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 Longwangmiao Fm gas pool was found in 2012 in Moxi area in Leshan-Longnüsi Paleouplift,central Sichuan Basin.Previous geological studies showed that the Lower Cambrian Longwangmiao Fm reservoir is mainly pore...The Longwangmiao Fm gas pool was found in 2012 in Moxi area in Leshan-Longnüsi Paleouplift,central Sichuan Basin.Previous geological studies showed that the Lower Cambrian Longwangmiao Fm reservoir is mainly pore type reservoir of grain shoal facies,locally superimposed by the vuggy reservoir formed by Caledonian karstification,and the distribution of the reservoir has a critical control effect on the gas pool there.Therefore,the reservoir prediction in this area follows the approach of“looking for the overlap of shoal facies,karst,bright spots,and traps”.First,the favorable facies boundary and karstification effect range are defined based on sedimentary facies;on the basis of precise correlation of the top and bottom horizons of the reservoir,the favorable development area of the reservoir was then predicted according to the seismic response characteristics of“bright spots”of the Longwangmiao Fm reservoir;finally,favorable exploration areas were selected according to the effective configuration of reservoir and trap.Due to the horizontal change in reservoir and lithology,Longwangmiao Fm top has no uniform interface features on the seismic profile,making it difficult to trace.In the actual interpretation process,the underlying reference horizon is sought out first,then the bottom boundary of Longwangmiao Fm is correlated,and finally its top boundary is correlated.The prediction results indicated that the Longwangmiao reservoir distributes in band shape in a wide range around the Paleouplift;and the exploration prospects mainly involve three domains:lithologic-stratigraphic traps near the pinchout line of Longwangmiao Fm;lithologic traps formed by isolated shoal body;and structural and lithologic traps at the north flank of the Paleouplift.展开更多
Based on 2D and 3D seismic data and well logging data,this paper studies the distribution of well-seismic stratigraphic filling and shoal controlled reservoirs of Upper Cambrian Xixiangchi Formation in the south slope...Based on 2D and 3D seismic data and well logging data,this paper studies the distribution of well-seismic stratigraphic filling and shoal controlled reservoirs of Upper Cambrian Xixiangchi Formation in the south slope of Leshan-Longnüsi paleouplift in the Sichuan Basin,to reveal the genetic relationship between stratigraphic filling,paleogeomorphology and large-scale grain shoal.(1)The Xixiangchi Formation in the study area is overlapped and filled gradually to the Leshan-Longnüsi paleouplift,but gets thin sharply due to truncation only near the denudation pinch-out line of the paleouplift.Two overlap slope break belts and one erosion slope break belt are identified,and the Xixiangchi Formation is divided into 4 members from bottom to top.(2)The filling pattern of the overlapping at the base and erosion at the top indicates that the thickness of Xixiangchi Formation can reflect the pre-depositional paleogeomorphology,and reveals that the studied area has a monoclinal geomorphic feature of plunging to southeast and being controlled by multistage slope break belts.(3)The large-scale grain shoals and shoal controlled reservoirs are developed longitudinally in the third and fourth members of the Xixiangchi Formation,and laterally in the vicinity of the multistage overlap slope break belts.(4)Overlap slope break belts are closely related to northwest trending reverse faults.The western margin of the South China Plate converging with the Qiangtang-Himalaya massif in the middle-late Cambrian resulted in the rapid uplift of the northwestern margin of the Yangtze Plate and expanding toward southeast,leaving gradually plunging multistage slope breaks and large-scale northeast grain shoal reservoir belts.Considering oil and gas test results,it is predicted that the favorable exploration zone of the grain shoal controlled reservoirs covers an area of 3340 km^(2).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Major Project of National Science and Technology(No.2011ZX05004-005)Major Project of Exploration of PetroChina“Hydrocarbon Evaluation of Leshan-Longnüsi Palaeohigh in Sichuan Basin and Research on Exploration Support Technologies”(No.2012ZD01-03-01)。
文摘The Longwangmiao Fm gas pool was found in 2012 in Moxi area in Leshan-Longnüsi Paleouplift,central Sichuan Basin.Previous geological studies showed that the Lower Cambrian Longwangmiao Fm reservoir is mainly pore type reservoir of grain shoal facies,locally superimposed by the vuggy reservoir formed by Caledonian karstification,and the distribution of the reservoir has a critical control effect on the gas pool there.Therefore,the reservoir prediction in this area follows the approach of“looking for the overlap of shoal facies,karst,bright spots,and traps”.First,the favorable facies boundary and karstification effect range are defined based on sedimentary facies;on the basis of precise correlation of the top and bottom horizons of the reservoir,the favorable development area of the reservoir was then predicted according to the seismic response characteristics of“bright spots”of the Longwangmiao Fm reservoir;finally,favorable exploration areas were selected according to the effective configuration of reservoir and trap.Due to the horizontal change in reservoir and lithology,Longwangmiao Fm top has no uniform interface features on the seismic profile,making it difficult to trace.In the actual interpretation process,the underlying reference horizon is sought out first,then the bottom boundary of Longwangmiao Fm is correlated,and finally its top boundary is correlated.The prediction results indicated that the Longwangmiao reservoir distributes in band shape in a wide range around the Paleouplift;and the exploration prospects mainly involve three domains:lithologic-stratigraphic traps near the pinchout line of Longwangmiao Fm;lithologic traps formed by isolated shoal body;and structural and lithologic traps at the north flank of the Paleouplift.
基金Supported by the Cooperation Project of China National Natural Science Foundation and Petro China(U23B20154)Science and Technology Cooperation Project of Petro China and Southwest Petroleum University(2020CX010000)。
文摘Based on 2D and 3D seismic data and well logging data,this paper studies the distribution of well-seismic stratigraphic filling and shoal controlled reservoirs of Upper Cambrian Xixiangchi Formation in the south slope of Leshan-Longnüsi paleouplift in the Sichuan Basin,to reveal the genetic relationship between stratigraphic filling,paleogeomorphology and large-scale grain shoal.(1)The Xixiangchi Formation in the study area is overlapped and filled gradually to the Leshan-Longnüsi paleouplift,but gets thin sharply due to truncation only near the denudation pinch-out line of the paleouplift.Two overlap slope break belts and one erosion slope break belt are identified,and the Xixiangchi Formation is divided into 4 members from bottom to top.(2)The filling pattern of the overlapping at the base and erosion at the top indicates that the thickness of Xixiangchi Formation can reflect the pre-depositional paleogeomorphology,and reveals that the studied area has a monoclinal geomorphic feature of plunging to southeast and being controlled by multistage slope break belts.(3)The large-scale grain shoals and shoal controlled reservoirs are developed longitudinally in the third and fourth members of the Xixiangchi Formation,and laterally in the vicinity of the multistage overlap slope break belts.(4)Overlap slope break belts are closely related to northwest trending reverse faults.The western margin of the South China Plate converging with the Qiangtang-Himalaya massif in the middle-late Cambrian resulted in the rapid uplift of the northwestern margin of the Yangtze Plate and expanding toward southeast,leaving gradually plunging multistage slope breaks and large-scale northeast grain shoal reservoir belts.Considering oil and gas test results,it is predicted that the favorable exploration zone of the grain shoal controlled reservoirs covers an area of 3340 km^(2).
