The Tazhong reef-fiat oil-gas field is the first large-scale Ordovician organic reef type oil-gas field found in China. Its organic reefs were developed in the early Late Ordovician Lianglitag Formation, and are the f...The Tazhong reef-fiat oil-gas field is the first large-scale Ordovician organic reef type oil-gas field found in China. Its organic reefs were developed in the early Late Ordovician Lianglitag Formation, and are the first large reefs of the coral-stromatoporoid hermatypic community found in China. The organic reefs and platform-margin grain banks constitute a reef-flat complex, mainly consisting of biolithites and grainstones. The biolithites can be classified into the framestone, baffiestone, bindstone etc. The main body of the complex lies around the wells from Tazhong-24 to Tazhong-82, trending northwest, with the thickness from 100 to 300 m, length about 220 km and width 5-10 km. It is a reef-flat lithologic hydrocarbon reservoir, with a very complex hydrocarbon distribution： being a gas condensate reservoir as a whole with local oil reservoirs. The hydrocarbon distribution is controlled by the reef complex, generally located in the upper 100-200 m part of the complex, and largely in a banded shape along the complex. On the profile, the reservoir shows a stratified feature, with an altitude difference of almost 2200 m from southeast to northwest. The petroleum accumulation is controlled by karst reservoir beds and the northeast strike-slip fault belt. The total geologic reserves had reached 297.667 Mt by 2007.展开更多
Carbon and oxygen isotopes of marine carbonate rocks or fossil shells could indicate global sea-level relative change.Generally,heavier carbon isotopes or lighter oxygen isotopes reflected rise of global sea-level rel...Carbon and oxygen isotopes of marine carbonate rocks or fossil shells could indicate global sea-level relative change.Generally,heavier carbon isotopes or lighter oxygen isotopes reflected rise of global sea-level relative changes,and vice versa.For carbonate rocks deposited before Tertiary,carbon isotope was more stable than oxygen isotope,and thus it was more suitable to indicate global sea-level relative fluctuation.Within time limit of the 3rd-order sequence(1-10Ma),large scale migration of carbonate platforms would not occur and carbonate productivity would not change greatly,therefore,a research method of marine tectonic sequence(i.e,a contrastive analysis method of carbon and oxygen isotopessedimentary cycles)was proposed.Thus,the marine 3rd-order sequences were divided the global sealevel sequence which was controlled by global sea-level change and the tectonic sequence which was controlled by regional tectonic subsidence and uplift.The global sea-level fluctuation indicated by carbon and oxygen isotopes were consistent with variation of sedimentary cycles and water depth of the global sea-level sequence,but were not consistent with variation of sedimentary cycles and water depth of the tectonic sequence.As a case study of Ordovician in Tarim Basin,two 3rd-order global sea-level sequences were identified in the Lower Ordovician,while six 3rd-order tectonic sequences controlled by collision and compression between Arkin island arc,Kudi active continental margin uplift and Tarim Plate were identified in the Middle and Upper Ordovician.Particularly,OSQ6 in the Upper Ordovician(Lianglitage Formation)was a typical tectonic sequence.展开更多
文摘The Tazhong reef-fiat oil-gas field is the first large-scale Ordovician organic reef type oil-gas field found in China. Its organic reefs were developed in the early Late Ordovician Lianglitag Formation, and are the first large reefs of the coral-stromatoporoid hermatypic community found in China. The organic reefs and platform-margin grain banks constitute a reef-flat complex, mainly consisting of biolithites and grainstones. The biolithites can be classified into the framestone, baffiestone, bindstone etc. The main body of the complex lies around the wells from Tazhong-24 to Tazhong-82, trending northwest, with the thickness from 100 to 300 m, length about 220 km and width 5-10 km. It is a reef-flat lithologic hydrocarbon reservoir, with a very complex hydrocarbon distribution： being a gas condensate reservoir as a whole with local oil reservoirs. The hydrocarbon distribution is controlled by the reef complex, generally located in the upper 100-200 m part of the complex, and largely in a banded shape along the complex. On the profile, the reservoir shows a stratified feature, with an altitude difference of almost 2200 m from southeast to northwest. The petroleum accumulation is controlled by karst reservoir beds and the northeast strike-slip fault belt. The total geologic reserves had reached 297.667 Mt by 2007.
文摘Carbon and oxygen isotopes of marine carbonate rocks or fossil shells could indicate global sea-level relative change.Generally,heavier carbon isotopes or lighter oxygen isotopes reflected rise of global sea-level relative changes,and vice versa.For carbonate rocks deposited before Tertiary,carbon isotope was more stable than oxygen isotope,and thus it was more suitable to indicate global sea-level relative fluctuation.Within time limit of the 3rd-order sequence(1-10Ma),large scale migration of carbonate platforms would not occur and carbonate productivity would not change greatly,therefore,a research method of marine tectonic sequence(i.e,a contrastive analysis method of carbon and oxygen isotopessedimentary cycles)was proposed.Thus,the marine 3rd-order sequences were divided the global sealevel sequence which was controlled by global sea-level change and the tectonic sequence which was controlled by regional tectonic subsidence and uplift.The global sea-level fluctuation indicated by carbon and oxygen isotopes were consistent with variation of sedimentary cycles and water depth of the global sea-level sequence,but were not consistent with variation of sedimentary cycles and water depth of the tectonic sequence.As a case study of Ordovician in Tarim Basin,two 3rd-order global sea-level sequences were identified in the Lower Ordovician,while six 3rd-order tectonic sequences controlled by collision and compression between Arkin island arc,Kudi active continental margin uplift and Tarim Plate were identified in the Middle and Upper Ordovician.Particularly,OSQ6 in the Upper Ordovician(Lianglitage Formation)was a typical tectonic sequence.
