozoic continental basin in China. Sequence stratigraphy conventional sequence stratigraphy interpretation techniques based on seismic stratigraphy in passive continental margin is generally considered difficult to be applied to fluvial facies due to the sequence complexity and multiple mixed facies. The paper studies sequence architecture of fluvial strata by using high-resolution sequence stratigraphy based on base-level cycle recognition. Geological-seismic response models of fluvial reservoirs have been established, which are also illustrated by an example in Guantao Formation, Upper Tertiary, Offshore area in Shengli Oilfield.
2004, 22(3): 387-392.
Abstract:
During the depositional stage of Cretaceous Qingshankou, Yaojia and Nenjiang Formation, Songliao basin was a depression lake with deep-water, the slope of the basin was gentle along the long-axis, and was steep along the short-axis. The migration of depositional facies is characteristics of the third-order sequence boundary in gentle slope, but the onlap and truncation in seismic profile is not clear. In the steep slope, the third-order sequence boundary displayed as migration of depositional facies, but the onlap and truncation in seismic profile is very clear. The LST, TST and HST can be recognized in the third-order sequence. Along the long-axis, the distributary channel of delta developed very well, but mouth-bar, distal-bar and lake-floor-fan sediments are thin. Along the short-axis, mouth-bar, distal-bar and lake-floor-fan sediments developed in order along the lake-direction, but lack of the sediments from distributary channel of delta.
During the depositional stage of Cretaceous Qingshankou, Yaojia and Nenjiang Formation, Songliao basin was a depression lake with deep-water, the slope of the basin was gentle along the long-axis, and was steep along the short-axis. The migration of depositional facies is characteristics of the third-order sequence boundary in gentle slope, but the onlap and truncation in seismic profile is not clear. In the steep slope, the third-order sequence boundary displayed as migration of depositional facies, but the onlap and truncation in seismic profile is very clear. The LST, TST and HST can be recognized in the third-order sequence. Along the long-axis, the distributary channel of delta developed very well, but mouth-bar, distal-bar and lake-floor-fan sediments are thin. Along the short-axis, mouth-bar, distal-bar and lake-floor-fan sediments developed in order along the lake-direction, but lack of the sediments from distributary channel of delta.
2004, 22(3): 400-407.
Abstract:
The two scores which Shengli Oilfields'oil exploration and production have experienced just coincide with the coursethat sedimentology research and application have done, i.e. sedimentologymarkedly has presentedits boost on oil exploration and exploitation, not only through the studies on sediment facies, depositional systems, but also on seismic and sequence stratigraphy, faulting control on lacustrine deposition, and anisotropic modeling of reservoirs. In the past years, a series of theories, technologies, and their effects involved in sediment dynamics, sequence stratigraphy and lithological pools'exploration and development, as well as sediment units and flow units, has been discussed deeply in a this paper, which promotes the development of reservoir sedimentology of lacustrine rift-subsidence basin.
The two scores which Shengli Oilfields'oil exploration and production have experienced just coincide with the coursethat sedimentology research and application have done, i.e. sedimentologymarkedly has presentedits boost on oil exploration and exploitation, not only through the studies on sediment facies, depositional systems, but also on seismic and sequence stratigraphy, faulting control on lacustrine deposition, and anisotropic modeling of reservoirs. In the past years, a series of theories, technologies, and their effects involved in sediment dynamics, sequence stratigraphy and lithological pools'exploration and development, as well as sediment units and flow units, has been discussed deeply in a this paper, which promotes the development of reservoir sedimentology of lacustrine rift-subsidence basin.
2004, 22(3): 417-424.
Abstract:
Jinhua-QuzhouBasin developed on the metamorphosed basement of Palaeozoic fold, and its formation and development was greatly influenced by pre-mesozoic tectonic framework and geological characteristics. In this paper, the author studied paleogeographic environment, sedimentary structure, depocenter and paleolithological changes etc., analyzed Jinhua-Quzhou Basin's history of formation and evolution and discussed its evolution of tectonic setting from Late-Mesozoic to Cenozoic. From what was studied, four conclusions have been reached: ①Jinhua-Quzhou basin was a fault basin because of compression and then extention; and its boundaries were mostly normal faults. ②In different areas of the basin, there were different stratigraphic sequences. ③Sedimentary facies: the distribution of Jinhua-Quzhou Basin's sedimentary facies varied in different stages, and to some extent, the evolution sequences were clear. Alluvial fan facies spread in northern and southern borders of Jinhua-Quzhou basin as alluvial fan apron with some differences. River facies and sand bank facies distributed in the middle of Jinhua-Quzhou Basin, locating in sectors between Quxian and Longyou. Delta facies included fan delta, braided delta and normal delta. Also, in areas we studied, there were lake facies, but shore shallow lake subfacies and semi-deep lake subfacies were the most important ones.
Jinhua-QuzhouBasin developed on the metamorphosed basement of Palaeozoic fold, and its formation and development was greatly influenced by pre-mesozoic tectonic framework and geological characteristics. In this paper, the author studied paleogeographic environment, sedimentary structure, depocenter and paleolithological changes etc., analyzed Jinhua-Quzhou Basin's history of formation and evolution and discussed its evolution of tectonic setting from Late-Mesozoic to Cenozoic. From what was studied, four conclusions have been reached: ①Jinhua-Quzhou basin was a fault basin because of compression and then extention; and its boundaries were mostly normal faults. ②In different areas of the basin, there were different stratigraphic sequences. ③Sedimentary facies: the distribution of Jinhua-Quzhou Basin's sedimentary facies varied in different stages, and to some extent, the evolution sequences were clear. Alluvial fan facies spread in northern and southern borders of Jinhua-Quzhou basin as alluvial fan apron with some differences. River facies and sand bank facies distributed in the middle of Jinhua-Quzhou Basin, locating in sectors between Quxian and Longyou. Delta facies included fan delta, braided delta and normal delta. Also, in areas we studied, there were lake facies, but shore shallow lake subfacies and semi-deep lake subfacies were the most important ones.
2004, 22(3): 434-442.
Abstract:
Typical reefs are discovered in the Maokou'an deposits of Zhesiaobo, Inner Mongolia. They extend from east to west, and can be divided into backreef facies, reef front facies and reef core facies clearly. Reef flat, reef crest and reef front margin can be recognized in the reef core facies. The relationship among the various facies suggests that southern part of the reefs are landward, and the northern part seaward. The reefs are very rich in fossils, in which different bioassemblages can be distinguished. The spatial distribution of those assemblages seems to be controlled by facies belts of reefs, and they may exchange laterally from one to anothe.
Typical reefs are discovered in the Maokou'an deposits of Zhesiaobo, Inner Mongolia. They extend from east to west, and can be divided into backreef facies, reef front facies and reef core facies clearly. Reef flat, reef crest and reef front margin can be recognized in the reef core facies. The relationship among the various facies suggests that southern part of the reefs are landward, and the northern part seaward. The reefs are very rich in fossils, in which different bioassemblages can be distinguished. The spatial distribution of those assemblages seems to be controlled by facies belts of reefs, and they may exchange laterally from one to anothe.
2004, 22(3): 449-454.
Abstract:
According to the thickness and distribution of coals in a sequence stratigraphic framework, the influence of depositional environments, the evolution of depositional system and the fluctuation of lake-level on the coal accumulation, during the deposition of Jurassic Badaowan formation in Junggar basin, has been discussed. The favorable settings for coal accumulation were the interdelta bay, fluvial plain and delta plain during the earlier Jurassic in Junggar basin, which always kept the balance between the rate of peat accumulation and the rate of accommodation creation, and acted as the expressing form of the basic control of the coal accumulation. In fact, the basic control on coal accumulation was the rate of accommodation increase mainly controlled by the fluctuation of relative lake-level for the Jurassic Badaowan formation in Junggar basin.
According to the thickness and distribution of coals in a sequence stratigraphic framework, the influence of depositional environments, the evolution of depositional system and the fluctuation of lake-level on the coal accumulation, during the deposition of Jurassic Badaowan formation in Junggar basin, has been discussed. The favorable settings for coal accumulation were the interdelta bay, fluvial plain and delta plain during the earlier Jurassic in Junggar basin, which always kept the balance between the rate of peat accumulation and the rate of accommodation creation, and acted as the expressing form of the basic control of the coal accumulation. In fact, the basic control on coal accumulation was the rate of accommodation increase mainly controlled by the fluctuation of relative lake-level for the Jurassic Badaowan formation in Junggar basin.
Depositional Features of the Zhongwei Basin, Ningxia, and Its Implications for Neotectonic Movements
2004, 22(3): 465-473.
Abstract:
The Zhongwei Basin is the largest compressional basin situated between the arc-form mountains along the northeast margin of Tibetan Plateau. Based upon our investigation in the field and in borehole data, depositional features and their variations in space and time are analyzed in this paper. In the Pliocene, the Xiangshan Mountain began to thrust northeast strongly along the Xiangshan-Tianjingshan fault zone, resulting in the depression in foreland and formation of the Zhongwei Basin. The strong compression also made some earlier sediments in the southern part of the basin thrust and uplift northward along some south-dip imbricate faults, producing wedge-like basin in the north-south profile with deep southward and shallow northward. Combing the thrusting, later sedimentation, including the one of the Yellow River, which flew through the basin from the west to east, had continuously moved northwards, occurring in diachronism of the sediments. Approximately in the end of the middle Pleistocene, the Zhongwei Basin was elevated responsible for strong activities of Yantongshan fault zone situated in the northeast of the basin, resulting in the down-cutting of the Yellow River, which ended the depositional process of the Zhongwei Basin. The end of depositional process of the Zhongwei Basin possibly means the starting of the strong activities of the Yantonshan fault zone rather than the end of the activities of the Xiangshan Tianjingshan fault zone. The process above probably implies the shifting processes of the strong compressional deformation from southwest to northeast along the northeast margin of Tibetan Plateau.
The Zhongwei Basin is the largest compressional basin situated between the arc-form mountains along the northeast margin of Tibetan Plateau. Based upon our investigation in the field and in borehole data, depositional features and their variations in space and time are analyzed in this paper. In the Pliocene, the Xiangshan Mountain began to thrust northeast strongly along the Xiangshan-Tianjingshan fault zone, resulting in the depression in foreland and formation of the Zhongwei Basin. The strong compression also made some earlier sediments in the southern part of the basin thrust and uplift northward along some south-dip imbricate faults, producing wedge-like basin in the north-south profile with deep southward and shallow northward. Combing the thrusting, later sedimentation, including the one of the Yellow River, which flew through the basin from the west to east, had continuously moved northwards, occurring in diachronism of the sediments. Approximately in the end of the middle Pleistocene, the Zhongwei Basin was elevated responsible for strong activities of Yantongshan fault zone situated in the northeast of the basin, resulting in the down-cutting of the Yellow River, which ended the depositional process of the Zhongwei Basin. The end of depositional process of the Zhongwei Basin possibly means the starting of the strong activities of the Yantonshan fault zone rather than the end of the activities of the Xiangshan Tianjingshan fault zone. The process above probably implies the shifting processes of the strong compressional deformation from southwest to northeast along the northeast margin of Tibetan Plateau.
2004, 22(3): 481-486.
Abstract:
Basin subsidence can be induced by many factors, such as tectonic activity, sedimentary loading, and water loading, and so on. This paper puts forward a concept of water loads subsidence, deduces a calculation formula of water loads subsidence, quantitatively analyzes the contribution of water loads to basin subsidence. Furthermore, fully considering the effects of sediment loads,water loads,sea-level changes, and paleao-water depth on basin subsidence, this paper gives a revision to the formula used to calculate the tectonic subsidence by Steckler and Watts. The quantitative analysis of the COST B-2 well located in Atlantic-type continental margin of New York, U.S.A indicated that each 1km tectonic subsidence can simultaneously results in 0.435 km water loads subsidence, the "true" tectonic subsidence that removed water loads effect on basin subsidence is about 30.3% lower than the result calculated using Steckler and Watts formula. So, we can conclude that water loads are one of the important factors, which result in the intensive subsidence of Atlantic-type continental margin.
Basin subsidence can be induced by many factors, such as tectonic activity, sedimentary loading, and water loading, and so on. This paper puts forward a concept of water loads subsidence, deduces a calculation formula of water loads subsidence, quantitatively analyzes the contribution of water loads to basin subsidence. Furthermore, fully considering the effects of sediment loads,water loads,sea-level changes, and paleao-water depth on basin subsidence, this paper gives a revision to the formula used to calculate the tectonic subsidence by Steckler and Watts. The quantitative analysis of the COST B-2 well located in Atlantic-type continental margin of New York, U.S.A indicated that each 1km tectonic subsidence can simultaneously results in 0.435 km water loads subsidence, the "true" tectonic subsidence that removed water loads effect on basin subsidence is about 30.3% lower than the result calculated using Steckler and Watts formula. So, we can conclude that water loads are one of the important factors, which result in the intensive subsidence of Atlantic-type continental margin.
2004, 22(3): 494-499.
Abstract:
Cs and 14C AMS were analyzed for the Bosten Lake sediment cores in Xinjiang, arid China. In the BST-4 core 137 Cs section, there are obvious 1986 Chemobyl nucleus accident peak and 1975, 1963 peaks, which are important age characteristics for the Bosten lake sediment. The sedimentation rate, which was average 0.13±0.01 g/cm 2 .a, was stable in the Bosten Lake by analysing the mass depth and ages. It is very similar to that from the 14C age, 0.13±0.03cm/a for BSTC-1 core and 0.12±0.05cm/a for xb46 core, in Bosten Lake after middle Holocene and show that the depositional environment was stable and the 14C ages were accurate. From the 14C age of the samples in Bosten Lake, it can be calibrated the old carbon effect produced by the hard water in the lakes and old carbon effect can lead to the old age for the 14C age in analysing the lake organic matters in sediments. We obtained the result of about 650a old effect in Bosten lake from the 14C age and the sedimentation rate by the 137 Cs data.
Cs and 14C AMS were analyzed for the Bosten Lake sediment cores in Xinjiang, arid China. In the BST-4 core 137 Cs section, there are obvious 1986 Chemobyl nucleus accident peak and 1975, 1963 peaks, which are important age characteristics for the Bosten lake sediment. The sedimentation rate, which was average 0.13±0.01 g/cm 2 .a, was stable in the Bosten Lake by analysing the mass depth and ages. It is very similar to that from the 14C age, 0.13±0.03cm/a for BSTC-1 core and 0.12±0.05cm/a for xb46 core, in Bosten Lake after middle Holocene and show that the depositional environment was stable and the 14C ages were accurate. From the 14C age of the samples in Bosten Lake, it can be calibrated the old carbon effect produced by the hard water in the lakes and old carbon effect can lead to the old age for the 14C age in analysing the lake organic matters in sediments. We obtained the result of about 650a old effect in Bosten lake from the 14C age and the sedimentation rate by the 137 Cs data.
2004, 22(3): 507-512.
Abstract:
Sedimentation rates,element concentrations and grain sizes distribution of Cores MS and DLS sediments from Taihu Lake are investigated.According to 137 Cs dating,modern accumulation rates of Cores MS and DLS are 1.7 mm/a and 0.9mm/a.The pollution history of Taihu Lake is studied based on the geochemical characteristics in Core MS sediments.Pb,Zn,As,Hg,Mn and Ni are the main pollution heavy metals,which have different pollution history and pollution degree.The concentration of As in sediments increased since 1930s'due to the private industries development,and that of Hg increased since 1940s',which is the important pollution element due to the bio-accumulative effect.Pb,Zn,Ni and Mn pollution began at late 1970s'and the concentration in sediments became higher as As and Hg.The concentration of TP increased since 1940s',and that of TN and TOC was from late 1970s',which have close correlation with the eutrophication of lake.The history of elements pollution is correspondent with the economy development in the catchment of Taihu Lake.
Sedimentation rates,element concentrations and grain sizes distribution of Cores MS and DLS sediments from Taihu Lake are investigated.According to 137 Cs dating,modern accumulation rates of Cores MS and DLS are 1.7 mm/a and 0.9mm/a.The pollution history of Taihu Lake is studied based on the geochemical characteristics in Core MS sediments.Pb,Zn,As,Hg,Mn and Ni are the main pollution heavy metals,which have different pollution history and pollution degree.The concentration of As in sediments increased since 1930s'due to the private industries development,and that of Hg increased since 1940s',which is the important pollution element due to the bio-accumulative effect.Pb,Zn,Ni and Mn pollution began at late 1970s'and the concentration in sediments became higher as As and Hg.The concentration of TP increased since 1940s',and that of TN and TOC was from late 1970s',which have close correlation with the eutrophication of lake.The history of elements pollution is correspondent with the economy development in the catchment of Taihu Lake.
2004, 22(3): 518-524.
Abstract:
Wayaopu coal formation is one of the most important coal formations and the earliest idea of oils from terrigenous deposit possibly origin ated from it. Based on the research results of the organic petrology and coal petrology, it is fromed to peat bog facies in deep underwater forest, the coals contain high-content liptinites, and the desmocollinites are the main type of vitrinite group of the coals and the desmocollinites have higher petroleum potential. Organic geochemistry shows that the kerogen type of WaYaoPu coal formations is Ⅱ, lower-middle maturity. The result of thermal simulation experiment on the coal shows that the coal has higher oil production, but it is difficult to form industrial oil-gas accumulation because of the low potential oil generating ability of the darker mudstones and the low maturity of the main macerals in the coal, and small scale and thin coal-beds of the coal in spite of its high potential oil generating ability.
Wayaopu coal formation is one of the most important coal formations and the earliest idea of oils from terrigenous deposit possibly origin ated from it. Based on the research results of the organic petrology and coal petrology, it is fromed to peat bog facies in deep underwater forest, the coals contain high-content liptinites, and the desmocollinites are the main type of vitrinite group of the coals and the desmocollinites have higher petroleum potential. Organic geochemistry shows that the kerogen type of WaYaoPu coal formations is Ⅱ, lower-middle maturity. The result of thermal simulation experiment on the coal shows that the coal has higher oil production, but it is difficult to form industrial oil-gas accumulation because of the low potential oil generating ability of the darker mudstones and the low maturity of the main macerals in the coal, and small scale and thin coal-beds of the coal in spite of its high potential oil generating ability.
2004, 22(3): 535-540.
Abstract:
Semibathile facies was developed in the upper Dacangfang formation of Biyang depression, and its dark mudstones with parent material of type Ⅱ1 and being organic abundant, have reached a high maturation stage suggesting a strong generation potential. Based on oil-source correlation, the authors believe that the oil of Dacangfang much differs from those of Eh2 and Eh3 members in terms of physical properties, carbon isotopics, chromatography of saturated hydrocarbons, GC-MS characteristics of aromatic hydrocarbons, but geochemically similar to the dark grey mudstones in Dacangfang formation, i.e. attributed to authigenic and authi-reservoired deposits. The belt of Shuanghe-Zhaoao-Anpeng in the steep slope th the south is considered as a favourable area in Dacangfang formation.
Semibathile facies was developed in the upper Dacangfang formation of Biyang depression, and its dark mudstones with parent material of type Ⅱ1 and being organic abundant, have reached a high maturation stage suggesting a strong generation potential. Based on oil-source correlation, the authors believe that the oil of Dacangfang much differs from those of Eh2 and Eh3 members in terms of physical properties, carbon isotopics, chromatography of saturated hydrocarbons, GC-MS characteristics of aromatic hydrocarbons, but geochemically similar to the dark grey mudstones in Dacangfang formation, i.e. attributed to authigenic and authi-reservoired deposits. The belt of Shuanghe-Zhaoao-Anpeng in the steep slope th the south is considered as a favourable area in Dacangfang formation.
2004, 22(3): 380-386.
Abstract:
The Paleocene Mingyuefeng Formation, an important oil/gas bearing segment of the west Lishui sag, filled shallow sea and deltaic deposit which has formed an integrated third order sequence. The sequence boundaries show downlap, truncation and incised characteristic on seismic profiles. The incised valley shows blocky and trunk configuration on well logs. According to the initial and maximal transgression surfaces, the sequence may be classified into lowstand tract, transgression tract and highstand tract. According to the minor regression surface, there has been recognized the falling sea level system tract in the late highstand tract. Sequence boundary, major transgression surfaces and the minor regression surface have been confirmed by the enrichment and differences of paleobiology fossils. Through the sequence-tract mapping of the above 4 tracts, the distribution and evolution of depositional systems in different periods have been revealed. There developed incised valley, shoreline delta classtic and prodelta turbidite in lowstand and transgression tract. The incised valley and shoreline delta distributed on the western slope margin of the basin, and the depositional systems mainly came from the northwest and the southeast of the basin. The sparse prodelta turbidite distributed on the eastern abrupt margin of the basin and the depositional systems came from the east. It is charactered by large-scale progradation delta front sandstone in the highstand tract and falling sea level tract. The highstand tract delta distributed on the west margin of the basin, and there developed more on the south than on the north. The depositional area of the basin has obviously shrunk in the falling sea level tract so that the deltaic sandbody centralized on the central section of the western of the basin.
The Paleocene Mingyuefeng Formation, an important oil/gas bearing segment of the west Lishui sag, filled shallow sea and deltaic deposit which has formed an integrated third order sequence. The sequence boundaries show downlap, truncation and incised characteristic on seismic profiles. The incised valley shows blocky and trunk configuration on well logs. According to the initial and maximal transgression surfaces, the sequence may be classified into lowstand tract, transgression tract and highstand tract. According to the minor regression surface, there has been recognized the falling sea level system tract in the late highstand tract. Sequence boundary, major transgression surfaces and the minor regression surface have been confirmed by the enrichment and differences of paleobiology fossils. Through the sequence-tract mapping of the above 4 tracts, the distribution and evolution of depositional systems in different periods have been revealed. There developed incised valley, shoreline delta classtic and prodelta turbidite in lowstand and transgression tract. The incised valley and shoreline delta distributed on the western slope margin of the basin, and the depositional systems mainly came from the northwest and the southeast of the basin. The sparse prodelta turbidite distributed on the eastern abrupt margin of the basin and the depositional systems came from the east. It is charactered by large-scale progradation delta front sandstone in the highstand tract and falling sea level tract. The highstand tract delta distributed on the west margin of the basin, and there developed more on the south than on the north. The depositional area of the basin has obviously shrunk in the falling sea level tract so that the deltaic sandbody centralized on the central section of the western of the basin.
2004, 22(3): 393-399.
Abstract:
Based on the analysis of seismic data, borehole and well-logging,core and paleontology of Tertiary and upper Cretaceous with thickness of more than 7000m in Gaoyou Sag, Subei Basin, two first-level sequences, four second-level sequences and 11 third-sequences have been identified. System tracts were also identified within each sequence based on the maximum flooding surface and fault-break(first flooding surface). Each of the 11 sequences consists of either complete lowstand, transgressive and highstand system tracts or one or two of them. Due to the different activity of Hanliu fault in the east and west part of Gaoyou sag, the west part is characterized by bi-fault subsiding basin, and the east part single-fault basin. Based on structural analysis, sequence pattern in Gaoyou sag may be described as the west part with fault-break and east without break. The main controlling factors of sequence stratigraphy was analyzed and were believed to be tectonics and climate.
Based on the analysis of seismic data, borehole and well-logging,core and paleontology of Tertiary and upper Cretaceous with thickness of more than 7000m in Gaoyou Sag, Subei Basin, two first-level sequences, four second-level sequences and 11 third-sequences have been identified. System tracts were also identified within each sequence based on the maximum flooding surface and fault-break(first flooding surface). Each of the 11 sequences consists of either complete lowstand, transgressive and highstand system tracts or one or two of them. Due to the different activity of Hanliu fault in the east and west part of Gaoyou sag, the west part is characterized by bi-fault subsiding basin, and the east part single-fault basin. Based on structural analysis, sequence pattern in Gaoyou sag may be described as the west part with fault-break and east without break. The main controlling factors of sequence stratigraphy was analyzed and were believed to be tectonics and climate.
2004, 22(3): 408-416.
Abstract:
Along with deepening of oil-gas exploration in Tarim basin in recent years, many progresses have been obtained in sedimentological research of several chief target strata: ① as the recognition progress of formation mechanism to the Ordovician heterogeneous carbonate paleo-karst reservoir and establishment of its seismic identification technology in Lun'nan-Tahe oil field with more than hundred million tons reserve, the exploration success ratio has been enhanced greaty . Recent breakthrough of oil-gas exploration also indicates that there exists wider exploration foreground in platform margin belt out of main Ordovician karst region in Lun'nan area; ② due to establishment of sequence stratigraphy framework and distribution model of the Upper Devonian-Lower Carboniferous Donghe Fm. unsynchronous shore sandstone in Hade 4 oil field, it has broadened to prospect for reservoirs of stratigraphic traps and stratigraphy-structure compound traps in Donghe Sandstone; as the discovery of special reservoir-cap rocks combination in which low porosity permeability sandstone as reservoir rocks and reticulation clay cementated sandstone as gas cap rocks because of water-locking effect in Jurassic of Yin'nan 2 gas field, the gas prospect domain has been broadened; the high-pressure gas reservoir-cap rocks combinations as in Kela 2 large gas field, in which Lower Cretaceous Basijiqike Fm. thick sandstones formed in braided river delta alluvial fan delta under arid climate as the reservoir rocks and the Paleogene thick gypsum-salt mudstones formed in evaporite bay lagoon as good cap rocks, are widespread distributed in Kuche depression and southwestern Tarim basin. So there is a great potential for exploration.
Along with deepening of oil-gas exploration in Tarim basin in recent years, many progresses have been obtained in sedimentological research of several chief target strata: ① as the recognition progress of formation mechanism to the Ordovician heterogeneous carbonate paleo-karst reservoir and establishment of its seismic identification technology in Lun'nan-Tahe oil field with more than hundred million tons reserve, the exploration success ratio has been enhanced greaty . Recent breakthrough of oil-gas exploration also indicates that there exists wider exploration foreground in platform margin belt out of main Ordovician karst region in Lun'nan area; ② due to establishment of sequence stratigraphy framework and distribution model of the Upper Devonian-Lower Carboniferous Donghe Fm. unsynchronous shore sandstone in Hade 4 oil field, it has broadened to prospect for reservoirs of stratigraphic traps and stratigraphy-structure compound traps in Donghe Sandstone; as the discovery of special reservoir-cap rocks combination in which low porosity permeability sandstone as reservoir rocks and reticulation clay cementated sandstone as gas cap rocks because of water-locking effect in Jurassic of Yin'nan 2 gas field, the gas prospect domain has been broadened; the high-pressure gas reservoir-cap rocks combinations as in Kela 2 large gas field, in which Lower Cretaceous Basijiqike Fm. thick sandstones formed in braided river delta alluvial fan delta under arid climate as the reservoir rocks and the Paleogene thick gypsum-salt mudstones formed in evaporite bay lagoon as good cap rocks, are widespread distributed in Kuche depression and southwestern Tarim basin. So there is a great potential for exploration.
2004, 22(3): 425-433.
Abstract:
In the western Qaidam basin, Tertiary lacustrine reef has been discovered recently in several kilometers strata from the lower member of lower Ganchaigou formation to lower Youshashan formation in Ganchaigou area. On the basis of numerous observations on outcrop, thin sections and casting sections of the reef, and the application of various analytical techniques including analysis of capillary pressure curve and pattern analysis of pore structure, reservoir characteristics of reef have been thoroughly studied. The reef has complex types of pores, such as skeletal pores, intraparticle pores, moldic pores and corroded cavities, and so on. The reef underwent four diagenetic period, such as syngenetic, eogenetic, telogenetic, and hypergene diagenetic period. The formation of the pores are mainly affected by the cementation and dissolution with few primary pores, however, the secondary pores are abundant and form excellent reservoir for oil and gas. The discovery of the Tertiary lacustrine reef in the Qaidam Basin is of important practical significance for the exploration and development of the Qinghai oilfield.
In the western Qaidam basin, Tertiary lacustrine reef has been discovered recently in several kilometers strata from the lower member of lower Ganchaigou formation to lower Youshashan formation in Ganchaigou area. On the basis of numerous observations on outcrop, thin sections and casting sections of the reef, and the application of various analytical techniques including analysis of capillary pressure curve and pattern analysis of pore structure, reservoir characteristics of reef have been thoroughly studied. The reef has complex types of pores, such as skeletal pores, intraparticle pores, moldic pores and corroded cavities, and so on. The reef underwent four diagenetic period, such as syngenetic, eogenetic, telogenetic, and hypergene diagenetic period. The formation of the pores are mainly affected by the cementation and dissolution with few primary pores, however, the secondary pores are abundant and form excellent reservoir for oil and gas. The discovery of the Tertiary lacustrine reef in the Qaidam Basin is of important practical significance for the exploration and development of the Qinghai oilfield.
2004, 22(3): 443-448.
Abstract:
The quantitative division of sedimentary subfacies is a difficult problem of sedimentology. By flume experiment, it is found that during the formation the fan delta prograde forward and accrete upward constantly. The accretion set and foreset represent respectively the fan delta plain and front subfacies. In the section, the thickness of plain becomes thinner from root to former, and the thickness of front becomes thicker. This paper puts forward that the point where the thicknesses of accretion set and foreset are equal can be regarded as the borderline of fan delta plain and front, which resolves the problem of the quantitative division of fan delta subfacies on the plane. Based on simulation experiment of fan delta in steep slope, the points where the thicknesses of accretion set and foreset are equal change with the development of fan delta, but the ratio of the plain length to the whole fan length is unchangeable, which is affected only by the gradient of original forms and fan surface. The gradient of fan surface is an experiental constant. So, in the exploration, after we get the gradients of original forms by dipmeter and the length of fan delta by seismic profile or the statistics of single-well data, we can calculate the distribution of the front, which provide foundations for the prediction of favorable facies in petroleum exploration.
The quantitative division of sedimentary subfacies is a difficult problem of sedimentology. By flume experiment, it is found that during the formation the fan delta prograde forward and accrete upward constantly. The accretion set and foreset represent respectively the fan delta plain and front subfacies. In the section, the thickness of plain becomes thinner from root to former, and the thickness of front becomes thicker. This paper puts forward that the point where the thicknesses of accretion set and foreset are equal can be regarded as the borderline of fan delta plain and front, which resolves the problem of the quantitative division of fan delta subfacies on the plane. Based on simulation experiment of fan delta in steep slope, the points where the thicknesses of accretion set and foreset are equal change with the development of fan delta, but the ratio of the plain length to the whole fan length is unchangeable, which is affected only by the gradient of original forms and fan surface. The gradient of fan surface is an experiental constant. So, in the exploration, after we get the gradients of original forms by dipmeter and the length of fan delta by seismic profile or the statistics of single-well data, we can calculate the distribution of the front, which provide foundations for the prediction of favorable facies in petroleum exploration.
2004, 22(3): 455-464.
Abstract:
Triassic to Paleogene,Tethyan Himalaya went through the forming, exaggerating, attenuating, closing and finally transforming into foreland basin of the oceanic basin. During the passive continental margin stage (T-K),a set of sedimentary sequence of clastic shelf to carbonate platform was developed in the northern Indian continent margin. At the earliest Paleogene,Tibet-Tethys was closed down,causing the forming of the southern Tibet peripheral foreland basin system. In late Eocene,the returning of the southern Tibet foreland basin caused the sea-water to retreat gradually from Tibet area from east to west. The Paleocene supersequence of the southern Tibet was formed under the background of the India/Asia collision,the sedimentary environment of which was a foreland basin with strong tectonic activity. Sedimentary facies is the substance exhibition of depositional environments. In this study, 13 biofacies and 14 sedimentary facies were recognized from the Paleogene sediments of the southern Tibet. The supersequence with 200-2000m thickness and 30Ma age is composed of nine large-scale third-class sequences which could be regionally correlated on the outcrops. Small-scale third-class parasequence sets, which resulted from the global sea-level change and unbalancedly flexual subsidence of basin basement caused by collision and only can be locally correlated, formed larger-scale sequences. Every large-scale third class sequence is asymmetrical and characterized by LST,TST and HST with special lithologic associations and palaeontological assemblages. The evolution of the southern Tibet foreland basin is accordant with the usual evolutional model of foreland basin and its sedimentary sequence shows that it had a multi-cycle sediment-tectonic evolutional history.
Triassic to Paleogene,Tethyan Himalaya went through the forming, exaggerating, attenuating, closing and finally transforming into foreland basin of the oceanic basin. During the passive continental margin stage (T-K),a set of sedimentary sequence of clastic shelf to carbonate platform was developed in the northern Indian continent margin. At the earliest Paleogene,Tibet-Tethys was closed down,causing the forming of the southern Tibet peripheral foreland basin system. In late Eocene,the returning of the southern Tibet foreland basin caused the sea-water to retreat gradually from Tibet area from east to west. The Paleocene supersequence of the southern Tibet was formed under the background of the India/Asia collision,the sedimentary environment of which was a foreland basin with strong tectonic activity. Sedimentary facies is the substance exhibition of depositional environments. In this study, 13 biofacies and 14 sedimentary facies were recognized from the Paleogene sediments of the southern Tibet. The supersequence with 200-2000m thickness and 30Ma age is composed of nine large-scale third-class sequences which could be regionally correlated on the outcrops. Small-scale third-class parasequence sets, which resulted from the global sea-level change and unbalancedly flexual subsidence of basin basement caused by collision and only can be locally correlated, formed larger-scale sequences. Every large-scale third class sequence is asymmetrical and characterized by LST,TST and HST with special lithologic associations and palaeontological assemblages. The evolution of the southern Tibet foreland basin is accordant with the usual evolutional model of foreland basin and its sedimentary sequence shows that it had a multi-cycle sediment-tectonic evolutional history.
2004, 22(3): 474-480.
Abstract:
The wave process analysis of sedimentary basin is bran-new theory and method on oil and gas basin analysis. Based on the wave principle and method, the deposition and erosion processes of the deeper part or its vicinity, where strata data are unknown, can be predicted, and the erosion thickness can be calculated and the evolutionary history of the basin can be restored in detail. The transferred law of deposition and subsidence center can be found, and the relativity between wave characteristic and petroleum geologic factors can be recognized,so all of these results make it possible that we discuss the low of petroleum forming and distributing from bran-new point of view. In this paper, a case study on Chuxiong basin is given. These coupling relationships between wave characteristic curve and source,reservoir and cap rocks are established by wave processes analysis for wells and sections of Chuxiong basin, and four kinds of coupling patterns are given, in which the source layer occur at the transition position of the wave curve in the right of datum line, the reservoir lie in the wave crest position of the wave curve in the right of datum line, the cover locate in the trough position of the wave curve the in right of datum line, and the migration channel(unconformity) appear on the trough position of the wave curve in the left of datum line. These research achievements are of important significance for predicting space-time distribution law of source,reservoir and cap rocks, and for effectively instructing oil and gas exploration.
The wave process analysis of sedimentary basin is bran-new theory and method on oil and gas basin analysis. Based on the wave principle and method, the deposition and erosion processes of the deeper part or its vicinity, where strata data are unknown, can be predicted, and the erosion thickness can be calculated and the evolutionary history of the basin can be restored in detail. The transferred law of deposition and subsidence center can be found, and the relativity between wave characteristic and petroleum geologic factors can be recognized,so all of these results make it possible that we discuss the low of petroleum forming and distributing from bran-new point of view. In this paper, a case study on Chuxiong basin is given. These coupling relationships between wave characteristic curve and source,reservoir and cap rocks are established by wave processes analysis for wells and sections of Chuxiong basin, and four kinds of coupling patterns are given, in which the source layer occur at the transition position of the wave curve in the right of datum line, the reservoir lie in the wave crest position of the wave curve in the right of datum line, the cover locate in the trough position of the wave curve the in right of datum line, and the migration channel(unconformity) appear on the trough position of the wave curve in the left of datum line. These research achievements are of important significance for predicting space-time distribution law of source,reservoir and cap rocks, and for effectively instructing oil and gas exploration.
2004, 22(3): 487-493.
Abstract:
Analysis of sediment grain size showed that the grain size grade changed greatly in the Pearl estuary. Frequency distribution curves indicated the different sources of the suspended matters in the Pearl River estuary. In spatial distribution, content of coarser sediment component decreased quickly from north and northwest to southeast. However, finer sediment component always had higher contents in the middle of the estuary where a turbidity maximum zone existed, which was related to the resuspension and flocculation in this zone. Mean grain sizes and coarser components of sediments were successfully used to inverse the direction and velocity of bottom currents before the accumulation of sediments. The grade direction of mean grain sizes was basically coincident to the transport direction of the suspended matter. The predominant velocity of bottom current in various zone were consistent with data obtained on-the-spot survey.
Analysis of sediment grain size showed that the grain size grade changed greatly in the Pearl estuary. Frequency distribution curves indicated the different sources of the suspended matters in the Pearl River estuary. In spatial distribution, content of coarser sediment component decreased quickly from north and northwest to southeast. However, finer sediment component always had higher contents in the middle of the estuary where a turbidity maximum zone existed, which was related to the resuspension and flocculation in this zone. Mean grain sizes and coarser components of sediments were successfully used to inverse the direction and velocity of bottom currents before the accumulation of sediments. The grade direction of mean grain sizes was basically coincident to the transport direction of the suspended matter. The predominant velocity of bottom current in various zone were consistent with data obtained on-the-spot survey.
2004, 22(3): 500-506.
Abstract:
The study showed that the change of LREE total content in the suspended matter and surface sediment along the Baotou section of the Yellow River was very similar to that of every unstable speciation content, sum of unstable speciation content and distribution pattern and geochemistry parameters of rare earth elements, which all indicated that obviously pile-effect brought about by the REE industrial wastewater onto REE in the Yellow River mainstream, particularly LREE, but the pile-effect weakened gradually in recent years. The tendency of LREE total content, every unstable speciation content and sum of unstable speciation content was decreasing from bottom to top, which indicated that pile-up of external LREE from industry wastewater was in a fall trend on LREE of the Yellow River mainstream. And speciation and content of REE in the branch still showed that there was potential pile-up of REE, particularly LREE in the mainstream.
The study showed that the change of LREE total content in the suspended matter and surface sediment along the Baotou section of the Yellow River was very similar to that of every unstable speciation content, sum of unstable speciation content and distribution pattern and geochemistry parameters of rare earth elements, which all indicated that obviously pile-effect brought about by the REE industrial wastewater onto REE in the Yellow River mainstream, particularly LREE, but the pile-effect weakened gradually in recent years. The tendency of LREE total content, every unstable speciation content and sum of unstable speciation content was decreasing from bottom to top, which indicated that pile-up of external LREE from industry wastewater was in a fall trend on LREE of the Yellow River mainstream. And speciation and content of REE in the branch still showed that there was potential pile-up of REE, particularly LREE in the mainstream.
2004, 22(3): 513-517.
Abstract:
The middle Permian Lucaogou Fm. was distributed within Malang sag and the southwestern part of Tiaohu sag. It was the main source rock composed from carbonate rocks and dark shale. Lucaogou Fm. was deposited in the paleao-environment from saltwater to half-saltwater based on carbonate rocks, gammacerane index (GI) and carbon isotopes of crude oils. Its depositional center, located on the eastern side of the southwest thrust structure belt, extended along the northwest-southeast direction and paralleled to the regional structural range. The prototype basin's scope of Lucaogou Fm. was greater than present. In particular, its southwest boundary should be out of the Lucaogou Fm. basin. Santanghu basin was separated reciprocally with Tu-Ha basin and Junggar basin based on the variations of carbonate rock's thickness and gammacerane index during Lucaogou Fm. sedimentation.
The middle Permian Lucaogou Fm. was distributed within Malang sag and the southwestern part of Tiaohu sag. It was the main source rock composed from carbonate rocks and dark shale. Lucaogou Fm. was deposited in the paleao-environment from saltwater to half-saltwater based on carbonate rocks, gammacerane index (GI) and carbon isotopes of crude oils. Its depositional center, located on the eastern side of the southwest thrust structure belt, extended along the northwest-southeast direction and paralleled to the regional structural range. The prototype basin's scope of Lucaogou Fm. was greater than present. In particular, its southwest boundary should be out of the Lucaogou Fm. basin. Santanghu basin was separated reciprocally with Tu-Ha basin and Junggar basin based on the variations of carbonate rock's thickness and gammacerane index during Lucaogou Fm. sedimentation.
2004, 22(3): 525-528.
Abstract:
The effects of catalysts on hydrocarbon generation from kerogen have been investigated by using simulation experiment and chemical catalysis mechanism. The simulated samples were selected from Estonia area. The catalytic action of different catalysts was studied on the product composition, hydrocarbon yield, kinetics of hydrocarbon generation. In the presence of carbonatite, the yield of generated hydrocarbon S2 has been decreased because of the adsorption of carbonatite on pyrolysates. The insoluble salt, CaSO4, as a catalyst, has enhanced kerogen degradation to increase the yield of hydrocarbon(S2).The soluble salts including CaCl2,Na2SO4 and NaHCO3 have no effect on the hydrocarbon generation from kerogen. As the kinetics is concerned, carbonatite has a negative catalytic effect and decreases the reaction rate, but CaSO4 has a positive effect and gives rise to the reaction rate. In addition, it is also found that the kinetic parameters, apparent activation energy and frequency factor, have a relationship with each other, which can be reasonably described by an exponential function.
The effects of catalysts on hydrocarbon generation from kerogen have been investigated by using simulation experiment and chemical catalysis mechanism. The simulated samples were selected from Estonia area. The catalytic action of different catalysts was studied on the product composition, hydrocarbon yield, kinetics of hydrocarbon generation. In the presence of carbonatite, the yield of generated hydrocarbon S2 has been decreased because of the adsorption of carbonatite on pyrolysates. The insoluble salt, CaSO4, as a catalyst, has enhanced kerogen degradation to increase the yield of hydrocarbon(S2).The soluble salts including CaCl2,Na2SO4 and NaHCO3 have no effect on the hydrocarbon generation from kerogen. As the kinetics is concerned, carbonatite has a negative catalytic effect and decreases the reaction rate, but CaSO4 has a positive effect and gives rise to the reaction rate. In addition, it is also found that the kinetic parameters, apparent activation energy and frequency factor, have a relationship with each other, which can be reasonably described by an exponential function.
2004, 22(3): 541-546.
Abstract:
The present temperature has been studied with testing data and the paleotemperature has been restored with fission track in apatite and fluid inclusion in Damingtun sag. The thermal history has been displayed by the model of EasyRo and the comparison has been carried out with East sag and West sag. Conclusion has been drawn as follows: (1) The present geothermal gradient is low, the average is 2.9℃/100m. (2) The paleotemperature restored by fission track in apatite shows that paleotemperature is relatively high,and that of Anfutun sag is 4.07 ℃/100m while that of Rongshenpu is 3.6℃/100m. (3) The homogenization temperature of fluid inclusion shows that the thermal fluid was active. The filling model of Anfutun sag features with high pour point oil is episodic while that of Rongshengpu sag features with normal oil is the combination of episodic movement under the overpressure and the relative slow movement forced by buoyancy. (4). The thermal history difference exists between Damingtun sag and East sag and West sag. The former features with low thermal evolution as a whole, which is favarable for the preservation of high pout point reservoir.
The present temperature has been studied with testing data and the paleotemperature has been restored with fission track in apatite and fluid inclusion in Damingtun sag. The thermal history has been displayed by the model of EasyRo and the comparison has been carried out with East sag and West sag. Conclusion has been drawn as follows: (1) The present geothermal gradient is low, the average is 2.9℃/100m. (2) The paleotemperature restored by fission track in apatite shows that paleotemperature is relatively high,and that of Anfutun sag is 4.07 ℃/100m while that of Rongshenpu is 3.6℃/100m. (3) The homogenization temperature of fluid inclusion shows that the thermal fluid was active. The filling model of Anfutun sag features with high pour point oil is episodic while that of Rongshengpu sag features with normal oil is the combination of episodic movement under the overpressure and the relative slow movement forced by buoyancy. (4). The thermal history difference exists between Damingtun sag and East sag and West sag. The former features with low thermal evolution as a whole, which is favarable for the preservation of high pout point reservoir.
