The Tazhong paleouplift is divided into the upper and the lower structural layers, bounded by the unconformity surface at the top of the Ordovician carbonate rock. The reservoirs in the two layers from different parts...The Tazhong paleouplift is divided into the upper and the lower structural layers, bounded by the unconformity surface at the top of the Ordovician carbonate rock. The reservoirs in the two layers from different parts vary in number, type and reserves, but the mechanism was rarely researched before. Therefore, an explanation of the mechanism will promote petroleum exploration in Tazhong paleouplift. After studying the evolution and reservoir distribution of the Tazhong paleouplift, it is concluded that the evolution in late Caledonian, late Hercynian and Himalayan periods resulted in the upper and the lower structural layers. It is also defined that in the upper structural layer, structural and stratigraphic overlap reservoirs are developed at the top and the upper part of the paleouplift, which are dominated by oil reservoirs, while for the lower structural layer, lithological reservoirs are developed in the lower part of the paleouplift, which are dominated by gas reservoirs, and more reserves are discovered in the lower structural layer than the upper. Through a comparative analysis of accumulation conditions of the upper and the lower structural layers, the mechanism of enrichment differences is clearly explained. The reservoir and seal conditions of the lower structural layer are better than those of the upper layer, which is the reason why more reservoirs have been found in the former. The differences in the carrier system types, trap types and charging periods between the upper and the lower structural layers lead to differences in the reservoir types and distribution. An accumulation model is established for the Tazhong paleouplift. For the upper structural layer, the structural reservoirs and the stratigraphic overlap reservoirs are formed at the upper part of the paleouplift, while for the lower structural layer, the weathering crust reservoirs are formed at the top, the reef-flat reservoirs are formed on the lateral margin, the karst and inside reservoirs are formed in the lower part of the paleouplift.展开更多
The reservoirs in the TZ1-TZ4 well block of the Tarim Basin are complex, and the hydrocarbon enrichment shows differences. The three Carboniferous oil layers are characterized by ＂oil in the upper and lower layers an...The reservoirs in the TZ1-TZ4 well block of the Tarim Basin are complex, and the hydrocarbon enrichment shows differences. The three Carboniferous oil layers are characterized by ＂oil in the upper and lower layers and gas in the middle＂ in profile and ＂oil in the west and gas in the east＂ in plane view. In order to discuss the complex reservoir accumulation mechanisms, based on the petroleum geology and reservoir distribution, we studied the generation history of source rocks, the fault evolution and sealing, the accumulation periods and gas washing, and reconstructed the accumulation process of the TZ1-TZ4 well block. It is concluded that the hydrocarbon enrichment differences of oil layers CIII, CII and CI were caused by multiple sources and multi-period hydrocarbon charging and adjustment. The CII was closely related to CIII, but CI was formed by reservoir adjustment during the Yanshan period and was not affected by gas washing after it was formed. During the Himalayan period, different degrees of gas washing in the east and west led to hydrocarbon enrichment differences on the plane. The Carboniferous accumulation process of two-stage charging and one-stage adjustment is summarized： oil charging during the late Hercynian period is the first accumulation period of CIII and CII; oil reservoirs were adjusted into CI in the Yanshan period; finally gas washing in the Himalayan period is the second accumulation period of CIII and CII, but CI was not affected by gas washing. This complex accumulation process leads to the hydrocarbon enrichment differences in the TZ1-TZ4 well block.展开更多
During the progressive exploration of the Jingbian Gas Field in the Ordos Basin,multiple gas-bearing regions have been discovered in the dolomite reservoirs in the Middle Ordovician assemblages of Lower Paleozoic in J...During the progressive exploration of the Jingbian Gas Field in the Ordos Basin,multiple gas-bearing regions have been discovered in the dolomite reservoirs in the Middle Ordovician assemblages of Lower Paleozoic in Jingxi area,but these gas-bearing regions and intervals are significantly different in terms of gas enrichment degrees.So far,however,the reasons for the difference have not been figured out.In this paper,the origin and source of natural gas in the Middle Ordovician assemblages in Jingxi area was investigated on the basis of geochemical data(e.g.natural gas composition and carbon isotope),and then the main factors controlling the gas accumulation were analyzed.It is shown that the natural gas in the Middle Ordovician assemblages in the Middle Ordovician assemblages in Jingxi area is similar to that in the Upper Ordovician assemblages and Upper Paleozoic reservoir in terms of genesis and sources,and they are mainly the Upper Paleozoic coaliferous gas with some oil-derived gas.Under the influence of hydrocarbon generation center of coal source rocks and the source-rock-reservoir contact relationship,the proportion of coaliferous gas increases areally from the north to the south and vertically from Ma55 sub-member of the Lower Ordovician Majiagou Fm.It is concluded that the natural gas enrichment degree is controlled by the gas charging capacity at the hydrocarbon-supplying windows.Second,the vertical migration and distribution of natural gas is dominated by the differences of Ma_(5)^(5)-Ma_(5)^(10)transport pathways.And third,the lateral migration direction of natural gas and the range of gas accumulation are controlled by the superimposition relationship between structures and reservoirs.展开更多
基金supported by the National 973 Key Development Program for Basic Research of China(S/N: 2006CB202308)the National Natural Science Foundation of China(Grant No.40972088)
文摘The Tazhong paleouplift is divided into the upper and the lower structural layers, bounded by the unconformity surface at the top of the Ordovician carbonate rock. The reservoirs in the two layers from different parts vary in number, type and reserves, but the mechanism was rarely researched before. Therefore, an explanation of the mechanism will promote petroleum exploration in Tazhong paleouplift. After studying the evolution and reservoir distribution of the Tazhong paleouplift, it is concluded that the evolution in late Caledonian, late Hercynian and Himalayan periods resulted in the upper and the lower structural layers. It is also defined that in the upper structural layer, structural and stratigraphic overlap reservoirs are developed at the top and the upper part of the paleouplift, which are dominated by oil reservoirs, while for the lower structural layer, lithological reservoirs are developed in the lower part of the paleouplift, which are dominated by gas reservoirs, and more reserves are discovered in the lower structural layer than the upper. Through a comparative analysis of accumulation conditions of the upper and the lower structural layers, the mechanism of enrichment differences is clearly explained. The reservoir and seal conditions of the lower structural layer are better than those of the upper layer, which is the reason why more reservoirs have been found in the former. The differences in the carrier system types, trap types and charging periods between the upper and the lower structural layers lead to differences in the reservoir types and distribution. An accumulation model is established for the Tazhong paleouplift. For the upper structural layer, the structural reservoirs and the stratigraphic overlap reservoirs are formed at the upper part of the paleouplift, while for the lower structural layer, the weathering crust reservoirs are formed at the top, the reef-flat reservoirs are formed on the lateral margin, the karst and inside reservoirs are formed in the lower part of the paleouplift.
基金supported by the 973 Program (2006CB202308)the Foundation of State Key Laboratory of Petroleum Resources and Prospecting (PRPDX2008-05) the National Natural Science Foundation of China (Grant No. 40972088)
文摘The reservoirs in the TZ1-TZ4 well block of the Tarim Basin are complex, and the hydrocarbon enrichment shows differences. The three Carboniferous oil layers are characterized by ＂oil in the upper and lower layers and gas in the middle＂ in profile and ＂oil in the west and gas in the east＂ in plane view. In order to discuss the complex reservoir accumulation mechanisms, based on the petroleum geology and reservoir distribution, we studied the generation history of source rocks, the fault evolution and sealing, the accumulation periods and gas washing, and reconstructed the accumulation process of the TZ1-TZ4 well block. It is concluded that the hydrocarbon enrichment differences of oil layers CIII, CII and CI were caused by multiple sources and multi-period hydrocarbon charging and adjustment. The CII was closely related to CIII, but CI was formed by reservoir adjustment during the Yanshan period and was not affected by gas washing after it was formed. During the Himalayan period, different degrees of gas washing in the east and west led to hydrocarbon enrichment differences on the plane. The Carboniferous accumulation process of two-stage charging and one-stage adjustment is summarized： oil charging during the late Hercynian period is the first accumulation period of CIII and CII; oil reservoirs were adjusted into CI in the Yanshan period; finally gas washing in the Himalayan period is the second accumulation period of CIII and CII, but CI was not affected by gas washing. This complex accumulation process leads to the hydrocarbon enrichment differences in the TZ1-TZ4 well block.
基金Project supported by the PetroChina's Key Special Petroleum S&T Project“PetroChina's Fourth Assessment of Oil&Gas Resources”(No.2013E-050207).
文摘During the progressive exploration of the Jingbian Gas Field in the Ordos Basin,multiple gas-bearing regions have been discovered in the dolomite reservoirs in the Middle Ordovician assemblages of Lower Paleozoic in Jingxi area,but these gas-bearing regions and intervals are significantly different in terms of gas enrichment degrees.So far,however,the reasons for the difference have not been figured out.In this paper,the origin and source of natural gas in the Middle Ordovician assemblages in Jingxi area was investigated on the basis of geochemical data(e.g.natural gas composition and carbon isotope),and then the main factors controlling the gas accumulation were analyzed.It is shown that the natural gas in the Middle Ordovician assemblages in the Middle Ordovician assemblages in Jingxi area is similar to that in the Upper Ordovician assemblages and Upper Paleozoic reservoir in terms of genesis and sources,and they are mainly the Upper Paleozoic coaliferous gas with some oil-derived gas.Under the influence of hydrocarbon generation center of coal source rocks and the source-rock-reservoir contact relationship,the proportion of coaliferous gas increases areally from the north to the south and vertically from Ma55 sub-member of the Lower Ordovician Majiagou Fm.It is concluded that the natural gas enrichment degree is controlled by the gas charging capacity at the hydrocarbon-supplying windows.Second,the vertical migration and distribution of natural gas is dominated by the differences of Ma_(5)^(5)-Ma_(5)^(10)transport pathways.And third,the lateral migration direction of natural gas and the range of gas accumulation are controlled by the superimposition relationship between structures and reservoirs.
