The Research Of Sequence Stratigraphy, Sedimentary Facies And Reservoir In The Middle Traiassic Series Of Northern Sichuan Basin

The Middle Triassic series is the first series ,when oil and gas exploration in Sichuan basin,which is important to realize and master the distributed rules of marine hydrocarbon.Based on the principles of sedimentrary petrography ,sequence stratigraphy, by the data of cutting , core, well logging ,and by means of description of lithology, sequence stratigraphic classification,the A/S analysis and sequence- sedimentary facies analysis,we summarize the character of sequence , facies , and establish the sequence stratigraphic framework and sedimentary model.At last,In the view of sedimentary ,we discrible distibution and quality of reservoir ,make some progress.According to a quantity of the observations of cores and thin sections as well as the data of testing well and well logging, this paper conclude that dolomite,gypsum-dolomite, halite, muddy microcrystalline dolomite.grain structure is undeveloped,the main grain structure is algo detrinite ,calcarenite,oolites,bioclast; biodetritus and crystalline grain;the character of reconstruction in the late stage and evaporites is obvious .In the respect of sequence,basing on the analysis of regional geological data and survey on outcrops and wells,something have been done ,such as recognization of sequence boundaries,analysis of lithology and facies combination.Then it summarize that there are two third-order sequece in the Middle Triassic.To be exact,the formation includes 1.5 third-order sequece ,which losts HST of the upper sequence,7 forth-order sequence,13 fifth-order sequence .This platform developes TST and HST, and lack LST.At last ,contrast with each outcrop and each well establish sequence stratigraphThis essay is based on the theory of sequence,and according to(rests on) the material of lithology, electrical property, geochemical, it classify the well section of sedimentary facies with dividing unit upon the system tract, while it formulate the distribution of sedimentary facies. Sedimentary framework carry on the features of the period of JiaLing River, and it inherited in the order of the west-east of China,from the Bayankala sea basins in Ganzi and Aba regions to the platform edge bank facies with the sequence of MaJiaoba-Hanwang-Shifang,from the tidal-lagoon facies in the east of Guangdong to the evaporation facies in the west of Dazhou and the east of Suining,to the mixed tidal-flat facies in the sequence of Honghua-Yunyang-The esat of Zhongxian. At the west part of the framework, there is the Bayankala sea basins, at the north there stands the Qingling trough, and in the south, the Sanjing basin has surround it, and in the paraplatform, it is forbided by the Longmenshan swell,Kangdian archicontinent, Kaijiang bulge, Luzhou rise. The essay bulids the sedimentary model in the period of middle Traissic Epoch, and summarized that Sichuan Basin in the middle Traissic Epoch is mainly develop from the typical edged and restricted epicontinental sea platform with a steep slope.Summarizing the formation mechanism of reservoir , I think cementation and argillaceous fill are the main destroy to the middle triassic, at the same time we can see that, dolomitization develops in whole area which remakes reservoir property obviously, and transformation of the later period karst is very important to the middle triassic.From the features of reservoir, we can see that this area are mainly develop three types of sedimentations: platform edge sedimentation, tidal-flat reservoir and Caledonian Karstification Reservoir. Through the decentralized evaluation for these reservoirs, I summaried that development characteristics of LeiKoupo reservoir appeared obvious difference in different region. Category 1 reservoir is platform edge face sedimentation, category 2 is platform inside, category 3 is tidal-flat reservoir. While I also provides a preliminary probe into the Middle Traissic Epoch Caledonian Karstification Reservoir, and together with mechanism of reservoir, we can see that the development of excellent reservoir is due to the remake which later karstification act on the early sedimentary siphonoal goclastic face, and the karst fissure typed reservoirs also develop well. At the last part of essay, according to the comprehensive analysis, it predict the reservoir distribution under the sedimentary facies.