2015 Vol. 33, No. 4
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2015, 33(4): 633-640.
doi: 10.14027/j.cnki.cjxb.2015.04.001
Abstract:
The characteristics of the event transgression and its depositions have been studied by ways of sedimentology, coal geology, paleontology, and geochemistry association with comparative analysis. The results are as follows. The sedimentary assemblage (exposure deposition, coal seam and limestone) have characteristics of regionally correlative, the successive deposition, and facies gap. The key identification mark is the exposure deposition under coal seams. The paleontology has small size and is broken into some fragments. All the characteristics can proof paleontology the depositional environment of high energy water. And there are lower content of monolete spore and Gymnosperm with higher content of trilete spore in the transgressive event deposition. The author found the depositional environment of different beds. The exposure deposition formed in terrestrial environment. Coal beds were formed in the peat moor and preserved under the sea water. Then the differences between transgressive event coal and transgressive process coal can be concluded. Firstly, there are differences in basin characteristics. The transgressive event coals are often found in epicontinental basin while the transgressive progressive coals are found in marginal basins. Secondly, there are differences in coal-forming principle. The former theory emphasis that the peat moor were formed in the abandon stage of the clastic system and then were stopped by the event transgression, the later think that the peat moor were formed in the coast of activity system and were stopped by the slow transgression.
The characteristics of the event transgression and its depositions have been studied by ways of sedimentology, coal geology, paleontology, and geochemistry association with comparative analysis. The results are as follows. The sedimentary assemblage (exposure deposition, coal seam and limestone) have characteristics of regionally correlative, the successive deposition, and facies gap. The key identification mark is the exposure deposition under coal seams. The paleontology has small size and is broken into some fragments. All the characteristics can proof paleontology the depositional environment of high energy water. And there are lower content of monolete spore and Gymnosperm with higher content of trilete spore in the transgressive event deposition. The author found the depositional environment of different beds. The exposure deposition formed in terrestrial environment. Coal beds were formed in the peat moor and preserved under the sea water. Then the differences between transgressive event coal and transgressive process coal can be concluded. Firstly, there are differences in basin characteristics. The transgressive event coals are often found in epicontinental basin while the transgressive progressive coals are found in marginal basins. Secondly, there are differences in coal-forming principle. The former theory emphasis that the peat moor were formed in the abandon stage of the clastic system and then were stopped by the event transgression, the later think that the peat moor were formed in the coast of activity system and were stopped by the slow transgression.
2015, 33(4): 649-658.
doi: 10.14027/j.cnki.cjxb.2015.04.003
Abstract:
The analysis of sediment source has vital significance to the sedimentary area, reservoir characteristics and tectonic evolution. Based on the analysis of detrital composition, lithic type, heavy mineral assemblage, cathode luminescence, REE and seismic data, the provenance of Eboliang region in Qaidam Basin during the Paleogene has been specifically studied. The provenance of Eboliang No.Ⅰ structure mainly comes from the Altyn Tagh Mountain in the north. The Dongping structure belt in the west and Eboliang No.Ⅰ structure have relatively independent provenance. Eboliang No.Ⅱ structure is in mixed provenance area, which is influenced by two source directions. The main provenance is from the Altyn Tagh Mountain in the north through Eboliang No.Ⅰ structure. One of the other is from Xiaosaishiteng Mountain in the northeast of the study area through Lenghu No. 3, 4 and 5 structures. Provenance of Eboliang No.Ⅲ structure mainly comes from Saishiteng Mountain in northeast of study area through Lenghu No.6 and Lenghu No.7 structures without the influence by ancient Yuka largh fluvial-dominated delta from Nanbaxian direction.
The analysis of sediment source has vital significance to the sedimentary area, reservoir characteristics and tectonic evolution. Based on the analysis of detrital composition, lithic type, heavy mineral assemblage, cathode luminescence, REE and seismic data, the provenance of Eboliang region in Qaidam Basin during the Paleogene has been specifically studied. The provenance of Eboliang No.Ⅰ structure mainly comes from the Altyn Tagh Mountain in the north. The Dongping structure belt in the west and Eboliang No.Ⅰ structure have relatively independent provenance. Eboliang No.Ⅱ structure is in mixed provenance area, which is influenced by two source directions. The main provenance is from the Altyn Tagh Mountain in the north through Eboliang No.Ⅰ structure. One of the other is from Xiaosaishiteng Mountain in the northeast of the study area through Lenghu No. 3, 4 and 5 structures. Provenance of Eboliang No.Ⅲ structure mainly comes from Saishiteng Mountain in northeast of study area through Lenghu No.6 and Lenghu No.7 structures without the influence by ancient Yuka largh fluvial-dominated delta from Nanbaxian direction.
2015, 33(4): 665-678.
doi: 10.14027/j.cnki.cjxb.2015.04.005
Abstract:
Through the peak age of detrital zircons(420±3 Ma and 419.6±3.6 Ma) and the fossils of graptolites and cephalopods in the Yuanbaoshan Formation in Hangwula area, the north of Alxa, the conclusion is that the age of Yuanbaoshan Formation is Devonian, not Early Silurian. The information of lithology, sediment structures of Yuanbaoshan Formation shows that the Yuanbaoshan Formation is bathyal- pelagic deposit, but the Bouma sequence is not complete, including the ae, abe, ade, abde and other combinations, and the Formation is divided into three sedimentary subfacies which are inner fan, middle fan and outer fan. The study area, located in the north of Alxa region which belongs to the southern margin of the Siberian plate, is the key part of the study to the closing time of Paleo-Asian Ocean. The characteristics of Early Paleozoic cherts indicate that the tectonic setting of the study area is a stable passive continental margin in the early Paleozoic. Since Late Paleozoic, the tectonic activity in the study area began to increase, and gradually the tectonic setting transformed from a passive continental margin to an active continental margin, to form a thick turbidite. Source area is the Siberian plate in the north of the study area, according to the flute cast and gloove cast in the turbidite. And according to the study of lithology, sedimentary characteristics and geochemical characteristics of the turbidite, the tubidite in the study area formed in the continental margin in the southern margin of the Siberian plate, and also is affected by the island arc, resulting in the turbidite with island arc attributes. It should be noted that the peak age of detrital zircons of the turbidite is in accord with the age of island arc diorite in the Sunite Left Banner, therefore, the subduction from Tarim plate(or the oceanic crust of Paleo-Asian Ocean) to the Siberia plate began in 420 Ma.
Through the peak age of detrital zircons(420±3 Ma and 419.6±3.6 Ma) and the fossils of graptolites and cephalopods in the Yuanbaoshan Formation in Hangwula area, the north of Alxa, the conclusion is that the age of Yuanbaoshan Formation is Devonian, not Early Silurian. The information of lithology, sediment structures of Yuanbaoshan Formation shows that the Yuanbaoshan Formation is bathyal- pelagic deposit, but the Bouma sequence is not complete, including the ae, abe, ade, abde and other combinations, and the Formation is divided into three sedimentary subfacies which are inner fan, middle fan and outer fan. The study area, located in the north of Alxa region which belongs to the southern margin of the Siberian plate, is the key part of the study to the closing time of Paleo-Asian Ocean. The characteristics of Early Paleozoic cherts indicate that the tectonic setting of the study area is a stable passive continental margin in the early Paleozoic. Since Late Paleozoic, the tectonic activity in the study area began to increase, and gradually the tectonic setting transformed from a passive continental margin to an active continental margin, to form a thick turbidite. Source area is the Siberian plate in the north of the study area, according to the flute cast and gloove cast in the turbidite. And according to the study of lithology, sedimentary characteristics and geochemical characteristics of the turbidite, the tubidite in the study area formed in the continental margin in the southern margin of the Siberian plate, and also is affected by the island arc, resulting in the turbidite with island arc attributes. It should be noted that the peak age of detrital zircons of the turbidite is in accord with the age of island arc diorite in the Sunite Left Banner, therefore, the subduction from Tarim plate(or the oceanic crust of Paleo-Asian Ocean) to the Siberia plate began in 420 Ma.
2015, 33(4): 687-696.
doi: 10.14027/j.cnki.cjxb.2015.04.007
Abstract:
Studying lithology-lithofacies characteristics of Lower Xishanyao Formation, the main uranium-bearing stratum, in Kuosijiaer area of Yili Basin, summarizing it's relationship to uranium deposit, it will provide important theory evidence for following uranium exploration in the study area. Based on the characteristics of lithology, lithofacies structure of connecting-well profile, development of sand bodies, plane distribution of lithofacies structure, and combined with sedimentary geological features of the whole southern margin of Yili Basin, our analysis suggests that the sedimentary subfacies of mainly ore-bearing layer, the Lower sub-member of Lower Xishanyao Formation Middle Jurassic in Kuosijiaer area was fan delta front, and sedimentary micro-facies including the underwater distributary channel with distribution direction towards north and northeast and interdistributary estuary was further detected. Through the study of relationship between lithology-lithofacies characteristics and uranium deposit of target intervals in the study area, the uranium ore bodies occurred in Lower Xishanyao Formation in Kuosijiaer area were mainly controlled by the distribution direction of distributary channel sandbody, the thickness of distributary channel sandbody, the hydrodynamics of sedimentation, the shape or sudden change of sedimentary micro facies, and the post-sedimentary tectonic evolution.
Studying lithology-lithofacies characteristics of Lower Xishanyao Formation, the main uranium-bearing stratum, in Kuosijiaer area of Yili Basin, summarizing it's relationship to uranium deposit, it will provide important theory evidence for following uranium exploration in the study area. Based on the characteristics of lithology, lithofacies structure of connecting-well profile, development of sand bodies, plane distribution of lithofacies structure, and combined with sedimentary geological features of the whole southern margin of Yili Basin, our analysis suggests that the sedimentary subfacies of mainly ore-bearing layer, the Lower sub-member of Lower Xishanyao Formation Middle Jurassic in Kuosijiaer area was fan delta front, and sedimentary micro-facies including the underwater distributary channel with distribution direction towards north and northeast and interdistributary estuary was further detected. Through the study of relationship between lithology-lithofacies characteristics and uranium deposit of target intervals in the study area, the uranium ore bodies occurred in Lower Xishanyao Formation in Kuosijiaer area were mainly controlled by the distribution direction of distributary channel sandbody, the thickness of distributary channel sandbody, the hydrodynamics of sedimentation, the shape or sudden change of sedimentary micro facies, and the post-sedimentary tectonic evolution.
2015, 33(4): 706-712.
doi: 10.14027/j.cnki.cjxb.2015.04.009
Abstract:
Since the Holocene, the barrier coast depositional system, and the special barrier-coast delta formed in this environment extensively development in south China coastal. Based on the modern geological investigation in the Chaoshan region, and summarizing the former researches, we found that evolution of Hanjiang delta in this region mainly affected by sea level change, the development of barrier-lagoon system, the ability of river transportation, and clarified evolution characteristics of delta and regularity of sand-body distribution in different periods. Then, combined with the developmental characteristics of Luohe delta and Wanning Xiaohai, the evolution of barrier-coast delta can be divided into three stages: formation period, the barrier-lagoon system formed, delta began to develop in the lagoon; development period, with the high stability of the lagoon water, the delta rapidly prograde, at the same time, the barrier bars migration to the sea; reforming period, lagoon disappeared gradually, sediments began to deposit on the outside of barrier bars, delta seaward progradation; Finally, the barrier-coast delta depositional model has been established in the Chaoshan region, and the former period controlled by fluvial in the lagoon, the later period influenced by variety of dynamic interaction out of the barrier.
Since the Holocene, the barrier coast depositional system, and the special barrier-coast delta formed in this environment extensively development in south China coastal. Based on the modern geological investigation in the Chaoshan region, and summarizing the former researches, we found that evolution of Hanjiang delta in this region mainly affected by sea level change, the development of barrier-lagoon system, the ability of river transportation, and clarified evolution characteristics of delta and regularity of sand-body distribution in different periods. Then, combined with the developmental characteristics of Luohe delta and Wanning Xiaohai, the evolution of barrier-coast delta can be divided into three stages: formation period, the barrier-lagoon system formed, delta began to develop in the lagoon; development period, with the high stability of the lagoon water, the delta rapidly prograde, at the same time, the barrier bars migration to the sea; reforming period, lagoon disappeared gradually, sediments began to deposit on the outside of barrier bars, delta seaward progradation; Finally, the barrier-coast delta depositional model has been established in the Chaoshan region, and the former period controlled by fluvial in the lagoon, the later period influenced by variety of dynamic interaction out of the barrier.
2015, 33(4): 724-734.
doi: 10.14027/j.cnki.cjxb.2015.04.011
Abstract:
Surface sediments in Fujian Anhai gulf were collected and analyzed by grain size laser particle sizer. The grain size distribution characteristics, sedimentary environment partition, trend of surface sediment transport and its influencing factors were discussed by application system clustering analysis, grain size trend model and the formula of shear stress. The results shows that surface sediment include six types of sediment, give priority to the two main types which are clayey silt and silty sand. The grain size trends to coarse form tidal flat in both sides of the bay to the tidal channel. The grain size distribution characteristics are closely related to the hydrodynamic and material source. The fine particles material were removed by resuspension near the bay mouth and in tidal channel, lead to the content of coarse particles increased. On the tidal flat in the bay, the selective deposition of suspended material happen due to the hydrodynamic effect weakened, formed the horizontal differentiation which particles material become more finer toward the shore. The transportation to the east side tidal flats of the suspended sediment carried by the tide current form the outside bay, and the discharge of terrigenous sediment derived from surrounding the gulf towards the top of the bay to the bay mouth, can influence the migration trend of sediment shows obviously clockwise convergence. The formation and change of the shoals are affected by the migration trend of sediment and transport of suspended sediment together with vegetation and the shading effect of the sand spit in bay mouth. The study area can be divided into four types of sedimentary environment, give priority to tidal flat and tidal channel environment. The grain size parameters, frequency and sensitive fraction have difference in different sedimentary environment. The modern pattern sediment environment is mainly impacted by hydrodynamic difference and the influence of different material source.
Surface sediments in Fujian Anhai gulf were collected and analyzed by grain size laser particle sizer. The grain size distribution characteristics, sedimentary environment partition, trend of surface sediment transport and its influencing factors were discussed by application system clustering analysis, grain size trend model and the formula of shear stress. The results shows that surface sediment include six types of sediment, give priority to the two main types which are clayey silt and silty sand. The grain size trends to coarse form tidal flat in both sides of the bay to the tidal channel. The grain size distribution characteristics are closely related to the hydrodynamic and material source. The fine particles material were removed by resuspension near the bay mouth and in tidal channel, lead to the content of coarse particles increased. On the tidal flat in the bay, the selective deposition of suspended material happen due to the hydrodynamic effect weakened, formed the horizontal differentiation which particles material become more finer toward the shore. The transportation to the east side tidal flats of the suspended sediment carried by the tide current form the outside bay, and the discharge of terrigenous sediment derived from surrounding the gulf towards the top of the bay to the bay mouth, can influence the migration trend of sediment shows obviously clockwise convergence. The formation and change of the shoals are affected by the migration trend of sediment and transport of suspended sediment together with vegetation and the shading effect of the sand spit in bay mouth. The study area can be divided into four types of sedimentary environment, give priority to tidal flat and tidal channel environment. The grain size parameters, frequency and sensitive fraction have difference in different sedimentary environment. The modern pattern sediment environment is mainly impacted by hydrodynamic difference and the influence of different material source.
2015, 33(4): 744-753.
doi: 10.14027/j.cnki.cjxb.2015.04.013
Abstract:
The spatial characteristics of pollen assemblages of the lake surface sediments and associated dynamics on deposition, perseveration and transport process is important to the paleoclimate and paleoenvironment reconstruction. Lake Hulun, which is situated in the northeast of China, with a lake surface area of ~2 100 km2 and an average water depth of 3 m, and four inflow rivers in the north, east and the south, provide an ideal site for such researches. In addition, the widely varied lake basin (the differences of the water depth between each sample site) and the changed vegetation pattern around the lake, provide chances to explore the impact of the resuspension and redeposition process, the influencing of drift and the influence of non-zonal vegetation to the pollen assemblage in the lake. Investigations on pollen assemblages of 29 surface sediment samples throughout Lake Hulun were carried and ordination analysis on the pollen percentage data and environmental data were conducted to disclose the spatial characteristics of pollen assemblages and the potential dynamics between the pollen data and the environmental factors. Specifically, 29 lake surface sediment samples (top 2 cm sediment) were collected at a spatial interval of 5×5 minutes along a snake line in the lake and three types of environmental impact factors including water depth (in relation to resuspension and redeposition), the distance to the rivers mouth (in relation to river transportation process) and the distance to the east coast of the lake (in relation to the drift caused by dominant wind in warm season and the influence of the non-zonal vegetation in the east of the lake) were constructed. Ordination analysis including principal component analysis (PCA) and redundancy analysis (RDA) were selected according to the data type of the pollen data (i.e., liner model as indicated by the gradient length of the detrended correspondence analysis, DCA) and were conducted on the pollen data and environmental data. As suggested by the result of the PCA, remarkable spatial differentiations of the pollen assemblage could be distinguished. That is, the pollen percentages of Chenopodiaceae and Pinus are high in the sample sites in the eastern littoral area, while the pollen percentages of Betula and Artemisia are high in the sample sites in the central and western profundal area. As revealed by the results of RDA, the distance to the east coast (D5), the distance to the Xinkai River mouth (D2) and the water depth (WD) are statistically correlated to the spatial patterns of pollen assemblages and are responsible for the spatial differentiations of pollen assemblages. The distance to the east coast (D5), on behalf of the influence of the drift caused by the dominant wind and the influence of the non-zonal halophytic vegetation developed in the east shore of Lake Hulun, is the most important environmental factor correlated to the spatial difference of pollen assemblage. The non-zonal halophytic vegetation developed in the east shore of Lake Hulun make a contribution to the high content of Chenopodiaceae in the eastern littoral area, while the drift caused by the dominant west-southward wind lead to the high Pinus percentages in the eastern littoral area.
The spatial characteristics of pollen assemblages of the lake surface sediments and associated dynamics on deposition, perseveration and transport process is important to the paleoclimate and paleoenvironment reconstruction. Lake Hulun, which is situated in the northeast of China, with a lake surface area of ~2 100 km2 and an average water depth of 3 m, and four inflow rivers in the north, east and the south, provide an ideal site for such researches. In addition, the widely varied lake basin (the differences of the water depth between each sample site) and the changed vegetation pattern around the lake, provide chances to explore the impact of the resuspension and redeposition process, the influencing of drift and the influence of non-zonal vegetation to the pollen assemblage in the lake. Investigations on pollen assemblages of 29 surface sediment samples throughout Lake Hulun were carried and ordination analysis on the pollen percentage data and environmental data were conducted to disclose the spatial characteristics of pollen assemblages and the potential dynamics between the pollen data and the environmental factors. Specifically, 29 lake surface sediment samples (top 2 cm sediment) were collected at a spatial interval of 5×5 minutes along a snake line in the lake and three types of environmental impact factors including water depth (in relation to resuspension and redeposition), the distance to the rivers mouth (in relation to river transportation process) and the distance to the east coast of the lake (in relation to the drift caused by dominant wind in warm season and the influence of the non-zonal vegetation in the east of the lake) were constructed. Ordination analysis including principal component analysis (PCA) and redundancy analysis (RDA) were selected according to the data type of the pollen data (i.e., liner model as indicated by the gradient length of the detrended correspondence analysis, DCA) and were conducted on the pollen data and environmental data. As suggested by the result of the PCA, remarkable spatial differentiations of the pollen assemblage could be distinguished. That is, the pollen percentages of Chenopodiaceae and Pinus are high in the sample sites in the eastern littoral area, while the pollen percentages of Betula and Artemisia are high in the sample sites in the central and western profundal area. As revealed by the results of RDA, the distance to the east coast (D5), the distance to the Xinkai River mouth (D2) and the water depth (WD) are statistically correlated to the spatial patterns of pollen assemblages and are responsible for the spatial differentiations of pollen assemblages. The distance to the east coast (D5), on behalf of the influence of the drift caused by the dominant wind and the influence of the non-zonal halophytic vegetation developed in the east shore of Lake Hulun, is the most important environmental factor correlated to the spatial difference of pollen assemblage. The non-zonal halophytic vegetation developed in the east shore of Lake Hulun make a contribution to the high content of Chenopodiaceae in the eastern littoral area, while the drift caused by the dominant west-southward wind lead to the high Pinus percentages in the eastern littoral area.
2015, 33(4): 764-772.
doi: 10.14027/j.cnki.cjxb.2015.04.015
Abstract:
The Caledonian movement impacted Tarim Basin and its periphery in Ordovician, during which the structure and sedimentary evolution were intensively transformed. The lithology, facies and biofacies began to segregate in Bachu, Keping and Wushi outcrop area of northwest Tarim basin. The sedimentary environment was apparently changed. The essential characteristics were as follows. (1) The Yingshan Group glacis sedimentation during Lower-Middle Ordovician was developed under pull-apart background with remote precipitous characteristic. It was divided into inner, middle and outer gentle slope from south to north in plain. And aquifer deepened from bottom to top in vertical. (2) The Yijianfang and Tumuxiuke of Middle-Upper Ordovician were the key period of sedimentary and structure transformation. The Aman platform trough was formed. Sedimentary framework was evolved from weak edge gentle slope to uniform gentle slope. It overall exhabited South Slow North Steep. (3) The black shale of Saergan group which sedimented in Aman platform trough, probably extended some distance to Awati Depression. It belongs to good source rock and has potential oil and gas exploration area in early and later strata.
The Caledonian movement impacted Tarim Basin and its periphery in Ordovician, during which the structure and sedimentary evolution were intensively transformed. The lithology, facies and biofacies began to segregate in Bachu, Keping and Wushi outcrop area of northwest Tarim basin. The sedimentary environment was apparently changed. The essential characteristics were as follows. (1) The Yingshan Group glacis sedimentation during Lower-Middle Ordovician was developed under pull-apart background with remote precipitous characteristic. It was divided into inner, middle and outer gentle slope from south to north in plain. And aquifer deepened from bottom to top in vertical. (2) The Yijianfang and Tumuxiuke of Middle-Upper Ordovician were the key period of sedimentary and structure transformation. The Aman platform trough was formed. Sedimentary framework was evolved from weak edge gentle slope to uniform gentle slope. It overall exhabited South Slow North Steep. (3) The black shale of Saergan group which sedimented in Aman platform trough, probably extended some distance to Awati Depression. It belongs to good source rock and has potential oil and gas exploration area in early and later strata.
2015, 33(4): 786-794.
doi: 10.14027/j.cnki.cjxb.2015.04.017
Abstract:
Unifying the domestic and international research information and using chlorite cement as the research object in the Daniudi Gas Field, we have discussed the cause of chlorite coatings and its influence on reservoir physical property, moreover studies on its environment designating signification. The chlorite cement of Daniudi Gas Field which thickness is 10~20 μm formed in early stage of diagenesis, and the crystal becomes better, the particlebecomes bigger gradually from the edge of primary intergranular pores to the center. Chlorite coatings can be divided into in autochthonous genesis and allochthonous genesis according to the source of ferruginous. The autochthonous chlorite coatings existing as mixed layer clay and the smaller crystal coatings was generated from the undischarged Fe-rich fluid which was produced by precursory clay mineral and the dissolution of rock fragment. The allochthonous chlorite coatings crystallizing fully and well was generated from the Fe-rich fluid which was produced by Fe-rich minerals and cuttings dissolution flocculating offsite through rivers. Mechanism of reservoir protection of chlorite coatings: ①inhibition of secondary quartz increases; ②increased mineral particle compaction strength and restrain pressure solution; ③inhibition of carbonate cementation and promote corrosion. The chlorite coatings of Daniudi Gas Field mainly developed in H1(63%) and S2. Porosity rises linearly with the increase of content of chlorite when chlorite content below 15%. Chlorite coatings can be used as delta (braided river delta) front of underwater distributary channel (underwater braided rivers) and other microfacies marker of strong hydrodynamic conditions.
Unifying the domestic and international research information and using chlorite cement as the research object in the Daniudi Gas Field, we have discussed the cause of chlorite coatings and its influence on reservoir physical property, moreover studies on its environment designating signification. The chlorite cement of Daniudi Gas Field which thickness is 10~20 μm formed in early stage of diagenesis, and the crystal becomes better, the particlebecomes bigger gradually from the edge of primary intergranular pores to the center. Chlorite coatings can be divided into in autochthonous genesis and allochthonous genesis according to the source of ferruginous. The autochthonous chlorite coatings existing as mixed layer clay and the smaller crystal coatings was generated from the undischarged Fe-rich fluid which was produced by precursory clay mineral and the dissolution of rock fragment. The allochthonous chlorite coatings crystallizing fully and well was generated from the Fe-rich fluid which was produced by Fe-rich minerals and cuttings dissolution flocculating offsite through rivers. Mechanism of reservoir protection of chlorite coatings: ①inhibition of secondary quartz increases; ②increased mineral particle compaction strength and restrain pressure solution; ③inhibition of carbonate cementation and promote corrosion. The chlorite coatings of Daniudi Gas Field mainly developed in H1(63%) and S2. Porosity rises linearly with the increase of content of chlorite when chlorite content below 15%. Chlorite coatings can be used as delta (braided river delta) front of underwater distributary channel (underwater braided rivers) and other microfacies marker of strong hydrodynamic conditions.
2015, 33(4): 809-816.
doi: 10.14027/j.cnki.cjxb.2015.04.019
Abstract:
The west segment of Central Canyon in Qiongdongnan Basin, which wanders from Ledong, Lingshui depression to Songnan low uplift, received over 700 m of gravity flow deposits in the early stage. Mainly based on 2 wells and 2 blocks of 3D seismic data, this paper studied the sedimentary architectures and evolution stages of Yinggehai Formation in the canyon. The canyon infill were divided into 5 depositional sets (DS) vertically according to seismic wave group and seismic-well tie; 4 significant depositional types were recognized by analyzing reflection features, seismic slice and attribute analysis: channel complex (CC), channel-levee(C-L), sheet-like turbidity sand(STS) and mass transport deposits (MTDs). DS1 was primarily CC, DS2 and DS3 were mainly C-L, DS4 consisted of both MTDs and C-L while DS5 was mostly MTDs and STS. During early stages (DS1~DS3), the canyon was dominated by axial sand-rich turbidity currents, while in later stages (DS4~DS5), the canyon was gradually controlled by mass transport deposits from northern slope and rich in mud. Turbidite deposits are ideal reservoir which lays in the lower parts of the canyon, together with the upper MTDs can form perfect reservoir-seal assemblage, thus shows great potential for hydrocarbon exploration.
The west segment of Central Canyon in Qiongdongnan Basin, which wanders from Ledong, Lingshui depression to Songnan low uplift, received over 700 m of gravity flow deposits in the early stage. Mainly based on 2 wells and 2 blocks of 3D seismic data, this paper studied the sedimentary architectures and evolution stages of Yinggehai Formation in the canyon. The canyon infill were divided into 5 depositional sets (DS) vertically according to seismic wave group and seismic-well tie; 4 significant depositional types were recognized by analyzing reflection features, seismic slice and attribute analysis: channel complex (CC), channel-levee(C-L), sheet-like turbidity sand(STS) and mass transport deposits (MTDs). DS1 was primarily CC, DS2 and DS3 were mainly C-L, DS4 consisted of both MTDs and C-L while DS5 was mostly MTDs and STS. During early stages (DS1~DS3), the canyon was dominated by axial sand-rich turbidity currents, while in later stages (DS4~DS5), the canyon was gradually controlled by mass transport deposits from northern slope and rich in mud. Turbidite deposits are ideal reservoir which lays in the lower parts of the canyon, together with the upper MTDs can form perfect reservoir-seal assemblage, thus shows great potential for hydrocarbon exploration.
2015, 33(4): 828-835.
doi: 10.14027/j.cnki.cjxb.2015.04.021
Abstract:
Carbonate reservoir, where is the Miocene Zhujiang Formation in H block of the Pearl River Mouth Basin, has two problems. Firstly, it is the thin reservoir thickness, which is between 6~35 m, generally less than the vertical resolution of 1/4 wavelength; Secondly, the reservoir is heterogeneity; The sedimentary facies is changing fastly; the reservoir is controlled by sedimentary facies, but the research area has not been studied for the regional carbonate sedimentary facies. Aiming at the above problems, this paper is in order to carry out the 3D poststack seismic data waveform analysis as auxiliary, using wells's log, logging division phase. At the same time, building the relationship of elastic wave impedance and lithology, then calibrating the body of prestack inversion elastic wave impedance. The attempt is made to study the seismic imaging in the study area, identifying the range of platform edge reef, patch reef and the bioclastic beach inside of platform. The favorable reservoir have been confirmed by drilling.
Carbonate reservoir, where is the Miocene Zhujiang Formation in H block of the Pearl River Mouth Basin, has two problems. Firstly, it is the thin reservoir thickness, which is between 6~35 m, generally less than the vertical resolution of 1/4 wavelength; Secondly, the reservoir is heterogeneity; The sedimentary facies is changing fastly; the reservoir is controlled by sedimentary facies, but the research area has not been studied for the regional carbonate sedimentary facies. Aiming at the above problems, this paper is in order to carry out the 3D poststack seismic data waveform analysis as auxiliary, using wells's log, logging division phase. At the same time, building the relationship of elastic wave impedance and lithology, then calibrating the body of prestack inversion elastic wave impedance. The attempt is made to study the seismic imaging in the study area, identifying the range of platform edge reef, patch reef and the bioclastic beach inside of platform. The favorable reservoir have been confirmed by drilling.
2015, 33(4): 641-648.
doi: 10.14027/j.cnki.cjxb.2015.04.002
Abstract:
By measuring and describing the section in detail, it comes to a discovery that the Lower Ordovician Panjiazui Formation in Yuanguping area is composed of deep-water carbonate rocks. The rocks are mainly gray micrite, calcarenite and bioclastic limestone. Three types of sediments are developed, namely, vertical landing sediments, gravity flow sediments and contourites. According to lithological characters, the contourites are divided into three types. They are respectively calcilutitic contourite, calcarenitic contourite, and bioclastic contourite. Among them, calcilutitic contourite is well developed, followed by calcarenitic contourite and bioclastic contourite. The development characteristics and the vertical sequences are summarized. Our study shows that there are three types of incomplete contourite sequences in the study area, namely, a single calcilutitic contourite sequence, a calcilutitic-calcarenitic contourite sequence, and a bioclastic-calcarenitic contourite sequence. In the section, the Panjiazui Formation is divided into three parts according to the type and extent of development. From PartⅠ to Part Ⅲ, the proportion of contourite thickness tends to increase. Considering the regional sedimentary background, the contour current strength of this area varied from weak to strong during the sedimentary period of Early Ordovician Panjiazui Formation on the whole, which should form in the mature period of the contourites, so it is significant to study the formation mechanism of this contourites and to define its distribution range.
By measuring and describing the section in detail, it comes to a discovery that the Lower Ordovician Panjiazui Formation in Yuanguping area is composed of deep-water carbonate rocks. The rocks are mainly gray micrite, calcarenite and bioclastic limestone. Three types of sediments are developed, namely, vertical landing sediments, gravity flow sediments and contourites. According to lithological characters, the contourites are divided into three types. They are respectively calcilutitic contourite, calcarenitic contourite, and bioclastic contourite. Among them, calcilutitic contourite is well developed, followed by calcarenitic contourite and bioclastic contourite. The development characteristics and the vertical sequences are summarized. Our study shows that there are three types of incomplete contourite sequences in the study area, namely, a single calcilutitic contourite sequence, a calcilutitic-calcarenitic contourite sequence, and a bioclastic-calcarenitic contourite sequence. In the section, the Panjiazui Formation is divided into three parts according to the type and extent of development. From PartⅠ to Part Ⅲ, the proportion of contourite thickness tends to increase. Considering the regional sedimentary background, the contour current strength of this area varied from weak to strong during the sedimentary period of Early Ordovician Panjiazui Formation on the whole, which should form in the mature period of the contourites, so it is significant to study the formation mechanism of this contourites and to define its distribution range.
2015, 33(4): 659-664.
doi: 10.14027/j.cnki.cjxb.2015.04.004
Abstract:
The Central Canyon is one of the most important sedimentary body in the northwestern part of South China Sea. The provenance problem has always been the focus of the research, and has no uniform understanding. In order to solve the problem, the heavy minerals, rare earth elements and zircon age are used to analyze provenance, by comparing with the sediment of potential provenance and discusses the significance of the research. The results show that: (1) the Red River is the main provenance to the Central Canyon and take the leading role in the formation of the Central Canyon; (2) The Red River drainage had been changed significantly in the history of its evolution. Such changes may occurs in a period of 3.6 Ma to now; (3) The Central Canyon derived from the red river, and formed large reservoirs in the central sag belt of Qiongdongnan Basin. It laid the material foundation for the oil and gas exploration target in deep water.
The Central Canyon is one of the most important sedimentary body in the northwestern part of South China Sea. The provenance problem has always been the focus of the research, and has no uniform understanding. In order to solve the problem, the heavy minerals, rare earth elements and zircon age are used to analyze provenance, by comparing with the sediment of potential provenance and discusses the significance of the research. The results show that: (1) the Red River is the main provenance to the Central Canyon and take the leading role in the formation of the Central Canyon; (2) The Red River drainage had been changed significantly in the history of its evolution. Such changes may occurs in a period of 3.6 Ma to now; (3) The Central Canyon derived from the red river, and formed large reservoirs in the central sag belt of Qiongdongnan Basin. It laid the material foundation for the oil and gas exploration target in deep water.
2015, 33(4): 679-686.
doi: 10.14027/j.cnki.cjxb.2015.04.006
Abstract:
During the Devonian, a complicated carbonate platform-basin configuration was created through transtensional rifting; extensive bedded chert, commonly interbedded with tuffaceous beds, occurred in the narrow, elongate interplatform basins (or troughs) in South China. In order to unravel the origin and distribution of the bedded chert successions, and their relationships to basement faulting activities during the opening of the Devonian South China Sea, geochemistry and Rb-Sr, Sm-Nd isotopic systematics are carried out upon the chert deposits. The initial (87Sr/86Sr)0 ratios of chert generally vary from 0.712 000 to 0.730 000, suggesting influences both from terrigenous influx and seawater. The Nd isotopic model ages (tDM or t2DM) and initial εNd(0) values of chert vary mostly from 1.5 to 2.1 Ga, and from -16 to -21, respectively, implying that the silica sources were derived from the provenances of the Palaeoproterozoic crust relics at depth. The high εNd(0) values of chert (-0.22 to 14.7) in some localities, mostly along the elongate troughs, suggest that silica sources may have been derived from deeper-seated mantle, being channeled through the interplate boundary fault zones extending downwards to the mantle.
During the Devonian, a complicated carbonate platform-basin configuration was created through transtensional rifting; extensive bedded chert, commonly interbedded with tuffaceous beds, occurred in the narrow, elongate interplatform basins (or troughs) in South China. In order to unravel the origin and distribution of the bedded chert successions, and their relationships to basement faulting activities during the opening of the Devonian South China Sea, geochemistry and Rb-Sr, Sm-Nd isotopic systematics are carried out upon the chert deposits. The initial (87Sr/86Sr)0 ratios of chert generally vary from 0.712 000 to 0.730 000, suggesting influences both from terrigenous influx and seawater. The Nd isotopic model ages (tDM or t2DM) and initial εNd(0) values of chert vary mostly from 1.5 to 2.1 Ga, and from -16 to -21, respectively, implying that the silica sources were derived from the provenances of the Palaeoproterozoic crust relics at depth. The high εNd(0) values of chert (-0.22 to 14.7) in some localities, mostly along the elongate troughs, suggest that silica sources may have been derived from deeper-seated mantle, being channeled through the interplate boundary fault zones extending downwards to the mantle.
2015, 33(4): 697-705.
doi: 10.14027/j.cnki.cjxb.2015.04.008
Abstract:
A prerequisite for the dynamic monitor of modern cave is to provide a reliable basis for the interpretation of a variety or multiple proxies from modern carbonate (CaCO3) sediment-stalagmites in cave, and to make full use of the multiple proxies from modern carbonate (CaCO3) sediment in field cave monitoring, and compared to local measuring meteorological data each other and correction, is the key of the accurate and quantitative interpreting multiple climate proxies in stalagmites.The four hydrological years of the meteoric precipitation, cave drips, modern carbonate sediments for 5 sites in No.15 branching cave of Seven Star Cave in Guilin during 2008-2011 were continuously monitored, and the correlation between the δ18O of cave drip and modern carbonate (CaCO3) and δ18O of the meteoric precipitation were also discussed. The study results have shown that the annual average δ18O value of cave drip and modern carbonate (CaCO3) is very close to δ18O of the meteoric precipitation and the same change trend, and indicated that the δ18O of cave drip and modern carbonate (CaCO3) came mainly from δ18O of the meteoric precipitation, that is, it is obviously controlled by δ18O of the meteoric precipitation.In four hydrological years, the year (or annual) change and or many years change trends of δ18O record from the modern secondary chemical carbonate sediments (CaCO3) and drop water in cave are basically the same and show obvious change characteristics of four peak (low value area of δ18O) and four trough (high value area of δ18O), and has obvious rule of the seasonal change and year change and has the same seasonal characteristics of the meteoric precipitation or heat. The research results shown that δ18O of drip water and modern carbonate (CaCO3) sediments in cave can record the climate change signal at local or at the top of the cave. So that it has been considered that δ18O of modern carbonate (CaCO3) sediment in cave is mainly taken as the alternative proxies of the summer monsoon intensity and rainfall amount.
A prerequisite for the dynamic monitor of modern cave is to provide a reliable basis for the interpretation of a variety or multiple proxies from modern carbonate (CaCO3) sediment-stalagmites in cave, and to make full use of the multiple proxies from modern carbonate (CaCO3) sediment in field cave monitoring, and compared to local measuring meteorological data each other and correction, is the key of the accurate and quantitative interpreting multiple climate proxies in stalagmites.The four hydrological years of the meteoric precipitation, cave drips, modern carbonate sediments for 5 sites in No.15 branching cave of Seven Star Cave in Guilin during 2008-2011 were continuously monitored, and the correlation between the δ18O of cave drip and modern carbonate (CaCO3) and δ18O of the meteoric precipitation were also discussed. The study results have shown that the annual average δ18O value of cave drip and modern carbonate (CaCO3) is very close to δ18O of the meteoric precipitation and the same change trend, and indicated that the δ18O of cave drip and modern carbonate (CaCO3) came mainly from δ18O of the meteoric precipitation, that is, it is obviously controlled by δ18O of the meteoric precipitation.In four hydrological years, the year (or annual) change and or many years change trends of δ18O record from the modern secondary chemical carbonate sediments (CaCO3) and drop water in cave are basically the same and show obvious change characteristics of four peak (low value area of δ18O) and four trough (high value area of δ18O), and has obvious rule of the seasonal change and year change and has the same seasonal characteristics of the meteoric precipitation or heat. The research results shown that δ18O of drip water and modern carbonate (CaCO3) sediments in cave can record the climate change signal at local or at the top of the cave. So that it has been considered that δ18O of modern carbonate (CaCO3) sediment in cave is mainly taken as the alternative proxies of the summer monsoon intensity and rainfall amount.
2015, 33(4): 713-723.
doi: 10.14027/j.cnki.cjxb.2015.04.010
Abstract:
Applying concepts of sequence stratigraphy to the interpretation of high resolution seismic profiles on the northern continental shelf of the South China Sea, and to borehole records of the modern Pearl River Delta, north of the continental shelf, permit the recognition of the stratigraphy evolution model during the past ca. 200 kyr. Previous research on the Pearl River Delta indicates that the delta has two marine transgression cycles. Although there has been consensus on the age of the 2nd cycle, which resulted from a postglacial sea level rise, the age of the 1st cycle is greatly debated. Based on 14C and TL dating (40~50 ka B.P.), the 1st cycle was regarded as deposits during MIS3. But the sea level of MIS3 was about 50 m lower than present, and the altitudes of the marine deposits of the 1st cycle, i.e. -25~-1+0 m, in the delta do not match with the sea level of MIS3. Correlation of the sedimentary sequence between the Pearl River Delta and its offshore continental shelf provides a reconsideration of this problem. Four sets of delta formation, six sets of sequence stratigraphy and system tracts of each sequence on the continental shelf are identified. Sequence C, which indicates the transgression during MIS3, did not extend northwards to modern delta area, where only fluvial sediments and weathered deposits are found during the MIS4-MIS3 marine transgression and the MIS3-MIS2 regression. While the HST of sequence D, which indicates the high sea level during MIS5e, can be correlated with the 1st cycle in the Pearl River Delta. The last transgression cycle, represented by sequence B, A, and the upper cycle of the modern Pearl River Delta, indicates the rapid sea level rise after the Last Glacial Maximum to the early Holocene, and the highstand progradation during the last 6 000 yrs. The delta-continental shelf environmental transition was controlled by both global sea level change and regional neotectonic subsidence related to divergent continental margin of South China Sea.
Applying concepts of sequence stratigraphy to the interpretation of high resolution seismic profiles on the northern continental shelf of the South China Sea, and to borehole records of the modern Pearl River Delta, north of the continental shelf, permit the recognition of the stratigraphy evolution model during the past ca. 200 kyr. Previous research on the Pearl River Delta indicates that the delta has two marine transgression cycles. Although there has been consensus on the age of the 2nd cycle, which resulted from a postglacial sea level rise, the age of the 1st cycle is greatly debated. Based on 14C and TL dating (40~50 ka B.P.), the 1st cycle was regarded as deposits during MIS3. But the sea level of MIS3 was about 50 m lower than present, and the altitudes of the marine deposits of the 1st cycle, i.e. -25~-1+0 m, in the delta do not match with the sea level of MIS3. Correlation of the sedimentary sequence between the Pearl River Delta and its offshore continental shelf provides a reconsideration of this problem. Four sets of delta formation, six sets of sequence stratigraphy and system tracts of each sequence on the continental shelf are identified. Sequence C, which indicates the transgression during MIS3, did not extend northwards to modern delta area, where only fluvial sediments and weathered deposits are found during the MIS4-MIS3 marine transgression and the MIS3-MIS2 regression. While the HST of sequence D, which indicates the high sea level during MIS5e, can be correlated with the 1st cycle in the Pearl River Delta. The last transgression cycle, represented by sequence B, A, and the upper cycle of the modern Pearl River Delta, indicates the rapid sea level rise after the Last Glacial Maximum to the early Holocene, and the highstand progradation during the last 6 000 yrs. The delta-continental shelf environmental transition was controlled by both global sea level change and regional neotectonic subsidence related to divergent continental margin of South China Sea.
2015, 33(4): 735-743.
doi: 10.14027/j.cnki.cjxb.2015.04.012
Abstract:
The DGS1 segment of the Dishaogouwan section in the Salawusu River Valley on the southeast edge of the Mu Us Desert is selected to study the climate fluctuations on millennium-scale during the Holocene. Based on the trace elements analysis and age determination, we find that the contents of P, V, Cu, Zn, Sr, Ni, As, Cr, Pb are least in the paleosols, less in the dune sands than that in the lacustrine facies, because they are easy to migrate and slightly stable; the contents of Co, Rb, Nb, Ba, Cl, Zr, are most in the paleosols, more in the dune sands than that in the lacustrine facies, because they are stable inert elements. The results suggest that the dune sands are mainly the aeolian sediments in the dominance of the winter monsoon, and the paleosols and lacustrine facies are the sediments in the dominance of the summer monsoon. According to the changes in the alternations of peaks and valleys of these trace elements, the DGS1 is divided into four periods: warming period(11 000~10 130 a B.P.), Megathermal period(10 130~6 590 a B.P.), cooling period (6 590~3 760 a B.P.)and cold period(3 760~0 a B.P.), which are consistent with the related research results abroad and domestic. It reveals that the climate variations in the Salawusu River Valley are subject to the global environmental changes.
The DGS1 segment of the Dishaogouwan section in the Salawusu River Valley on the southeast edge of the Mu Us Desert is selected to study the climate fluctuations on millennium-scale during the Holocene. Based on the trace elements analysis and age determination, we find that the contents of P, V, Cu, Zn, Sr, Ni, As, Cr, Pb are least in the paleosols, less in the dune sands than that in the lacustrine facies, because they are easy to migrate and slightly stable; the contents of Co, Rb, Nb, Ba, Cl, Zr, are most in the paleosols, more in the dune sands than that in the lacustrine facies, because they are stable inert elements. The results suggest that the dune sands are mainly the aeolian sediments in the dominance of the winter monsoon, and the paleosols and lacustrine facies are the sediments in the dominance of the summer monsoon. According to the changes in the alternations of peaks and valleys of these trace elements, the DGS1 is divided into four periods: warming period(11 000~10 130 a B.P.), Megathermal period(10 130~6 590 a B.P.), cooling period (6 590~3 760 a B.P.)and cold period(3 760~0 a B.P.), which are consistent with the related research results abroad and domestic. It reveals that the climate variations in the Salawusu River Valley are subject to the global environmental changes.
2015, 33(4): 754-763.
doi: 10.14027/j.cnki.cjxb.2015.04.014
Abstract:
The cementation and its relationship with tectonic fractures of sandstone of Bashijiqike Formation of Cretaceous in DB gas field of Kuqa Sub-basin were researched through thin-section analysis, core observation, cathodoluminescence analysis, scan electricity microscope observation, X-ray diffraction, fluid inclusion and reservoir physical parameters analysis, etc and combining histories of tectonic development. It is recognized that the sandstone of Cretaceous in DB gas field is fracture-pore reservoir and with ultra-low porosity and ultra-low permeability. The developed fractures are the main factor of high production capacity. The sandstone has strong diagenesis and the main cements are authigenic carbonate minerals. The cementation and transformation of clay minerals have strong causal relationship. There are three cementation stages, which are “before 6 Ma”, “6~5 Ma” and “3~2 Ma”, respectively. Multi stage cementations are closely related to the validity of three stages tectonic factures in DB gas field. Only the third stage fracture (formed at the end of N2) is the most effective reservoir space for missing completely main cementation.
The cementation and its relationship with tectonic fractures of sandstone of Bashijiqike Formation of Cretaceous in DB gas field of Kuqa Sub-basin were researched through thin-section analysis, core observation, cathodoluminescence analysis, scan electricity microscope observation, X-ray diffraction, fluid inclusion and reservoir physical parameters analysis, etc and combining histories of tectonic development. It is recognized that the sandstone of Cretaceous in DB gas field is fracture-pore reservoir and with ultra-low porosity and ultra-low permeability. The developed fractures are the main factor of high production capacity. The sandstone has strong diagenesis and the main cements are authigenic carbonate minerals. The cementation and transformation of clay minerals have strong causal relationship. There are three cementation stages, which are “before 6 Ma”, “6~5 Ma” and “3~2 Ma”, respectively. Multi stage cementations are closely related to the validity of three stages tectonic factures in DB gas field. Only the third stage fracture (formed at the end of N2) is the most effective reservoir space for missing completely main cementation.
2015, 33(4): 773-785.
doi: 10.14027/j.cnki.cjxb.2015.04.016
Abstract:
Currently, Sulige gas field is in increasing production stage, the reservoir of He8 remember in Permian are more and more complex with the rolling exploration in progresses. Originally one well drilled into a thick channel sandbody, but the one of neighboring well was instead of inter-channel mudstone. The characteristics of fast facies transition have brought great challenges for large-scale implementation of horizontal wells. In fact, the main reason is that the overlay rules of sandbody are not clear. The reason of sandbody was not single stage, but multi-stage. The multi-causes, multi-stage and criss-cross stacked channel sandbodies in space were the main reasons which took shape the huge thick braided river sandbody. The center often is made of multi-stage channel sandbodies.The Suxi block in Sulige gas field has been researched by predecessors who concluded that He8 member mianly developed braided river, and the result has been achieved wide recognition. The target bed thickness generally is 15~20 m. The study area located between the southeastern Su48 block and he northeastern Su47 block whose area is about 627 km2. The core and drilling well data can not only show the underwater deposition, but also no obvious delta front sedimentary, and the lower He82 sub-member mainly developed braided river deposits. The division time of stage is actually a part of the reservoir configuration. According to the previous configuration theory, braided river reservoir architecture can be divided into four levels (composite channel, single channel, channel bar, hyperplasia body), this study belong to the second level. The braided river of sedimentary micro-facies belongs to level, therefore, the identification of single stage river, compound, and sedimentary evolution analysis from composite channels can been researched based on the result of sedimentary micro-facies.It is always the emphasis and difficulty of single stage fluvial sandbodies from composite braided riveway in reservoir architecture. Especially, it is the most difficult at the aspect of single stage identification and combinations from multi-stage stacked sandbodies, and the evolution of sedimentary braided river was finished. In the process of the research, the complex river stages were divided through continuous cores verification and “single stage calibration method based on removal compaction effects”, the riverways had been reset by “relaxation rebound techniques” based on removal compaction effects. The single stage riverway were tracked and compared after using “the sand thickness center line connecting method” based on modern sedimentary and geological models and theories, then, the results were confirmed by interference well testing which can confirm that the time of stage redefinition and the predicted results were reliable. Based on above the evolution and sedimentary history was researched according to the order of sedimentary development. The research result show that these research methods will help to reveal stacked sands, improve the rate of sand drilling, and it is also convenient to carry out large-scale deployment and post-horizontal well geosteering operations and to provide a theoretical basis so on for oil production practice simultaneously.
Currently, Sulige gas field is in increasing production stage, the reservoir of He8 remember in Permian are more and more complex with the rolling exploration in progresses. Originally one well drilled into a thick channel sandbody, but the one of neighboring well was instead of inter-channel mudstone. The characteristics of fast facies transition have brought great challenges for large-scale implementation of horizontal wells. In fact, the main reason is that the overlay rules of sandbody are not clear. The reason of sandbody was not single stage, but multi-stage. The multi-causes, multi-stage and criss-cross stacked channel sandbodies in space were the main reasons which took shape the huge thick braided river sandbody. The center often is made of multi-stage channel sandbodies.The Suxi block in Sulige gas field has been researched by predecessors who concluded that He8 member mianly developed braided river, and the result has been achieved wide recognition. The target bed thickness generally is 15~20 m. The study area located between the southeastern Su48 block and he northeastern Su47 block whose area is about 627 km2. The core and drilling well data can not only show the underwater deposition, but also no obvious delta front sedimentary, and the lower He82 sub-member mainly developed braided river deposits. The division time of stage is actually a part of the reservoir configuration. According to the previous configuration theory, braided river reservoir architecture can be divided into four levels (composite channel, single channel, channel bar, hyperplasia body), this study belong to the second level. The braided river of sedimentary micro-facies belongs to level, therefore, the identification of single stage river, compound, and sedimentary evolution analysis from composite channels can been researched based on the result of sedimentary micro-facies.It is always the emphasis and difficulty of single stage fluvial sandbodies from composite braided riveway in reservoir architecture. Especially, it is the most difficult at the aspect of single stage identification and combinations from multi-stage stacked sandbodies, and the evolution of sedimentary braided river was finished. In the process of the research, the complex river stages were divided through continuous cores verification and “single stage calibration method based on removal compaction effects”, the riverways had been reset by “relaxation rebound techniques” based on removal compaction effects. The single stage riverway were tracked and compared after using “the sand thickness center line connecting method” based on modern sedimentary and geological models and theories, then, the results were confirmed by interference well testing which can confirm that the time of stage redefinition and the predicted results were reliable. Based on above the evolution and sedimentary history was researched according to the order of sedimentary development. The research result show that these research methods will help to reveal stacked sands, improve the rate of sand drilling, and it is also convenient to carry out large-scale deployment and post-horizontal well geosteering operations and to provide a theoretical basis so on for oil production practice simultaneously.
2015, 33(4): 795-808.
doi: 10.14027/j.cnki.cjxb.2015.04.018
Abstract:
The thickness of shale in the Lower 3th Member of Shahejie Formation, Luojia area, Zhanhua sag ranges 100~300 m, which has a larger amount of oil and gas resources and exploration potential. Studies have shown that, the sedimentary environment of the shale is deep-semi-deep lake with high salinity, strong reduction; the rock types of the Lower 3th Member of Shahejie Formation, Luojia area, Zhanhua sag include mudstone, limestone, and the transitional types between them, content of carbonate is generally higher than 50%, according to the thickness, the combination way, different proportions and stability of the lamina, the rocks are divided into different types, the most important rock types are thin laminated-bedded argillaceous limestone. Reservoir porosity is 1.4%~13.7%, average value is 5.3%, reservoir permeability changes significantly, general ranges from 1×10-3 μm2 to 10×10-3 μm2, average value is 7.5×10-3 μm2, which is low porosity and permeability reservoir, Reservoir fractures include tectonic fractures, micro- fractures between layers and diagenetic fractures, pores include minerals intergranular pores, dissolution pores and the organic matter micro-pores; reservoir properties are controlled by mineral composition and rock types, diagenesis, organic matter content and other factors, organic matter is a major internal factor that affects shale reservoir properties.
The thickness of shale in the Lower 3th Member of Shahejie Formation, Luojia area, Zhanhua sag ranges 100~300 m, which has a larger amount of oil and gas resources and exploration potential. Studies have shown that, the sedimentary environment of the shale is deep-semi-deep lake with high salinity, strong reduction; the rock types of the Lower 3th Member of Shahejie Formation, Luojia area, Zhanhua sag include mudstone, limestone, and the transitional types between them, content of carbonate is generally higher than 50%, according to the thickness, the combination way, different proportions and stability of the lamina, the rocks are divided into different types, the most important rock types are thin laminated-bedded argillaceous limestone. Reservoir porosity is 1.4%~13.7%, average value is 5.3%, reservoir permeability changes significantly, general ranges from 1×10-3 μm2 to 10×10-3 μm2, average value is 7.5×10-3 μm2, which is low porosity and permeability reservoir, Reservoir fractures include tectonic fractures, micro- fractures between layers and diagenetic fractures, pores include minerals intergranular pores, dissolution pores and the organic matter micro-pores; reservoir properties are controlled by mineral composition and rock types, diagenesis, organic matter content and other factors, organic matter is a major internal factor that affects shale reservoir properties.
2015, 33(4): 817-827.
doi: 10.14027/j.cnki.cjxb.2015.04.020
Abstract:
There commonly exists overpressure in Wufeng-Longmaxi shales in the area with favorable preservation conditions in the south-eastern part of Sichuan Basin and the porosity of reservoirs with overpressure is higher than that of reservoirs with common or lower pressure. The studies show that during the course of evaluation, a great deal of hydrocarbons generated in organic-rich shales led to the development of overpressure system: on one side a great deal of hydrodarbons are generated and a great deal of organic pores are formed to increase the reservoir space; on the other side the overpressure system due to a great deal of hydrodarbons generated is favorable to preserve the reservoir space. The pores of shale reservoirs of Wufeng-Longmaxi Formation are dominated by plastic pores such as organic pores, clay mineral pores etc., which are easy to be compacted by overlying strata. It is considered that the existence of overpressure system can partially resist the mechanical compaction from the overlying strata to protect shale reservoirs and preserve the storage space. It is important to study the mechanism and mode of pores in shale reservoirs in Wufeng-Longmaxi Formation in Sichuan Basin for shale gas exploration and development.
There commonly exists overpressure in Wufeng-Longmaxi shales in the area with favorable preservation conditions in the south-eastern part of Sichuan Basin and the porosity of reservoirs with overpressure is higher than that of reservoirs with common or lower pressure. The studies show that during the course of evaluation, a great deal of hydrocarbons generated in organic-rich shales led to the development of overpressure system: on one side a great deal of hydrodarbons are generated and a great deal of organic pores are formed to increase the reservoir space; on the other side the overpressure system due to a great deal of hydrodarbons generated is favorable to preserve the reservoir space. The pores of shale reservoirs of Wufeng-Longmaxi Formation are dominated by plastic pores such as organic pores, clay mineral pores etc., which are easy to be compacted by overlying strata. It is considered that the existence of overpressure system can partially resist the mechanical compaction from the overlying strata to protect shale reservoirs and preserve the storage space. It is important to study the mechanism and mode of pores in shale reservoirs in Wufeng-Longmaxi Formation in Sichuan Basin for shale gas exploration and development.
2015, 33(4): 836-844.
doi: 10.14027/j.cnki.cjxb.2015.04.022
Abstract:
In order to find out the relations between paleogeothermal field and hydrocarbon accumulation, vitrinite reflectance(Ro), apatite fission track(AFT) and homogenization temperature of fluid inclusions were discussed for revealing the paleotemperature. Hydrocarbon accumulation period was judged by the results of homogenization temperature of fluid inclusions based on the thermal history simulation. In the study area, the temperature of current-geothermal field is low and conductive with the geothermal gradient of 2.76 ℃/100m. The paleogeothermal field of each secondary tectonic unit in Sartai depression was different: The paleogeothermal field of Yanchang and Xiaohuzi sub-sag was conductive with the paleo-geothermal gradient of 2.8~3.4 ℃/100m and the paleotemperature was 81.2℃~128.1℃; The paleotemperature and paleo-geothermal gradient in Heisha Low Uplift were 103.2℃~140.2℃ and 4.2~4.8 ℃/100m, much higher than that in sedimentary depression because of the thermal polymerization and thermal anomaly of the low uplift. The Evolution of maturity was mainly controlled by paleogeothermal field,because the paleotemperature of Middle Jurassic was higher than the present. The analysis of thermal history simulation and hydrocarbon accumulation period show that the hydrocarbon filling process of the three second tectonic units are different. However, for the whole Middle Jurassic reservoir in Sartai depression, there were two times of hydrocarbon filling process happened at early stage of Late Jurassic (145.0~152.0 Ma)and Early Cretaceous(100.0~134.0 Ma)about the same time of peak paleogeothermal which reflected the importance of geothermal evolution in the process of hydrocarbon accumulation.
In order to find out the relations between paleogeothermal field and hydrocarbon accumulation, vitrinite reflectance(Ro), apatite fission track(AFT) and homogenization temperature of fluid inclusions were discussed for revealing the paleotemperature. Hydrocarbon accumulation period was judged by the results of homogenization temperature of fluid inclusions based on the thermal history simulation. In the study area, the temperature of current-geothermal field is low and conductive with the geothermal gradient of 2.76 ℃/100m. The paleogeothermal field of each secondary tectonic unit in Sartai depression was different: The paleogeothermal field of Yanchang and Xiaohuzi sub-sag was conductive with the paleo-geothermal gradient of 2.8~3.4 ℃/100m and the paleotemperature was 81.2℃~128.1℃; The paleotemperature and paleo-geothermal gradient in Heisha Low Uplift were 103.2℃~140.2℃ and 4.2~4.8 ℃/100m, much higher than that in sedimentary depression because of the thermal polymerization and thermal anomaly of the low uplift. The Evolution of maturity was mainly controlled by paleogeothermal field,because the paleotemperature of Middle Jurassic was higher than the present. The analysis of thermal history simulation and hydrocarbon accumulation period show that the hydrocarbon filling process of the three second tectonic units are different. However, for the whole Middle Jurassic reservoir in Sartai depression, there were two times of hydrocarbon filling process happened at early stage of Late Jurassic (145.0~152.0 Ma)and Early Cretaceous(100.0~134.0 Ma)about the same time of peak paleogeothermal which reflected the importance of geothermal evolution in the process of hydrocarbon accumulation.
