| Sichuan petroliferous basin is one of the key petroliferous basin in China, it attractive many geologists all around the world that starting from the50s. In the South-East of the Sichuan petroliferous basin there is a paleo-uplift called Leshan-Longnvsi paleo-uplift which is very famous in the geology because of its Sinian system reservoir was found in1964. Until now there are many new geologic cognitions about Leshan-Longnvsi paleo-uplift Sinina system reservoir because of many deeply geologic theories, modern exploration technology and enormous researches. Based on the achievements of predecessors, the main idea of this thesis is through studying the tectonic evolution and the modern tectonic characteristics of Leshan-Longnvsi paleo-uplift in the central of Sichuan petroliferous basin to analysis the relationship between tectonic characteristics and Sinian system reservoir. In this thesis, there are two ways were combined to study the tectonic characteristics of Leshan-Longnvsi paleo-uplift which are geologic method and geophysical method. The main idea of geologic method is a progresses of combining point, line and plane, about this thesis’s research contents, the first step is collecting well data of Sichuan petroliferous basin,the wells should all be drilled out Cambrian system or deep layers, and then we should statistic the thickness of every layer. In Sichuan basin there are some areas have no wells that we can not afford to statistic the thickness of layers,so we must applicate some field sections and seismic sections those locate in places where have no wells in Sichuan basin to read the thickness of every layer, after that we can use these well points and the points of both field sections and seismic sections to recover the denudation quantity from Cambrian to siluric by the way of trend method, and then, the last step is drawing palaeotectonic pictures of the top surface of Sinian in every ages; Geophysical method is through elaborately interpreting the2D seismic lines in the central of Sichuan basin and3D seismic lines in the Moxi structure and Gaoshiti structure to manufacture the current tectonic sections and current tectonic plans of central Sichuan basin, then using2DMOVE software to draw the tectonic evolution sections. Because of organic combination of geologic method and geophysical method that we can draw many tectonic related pictures of Leshan-Longnvsi paleo-uplift, therefor we can deeply analysis the ancient tectonic evolution, current tectonic characteristics and the relationship between tectonic characteristics and Sinian reservoir, after that analysis we find some new geologic cognitions about Leshan-Longnvsi paleo-uplift in the central of Sichuan basin:(1)According to the Palaeotectonic maps of the Sinian top surface in every period can find that:Leshan-Longnvsi paleo-uplift has always been a huge NEE inheritance nose uplift, and also received some strengthens and changed by every tectonic movement from Cambrian to now; In the early Cambrian era, Ya’an, Leshan and Ziyang area was a nose uplift, Anyue, Wusheng, Nanchong, Guang’an area is an isolated huge trap, and then these two structures were combined into a huge nose-like structure which was made up of two high points and one saddle-like structure in the middle of the two high points. Anyue-Nanchong paleo-trap and the western saddle-like structure existed from early Cambrian to now even underwent some tectonic movements; The axes of Leshan-Longnvsi paleo-uplift occurred Southeast anticlockwise migration because the uplift is controlled by regional stress and basement; Ziyang paleo-trap was formated from Permian and destroyed by Xishan movement; The time of formated Weiyuan structure is late Paleogene;(2)From the tectonic evolution sections which was based on the2D seismic sections in the central of Sichuan we can find that:From Sinian to Cambrian in this area, layers continuous uplifted and stretched, formated a series normal faults, Lonvsi paleo-uplift and Gaoshiti paleo-uplift had been in an early form, these phenomena occurred was effected by Tongwan movement and early Caledonian movement; In Ordovician period, tectonic movement was stable, Ordovician strata sedimented slowly and gently, and the former normal faults did not continue growth; In the late silurian, Caledonian movement into the rush hour, Because of effecting of Caledonian uplift movement, Longnvsi paleo-uplift and Gaoshiti paleo-uplift further uplift which made Cambrian to siluric layers undergoing different degrees denudation, this period is a period of time for Longnvsi paleo-uplift and Gaoshiti paleo-uplift to quickly development while show that the episodic tectonic characteristic in the area is obvious; Permian to Triassic period, tectonic movement was stable, strata continuous sedimented without big thickness change; From Jurassic to now, Longnvsi paleo-uplift and Gaoshiti paleo-uplift was further folded uplift to form today’s structural framework by effected of Yanshan and Xishan tectonic movement;(3)According to the Sinian current tectonic maps of central of Sichuan basin which was made by2D seismic data in central of Sichuan basin and3D seismic data of Moxi structure and Gaoshiti structure we can realize that:Leshan-Longnvsi paleo-uplift perform as a huge NE nose-like structure, in which, Weiyuan dome-like structure is the top point, along the north-east of axes there are Ziyang slope area, Gaoshiti-Moxi structure and Longnvsi structure. Perpendicular to axes of Leshan-Longnvsi paleo-uplift, there are two huge slopes locate in the north-west and south-east,and Hebaochang trap locate in the lower place of south-east slope;(4) According to interpret the Moxi-Gaoshiti3D seismic lines can manufacture the tectonic plan of Sinian top surface and find that:Moxi-Gaoshiti3D seismic field can define as "one fault,two high points and two low-lying lands" or "chessboard type" structural framework; Moxi-Gaoshiti structure is divided into west and east units by one south-east steep belt, in the Eastern of3D seismic field is divided into two high points and one low-lying land which are Moxi structure and Gaoshiti structure and the lower place in the middle of them by one East-West main fault; The west of the steep belt is a deep low-lying land and further is a slope then uplift in the orientation of Ziyang;(5)By the interpret of2D seismic lines we can find that:Weiyuan structure is a highest point, North-East to Ziyang is a big slope, Gaoshiti area and Longnvsi area are related uplift structures; At the bottle of Permian is an obvious unconformity surface, Siluric and Ordovician in Gaoshiti area and Longnvsi area underwent serious denudation, so we can analysis that Gaoshiti area and Longnvsi area was two highest points in Caledonian movement period, and then Xishan movement caused Weiyuan structure uplifting to become the highest area in this field and made Weiyuan-Ziyang changing into a slope belt,but Gaoshiti structure and Longnvsi structure are also related high points; Faults were started by Tongwan movement and performed as high angle normal faults, and then was penetrated into Siluric by Caledonian movement, after Xishan movement, many low angle abnormal faults were appeared in the shallow of this field. |
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