Qiangtang Basin is located in the middle of Tethys, which is the famous oil and gas accumulation belt of the world. one of the few exploration areas in our continental petroleum industry at present. Previous studies s...Qiangtang Basin is located in the middle of Tethys, which is the famous oil and gas accumulation belt of the world. one of the few exploration areas in our continental petroleum industry at present. Previous studies show that this basin is a “composite basin" which has experienced, from Late Paleozoic to Cenozoic, a long time geological evolution. The major of this basin formed at Late Permian to Early Cretaceous, and its deformation generated after Late Cretaceous. The present part is just the remnants of the proto basin.Qiangtang Basin, about 180000km\+2, is located in the west part of Qiangtang\|Qamdo Terrane with Triassic Jurassic system as the main exploration systems.The tectonic framework of the basin displays the characteristic of one central uplift between the northern and the southern depressions, among of which the maximum burial depth of the substratums is 7km deep at Tubocuo in the northern depression. The deformation of the basin developed different kinds of structural styles, including compressive, wrench and extensive as well as inversive structures.The thickness of effective hydrocarbon source rocks (mudstone and carbonate rocks) is over 1500m, and the organic matter types are mainly of type I and type Ⅱ. In general the abundance of organic matter of the carbonate rocks is 0 1%~0 3%, the hydrocarbon generating potential (S1+S2) being 0 01~0 195mg/g. The abundance of organic matter of mudstone is generally over 0 5%, with the maximum over 2%. Its hydrocarbon generating potential is 0 018~28 1mg/g, and the organic matter is mainly at the mature to highly mature stage. More than 30 oil seeps have been found in the area, of which three are oil liquid ones and the others are solid bitumen and soft bitumen. Oil bearing rocks are concentrated in the Middle Upper Jurassic and Upper Triassic. Oil to source correlation analysis shows that the liquid oil is derived from the strata with oil reserves.The oil and gas shows, especially liquid oil seeps, indicate that the area experienced a history of hydrocarbon generation and migration. Preliminary prospecting shows that there exist two kinds of reservoirs: clastic rocks and carbonate rocks. The porosity of some carbonate reservoirs is up to 15%, which is favorable to the storage of oil and gas. Gypsum layers (single layer is generally 20~40m) are extensively distributed in Middle Jurassic of the Qiangtang Basin. Since Mesozoic marine strata in the basin has been strongly deformed and exposured on the surface of the earth during the Cenozoic, compared with other general bearing hydrocarbon basins, the preservative condition of Qiangtang Basin appears to be poor, but there still has a good prospects of exploration because of the Mesozoic strata containing abundant pliable layers such as gypsums and shales.展开更多
Qiangtang Basin in northern part of Tibet is significant on geological research, and it is also a prospect area for petroleum and gas exploration. Qiangtang Basin mainly consists of Triassic\|Jurassic carbonate strata...Qiangtang Basin in northern part of Tibet is significant on geological research, and it is also a prospect area for petroleum and gas exploration. Qiangtang Basin mainly consists of Triassic\|Jurassic carbonate strata, extending E—W. The basement of the Qiangtang Basin composed of Lower\|Middle Proterozoic exposed in the central part, and is called Central Upright Zone.The decollement and thrust structure occurred both in Qiangtang Basin and the Central Upright Zone, which have resulted in important influence for petroleum and gas exploration.(1) Tectonic style:① The suprastructure of Qiangtang Basin is dominated by parallel folds (Ramsay’s classification Ib\|Ic) and brittle faults.② Most of the folds are open folds with interlimb angles 80~120°and lack of axial cleavage.③ The 3\|D shape of fold is cylindrical, without or little change on area and volume.④ The folds association is ejective folds (i.e. with the characteristics of the Jura\|type fold).⑤ The plastic bed flowing with the higher zone of the folds formed diapir structure, which is the important evidence indicating decol lement.展开更多
The Qiangtang basin is located in the north of Qinghai—Tibet plateau and sandwiched by Nianqingtangula continental block and Kekexili\|Bayuankal continental block. Its southern boundary is the Bangongfu—Nujiang sutu...The Qiangtang basin is located in the north of Qinghai—Tibet plateau and sandwiched by Nianqingtangula continental block and Kekexili\|Bayuankal continental block. Its southern boundary is the Bangongfu—Nujiang suture zone and its northern boundary is the Xijinwulan\|Jinshajiang suture zone.The basement of Qiangtang basin is composed f metamorphic rock of Proterozoic age, which can be divided into two parts. The competent lower part with isotope age of 2056~2310Ma experienced multi\|stage deformation and the soft upper part is dated 1111~1205Ma. Within the basin, it groups into Northern Qiangtang Depression, Central Rise and Southern Depressions and are complicated by a number of subdepressions and subuplifts.The strata of Middle Devonian\|Tertiary are overlain on the basement and composed of marine carbonate rocks, clastic rocks and terrestrial sandstone and conglomerate. Several sets of faults and folds have developed in the cover sequence and the deformation is very strong, characterized by orientation, zonation and equidistance in space and by diversity and disharmony in the profile. The major deformation occurred in Yanshan\|Himalayan period.展开更多
Mesozoic Qiangtang foreland Basin is located between Jinshajiang suture belt and Bangong—Nujiang suture belt and an important petroliferous basin in the north of Qinghai—Xizang plateau. This foreland basin is E—W e...Mesozoic Qiangtang foreland Basin is located between Jinshajiang suture belt and Bangong—Nujiang suture belt and an important petroliferous basin in the north of Qinghai—Xizang plateau. This foreland basin is E—W elongated basin with 800km in length and 200km to 300km in width. Both margins of the basin are large suture belt and linked to thrusting of large suture belt, so Mesozoic Qiangtang foreland basin belongs to composite foreland basins according to Jordan’s classification of the foreland basin(1988). The foreland basin is filled with 5000~8000m thick late Triassic to Cretaceous marine sediments. The spacial changes of the stratigraphy indicates that the basin texture looks like a symmetric body, and it can be subdivided into three tectonic geomorphic units from north to south ,such as northern basin, center uplift, and southern basin. The depth in the north varies from 5000 to 8000m,the depth in center uplift varies from zero to 1000m, the depth in the south varies from 5000 to 7000m, Which show that the occurrence of the Mesozoic filling stratigraphy are thicker in the north and the south of the basin, but thinner in the center uplift of the basin. There are two center of subsidence of the basin, both of them are located in south and north foredeep belt, lying in the front of suture belt. The basin is one of common foreland basins between suture belt and belongs to typical symmetric foreland basin.This kind of basin geometry allows large thickness of synsedimentary molasse sediments to be preserved and related to basement uplifts and thrusts in the cratonic edge of the mountain belt.From late Triassic to Cretaceous the foreland basin is filled by four tectonic sequences, including late Triassic tectonic sequence(TS\-1),early Jurassic tectonic sequence(TS\-2), middle Jurassic to early Cretaceous tectonic sequence(TS\-3) and middle to late Cretaceous tectonic sequence (TS\-4).A tectonic Sequence is a body of genetically related strata isolated by unconformity ,deposited in a basining stage responding to a thrusting episode. Late Triassic tectonic sequence(TS\-1) is bounded by Ta and Tb and composed of the Xiaochaka formation which is more than 2500m in depth, it is a coarsing\|upward tectonic sequence,the lower is fan delta sediments with debris conglomerate,the middle is carbonate ramp sediments,the upper is delta sediments; early Jurassic tectonic sequence(TS\-2) is bounded by Tb and Tc and composed of the Nadigangri formation which is more than 1000m in depth, it is a thinning\|upward tectonic sequence,the lower is fan delta sediments with debris conglomerate,the upper is subaquatic detrital sediments; middle Jurassic to early Cretaceous tectonic sequence(TS\-3) is bounded by Tc and Td and composed of the Quemocuo formation,Buqu formation, Xiali formation, Suowa formation and Xueshan formation, which is more than 3000m in depth; middle to late Cretaceous tectonic sequence (TS\-4) is bounded by Td and Tf and composed of the Abushan formation, it is a thinning—upward alluvial fan sediments with more than 1000m in depth.展开更多
文摘Qiangtang Basin is located in the middle of Tethys, which is the famous oil and gas accumulation belt of the world. one of the few exploration areas in our continental petroleum industry at present. Previous studies show that this basin is a “composite basin" which has experienced, from Late Paleozoic to Cenozoic, a long time geological evolution. The major of this basin formed at Late Permian to Early Cretaceous, and its deformation generated after Late Cretaceous. The present part is just the remnants of the proto basin.Qiangtang Basin, about 180000km\+2, is located in the west part of Qiangtang\|Qamdo Terrane with Triassic Jurassic system as the main exploration systems.The tectonic framework of the basin displays the characteristic of one central uplift between the northern and the southern depressions, among of which the maximum burial depth of the substratums is 7km deep at Tubocuo in the northern depression. The deformation of the basin developed different kinds of structural styles, including compressive, wrench and extensive as well as inversive structures.The thickness of effective hydrocarbon source rocks (mudstone and carbonate rocks) is over 1500m, and the organic matter types are mainly of type I and type Ⅱ. In general the abundance of organic matter of the carbonate rocks is 0 1%~0 3%, the hydrocarbon generating potential (S1+S2) being 0 01~0 195mg/g. The abundance of organic matter of mudstone is generally over 0 5%, with the maximum over 2%. Its hydrocarbon generating potential is 0 018~28 1mg/g, and the organic matter is mainly at the mature to highly mature stage. More than 30 oil seeps have been found in the area, of which three are oil liquid ones and the others are solid bitumen and soft bitumen. Oil bearing rocks are concentrated in the Middle Upper Jurassic and Upper Triassic. Oil to source correlation analysis shows that the liquid oil is derived from the strata with oil reserves.The oil and gas shows, especially liquid oil seeps, indicate that the area experienced a history of hydrocarbon generation and migration. Preliminary prospecting shows that there exist two kinds of reservoirs: clastic rocks and carbonate rocks. The porosity of some carbonate reservoirs is up to 15%, which is favorable to the storage of oil and gas. Gypsum layers (single layer is generally 20~40m) are extensively distributed in Middle Jurassic of the Qiangtang Basin. Since Mesozoic marine strata in the basin has been strongly deformed and exposured on the surface of the earth during the Cenozoic, compared with other general bearing hydrocarbon basins, the preservative condition of Qiangtang Basin appears to be poor, but there still has a good prospects of exploration because of the Mesozoic strata containing abundant pliable layers such as gypsums and shales.
文摘Qiangtang Basin in northern part of Tibet is significant on geological research, and it is also a prospect area for petroleum and gas exploration. Qiangtang Basin mainly consists of Triassic\|Jurassic carbonate strata, extending E—W. The basement of the Qiangtang Basin composed of Lower\|Middle Proterozoic exposed in the central part, and is called Central Upright Zone.The decollement and thrust structure occurred both in Qiangtang Basin and the Central Upright Zone, which have resulted in important influence for petroleum and gas exploration.(1) Tectonic style:① The suprastructure of Qiangtang Basin is dominated by parallel folds (Ramsay’s classification Ib\|Ic) and brittle faults.② Most of the folds are open folds with interlimb angles 80~120°and lack of axial cleavage.③ The 3\|D shape of fold is cylindrical, without or little change on area and volume.④ The folds association is ejective folds (i.e. with the characteristics of the Jura\|type fold).⑤ The plastic bed flowing with the higher zone of the folds formed diapir structure, which is the important evidence indicating decol lement.
文摘The Qiangtang basin is located in the north of Qinghai—Tibet plateau and sandwiched by Nianqingtangula continental block and Kekexili\|Bayuankal continental block. Its southern boundary is the Bangongfu—Nujiang suture zone and its northern boundary is the Xijinwulan\|Jinshajiang suture zone.The basement of Qiangtang basin is composed f metamorphic rock of Proterozoic age, which can be divided into two parts. The competent lower part with isotope age of 2056~2310Ma experienced multi\|stage deformation and the soft upper part is dated 1111~1205Ma. Within the basin, it groups into Northern Qiangtang Depression, Central Rise and Southern Depressions and are complicated by a number of subdepressions and subuplifts.The strata of Middle Devonian\|Tertiary are overlain on the basement and composed of marine carbonate rocks, clastic rocks and terrestrial sandstone and conglomerate. Several sets of faults and folds have developed in the cover sequence and the deformation is very strong, characterized by orientation, zonation and equidistance in space and by diversity and disharmony in the profile. The major deformation occurred in Yanshan\|Himalayan period.
文摘Mesozoic Qiangtang foreland Basin is located between Jinshajiang suture belt and Bangong—Nujiang suture belt and an important petroliferous basin in the north of Qinghai—Xizang plateau. This foreland basin is E—W elongated basin with 800km in length and 200km to 300km in width. Both margins of the basin are large suture belt and linked to thrusting of large suture belt, so Mesozoic Qiangtang foreland basin belongs to composite foreland basins according to Jordan’s classification of the foreland basin(1988). The foreland basin is filled with 5000~8000m thick late Triassic to Cretaceous marine sediments. The spacial changes of the stratigraphy indicates that the basin texture looks like a symmetric body, and it can be subdivided into three tectonic geomorphic units from north to south ,such as northern basin, center uplift, and southern basin. The depth in the north varies from 5000 to 8000m,the depth in center uplift varies from zero to 1000m, the depth in the south varies from 5000 to 7000m, Which show that the occurrence of the Mesozoic filling stratigraphy are thicker in the north and the south of the basin, but thinner in the center uplift of the basin. There are two center of subsidence of the basin, both of them are located in south and north foredeep belt, lying in the front of suture belt. The basin is one of common foreland basins between suture belt and belongs to typical symmetric foreland basin.This kind of basin geometry allows large thickness of synsedimentary molasse sediments to be preserved and related to basement uplifts and thrusts in the cratonic edge of the mountain belt.From late Triassic to Cretaceous the foreland basin is filled by four tectonic sequences, including late Triassic tectonic sequence(TS\-1),early Jurassic tectonic sequence(TS\-2), middle Jurassic to early Cretaceous tectonic sequence(TS\-3) and middle to late Cretaceous tectonic sequence (TS\-4).A tectonic Sequence is a body of genetically related strata isolated by unconformity ,deposited in a basining stage responding to a thrusting episode. Late Triassic tectonic sequence(TS\-1) is bounded by Ta and Tb and composed of the Xiaochaka formation which is more than 2500m in depth, it is a coarsing\|upward tectonic sequence,the lower is fan delta sediments with debris conglomerate,the middle is carbonate ramp sediments,the upper is delta sediments; early Jurassic tectonic sequence(TS\-2) is bounded by Tb and Tc and composed of the Nadigangri formation which is more than 1000m in depth, it is a thinning\|upward tectonic sequence,the lower is fan delta sediments with debris conglomerate,the upper is subaquatic detrital sediments; middle Jurassic to early Cretaceous tectonic sequence(TS\-3) is bounded by Tc and Td and composed of the Quemocuo formation,Buqu formation, Xiali formation, Suowa formation and Xueshan formation, which is more than 3000m in depth; middle to late Cretaceous tectonic sequence (TS\-4) is bounded by Td and Tf and composed of the Abushan formation, it is a thinning—upward alluvial fan sediments with more than 1000m in depth.