| Through collecting the log data of typical structure, we can compile single well composite bar chart, dividing and comparing the formation of Jialingjiang formation, studying the formation development and the Vertical and horizontal Spread feature. According to the characteristics of the Jialing jiang formation petrological characteristics, paleontologic characteristics, electrical characteristics, combining the sedimentary background, sedimentary mode of Jialingjiang formation in Sichuan basin, compiling single well composite bar chart and formation thickness isoline maps, On this basis, using basic principle of sedimentology. And the method of compiling Lithofacies-paleogeographic map, compiled nine subsections'Lithofacies-paleogeographic map of Jialingjiang formation in Sichuan basin, and analyzing their characteristics. Through analyzing typical structure( Huangcaoxia structure in east of Sichuan basin, Moxi-Longnvsi structure in middle of Sichuan basin, Hejiang structure in south of Sichuan basin ): Gas reservoir gas source conditions, cap rock conditions, trap conditions,?dissected the mechanism and method of the natural gas accumulation of Jialingjiang formation in Sichuan basin. The papers'main results are as follows:( 1) Sichuan basin Jialingjiang formation can be divided into five sections, sections and sub sections are integration contacted,it is a transgressive—regressive sequence's dolomite, limestone, gypsum and salt deposits. During the deposition of Jialingjiang formation, through the restriction of Platform margin beach in southeast of Sichuan basin, overall,it is limited sea ~ evaporation tidal-flat sedimentary environment. In three times during sea advance and retreat, the sedimentary characteristics of Jialingjiang formation is shoalization to localization to salinization of platform. In east of Sichuan basin, early Triassicr, generally is the depositional system tract of shallow marine carbonate platform in craton basin,in every sedimentary cycle, generally, it always experiences three sedimentary stage: open sea platform, limited sea platform and evaporative platform. It can be divided into three phase belt in middle and east of Sichuan basin: sea platform , limited sea platform and evaporative platform. It only develops open sea platform semi-limited—limited sea platform phase in southt of Sichuan region. West of Sichuan basin in the early period of Jialingjiang formation ,mainly develops transitional facies and deposits clastic rock, and from T1j4 period, it changes into marine dolomitic-limemud flat and plaster-dolomite flat deposition.( 2) In the early period of Jialingjiang group, Sichuan maritime space inherited the paleogeographic features of "Southwest high and northeast low", seawater invaded from eastern and southern. After T1j2 sedimented, urrounding mountains rose, Jiangnan ancient land rose significantly, the east of Sichuan basin rose by Huayingshan fracture and Qiyaoshan fracture, levating speed is fast than other fracture such as Longmenshan, Then Luzhou -Kaijiang area also began to rise upward, it made the sea basal gradually evolved into the pattern of "Southeast high and northwest low".( 3) Jialingjiang formation's gas source rocks mainly argillaceous hydrocarbon source rocks in the middle and south Sichuan basin, Jialingjiang formation's gas mainly comes form upper Permian coal measures hydrocarbon source rocks in the east Sichuan basin,. Permian's high—over maturity oil splitting gas go to the upper rocks mainly rely on hydrocarbon source faults(eas tand south of Sichuan basin) or high pressure broken crack(middle of Sichuan basin), under the sealing gland condition of regional plaster covering strata,it gathered in carbonate reservoir of Jialingjiang formation. The type of trap is lithology trap or structure trap or their combination.( 4) The gas pools'formation of Jialingjiang formation today experienced ancient oil poolâ†'ancient gas poolâ†'present gas pool. The natural gas accumulation's rule of Jialingjiang formation in Sichuan Basin follow that: high pressure driving, fluid flow across formation, fault and fracture dredging, plaster covering and oil splitting gas accumulation. |
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