2008 Vol. 26, No. 2
Display Method:
2008, 26(2): 179-158.
Abstract:
The sediment geochemical composition between Oligocene and Miocene was different in the northern South China Sea, indicating a significant provenance change. This abrupt change coincided with a series of events including a seafloor spreading axis jump in the South China Sea and uplift of the Western Yunnan Plateau and Eastern Tibet Plateau, leading to obvious changes in drainage areas of the Pearl River and the sediment geochemical composition. The variations in Ca/Si, CIA and Al2O3 reflect that the erosion areas of the Pearl River transformed from closeto source neighboring areas in the Oligocene to the Western Yunnan Plateau and Eastern Tibet Plateau since the early Miocene, and the provenance rock types changed from silicate to carbonate, as well as the main sediment composition changed from sanddominated to muddominated material. Therefore, the evolution of the Pearl River and the uplift of the Tibet Plateau played a key role in the sedimentary transformation and accumulation in the Pearl River Mouth Basin. This abrupt change event has a profound influence on the evolution of petroleum offshore in the northern South China Sea.
The sediment geochemical composition between Oligocene and Miocene was different in the northern South China Sea, indicating a significant provenance change. This abrupt change coincided with a series of events including a seafloor spreading axis jump in the South China Sea and uplift of the Western Yunnan Plateau and Eastern Tibet Plateau, leading to obvious changes in drainage areas of the Pearl River and the sediment geochemical composition. The variations in Ca/Si, CIA and Al2O3 reflect that the erosion areas of the Pearl River transformed from closeto source neighboring areas in the Oligocene to the Western Yunnan Plateau and Eastern Tibet Plateau since the early Miocene, and the provenance rock types changed from silicate to carbonate, as well as the main sediment composition changed from sanddominated to muddominated material. Therefore, the evolution of the Pearl River and the uplift of the Tibet Plateau played a key role in the sedimentary transformation and accumulation in the Pearl River Mouth Basin. This abrupt change event has a profound influence on the evolution of petroleum offshore in the northern South China Sea.
2008, 26(2): 193-201.
Abstract:
The characteristics of Carboniferous lithofacies palaeogeography in the east of North Qilian Mountains have been discussed based on the analysis on outcrop sedimentary facies, clastic composition, particle size, rock texture and structure, paleontology, paleoecology. Shoreshallow marine facies, lagoon facies, delta facies and eleven sedimentary subfacies have been identified. In the early period of early Carboniferous，the marine water invaded the area from Qinling through the TianshuiJingning strait，resulting in a gulf surrounded by Alashan, Ordos, Longxi oldlands, mainly with salted lagoon facies and shoreshallow facies. In the late period of early Carboniferous, the transgression area became progressively extended, mainly with clastic rock and carbonate rock of shoreshallow marine facies. In the period of late Carboniferous, the transgression became high frequency, with several transgression and regressive cycle. In the period of Taiyuan Formation sediment, the North Qilian sea water conjoined with Ordos sea water to expand epicontinental sea. The chain shape uplift and below water uplift distribute into the Qilian marine basin. Palaeotopography is characteristic of high west and north, low east and south.
The characteristics of Carboniferous lithofacies palaeogeography in the east of North Qilian Mountains have been discussed based on the analysis on outcrop sedimentary facies, clastic composition, particle size, rock texture and structure, paleontology, paleoecology. Shoreshallow marine facies, lagoon facies, delta facies and eleven sedimentary subfacies have been identified. In the early period of early Carboniferous，the marine water invaded the area from Qinling through the TianshuiJingning strait，resulting in a gulf surrounded by Alashan, Ordos, Longxi oldlands, mainly with salted lagoon facies and shoreshallow facies. In the late period of early Carboniferous, the transgression area became progressively extended, mainly with clastic rock and carbonate rock of shoreshallow marine facies. In the period of late Carboniferous, the transgression became high frequency, with several transgression and regressive cycle. In the period of Taiyuan Formation sediment, the North Qilian sea water conjoined with Ordos sea water to expand epicontinental sea. The chain shape uplift and below water uplift distribute into the Qilian marine basin. Palaeotopography is characteristic of high west and north, low east and south.
2008, 26(2): 211-220.
Abstract:
Based on comprehensive investigation of a lot of coring data, outcrops and well logging data from Upper Triassic in central and south Sichuan Basin, delta facies and lacustrine facies are identified. Depending on the sedimentary environment and sedimentary developing features, the delta facies can be subdivided into three subfacies, namely, delta plain, delta front and predelta, and the lacustrine facies into shore lake subfacies and shallow lake subfacies. The distribution ranges of both facies fluctuated. During the sedimentary period of member 1, member 3, member 5 and member 6 of Xujiahe Formation, lacustrine facies predominated, with the water deepening increasingly from east to west. During the sedimentary period of member 2 and member 4 of Xujiahe Formation, delta facies predominated and the distribution range of lake was limited. During the sedimentary period of member 2 of Xujiahe Formation, because of strong tectonic action of source areas in north, delta spread mainly from north to south. During the sedimentary period of member 4 of Xujiahe Formation, tectonic action of source area in southeast enhanced, producing increasingly more deposit which formed delta spreading from southeast to northwest. Along with the fading tectonic action of source areas, depositional area in the region of interest extended. During the early stage, the depositional area was limited to the north of YibinLuzhou, while during the middle and late stage, the depositional area extended to the south of YibinLuzhou.
Based on comprehensive investigation of a lot of coring data, outcrops and well logging data from Upper Triassic in central and south Sichuan Basin, delta facies and lacustrine facies are identified. Depending on the sedimentary environment and sedimentary developing features, the delta facies can be subdivided into three subfacies, namely, delta plain, delta front and predelta, and the lacustrine facies into shore lake subfacies and shallow lake subfacies. The distribution ranges of both facies fluctuated. During the sedimentary period of member 1, member 3, member 5 and member 6 of Xujiahe Formation, lacustrine facies predominated, with the water deepening increasingly from east to west. During the sedimentary period of member 2 and member 4 of Xujiahe Formation, delta facies predominated and the distribution range of lake was limited. During the sedimentary period of member 2 of Xujiahe Formation, because of strong tectonic action of source areas in north, delta spread mainly from north to south. During the sedimentary period of member 4 of Xujiahe Formation, tectonic action of source area in southeast enhanced, producing increasingly more deposit which formed delta spreading from southeast to northwest. Along with the fading tectonic action of source areas, depositional area in the region of interest extended. During the early stage, the depositional area was limited to the north of YibinLuzhou, while during the middle and late stage, the depositional area extended to the south of YibinLuzhou.
2008, 26(2): 234-240.
Abstract:
The foreign geophysicists and geologists carried through a series of seismic sedimentological studies in North America and Indonesia Basins and got the obvious results in exploration and development of oil and gas. Therefore we carried out seismic sedimentological studies in Qikou Sag of Huanghua Depression using two techniques, that is, phase shift and stratal slicing. On the basis of the exact interpretation of the sequence boundaries, a series of stratal slices were displayed by the Recon software. Those stratal slices provided sequential imagery of depositional systems of Shayi sequence, depicted the distribution range of braidedfan delta deposit through the geologic time and the position of underwater branch channels and interchannels. This study provided the reliable evidence for searching the subtle traps of the area.
The foreign geophysicists and geologists carried through a series of seismic sedimentological studies in North America and Indonesia Basins and got the obvious results in exploration and development of oil and gas. Therefore we carried out seismic sedimentological studies in Qikou Sag of Huanghua Depression using two techniques, that is, phase shift and stratal slicing. On the basis of the exact interpretation of the sequence boundaries, a series of stratal slices were displayed by the Recon software. Those stratal slices provided sequential imagery of depositional systems of Shayi sequence, depicted the distribution range of braidedfan delta deposit through the geologic time and the position of underwater branch channels and interchannels. This study provided the reliable evidence for searching the subtle traps of the area.
2008, 26(2): 249-256.
Abstract:
By means of highresolution sequence stratigraphy study on Permian Wutonggou Formation reservoir in Jimsar Sag of Junggar Basin,we identified three parasequence types corresponding to three shortperiod base level cycle modes: base level rising parasequence, base level fallng parasequence, base level rising and falling half cycle composite parasequence. And two middleperiod base level cycles are discriminated. The formation of middle baselevel falling cycle is made up of mutliprograding shortperiod cycles whereas middle baselevel rising cycle stacking mode presents retrograding structures. The Permian Wu Tong Gou Formation can be classified 5 parasequence sets(corresponding to 5 middleperiod base level cycles) in this area,which is S1,S2,S3,S4,S5from bottom to top. S1,S2are formed during rising stage of baselevel while S3,S4,S5 formed during falling stage. According to the research conclusions we reckon the two petroliferous sand beds of Well Ji 7 and Well Ji 17 are not pertained to a same sand set as its forming reason is different. So we have resolved the practical question. One stratigraphic trap and five lithologic traps are recognized by the theory of highresolution sequence stratigraphy and the prospecting targets are offered.
By means of highresolution sequence stratigraphy study on Permian Wutonggou Formation reservoir in Jimsar Sag of Junggar Basin,we identified three parasequence types corresponding to three shortperiod base level cycle modes: base level rising parasequence, base level fallng parasequence, base level rising and falling half cycle composite parasequence. And two middleperiod base level cycles are discriminated. The formation of middle baselevel falling cycle is made up of mutliprograding shortperiod cycles whereas middle baselevel rising cycle stacking mode presents retrograding structures. The Permian Wu Tong Gou Formation can be classified 5 parasequence sets(corresponding to 5 middleperiod base level cycles) in this area,which is S1,S2,S3,S4,S5from bottom to top. S1,S2are formed during rising stage of baselevel while S3,S4,S5 formed during falling stage. According to the research conclusions we reckon the two petroliferous sand beds of Well Ji 7 and Well Ji 17 are not pertained to a same sand set as its forming reason is different. So we have resolved the practical question. One stratigraphic trap and five lithologic traps are recognized by the theory of highresolution sequence stratigraphy and the prospecting targets are offered.
2008, 26(2): 265-270.
Abstract:
Sedimentary microfacies on sandstone Group I of Sartu oilbearing layer of the Upper Cretaceous Yaojia Formation at Yueliangpao area in the South of Songliao Basin are studied with logging, geological and seismic data. By using horizon seismic attribute analysis technology, the distribution characteristics of river sandstone bodies are researched. After fitting analysis, it is concluded that the sandstone Group I of Sartu reservoir is the delta front sedimentary and the sedimentary microfacies types of the major sand bodies are underwater distributary channel, mouth bar and bays between distributary channel sedimentary microfacies. The result shows that the distributary channel sand bodies were developed widely for oil and gas accumulation. Combining the structural development, the beneficial areas for structurelithology reservoirs are predicted.
Sedimentary microfacies on sandstone Group I of Sartu oilbearing layer of the Upper Cretaceous Yaojia Formation at Yueliangpao area in the South of Songliao Basin are studied with logging, geological and seismic data. By using horizon seismic attribute analysis technology, the distribution characteristics of river sandstone bodies are researched. After fitting analysis, it is concluded that the sandstone Group I of Sartu reservoir is the delta front sedimentary and the sedimentary microfacies types of the major sand bodies are underwater distributary channel, mouth bar and bays between distributary channel sedimentary microfacies. The result shows that the distributary channel sand bodies were developed widely for oil and gas accumulation. Combining the structural development, the beneficial areas for structurelithology reservoirs are predicted.
2008, 26(2): 283-293.
Abstract:
The structural slope break zone (SSBZ), which constrains the change in the accommodation space of the basins, controlling the development of the depositional sequence and the distribution of the depositional system tracts and the sand bodies, resulting in the abrupt change of the depositional slope, is initiated by the long term activity of syndepositional structure. Researches show that distribution of petroleum is closely connected with the SSBZ. The paper introduce the term of “Structural SlopeBreak Zone” into the investigation and research of gas hydrate first time and concludes that SSBZ is an important structural unit for the formation and accumulation of gas hydrate. Furthermore, the paper analyzes the role of SSBZ controlling in gas hydrate in view of gradient of seafloor, fault, temperature, and pressure. Statistics show that the average gradient of the seafloor where BSR is recognized is between 10×10-2～30×10-2. The paper calculates the structural intensity of area D in the north slope of the SCS by introduction of structural intensity and design of algorithm, which shows that there are some favorable relationship between areas of hypovalue of structural intensity and BSR. The paper calculates the temperature and pressure in SSBZ based on high resolution seismic data and finds that the free gas can always meet the favorable PT environment and form gas hydrates when the gas transfers in the SSBZ because of the continuously various PT environment in the structure. We put forward a model of the accumulation of gas hydrate in SSBZ primarily in the end based on the summarizing of the achievements mentioned above.
The structural slope break zone (SSBZ), which constrains the change in the accommodation space of the basins, controlling the development of the depositional sequence and the distribution of the depositional system tracts and the sand bodies, resulting in the abrupt change of the depositional slope, is initiated by the long term activity of syndepositional structure. Researches show that distribution of petroleum is closely connected with the SSBZ. The paper introduce the term of “Structural SlopeBreak Zone” into the investigation and research of gas hydrate first time and concludes that SSBZ is an important structural unit for the formation and accumulation of gas hydrate. Furthermore, the paper analyzes the role of SSBZ controlling in gas hydrate in view of gradient of seafloor, fault, temperature, and pressure. Statistics show that the average gradient of the seafloor where BSR is recognized is between 10×10-2～30×10-2. The paper calculates the structural intensity of area D in the north slope of the SCS by introduction of structural intensity and design of algorithm, which shows that there are some favorable relationship between areas of hypovalue of structural intensity and BSR. The paper calculates the temperature and pressure in SSBZ based on high resolution seismic data and finds that the free gas can always meet the favorable PT environment and form gas hydrates when the gas transfers in the SSBZ because of the continuously various PT environment in the structure. We put forward a model of the accumulation of gas hydrate in SSBZ primarily in the end based on the summarizing of the achievements mentioned above.
2008, 26(2): 294-299.
Abstract:
A short sediment core Esdr1 from Shudu lake has been analysed of geochemistry elements and radionuclides. Accurate sediment chronology was established by 137Cs. Meteorological observation records reveal that climate changes experience two stages during past 44 years in the region of Shudu: a cold/wet stage during 1958～1983 a B.P, a warm/dry stage between 1983 and 2002. Climate changes reconstructed by Esdr1 core geochemical proxies are consistent with Meteorological observation records. Sediment in Shudu Hai documented in detail Regional climate changes and human activities which mean that the sediment from this lake could be the suitable archive for environment changes reconstruction in this region.
A short sediment core Esdr1 from Shudu lake has been analysed of geochemistry elements and radionuclides. Accurate sediment chronology was established by 137Cs. Meteorological observation records reveal that climate changes experience two stages during past 44 years in the region of Shudu: a cold/wet stage during 1958～1983 a B.P, a warm/dry stage between 1983 and 2002. Climate changes reconstructed by Esdr1 core geochemical proxies are consistent with Meteorological observation records. Sediment in Shudu Hai documented in detail Regional climate changes and human activities which mean that the sediment from this lake could be the suitable archive for environment changes reconstruction in this region.
2008, 26(2): 308-313.
Abstract:
The biogas generation period plays a very important role in its accumulation. But now there is not a creditable and effective method to appraise it. Aiming at this difficult problem, and considering it′s a carbon isotope balance process, regardless of the formation mechanisms of biogenic gas. The 13C and 12C amount of initial organic matter before generation and that of residual organic matter and other productions after generation should keep conservation. Carbon isotopic equilibrium method (model) is explored and established to assess biogenic gas in this paper, which is demarcated and applied according to the abundant analyzed data in Songliao basin. Results show that the accumulatively generated biogenic methane ofⅠ, Ⅱ and Ⅲ types organic matters are 193.94 ml/g, 175.64 ml/g and 161.71 ml/g, respectively. The biogasgenerated quantity of source rock in the research area is about 385.4 ×1012 m3. The major period of biogenic gas generation occurs before the end of Nenjiang period. The possible biogas resource is between 11.40×1011m3 and 24.8×1011m3.
The biogas generation period plays a very important role in its accumulation. But now there is not a creditable and effective method to appraise it. Aiming at this difficult problem, and considering it′s a carbon isotope balance process, regardless of the formation mechanisms of biogenic gas. The 13C and 12C amount of initial organic matter before generation and that of residual organic matter and other productions after generation should keep conservation. Carbon isotopic equilibrium method (model) is explored and established to assess biogenic gas in this paper, which is demarcated and applied according to the abundant analyzed data in Songliao basin. Results show that the accumulatively generated biogenic methane ofⅠ, Ⅱ and Ⅲ types organic matters are 193.94 ml/g, 175.64 ml/g and 161.71 ml/g, respectively. The biogasgenerated quantity of source rock in the research area is about 385.4 ×1012 m3. The major period of biogenic gas generation occurs before the end of Nenjiang period. The possible biogas resource is between 11.40×1011m3 and 24.8×1011m3.
2008, 26(2): 324-329.
Abstract:
Organicinorganic interactions are ubiquitous and unalterable in sedimentary basin. In this paper, effect of uranium substance on the mudstone pyrogenation was studied by hydrous pyrolysis. From the experiments, huge increase of the gas yields was observed. Further investigations showed that the content of carbon dioxide increased, while the content of methane decreased, and carbon monoxide was one of the metastable intermediates during the hydrous pyrolysis. At the same time, the high molecular weight hydrocarbons seemed to be more degraded by the uranium substance. The generated sterane and terpane from the hydrous pyrolysis were also affected by the uranium substance.
Organicinorganic interactions are ubiquitous and unalterable in sedimentary basin. In this paper, effect of uranium substance on the mudstone pyrogenation was studied by hydrous pyrolysis. From the experiments, huge increase of the gas yields was observed. Further investigations showed that the content of carbon dioxide increased, while the content of methane decreased, and carbon monoxide was one of the metastable intermediates during the hydrous pyrolysis. At the same time, the high molecular weight hydrocarbons seemed to be more degraded by the uranium substance. The generated sterane and terpane from the hydrous pyrolysis were also affected by the uranium substance.
2008, 26(2): 340-348.
Abstract:
Systemic geochemical analyses such as organic petrology, geochemistry, catalytic hydropyrolysis and GCIRMS show that, the solid bitumen in reservoir of Feixianguan Formation in northeastern Sichuan basin are residuals(pyrobitumen) generated from oil cracking, they have double reflection, high reflection ratio, high S/C and low H/C. Changxing Formation is the primary hydrocarbon source rock for the solid bitumen, while Feixianguan and lower Silurian are the subordination, according to the carbon isotopic compositions of the insoluble constituent and the biomarkers such as sterane and terpane in saturated hydrocarbons of the solvent extracts. There is an obviously genetic relationship between the solid bitumen in Well Po2 of Feixianguan Formation and the kerogen (derived from the hydrocarbon source rock) in Well Guan5 of Feixianguan Formation according to distribution and molecular carbon isotopic compositions of the saturated hydrocarbon of catalytic hydropyrolysis products. Conclusion that the source rock in Feixianguan Formation has contributions to the gas pools of Feixianguan Formation can be acquired.
Systemic geochemical analyses such as organic petrology, geochemistry, catalytic hydropyrolysis and GCIRMS show that, the solid bitumen in reservoir of Feixianguan Formation in northeastern Sichuan basin are residuals(pyrobitumen) generated from oil cracking, they have double reflection, high reflection ratio, high S/C and low H/C. Changxing Formation is the primary hydrocarbon source rock for the solid bitumen, while Feixianguan and lower Silurian are the subordination, according to the carbon isotopic compositions of the insoluble constituent and the biomarkers such as sterane and terpane in saturated hydrocarbons of the solvent extracts. There is an obviously genetic relationship between the solid bitumen in Well Po2 of Feixianguan Formation and the kerogen (derived from the hydrocarbon source rock) in Well Guan5 of Feixianguan Formation according to distribution and molecular carbon isotopic compositions of the saturated hydrocarbon of catalytic hydropyrolysis products. Conclusion that the source rock in Feixianguan Formation has contributions to the gas pools of Feixianguan Formation can be acquired.
2008, 26(2): 355-360.
Abstract:
To study migration horizons downward of oil from K1qn source rock in Sanzhao depression The mechanism and condition of oil migration downward was studied. It was considered that two conditions in F,Y oil lagers, they are ①enough high overpressure and ②T2 faults connected k1qn source rock and F,Y oil lagers. Oil from k1qn source rock can migrate downward into F,Y oil layer in the end of K1n, K2m, and E sedimentary period under the action of overpressure. The migration distance downward of oil from k1qn source rock in Sanzhao depression was studied by the principle of pressure seal. The migration distance downward of oil from k1qn source rock is generally more than 500 m, the maximum thickness of F,Y oil lagers is only 500 m, it indicates that oil from K1qn source rock can migrate downward into all F,Y oil layers. There is oil from top of F oil layer to bottom of Y oil layer now, and oil reservoirs found in F,Y oil layers of Sanzhao sag distribute in the migration areas downward of oil from K1qn source rock. It indicates that the migration horizon downward of oil from K1qn source rock controls the oil accumulation horizons, the migration areas downward of oil from K1qn source rock controls oil accumulation areas. The migration areas downward of oil from K1qn source rock and its around should be favorable areas for oil exploration in F,Y oil lagers of Sanzhao depression.
To study migration horizons downward of oil from K1qn source rock in Sanzhao depression The mechanism and condition of oil migration downward was studied. It was considered that two conditions in F,Y oil lagers, they are ①enough high overpressure and ②T2 faults connected k1qn source rock and F,Y oil lagers. Oil from k1qn source rock can migrate downward into F,Y oil layer in the end of K1n, K2m, and E sedimentary period under the action of overpressure. The migration distance downward of oil from k1qn source rock in Sanzhao depression was studied by the principle of pressure seal. The migration distance downward of oil from k1qn source rock is generally more than 500 m, the maximum thickness of F,Y oil lagers is only 500 m, it indicates that oil from K1qn source rock can migrate downward into all F,Y oil layers. There is oil from top of F oil layer to bottom of Y oil layer now, and oil reservoirs found in F,Y oil layers of Sanzhao sag distribute in the migration areas downward of oil from K1qn source rock. It indicates that the migration horizon downward of oil from K1qn source rock controls the oil accumulation horizons, the migration areas downward of oil from K1qn source rock controls oil accumulation areas. The migration areas downward of oil from K1qn source rock and its around should be favorable areas for oil exploration in F,Y oil lagers of Sanzhao depression.
2008, 26(2): 186-192.
Abstract:
Unequal thickness of turbidite sandbodies are found in the deeplake area of Triassic Yanchang Formation Ch7 and Ch6 member of Ordos Basin. Based on the integrated study of the sedimentary facies features, rock texture, structural attitude of the Ch6Ch7 drilling core, the turbidite was caused by the deltafront landsliding. The turbidite is concluded into two types: the coarse grains fluxoturbidite was mainly developed with braid river deltafront which the clastic source was from southwest; the fine grains fluxoturbidite was mainly developed with meandering river deltafront which the clastics source was from northwest. Figuring out the developmental distribution and regular pattern of turbidite in the Ordos Triassic lakebasin not only directs the exploration of the turbidite reservoir in the deep lake, but also benefits the study on hydrocarbon accumulation of the turbidite on the deeplake facies.
Unequal thickness of turbidite sandbodies are found in the deeplake area of Triassic Yanchang Formation Ch7 and Ch6 member of Ordos Basin. Based on the integrated study of the sedimentary facies features, rock texture, structural attitude of the Ch6Ch7 drilling core, the turbidite was caused by the deltafront landsliding. The turbidite is concluded into two types: the coarse grains fluxoturbidite was mainly developed with braid river deltafront which the clastic source was from southwest; the fine grains fluxoturbidite was mainly developed with meandering river deltafront which the clastics source was from northwest. Figuring out the developmental distribution and regular pattern of turbidite in the Ordos Triassic lakebasin not only directs the exploration of the turbidite reservoir in the deep lake, but also benefits the study on hydrocarbon accumulation of the turbidite on the deeplake facies.
2008, 26(2): 202-210.
Abstract:
The depositional environment was deeply analyzed in this paper by geochemical proxies, stratum and fossil distribution, and original sedimentary tectonics. The geochemical proxies in mudstone implied that tide and transgression reacted with the fresh water and mixed each other, concretely speaking, Element B implied the characteristics of longterm cycle of basic level, and Sr/Ba is a good proxy of super longterm cycle in the period of Shanxi in Eastern Ordos Basin. The sedimentary tectonics and fossil distribution indicated that the middlelevel tide has directly influenced the delta in southeastern part of the area in the early period of Shanxi, gradually the delta progradation become strong and tide evacuated to the southeastern fringe of the basin in the middle and late period. What's more, the stratum distribution and lithofacies also illuminated that the stratum in Eastern Ordos Basin and West Shanxi province belongs to the same deltasedimentary system, and the underwater dome in the east part of the area is not efficient to obstruct the flow to form the lake. Consequently, the delta in Shanxi Formation deposited in the shallowsea continental shelf.
The depositional environment was deeply analyzed in this paper by geochemical proxies, stratum and fossil distribution, and original sedimentary tectonics. The geochemical proxies in mudstone implied that tide and transgression reacted with the fresh water and mixed each other, concretely speaking, Element B implied the characteristics of longterm cycle of basic level, and Sr/Ba is a good proxy of super longterm cycle in the period of Shanxi in Eastern Ordos Basin. The sedimentary tectonics and fossil distribution indicated that the middlelevel tide has directly influenced the delta in southeastern part of the area in the early period of Shanxi, gradually the delta progradation become strong and tide evacuated to the southeastern fringe of the basin in the middle and late period. What's more, the stratum distribution and lithofacies also illuminated that the stratum in Eastern Ordos Basin and West Shanxi province belongs to the same deltasedimentary system, and the underwater dome in the east part of the area is not efficient to obstruct the flow to form the lake. Consequently, the delta in Shanxi Formation deposited in the shallowsea continental shelf.
2008, 26(2): 221-233.
Abstract:
Laiyang Formation of Jiaolai Basin is the target stratum for oil and gas exploration. By measuring several field sections, log datum, seismic datum paleocurrent direction,the paper indicated that different structural locations have different sedimentary facies. The Authors constructed sedimentary framework of Laiyang formation. Further more found two subside and deposition center, one is called ZhuwuJimo sag, along NNE direction, controlled by MupingJimo fault belt, another is called JuxianZhucheng sag, also NNE direction, along Shuriver rift and Zhucheng depression. Two sags is a relatively independent sedimentary unit in Laiyang period. The two sags dominated sedimentary formwork in Laiyang Formation period, Shuinan member was apex of lake development, mainly was lacustrine facieses. While Qugezhuang member, mainly was alluvial deposition. North border fault activity of Sulu Oregon belt controlled the Laiyang Formation deposition.
Laiyang Formation of Jiaolai Basin is the target stratum for oil and gas exploration. By measuring several field sections, log datum, seismic datum paleocurrent direction,the paper indicated that different structural locations have different sedimentary facies. The Authors constructed sedimentary framework of Laiyang formation. Further more found two subside and deposition center, one is called ZhuwuJimo sag, along NNE direction, controlled by MupingJimo fault belt, another is called JuxianZhucheng sag, also NNE direction, along Shuriver rift and Zhucheng depression. Two sags is a relatively independent sedimentary unit in Laiyang period. The two sags dominated sedimentary formwork in Laiyang Formation period, Shuinan member was apex of lake development, mainly was lacustrine facieses. While Qugezhuang member, mainly was alluvial deposition. North border fault activity of Sulu Oregon belt controlled the Laiyang Formation deposition.
2008, 26(2): 241-248.
Abstract:
Based on the theories and methods of sequence stratigraphy, sequence stratigraphic framework has been established in Chagannuoer depression of Hailaer basin by using core logging and 3D seismic. Zhalainuoer group of K1 is a super sequence, which can be divided into five third order sequences (Sq1, Sq2, Sq3, Sq4, and Sq5). Sedimentation volumes and the characters of sourcereservoircap combination have been analyzed and the favorable reservoir area was predicted within the sequence stratigraphic framework. Alluvial fan sands or fan delta sands that was deposited in palaeoslope zone or fault terrace belt and sublacustrine fan sands that was deposited in retrograding sequence groups (Sq2,Sq3)of this super sequence are good reservoir strata, they are the favorable exploration targets.
Based on the theories and methods of sequence stratigraphy, sequence stratigraphic framework has been established in Chagannuoer depression of Hailaer basin by using core logging and 3D seismic. Zhalainuoer group of K1 is a super sequence, which can be divided into five third order sequences (Sq1, Sq2, Sq3, Sq4, and Sq5). Sedimentation volumes and the characters of sourcereservoircap combination have been analyzed and the favorable reservoir area was predicted within the sequence stratigraphic framework. Alluvial fan sands or fan delta sands that was deposited in palaeoslope zone or fault terrace belt and sublacustrine fan sands that was deposited in retrograding sequence groups (Sq2,Sq3)of this super sequence are good reservoir strata, they are the favorable exploration targets.
2008, 26(2): 257-264.
Abstract:
The depth of the lower part of Enping Fm., Enping Sag is over 3 800 meters now, and the intensity of diagenesis is at the B period of middle diagenetic stage. Of course, it is a basic task that the lower part of the Enping Fm. is assessed objectively. Based on the numerous observations on thin sections and SEM analyses, the diagenetic sequences of Enping Formation, Enping Sag has been created. Also, we have found out the main controlling diageneses that affect the reservoir property strongly: first, compaction is the key factor that results in the reduction of porosity; second, the denudation of the acid fluid is the main reason that causes the enhancement of porosity partly.
The depth of the lower part of Enping Fm., Enping Sag is over 3 800 meters now, and the intensity of diagenesis is at the B period of middle diagenetic stage. Of course, it is a basic task that the lower part of the Enping Fm. is assessed objectively. Based on the numerous observations on thin sections and SEM analyses, the diagenetic sequences of Enping Formation, Enping Sag has been created. Also, we have found out the main controlling diageneses that affect the reservoir property strongly: first, compaction is the key factor that results in the reduction of porosity; second, the denudation of the acid fluid is the main reason that causes the enhancement of porosity partly.
2008, 26(2): 271-282.
Abstract:
Total organic carbon (TOC), and total sulfur (TS), total iron (TFe) contents were analyzed in the siliceous rocks (bedded chert) and shales sampled from the selenium deposit of Yutangba, western Hubei , based on which the mechanism of enrichment of multiple elements and depositional environments (i.e., redox conditions) are documented. The enrichmental factors of V，Se，Cd，Sb are larger than 10; those of Co，Ni，Cu，Zn，Ge，As，Tl，U are in the range between 1 and 10. The S/Fe ratios are generally greater than 1.15, suggesting that surplus sulfur may have occurred, which may have accelerated the precipitation of organicbound sulfur and some chalcophile elements. The triangular diagram of TOCTSTFe, the ratios of V/(V + Ni), and the relationship between some elements and TOC suggest that the seleniumrich black rocks (black shales and bedded chert) were deposited in anoxic and euxinic environments. In addition, some geochemical parameters, such as U/Th ratios,ZrCr, PY abundances in the sediments, suggest that hydrothermal processes might have occurred during the deposition. Multiple sources of trace elements, i.e., marine, hydrothermal inputs and Emeishan basalts, were likely responsible for deposition of the seleniumrich deposits at Yutangba, western Hubei.
Total organic carbon (TOC), and total sulfur (TS), total iron (TFe) contents were analyzed in the siliceous rocks (bedded chert) and shales sampled from the selenium deposit of Yutangba, western Hubei , based on which the mechanism of enrichment of multiple elements and depositional environments (i.e., redox conditions) are documented. The enrichmental factors of V，Se，Cd，Sb are larger than 10; those of Co，Ni，Cu，Zn，Ge，As，Tl，U are in the range between 1 and 10. The S/Fe ratios are generally greater than 1.15, suggesting that surplus sulfur may have occurred, which may have accelerated the precipitation of organicbound sulfur and some chalcophile elements. The triangular diagram of TOCTSTFe, the ratios of V/(V + Ni), and the relationship between some elements and TOC suggest that the seleniumrich black rocks (black shales and bedded chert) were deposited in anoxic and euxinic environments. In addition, some geochemical parameters, such as U/Th ratios,ZrCr, PY abundances in the sediments, suggest that hydrothermal processes might have occurred during the deposition. Multiple sources of trace elements, i.e., marine, hydrothermal inputs and Emeishan basalts, were likely responsible for deposition of the seleniumrich deposits at Yutangba, western Hubei.
2008, 26(2): 300-307.
Abstract:
Magnetic measurements were conducted on Core XL2 from Xinglong Sand, the Yangtze Estuary. The result indicates that ferromagnetic mineral of multidomain (MD)/pseudosingle domain (PSD) in size dominates the magnetic properties of the samples .The core of XL2 can be divided into four layers according to the variations of magnetic susceptibility and other magnetic parameters.On the basis of magnetic properties, lithofacies and foraminifer and assembled character, it can be found that the mode of environmental evolvement of Xinglong sand bar: tidal current ridge tidal channeltidal current ridgesupratidal zone (intertidal zone and supertidal zone), forming the sedimentary facial sequence of the filled estuary. In addition, the significance of some magnetic parameters on determining sedimentary hydrodynamics and geochemical environment is also discussed.
Magnetic measurements were conducted on Core XL2 from Xinglong Sand, the Yangtze Estuary. The result indicates that ferromagnetic mineral of multidomain (MD)/pseudosingle domain (PSD) in size dominates the magnetic properties of the samples .The core of XL2 can be divided into four layers according to the variations of magnetic susceptibility and other magnetic parameters.On the basis of magnetic properties, lithofacies and foraminifer and assembled character, it can be found that the mode of environmental evolvement of Xinglong sand bar: tidal current ridge tidal channeltidal current ridgesupratidal zone (intertidal zone and supertidal zone), forming the sedimentary facial sequence of the filled estuary. In addition, the significance of some magnetic parameters on determining sedimentary hydrodynamics and geochemical environment is also discussed.
2008, 26(2): 314-323.
Abstract:
Hydrocarbons in oolitic reservoir gases of Feixianguan Formation in northeastern Sichuan Basin mainly consist of methane with 75%～90% of CH4, 0～0.15% of C2, and the nonhydrocarbon mainly consists of H2S and CO2, and their relative contents are 5%～20% and 1%～10%，respectively. The high sulfurbearing gas distribution area is identical to the gypseous distribution area. These is a view that the H2S in natural gases is formed by thermochemical sulfate reduction (TSR). As largemiddle gas reservoirs with high H2S contents have been found in the northeastern of Sichuan basin, the study on the genetic mechanism of H2S has become the hotsport. Based on the analysis and summary of the current research status of H2S genetic mechanism at home and abroad，these experiment techniques of Gold tube pyrolysis, hydrous pyrolysis and quartz tube pyrolysis have been used to simulate the dyhrocarbon generation of marl source rock, and the stable sulfur isotopic composition of pyrolysis H2S, CaSO4 and S have been measured. The results show that it is very easy that the reaction of sulphur and nhexane, and the quantity of generating H2S is very large under the lower temperature. Reverse, it is very difficult that the reaction of CaSO4 and nhexane, and the quantity of generating H2S is very small under the higher temperature. The content of H2S is as high as or even over the methane during the simulation experiment of immature marl with high organic matter content，better type and large amount of FeS2 of Feixianguan formation. The stable sulfur isotopic composition of H2S originated from the reactions of nhexane and sulphur as well as CaSO4 is higher than that of sulphur and CaSO4. The H2S in marine formation is originally sourcing from the SO2－ 4in formation. It is the main reason of H2S concentration in the Lower Triassic Feixianguan Fm. carbonate reservoirs in the East Sichuan Basin that the source rocks with high FeS2 generate H2S directly and the H2S origin from the reactions of hydrocarbon and sulphur in reservoirs.
Hydrocarbons in oolitic reservoir gases of Feixianguan Formation in northeastern Sichuan Basin mainly consist of methane with 75%～90% of CH4, 0～0.15% of C2, and the nonhydrocarbon mainly consists of H2S and CO2, and their relative contents are 5%～20% and 1%～10%，respectively. The high sulfurbearing gas distribution area is identical to the gypseous distribution area. These is a view that the H2S in natural gases is formed by thermochemical sulfate reduction (TSR). As largemiddle gas reservoirs with high H2S contents have been found in the northeastern of Sichuan basin, the study on the genetic mechanism of H2S has become the hotsport. Based on the analysis and summary of the current research status of H2S genetic mechanism at home and abroad，these experiment techniques of Gold tube pyrolysis, hydrous pyrolysis and quartz tube pyrolysis have been used to simulate the dyhrocarbon generation of marl source rock, and the stable sulfur isotopic composition of pyrolysis H2S, CaSO4 and S have been measured. The results show that it is very easy that the reaction of sulphur and nhexane, and the quantity of generating H2S is very large under the lower temperature. Reverse, it is very difficult that the reaction of CaSO4 and nhexane, and the quantity of generating H2S is very small under the higher temperature. The content of H2S is as high as or even over the methane during the simulation experiment of immature marl with high organic matter content，better type and large amount of FeS2 of Feixianguan formation. The stable sulfur isotopic composition of H2S originated from the reactions of nhexane and sulphur as well as CaSO4 is higher than that of sulphur and CaSO4. The H2S in marine formation is originally sourcing from the SO2－ 4in formation. It is the main reason of H2S concentration in the Lower Triassic Feixianguan Fm. carbonate reservoirs in the East Sichuan Basin that the source rocks with high FeS2 generate H2S directly and the H2S origin from the reactions of hydrocarbon and sulphur in reservoirs.
2008, 26(2): 330-339.
Abstract:
Aromatic compositions and thermal maturity parameters of free organic matter (chloroform bitumen A) and inclusion organic matter (chloroform bitumen C) in deep carbonate rocks (>5 700 m) from Well Tacan 1 were studied. The relative distributions of phenanthrenes and dibenthiophenes are richer in the aromatic hydrocarbons of deep carbonate rocks, in the meantime, the abundance of phenanthrenes and chrysenes abundance increase with buried depth, but the dibenthiophenes, naphthobenzothiophenes and fluorenes abundance in aromatic hydrocarbons showed reverse trends, this probably reflect the different thermal stability of various aromatic hydrocarbons at high and overmature stages. There are obvious differences in aromatic compositions and maturity parameters between two occurrence states of deep carbonate rocks, comparing with free organic matter, the maturity of the inclusion organic matter are lower and retarded in the same source rock. There are some aromatic maturity parameters can still be used to assess maturity during overmatre stages, including alkylation ratios of phenanthrenes (C1P /C4P, C1P /C3P, C2P /C4P, C2P /C3P), and maturity parameters for dibenthiophene (MDR, C1/C3DBT,2,4/1,4DMDBT and 4,6/1,4DMDBT). Although DBT/P are thought to an indicator for organic facies, it is showen from this study that this parameter is related to maturation level, which is a good maturity parameter at the same organic facies in high and over maturity stage.
Aromatic compositions and thermal maturity parameters of free organic matter (chloroform bitumen A) and inclusion organic matter (chloroform bitumen C) in deep carbonate rocks (>5 700 m) from Well Tacan 1 were studied. The relative distributions of phenanthrenes and dibenthiophenes are richer in the aromatic hydrocarbons of deep carbonate rocks, in the meantime, the abundance of phenanthrenes and chrysenes abundance increase with buried depth, but the dibenthiophenes, naphthobenzothiophenes and fluorenes abundance in aromatic hydrocarbons showed reverse trends, this probably reflect the different thermal stability of various aromatic hydrocarbons at high and overmature stages. There are obvious differences in aromatic compositions and maturity parameters between two occurrence states of deep carbonate rocks, comparing with free organic matter, the maturity of the inclusion organic matter are lower and retarded in the same source rock. There are some aromatic maturity parameters can still be used to assess maturity during overmatre stages, including alkylation ratios of phenanthrenes (C1P /C4P, C1P /C3P, C2P /C4P, C2P /C3P), and maturity parameters for dibenthiophene (MDR, C1/C3DBT,2,4/1,4DMDBT and 4,6/1,4DMDBT). Although DBT/P are thought to an indicator for organic facies, it is showen from this study that this parameter is related to maturation level, which is a good maturity parameter at the same organic facies in high and over maturity stage.
2008, 26(2): 349-354.
Abstract:
The charging and migration direction as well as migration time, pathway and power of crude oil in Yan9 subsection of the Yanan Formation of Maling oilfield in Ordos Basin have been studied for the first time. The migration fractionation of neutral nitrogen compounds in the crude oils indicate that the lateral charging direction of crude oil is from the southeast of the oilfield to the northwest and from the northwest of the oilfield to the southeast. It is also observed by means of the migration fractionation features of neutral nitrogen compounds in the oils that vertical migration direction of crude oil is upward. The homogenization temperature of fluid inclusions in the reservoir exhibits two peak temperatures, reflecting the two stages of migration and accumulation of oil. The migration pathway of oil is river sandstones. The migration power of oil is capillary strength and abnormally high pressure.
The charging and migration direction as well as migration time, pathway and power of crude oil in Yan9 subsection of the Yanan Formation of Maling oilfield in Ordos Basin have been studied for the first time. The migration fractionation of neutral nitrogen compounds in the crude oils indicate that the lateral charging direction of crude oil is from the southeast of the oilfield to the northwest and from the northwest of the oilfield to the southeast. It is also observed by means of the migration fractionation features of neutral nitrogen compounds in the oils that vertical migration direction of crude oil is upward. The homogenization temperature of fluid inclusions in the reservoir exhibits two peak temperatures, reflecting the two stages of migration and accumulation of oil. The migration pathway of oil is river sandstones. The migration power of oil is capillary strength and abnormally high pressure.
