2009 Vol. 27, No. 2
Display Method:
2009, 27(2): 191-201.
Abstract:
The reservoir sandstones in Dongying Dongying Halfgraben, Shengli Oil Field have undergone four episodes of interaction of geofluids with sandstone. Dissolution, cementation and microvein filling are the major diagenesis under fluid flows. Normally, the dissolution enhances the reservoir quality, while the cementation damages the reservoir quality. But some earlier carbonate cements like coarse ankerite support the skeleton grains and prevent the reservoir sandstones from porous “collapse”. Based on the observation under microscope and probe analyses, four episodes Ⅰ, Ⅱ, Ⅲ and Ⅳ of geofluid activities have been identified for the study area
The reservoir sandstones in Dongying Dongying Halfgraben, Shengli Oil Field have undergone four episodes of interaction of geofluids with sandstone. Dissolution, cementation and microvein filling are the major diagenesis under fluid flows. Normally, the dissolution enhances the reservoir quality, while the cementation damages the reservoir quality. But some earlier carbonate cements like coarse ankerite support the skeleton grains and prevent the reservoir sandstones from porous “collapse”. Based on the observation under microscope and probe analyses, four episodes Ⅰ, Ⅱ, Ⅲ and Ⅳ of geofluid activities have been identified for the study area
2009, 27(2): 212-220.
Abstract:
Detailed study on the rock property, pore types, measured porosity and permeability, cement and diagenesis of sandstones of the Fuyang Reservoir in Songliao Basin indicates that the mechanical compression, cementation and dissolution are the main diagenesis types. Compression is one of the main factors reduced the reservoir quality, which resulted in 0.2%22% reduction of the total porosity. Cementation also plays an important role in the loss of porosity, and the major cement is calcite and quartz overgrowths. Homogenization temperature for inclusion suggests that quartz cementation and some authigenic minerals precipitation have continued after hydrocarbon emplacement during the late diagenetic phase. At the same time, the feldspar and calcite were dissolved by the organic acid liquids produced by reaction of hydrocarbon emplacement and penetrated meteoric water through the fault zones in strata, which resulted in lots of secondary porosity and contributed retention of reservoir quality of the sandstones.
Detailed study on the rock property, pore types, measured porosity and permeability, cement and diagenesis of sandstones of the Fuyang Reservoir in Songliao Basin indicates that the mechanical compression, cementation and dissolution are the main diagenesis types. Compression is one of the main factors reduced the reservoir quality, which resulted in 0.2%22% reduction of the total porosity. Cementation also plays an important role in the loss of porosity, and the major cement is calcite and quartz overgrowths. Homogenization temperature for inclusion suggests that quartz cementation and some authigenic minerals precipitation have continued after hydrocarbon emplacement during the late diagenetic phase. At the same time, the feldspar and calcite were dissolved by the organic acid liquids produced by reaction of hydrocarbon emplacement and penetrated meteoric water through the fault zones in strata, which resulted in lots of secondary porosity and contributed retention of reservoir quality of the sandstones.
2009, 27(2): 230-237.
Abstract:
Beach and bar sandbodies are main sedimentary reservoir of the upper part of the fourth member of the Shahejie formation(Es4s) in the west part of Dongying depression. Based on the comprehensive application of physical properties, oil production test, and mercury injection data, the petrophysical parameter cutoff of effective reservoir of beach and bar sandbodies of Es4s is determined by distribution function curve method, production test method, and irreducible water saturation method, and the functional equation between petrophysical parameter cutoff and depth is obtained. On the basis of the research of petrophysical parameter cutoff, combining the analysis of sedimentary characteristics, diagenesis characteristics and reservoir pressure characteristics of beach and bar sandbodies, the controlling factors of effective reservoirs are discussed. Sedimentary microfacies and thickness are main controlling factors, and the effective reservoir is the most developed in the microfacies of bar main body and beach ridge. It is not obvious that the diagenesis and reservoir pressure influence physical properties of reservoir.
Beach and bar sandbodies are main sedimentary reservoir of the upper part of the fourth member of the Shahejie formation(Es4s) in the west part of Dongying depression. Based on the comprehensive application of physical properties, oil production test, and mercury injection data, the petrophysical parameter cutoff of effective reservoir of beach and bar sandbodies of Es4s is determined by distribution function curve method, production test method, and irreducible water saturation method, and the functional equation between petrophysical parameter cutoff and depth is obtained. On the basis of the research of petrophysical parameter cutoff, combining the analysis of sedimentary characteristics, diagenesis characteristics and reservoir pressure characteristics of beach and bar sandbodies, the controlling factors of effective reservoirs are discussed. Sedimentary microfacies and thickness are main controlling factors, and the effective reservoir is the most developed in the microfacies of bar main body and beach ridge. It is not obvious that the diagenesis and reservoir pressure influence physical properties of reservoir.
2009, 27(2): 246-253.
Abstract:
The delta and fan delta deposits developed in the period of the upper fourth member of Shahejie Formation in the edge Huimin depression. The beach bars and tempestite which parallel or diagonal to the praya developed in the meare area in central uplift belt on the effect of lake wave and coastal current. The maturity of beach bar is higher and the shale content is short. The lithologic characters are mediumfine sandstones and siltstones mainly, and light conglomerates exist too. The dissoconch fossil, biogenicdebris and charcoal debris are usually observed in the sandstones. The microfacies of beach bar are divided into sandy bar, sandy beach and inter beach bar. The sandstones include nearshore sandy beach, nearshore sandy bar, and sandy beach between bar, infralittoral sandy bar, infralittoral sandy beach, underwater uplift sandy bar and underwater sandy beach plain. The tempestites formed in the belt of wave based surface and storm wave based surface. They are constituted of massive bedding section, graded bedding section, moundy cross bedding section, parallel bedding section and massive mud section. The formations of the mixed depositional systems are under the control of palaeotopography, provenance and change of lake surface, and so on.
The delta and fan delta deposits developed in the period of the upper fourth member of Shahejie Formation in the edge Huimin depression. The beach bars and tempestite which parallel or diagonal to the praya developed in the meare area in central uplift belt on the effect of lake wave and coastal current. The maturity of beach bar is higher and the shale content is short. The lithologic characters are mediumfine sandstones and siltstones mainly, and light conglomerates exist too. The dissoconch fossil, biogenicdebris and charcoal debris are usually observed in the sandstones. The microfacies of beach bar are divided into sandy bar, sandy beach and inter beach bar. The sandstones include nearshore sandy beach, nearshore sandy bar, and sandy beach between bar, infralittoral sandy bar, infralittoral sandy beach, underwater uplift sandy bar and underwater sandy beach plain. The tempestites formed in the belt of wave based surface and storm wave based surface. They are constituted of massive bedding section, graded bedding section, moundy cross bedding section, parallel bedding section and massive mud section. The formations of the mixed depositional systems are under the control of palaeotopography, provenance and change of lake surface, and so on.
2009, 27(2): 265-272.
Abstract:
In this paper, on the basis of previous studies, using geochemical method, the research was done on the Upper Permian sedimentary environment Linxi Group in northeast Inner Mongolia. The lithology in Linxi Group was black mudstone, silty mudstone, shale, gray muddy siltstone, and finegrained sandstone. By analyzing the constant element, trace element and rare earth elements, it was found that the entire sandmudstone sample had high SiO2, Al2O3, V, Zr, Ba, and low P2O5, Mn, CaO, Cd character. Through analyzing the discriminant index of the sedimentary environment, open freshwater was identified in Linxi Formation, mainly is the corresponding terrestrial facies, and belongs to marinecontinental alternating environment during the initial stage of deposition. Based on the sedimentary structure and lithologic association, Linxi Formation can be divided into lacustrine and delta facies, and the lacustrine can be subdivided into coastalshallow lacustrine and semideep and deep lakes, the delta facies includes delta front and prodelta.
In this paper, on the basis of previous studies, using geochemical method, the research was done on the Upper Permian sedimentary environment Linxi Group in northeast Inner Mongolia. The lithology in Linxi Group was black mudstone, silty mudstone, shale, gray muddy siltstone, and finegrained sandstone. By analyzing the constant element, trace element and rare earth elements, it was found that the entire sandmudstone sample had high SiO2, Al2O3, V, Zr, Ba, and low P2O5, Mn, CaO, Cd character. Through analyzing the discriminant index of the sedimentary environment, open freshwater was identified in Linxi Formation, mainly is the corresponding terrestrial facies, and belongs to marinecontinental alternating environment during the initial stage of deposition. Based on the sedimentary structure and lithologic association, Linxi Formation can be divided into lacustrine and delta facies, and the lacustrine can be subdivided into coastalshallow lacustrine and semideep and deep lakes, the delta facies includes delta front and prodelta.
2009, 27(2): 280-288.
Abstract:
With the application of the theory of highresolution sequence stratigraphy referred to the core and seismic and logging data, the sequence framework was established within the synrifting of Sunda basin based on the well to seismic calibration. Six sequence boundaries are identified by which five sequences are divided. At the same time, the source direction and sedimentary facies of each sequence are analyzed. The basin developed depositional system of fan delta, braided channel delta, fluvial, delta, Nearshore Subaqueous Fans and beach, which changed greatly in different time and position. Compared to the typical rifted basin in East China, Sunda basin has short duration of synrifting and seldom developed subsidiary fracture accompanying with the main fracture. The duration of lacustrine basin was shorter and the water depth was shallower than the basin in East China.
With the application of the theory of highresolution sequence stratigraphy referred to the core and seismic and logging data, the sequence framework was established within the synrifting of Sunda basin based on the well to seismic calibration. Six sequence boundaries are identified by which five sequences are divided. At the same time, the source direction and sedimentary facies of each sequence are analyzed. The basin developed depositional system of fan delta, braided channel delta, fluvial, delta, Nearshore Subaqueous Fans and beach, which changed greatly in different time and position. Compared to the typical rifted basin in East China, Sunda basin has short duration of synrifting and seldom developed subsidiary fracture accompanying with the main fracture. The duration of lacustrine basin was shorter and the water depth was shallower than the basin in East China.
2009, 27(2): 299-305.
Abstract:
The faulted basin has the characteristics of the extensive influence of tectonic subsiding, the abundant and unbalanced sediment supply, limited water area and multimaterial sources. Those lead to the difference between the marine basin and the faulted lake basin. The style of the parasequence sets differs with the position in the faulted lake. In some period, the change of the relative lake level has difference in the different place. At the lake marginal area, the accommodation becomes less and, in the mid part, the accommodation becomes larger, between those areas, there is an accommodation transition zone. The accommodation transition is predominated by the tectonic subsiding, sediment supply and water body. Tectonic subsiding and sediment supplying make the redistribution of the water body and the change of the relative lake level with the same water volume. Only under the situation of the water volume changing, the relative lake level has the accordant changing.
The faulted basin has the characteristics of the extensive influence of tectonic subsiding, the abundant and unbalanced sediment supply, limited water area and multimaterial sources. Those lead to the difference between the marine basin and the faulted lake basin. The style of the parasequence sets differs with the position in the faulted lake. In some period, the change of the relative lake level has difference in the different place. At the lake marginal area, the accommodation becomes less and, in the mid part, the accommodation becomes larger, between those areas, there is an accommodation transition zone. The accommodation transition is predominated by the tectonic subsiding, sediment supply and water body. Tectonic subsiding and sediment supplying make the redistribution of the water body and the change of the relative lake level with the same water volume. Only under the situation of the water volume changing, the relative lake level has the accordant changing.
2009, 27(2): 312-318.
Abstract:
In order to make a scrutiny into physical properties of formation in various depositional environments, we carried out a geological exploration and collected a lot of samples from platform edge clinoform system and chipping sedimentary system in outcrop area located in KepingBachu, Tarim Basin, and Northwestern China. After analysis of the ultrasonic measurements of the samples at normal temperature and standard atmosphere in the laboratory, the conclusions are given as follows: (1) There is a close relation between ultrasonic velocities of samples and depositional environment. In the bioherm profile, the velocity increases from reef base, reef core to reef cap; in the delta profile, the velocity increases from distributary channel to delta front. (2) In the bioherm profile, the biodetritus is the key influencing factor to velocity; the richer organism of the sample is, the higher the velocity is. In the sandstone profile, the larger the filling extent of the sandstone pore is, the higher the velocity is. (3) The growth direction of organisms is a principal factor, which controls the extent of the velocity anisotropy. The velocities are different between along and against growth direction of organisms. These results can be used to guide geophysical forward modeling, geophysical inversion, seismic interpretation and reservoir prediction.
In order to make a scrutiny into physical properties of formation in various depositional environments, we carried out a geological exploration and collected a lot of samples from platform edge clinoform system and chipping sedimentary system in outcrop area located in KepingBachu, Tarim Basin, and Northwestern China. After analysis of the ultrasonic measurements of the samples at normal temperature and standard atmosphere in the laboratory, the conclusions are given as follows: (1) There is a close relation between ultrasonic velocities of samples and depositional environment. In the bioherm profile, the velocity increases from reef base, reef core to reef cap; in the delta profile, the velocity increases from distributary channel to delta front. (2) In the bioherm profile, the biodetritus is the key influencing factor to velocity; the richer organism of the sample is, the higher the velocity is. In the sandstone profile, the larger the filling extent of the sandstone pore is, the higher the velocity is. (3) The growth direction of organisms is a principal factor, which controls the extent of the velocity anisotropy. The velocities are different between along and against growth direction of organisms. These results can be used to guide geophysical forward modeling, geophysical inversion, seismic interpretation and reservoir prediction.
2009, 27(2): 326-333.
Abstract:
Based on the information of potash deposits in the world, we analyzed the characteristics of importance of 26 marine origin potash deposits and found out potash characteristic parameters in marine origin. According to the information, we can draw a conclusion that the ratio of deposit area and basin area is 4.47%, the ratio of resource potential and deposit area is 1.616×106t/km2, the ratio of resource potential and basin area is 0.045×106t/km2 and the ratio of maximum thickness of potash and salt is 7.2%. Based on the sorts of structures, the basins located in comparative active zones are the most abundant potash resources distributed. Such as continental shelves, depression basins between continental edges and fold zones. Their ratio of deposit area and basin area is 6.87%, the ratio of resource quantity and deposit area is 5.068×106t/km2, the ratio of resource potential and basin area is 0.063×106t/km2 and the ratio of maximum thickness of potash and salt is 12.27%. Meanwhile, paper discussed the significance of marine origin potash deposit. It is helpful to research the factors of potash deposits forming and for us to forecast the resource potential of unfound potash deposits in the paleomarine basins in China.
Based on the information of potash deposits in the world, we analyzed the characteristics of importance of 26 marine origin potash deposits and found out potash characteristic parameters in marine origin. According to the information, we can draw a conclusion that the ratio of deposit area and basin area is 4.47%, the ratio of resource potential and deposit area is 1.616×106t/km2, the ratio of resource potential and basin area is 0.045×106t/km2 and the ratio of maximum thickness of potash and salt is 7.2%. Based on the sorts of structures, the basins located in comparative active zones are the most abundant potash resources distributed. Such as continental shelves, depression basins between continental edges and fold zones. Their ratio of deposit area and basin area is 6.87%, the ratio of resource quantity and deposit area is 5.068×106t/km2, the ratio of resource potential and basin area is 0.063×106t/km2 and the ratio of maximum thickness of potash and salt is 12.27%. Meanwhile, paper discussed the significance of marine origin potash deposit. It is helpful to research the factors of potash deposits forming and for us to forecast the resource potential of unfound potash deposits in the paleomarine basins in China.
2009, 27(2): 334-342.
Abstract:
On the basis of comparative analysis of foraminiferal assemblages zones for Holes XL1，XL2 and CY, integrating the characteristics of their aggradation and environmental magnetism, we probe into the evolvement of the deposit hydrodynamic condition in the North Branch, the Changjiang River Estuary. At the same time, it reveals the relation of sedimentary facies corresponding to their foraminiferal assemblages zones. That is the tidal current ridge corresponding to the E. naraensis, E. magellanicum and F. decorus assemblages zone; tidal channel to the A. convexidorsa, E. naraensis, E. magellanicum and A. beccarii vars. assemblages zone; supratidal zone to the A. beccarii vars., E. magellanicum, E. naraensis speciesassemblages zone, especially the T. inflate and J. macrescens are its characteristic species; sand dam to A. beccarii vars E. naraensis, et al. assemblages zone. The above sedimentary characteristics imply the function of tidal current during the burial of foraminiferal assemblage zones. Based on foraminiferal assemblages zones, magnetic properties and lithofacies, we also suggest that there are three modes of sedimentary environment for Hole XL1 , XL2 and CY in the North Branch estuary, the Changjiang River Esturary: tidal current ridge→tidal channel→supratidal zone, forming the sedimentary facial sequence of the filled estuary.
On the basis of comparative analysis of foraminiferal assemblages zones for Holes XL1，XL2 and CY, integrating the characteristics of their aggradation and environmental magnetism, we probe into the evolvement of the deposit hydrodynamic condition in the North Branch, the Changjiang River Estuary. At the same time, it reveals the relation of sedimentary facies corresponding to their foraminiferal assemblages zones. That is the tidal current ridge corresponding to the E. naraensis, E. magellanicum and F. decorus assemblages zone; tidal channel to the A. convexidorsa, E. naraensis, E. magellanicum and A. beccarii vars. assemblages zone; supratidal zone to the A. beccarii vars., E. magellanicum, E. naraensis speciesassemblages zone, especially the T. inflate and J. macrescens are its characteristic species; sand dam to A. beccarii vars E. naraensis, et al. assemblages zone. The above sedimentary characteristics imply the function of tidal current during the burial of foraminiferal assemblage zones. Based on foraminiferal assemblages zones, magnetic properties and lithofacies, we also suggest that there are three modes of sedimentary environment for Hole XL1 , XL2 and CY in the North Branch estuary, the Changjiang River Esturary: tidal current ridge→tidal channel→supratidal zone, forming the sedimentary facial sequence of the filled estuary.
2009, 27(2): 352-359.
Abstract:
A 76 cm core was drilled from Xingyun Lake, in the center of Yunnan Province, southwest China, to get the environment change record. Using GCMS analysis, a series of lipids, including nalkanes, nalkanoic acids and nalcohols, have been identified. This paper focuses on nalcohols in this core. Result shows that the distinct nalcohols distributions in different depth. The chromatographic peak of most of the samples are identified according to carbon number (arrangement) in double peak, in which the former and back main peak carbons are C16 and nC26, respectively; the evenodd carbon predominance both in the lower and higher carbon number nalcohols. The carbon number components of lower and higher are in the relative balance at 76~ 60 cm, dominated by higher at 60~38 cm, the higher present in less abundance at 38~12 cm and the lower show greater abundance at 12~0 c m depth. The rate of the higher carbonate components to the lower (Rl/h ) are between 0.13~4.1 , which have marked corresponding relation to the temperature curve under the less human effect. Four climate stages can be divided according to the records since about 130 a, i.e. cool period before 1920 ,warm period between 1920~1956 with the warmest period in 1940s′, cold period between 1957~1970s and warm period 1980s. Since 1993 Rl/h increase may record the euotrophic history of the lake. The carbon preference index (CPI) reveals the organic origin of the lake has some alternations. More attention must be paid to that the high effected by the euotrophic which may lead the the high Rl/h.The lipids are sensitive to the environment evolution. However, further and more detailed work should be done for better understanding the relationship between environment evolution and Lipid records.
A 76 cm core was drilled from Xingyun Lake, in the center of Yunnan Province, southwest China, to get the environment change record. Using GCMS analysis, a series of lipids, including nalkanes, nalkanoic acids and nalcohols, have been identified. This paper focuses on nalcohols in this core. Result shows that the distinct nalcohols distributions in different depth. The chromatographic peak of most of the samples are identified according to carbon number (arrangement) in double peak, in which the former and back main peak carbons are C16 and nC26, respectively; the evenodd carbon predominance both in the lower and higher carbon number nalcohols. The carbon number components of lower and higher are in the relative balance at 76~ 60 cm, dominated by higher at 60~38 cm, the higher present in less abundance at 38~12 cm and the lower show greater abundance at 12~0 c m depth. The rate of the higher carbonate components to the lower (Rl/h ) are between 0.13~4.1 , which have marked corresponding relation to the temperature curve under the less human effect. Four climate stages can be divided according to the records since about 130 a, i.e. cool period before 1920 ,warm period between 1920~1956 with the warmest period in 1940s′, cold period between 1957~1970s and warm period 1980s. Since 1993 Rl/h increase may record the euotrophic history of the lake. The carbon preference index (CPI) reveals the organic origin of the lake has some alternations. More attention must be paid to that the high effected by the euotrophic which may lead the the high Rl/h.The lipids are sensitive to the environment evolution. However, further and more detailed work should be done for better understanding the relationship between environment evolution and Lipid records.
2009, 27(2): 367-371.
Abstract:
Most of crude oils from the Banqiao Depression are condensate or light oils with lower density, lower viscosity, lower sulfur content and higher solidifying point as well as higher wax. The result of aromatic hydrocarbon fraction in oils by GCMS indicate that the content of regular polycyclic aromatic hydrocarbon series vary from 66.33% to 80.81%, the content of dibenzothiophene (SF), dibenzofuran (OF) and fluorene (F) series is 15% to 30%, and the content of fragrant sterane series is merely 5.55%. The naphthalene series and phenanthrene series are main components of regular polycyclic aromatic series. The maturity RC calculated from methylphenanthrene index (MPI1) showa that the crude oils from the Banqiao Depression are mature to higher mature, and the RC of Banshen 35 (Es3，4731m) reaches highly 1.60%. The correlation between the content of low carbon triaromatic sterane in all triaromatic sterane and MDR shows well, and the correlation of fragrant sterane content in aromatic hydrocarbon fraction and methylphenanthrene index (MPI3) or methyldibenzothiophene ratio (MDR) are also good. The distributed characteristics of SF, OF, and F series show that the primary depositional environments of the oils are pooroxidation and deoxidation environments with secondary paludal facies.
Most of crude oils from the Banqiao Depression are condensate or light oils with lower density, lower viscosity, lower sulfur content and higher solidifying point as well as higher wax. The result of aromatic hydrocarbon fraction in oils by GCMS indicate that the content of regular polycyclic aromatic hydrocarbon series vary from 66.33% to 80.81%, the content of dibenzothiophene (SF), dibenzofuran (OF) and fluorene (F) series is 15% to 30%, and the content of fragrant sterane series is merely 5.55%. The naphthalene series and phenanthrene series are main components of regular polycyclic aromatic series. The maturity RC calculated from methylphenanthrene index (MPI1) showa that the crude oils from the Banqiao Depression are mature to higher mature, and the RC of Banshen 35 (Es3，4731m) reaches highly 1.60%. The correlation between the content of low carbon triaromatic sterane in all triaromatic sterane and MDR shows well, and the correlation of fragrant sterane content in aromatic hydrocarbon fraction and methylphenanthrene index (MPI3) or methyldibenzothiophene ratio (MDR) are also good. The distributed characteristics of SF, OF, and F series show that the primary depositional environments of the oils are pooroxidation and deoxidation environments with secondary paludal facies.
2009, 27(2): 202-211.
Abstract:
In the lower Ordovician Penglaiba Formation of Tarim basin occur thick strata of interbeded dolostone and limestone, which show a relatively constant petrologic rhythm in Tazhong19 well: three parts can be observed in every rhythm, the upper part is microlite limestone, middle part is dolostone, and lower part is siliceous granular limestone. The geochemical research on the limestones and dolostones show: 1) compared with limestones, dolostones are enriched in most of trace elements. Dolostones show a higher content of total rare earth elements than limestones but similar PAASnormalized patterns were demonstrated between limestones and dolostones, which indicates that the rare earth elements in dolostones might have come from limestones by dolomitization. 2) There are two dolomitization events and the productions are Barich dolostones and Bapoor dolostones, respectively. Ba content in Barich dolostone is as high as 2 312×10-6. Meanwhile, high sulfur concentrations were demonstrated in Barich dolostones, which indicate that the Formation of Ba in dolostones is hydrothermal BaSO4. High Fe, Mn content in Barich dolostones also showed the hydrothermal origin of dolomitization fluid. 3) An obvious difference in carbon and oxygen isotope composition was shown between Barich dolostone and Bapoor dolostone. The carbon isotope compositons in Barich dolostone were similar to limestones, with values ranging from 2.5‰～2.3‰, but a higher oxygen isotope with value ranging from 6.0‰～3.2‰, maybe as a result of dolomitization by magmatic hydrothermal fluid; In Bapoor dolostone, δ18O values vary in a lower range of9.7‰～8.5‰, and a higher range of 1.7‰～1.5‰ for carbon isotope compositions, maybe as a result of dolomitization by evolved hydrothermal seawater; 4) 87Sr/86Sr values of dolostones vary in 0.708 914～0.709 409, higher than limestones (0.708 983～0.709 039), maybe as a result of the later diagenesis alternations. Because of the spatial relations between microlite limestone and dolostones, the dolomitization fluids can not penetrate the limestone to dolostone layers, therefore, the dolomitizations fluids must have originated from deep hydrothermal fluid. By some cleavage or tectonic movement the hydrothermal fluids upwelled, encountered the microlite limstones and started dolomitization along the bottom of limestones. We can define the model as “up erosion model”, by which the dolostones and the upper limestone will construct very good reservoircover combinations.
In the lower Ordovician Penglaiba Formation of Tarim basin occur thick strata of interbeded dolostone and limestone, which show a relatively constant petrologic rhythm in Tazhong19 well: three parts can be observed in every rhythm, the upper part is microlite limestone, middle part is dolostone, and lower part is siliceous granular limestone. The geochemical research on the limestones and dolostones show: 1) compared with limestones, dolostones are enriched in most of trace elements. Dolostones show a higher content of total rare earth elements than limestones but similar PAASnormalized patterns were demonstrated between limestones and dolostones, which indicates that the rare earth elements in dolostones might have come from limestones by dolomitization. 2) There are two dolomitization events and the productions are Barich dolostones and Bapoor dolostones, respectively. Ba content in Barich dolostone is as high as 2 312×10-6. Meanwhile, high sulfur concentrations were demonstrated in Barich dolostones, which indicate that the Formation of Ba in dolostones is hydrothermal BaSO4. High Fe, Mn content in Barich dolostones also showed the hydrothermal origin of dolomitization fluid. 3) An obvious difference in carbon and oxygen isotope composition was shown between Barich dolostone and Bapoor dolostone. The carbon isotope compositons in Barich dolostone were similar to limestones, with values ranging from 2.5‰～2.3‰, but a higher oxygen isotope with value ranging from 6.0‰～3.2‰, maybe as a result of dolomitization by magmatic hydrothermal fluid; In Bapoor dolostone, δ18O values vary in a lower range of9.7‰～8.5‰, and a higher range of 1.7‰～1.5‰ for carbon isotope compositions, maybe as a result of dolomitization by evolved hydrothermal seawater; 4) 87Sr/86Sr values of dolostones vary in 0.708 914～0.709 409, higher than limestones (0.708 983～0.709 039), maybe as a result of the later diagenesis alternations. Because of the spatial relations between microlite limestone and dolostones, the dolomitization fluids can not penetrate the limestone to dolostone layers, therefore, the dolomitizations fluids must have originated from deep hydrothermal fluid. By some cleavage or tectonic movement the hydrothermal fluids upwelled, encountered the microlite limstones and started dolomitization along the bottom of limestones. We can define the model as “up erosion model”, by which the dolostones and the upper limestone will construct very good reservoircover combinations.
2009, 27(2): 221-229.
Abstract:
By comparing characteristics of quartz sandstone reservoir of the Neopaleozoic of Yulin gas field with Sulige gas field in Ordos Basin, it is indicated that the Shan 2 Member quartz sandstone reservoir of the Yulin gas field is the low porosity and relatively high permeable reservoir while the He 8 Member quartz sandstone reservoir of the Sulige gas field is the high porosity and relatively low permeable reservoir，respectively. And based on analyzing of material source，depositional condition and diagenesis, and so on,of the two types quartz sandstones，it is suggested that the reservoir characteristics of Shan 2 member of Yulin gas field is formed by the alteration due to the sea water in depositional stage and diagenesis in the later stage，while He 8 member of Sulige gas field is the result of high content of matrix and diagenesis in the later stage.
By comparing characteristics of quartz sandstone reservoir of the Neopaleozoic of Yulin gas field with Sulige gas field in Ordos Basin, it is indicated that the Shan 2 Member quartz sandstone reservoir of the Yulin gas field is the low porosity and relatively high permeable reservoir while the He 8 Member quartz sandstone reservoir of the Sulige gas field is the high porosity and relatively low permeable reservoir，respectively. And based on analyzing of material source，depositional condition and diagenesis, and so on,of the two types quartz sandstones，it is suggested that the reservoir characteristics of Shan 2 member of Yulin gas field is formed by the alteration due to the sea water in depositional stage and diagenesis in the later stage，while He 8 member of Sulige gas field is the result of high content of matrix and diagenesis in the later stage.
2009, 27(2): 238-245.
Abstract:
By analyzing the thin sections and physical property,the petrology character, poroperm characteristics, pore texture and pore types of the reservoir of the He 8 Formation in the north of Ordos basin were tested, and the reservoir performance’ major influencing factor were analyzed. The result indicates that the reservoir of He 8 Formation which deposited in braidedstream have high compositional maturity and media textural maturity, the reservoir germinates secondary corroded pore and kaolinite intercrystalline pore primarily, microporetransitional pore was primary oil gas reservoir space, the micro larynx and thinness larynx were the basic seepage passage, and it is typical medialow hole, special hypotonic reservoir. In plan, the reservoir's physical property is controlled by provenance and sedimentary facies zone. In vertical directions, the compaction and cementation lead poov reservoir’s physical property, whereas secondary pores produced by dissolution result in the enhancement of reservoir property.
By analyzing the thin sections and physical property,the petrology character, poroperm characteristics, pore texture and pore types of the reservoir of the He 8 Formation in the north of Ordos basin were tested, and the reservoir performance’ major influencing factor were analyzed. The result indicates that the reservoir of He 8 Formation which deposited in braidedstream have high compositional maturity and media textural maturity, the reservoir germinates secondary corroded pore and kaolinite intercrystalline pore primarily, microporetransitional pore was primary oil gas reservoir space, the micro larynx and thinness larynx were the basic seepage passage, and it is typical medialow hole, special hypotonic reservoir. In plan, the reservoir's physical property is controlled by provenance and sedimentary facies zone. In vertical directions, the compaction and cementation lead poov reservoir’s physical property, whereas secondary pores produced by dissolution result in the enhancement of reservoir property.
2009, 27(2): 254-264.
Abstract:
The meandering fluvial deposits, preserved in Middle Triassic Youfangzhuang Formation of Jiyuan Area, western Henan，comprise mainly fine sandstone, siltstone and silty mudstone interbedded with conglomerate and coarse sandstone. According to Miall’s lithofacies classification, seventeen lithofacies can be recognized from Youfangzhuang Formation, the main lithofacies are Sts, Sps, Sws, Fh, Fr, Fc,Ch and Cr， which can be aligned to seven lithofacies associations. Based on the features of lithofacies types and sedimentary structures, the fluvial sedimentary facies of Youfangzhang Fm. can be subdivided into three sublithofacies and eight microlitofacies. The fluvial channel sinuosity(P) is 0.64, the fluvial deposits belong to lowsinuosity meandering fluvial deposits.
The meandering fluvial deposits, preserved in Middle Triassic Youfangzhuang Formation of Jiyuan Area, western Henan，comprise mainly fine sandstone, siltstone and silty mudstone interbedded with conglomerate and coarse sandstone. According to Miall’s lithofacies classification, seventeen lithofacies can be recognized from Youfangzhuang Formation, the main lithofacies are Sts, Sps, Sws, Fh, Fr, Fc,Ch and Cr， which can be aligned to seven lithofacies associations. Based on the features of lithofacies types and sedimentary structures, the fluvial sedimentary facies of Youfangzhang Fm. can be subdivided into three sublithofacies and eight microlitofacies. The fluvial channel sinuosity(P) is 0.64, the fluvial deposits belong to lowsinuosity meandering fluvial deposits.
2009, 27(2): 273-279.
Abstract:
Kazuo basin is Late Mesozoic era rift basin in the west of Liaoning, in which Jiufotang Formation is the filling stratum. On the basis of lithologic character analysis ,such as the color, structure, primary sedimentary structure of field outcrops , and also analysis of the spatial disposition and paleontology fossil combination, as well as drawing and integrated analysis in the laboratory, four sedimentary facies containing braided river delta facies, lake facies, lake gravity flow facies and fan delta facies are recognized from Jiufotang Formation finally.Among them, lake facies is the main body of Jiufotang Formation, which is in the shape of sliver and developing in the middle of each depression; braided river delta facies is formed in the northwest of Siguanyingzi depression and Dachengzi depression; fan delta facies chiefly occurs at southeast of Siguanyingzi depression and Meileyingzi depression; lake gravity flow facies mostly developed in the deep lake area of Kazuo basin. Restricted of the relative relation between sedimentation rate and deposit filling rate, from early to late,the evolution of Jiufotang Formation can be manifested as: lake expansion and retrogradation times, large lake aggradation times and lake atrophy and progradation times.
Kazuo basin is Late Mesozoic era rift basin in the west of Liaoning, in which Jiufotang Formation is the filling stratum. On the basis of lithologic character analysis ,such as the color, structure, primary sedimentary structure of field outcrops , and also analysis of the spatial disposition and paleontology fossil combination, as well as drawing and integrated analysis in the laboratory, four sedimentary facies containing braided river delta facies, lake facies, lake gravity flow facies and fan delta facies are recognized from Jiufotang Formation finally.Among them, lake facies is the main body of Jiufotang Formation, which is in the shape of sliver and developing in the middle of each depression; braided river delta facies is formed in the northwest of Siguanyingzi depression and Dachengzi depression; fan delta facies chiefly occurs at southeast of Siguanyingzi depression and Meileyingzi depression; lake gravity flow facies mostly developed in the deep lake area of Kazuo basin. Restricted of the relative relation between sedimentation rate and deposit filling rate, from early to late,the evolution of Jiufotang Formation can be manifested as: lake expansion and retrogradation times, large lake aggradation times and lake atrophy and progradation times.
2009, 27(2): 289-298.
Abstract:
Through integrated studies of outcrops, cores, drilling, well logging and seismic data, sequence interfaces are identified and sequence framework of the Upper Palaeozoic of Ordos Basin is established. The Upper Paleozoic of Ordos Basin can be divided into 5 second order sequences and 19 third order sequences, the basic characteristics and constitution of system tracts of which are also analyzed. Each second order sequence corresponds to specific tectonicdeposition evolution stages : SS1 corresponds to rift bay and restricted epiric sea coexistence stage; SS2 corresponds to unified epicontinental sea stage; SS3 corresponds to offshore plain swampdelta stage; SS4 corresponds to seaside lake basin deposition stage; SS5 corresponds to inland red clastic rock deposition stage. Three models are established for the development of sedimentary sandbodies in sequence frameworks (including tidal flatdelta model of marinecontinental alternative deposition in Taiyuan Formation, offshore plain swampdelta model in Shanxi Formation and braided riverbraided delta model in lower Shihezi Formation). The main sandbody types and their distribution in sequence frameworks are analyzed and predicated.
Through integrated studies of outcrops, cores, drilling, well logging and seismic data, sequence interfaces are identified and sequence framework of the Upper Palaeozoic of Ordos Basin is established. The Upper Paleozoic of Ordos Basin can be divided into 5 second order sequences and 19 third order sequences, the basic characteristics and constitution of system tracts of which are also analyzed. Each second order sequence corresponds to specific tectonicdeposition evolution stages : SS1 corresponds to rift bay and restricted epiric sea coexistence stage; SS2 corresponds to unified epicontinental sea stage; SS3 corresponds to offshore plain swampdelta stage; SS4 corresponds to seaside lake basin deposition stage; SS5 corresponds to inland red clastic rock deposition stage. Three models are established for the development of sedimentary sandbodies in sequence frameworks (including tidal flatdelta model of marinecontinental alternative deposition in Taiyuan Formation, offshore plain swampdelta model in Shanxi Formation and braided riverbraided delta model in lower Shihezi Formation). The main sandbody types and their distribution in sequence frameworks are analyzed and predicated.
2009, 27(2): 306-311.
Abstract:
Reservoir prediction based on sequence stratigraphy is one of popular and significant research subjects in hydrocarbon exploration. Based on the theory of sequence stratigraphy, comprehensively used the seismic, well logging, core and materials, comprehensively analyzed by wellseismic correlation, and verified by acoustic impedance, two thirdorder sequences which are mainly composed of fan delta lacustrine sedimentary system can be identified in Nantun group of Beier depression：sequence Ⅰequal to K1n1，sequence Ⅱ equal to K1n2. Every sequence develops well and all consist of lowstand system tracts (LST), transgressive system tracts(TST) and highstand system tracts (HST). According to the development characteristics of sequence in the formation in the region of interest, based on the identification and correlation of sequence stratigraphic units, characteristics of sediment and sequence stratigraphic model of different sequence framework are summarized, and the hydrocarbon accumulation model is established.
Reservoir prediction based on sequence stratigraphy is one of popular and significant research subjects in hydrocarbon exploration. Based on the theory of sequence stratigraphy, comprehensively used the seismic, well logging, core and materials, comprehensively analyzed by wellseismic correlation, and verified by acoustic impedance, two thirdorder sequences which are mainly composed of fan delta lacustrine sedimentary system can be identified in Nantun group of Beier depression：sequence Ⅰequal to K1n1，sequence Ⅱ equal to K1n2. Every sequence develops well and all consist of lowstand system tracts (LST), transgressive system tracts(TST) and highstand system tracts (HST). According to the development characteristics of sequence in the formation in the region of interest, based on the identification and correlation of sequence stratigraphic units, characteristics of sediment and sequence stratigraphic model of different sequence framework are summarized, and the hydrocarbon accumulation model is established.
2009, 27(2): 319-325.
Abstract:
The authors firstly make a study on Palaeoecology in upwelling phase region of Middle Permian in the Lower Yangtze area. The Qixia Formation is divided into five sedimentary ages, and the organic communities are recognized in this paper, at the same time, compositions, structures and ecologic environments are also discussed. Based on the analysis of characters of community association and deposition, two kinds of biofacies are recognized, namely benthonic biofacies of shelf glacis and planktonic biofacies of shelf basin, the relationship between biofacies and intensity of upwelling current is elucidated in the paper. Finally, the analysis of the control of upwelling current on paleoecologic features demonstrates that the intensity of upwelling current corresponds to abundance of organic community and discords from diversity.
The authors firstly make a study on Palaeoecology in upwelling phase region of Middle Permian in the Lower Yangtze area. The Qixia Formation is divided into five sedimentary ages, and the organic communities are recognized in this paper, at the same time, compositions, structures and ecologic environments are also discussed. Based on the analysis of characters of community association and deposition, two kinds of biofacies are recognized, namely benthonic biofacies of shelf glacis and planktonic biofacies of shelf basin, the relationship between biofacies and intensity of upwelling current is elucidated in the paper. Finally, the analysis of the control of upwelling current on paleoecologic features demonstrates that the intensity of upwelling current corresponds to abundance of organic community and discords from diversity.
2009, 27(2): 343-351.
Abstract:
By using highresolution laser grain size instrument Mastersizer 2000, the multimodal characteristics of grain size distribution of loess, desert, lake and river sediments are measured and carefully studied. The standard patterns and their grain size characteristics of various sediments are systemically summarized, the discrepancies of multimodal distribution among these sediments are concluded and the comparisons of grain size multimodal distribution of them are also discussed in this paper. The major conclusions are followed: 1)The multimodal characteristic of grain size distribution is a common feature in all sediments and results from properties of transportation medium, dynamic intensity, transportation manner and other factors; 2) There are three modes in loess grain size distribution: fine, median and coarse (the median size is <1 μm,1～10 μm,10～70 μm, respectively) and suspended particles which diameters are less than 70 μm are dominant; 3) There is a predominant coarse saltation mode in grain size distribution of sandy dunes, which median size is about 100～300 μm and the content is larger than that of other modes; 4) There are 6 modes (median size are <1 μm, 2～10 μm, 10～70 μm, 70～150 μm, 150～700 μm, >700 μm respectively) in grain size distribution of lake sediments. The former 4 modes are suspense and others are saltated and rolling. Lake sediments can be divided into three types: lake shore facies, transitional facies and central lake facies; 5) The grain size distribution of river sediments is the most complex and it's consist of suspension, saltation and rolling modes.6) The windblown depositions and aqueous sediments of predominant mode gradually decreases form sandy dunes to loess and river to lake sediments. But the grain size of modes of windblown depositions is usually finer than that of corresponding modes of aqueous sediments.
By using highresolution laser grain size instrument Mastersizer 2000, the multimodal characteristics of grain size distribution of loess, desert, lake and river sediments are measured and carefully studied. The standard patterns and their grain size characteristics of various sediments are systemically summarized, the discrepancies of multimodal distribution among these sediments are concluded and the comparisons of grain size multimodal distribution of them are also discussed in this paper. The major conclusions are followed: 1)The multimodal characteristic of grain size distribution is a common feature in all sediments and results from properties of transportation medium, dynamic intensity, transportation manner and other factors; 2) There are three modes in loess grain size distribution: fine, median and coarse (the median size is <1 μm,1～10 μm,10～70 μm, respectively) and suspended particles which diameters are less than 70 μm are dominant; 3) There is a predominant coarse saltation mode in grain size distribution of sandy dunes, which median size is about 100～300 μm and the content is larger than that of other modes; 4) There are 6 modes (median size are <1 μm, 2～10 μm, 10～70 μm, 70～150 μm, 150～700 μm, >700 μm respectively) in grain size distribution of lake sediments. The former 4 modes are suspense and others are saltated and rolling. Lake sediments can be divided into three types: lake shore facies, transitional facies and central lake facies; 5) The grain size distribution of river sediments is the most complex and it's consist of suspension, saltation and rolling modes.6) The windblown depositions and aqueous sediments of predominant mode gradually decreases form sandy dunes to loess and river to lake sediments. But the grain size of modes of windblown depositions is usually finer than that of corresponding modes of aqueous sediments.
2009, 27(2): 360-366.
Abstract:
On the basis of the new time scale and the analysis of oxide of Core DG03 samples from Gahai Lake in Qaidam Basin, this paper employs SiO2，Al2O3，TiO2，Fe2O3，MgO，ＣaO，K2O，Na2O and their ratios, which are sensitive to environmental changes, to reconstruct the palaeoenvironmental changes since 11.5 kaBP in Gahai Lake. The results show that there are four distinct climate changing periods in Gahai Lake Area since 11.5 kaBP. At the early stage of the Late Deglaciation, the climate was warm and a little bit dry in 11.511.16 kaBP, it soon turned to be extremely cold and dry in 11.16～10.16 kaBP, this dramatic changes should be correlated to the Younger Dryas events; When entering into the Holocene period, it was turned warm with some occurrence of short period of cold and dry events in 10.167.83kaBP; During the MidHolocene period （7.83～4.73kaBP）its climate was warm and wet, which was the best climatic stage since the Late Deglaciation period. The Late Holocene period （4.73～0 kaBP） was in the deterioration of climate which was cold and very arid.
On the basis of the new time scale and the analysis of oxide of Core DG03 samples from Gahai Lake in Qaidam Basin, this paper employs SiO2，Al2O3，TiO2，Fe2O3，MgO，ＣaO，K2O，Na2O and their ratios, which are sensitive to environmental changes, to reconstruct the palaeoenvironmental changes since 11.5 kaBP in Gahai Lake. The results show that there are four distinct climate changing periods in Gahai Lake Area since 11.5 kaBP. At the early stage of the Late Deglaciation, the climate was warm and a little bit dry in 11.511.16 kaBP, it soon turned to be extremely cold and dry in 11.16～10.16 kaBP, this dramatic changes should be correlated to the Younger Dryas events; When entering into the Holocene period, it was turned warm with some occurrence of short period of cold and dry events in 10.167.83kaBP; During the MidHolocene period （7.83～4.73kaBP）its climate was warm and wet, which was the best climatic stage since the Late Deglaciation period. The Late Holocene period （4.73～0 kaBP） was in the deterioration of climate which was cold and very arid.
2009, 27(2): 372-379.
Abstract:
High abundant diginanes and homodiginanes with 5α,14β,17β(H)stereochemistry (αββ) were detected in the crude oil (2 280 m,Ek) of Well Zhao7 from the Jinxian Sag, Bohao Bay Basin, China. The specific, characterized depositional environment with high abundant sulfur and sulfate minerals play an important role in the occurrence of high abundant diginanes and homodiginanes. High abundant shortchain diapregnanes and diahomopregnanes with 5β, 14β, 17α (H) (ββα) stereochemistry which reported by Requejo et al. (1997), generally occurred in the depositional environment with enough iron minerals. On the contrary, high abundant diginanes and homodiginanes occurred in this study which indicates an environment with enough sulfur.
High abundant diginanes and homodiginanes with 5α,14β,17β(H)stereochemistry (αββ) were detected in the crude oil (2 280 m,Ek) of Well Zhao7 from the Jinxian Sag, Bohao Bay Basin, China. The specific, characterized depositional environment with high abundant sulfur and sulfate minerals play an important role in the occurrence of high abundant diginanes and homodiginanes. High abundant shortchain diapregnanes and diahomopregnanes with 5β, 14β, 17α (H) (ββα) stereochemistry which reported by Requejo et al. (1997), generally occurred in the depositional environment with enough iron minerals. On the contrary, high abundant diginanes and homodiginanes occurred in this study which indicates an environment with enough sulfur.
