Reservoir Characteristics Of The Sequence Framework Of Xujiahe Formation Upper Triassic In Medieval Sichuan

Based on the previous research of exploration, this paper studies the Xujiahe formation in central Sichuan. Accordding to sedimentology, sequence stratigraphy, sedimentology of reservoir theory, and combined with the field profile, analyses of cores, cast thin-sections, SEM, and analyses of porosity and permeability properties, it researches the characteristics of sequence stratigraphy and the reserve layer distribution of stratigraphic framework of Xujiahe Formation T3X2,T3X4,T3X6 in Guangan-Hechuan-Anyue areas of northeast of the medieval SiChuan uplift, the main achieved results include the following:1. According to the previous studies, combined with the field profile, and analysis of the log data, it carried out the sequence stratigraphy research in the medieval SiChuan, proposed the division program of the stratigraphic in the study area, analysed the characteristics of the types and the causes of the sequence boundary, took "sub-belt" in T3X2 and the coal seam in T3X5 as a flood plain face. It is divided into six third-order sequences from T3X2 to T3X6 in Xujiahe formation of Guangan - Hechuan - Anyue region (SQ1 ~ SQ6). By comparing each sequence, it has a result that sequence comparison completely in T3X2,T3X4,T3X6 (SQ1, SQ2, SQ3, SQ6 ), the sandbody cloth well and has the characteristics of stable distribution.2. According to the analysis of sedimentary features, it is divided into braided river delta-shallow lake depositional system in medieval Sichuan region. By the results of lithofacies palaeogeography map from T3X2 to T3X6, it shows the main distributary channel of braided river delta system comes from the northeastern Sichuan MiCangshan-DaBashan, Chongqing and oldland in Sichuan Jiangnan and Washan of Emei Mountain region. The distribution of sedimentary facies is mainly affected by the north eastern side of the ancient topography characteristics in medieval Sichuan uplift.3. According to the analyses of porosity, permeability and cast sheet of sequence stratigraphic framework, it concludes that the minimum effective porosity is 6% in middle-lower abundance of oil and gas reservoir lithology of Guangan- Hechuan- Anyue regions. The reservoir in the vertical distribution of the various sequences is mainly in the sequence of T3X2,T3X4,T3X6 (SQ1, SQ2, SQ3, SQ6 ), and the physical properties of reservoir is good, and shows the physical properties is better in the bottom of sequence boundary of the sandbody; In the plane, the isopach map of each sequence of reservoir porosity is Superimposed into sedimentary facies, and it shows that the reservoirs of T3X2, T3X4 fomation are mainly distributed in Hechuan, Tongnan areas, and the distribution of properties is better in sandbody of channel. The reservoir of T3X6 fomation is mainly distributed in Guangan areas, and the distribution of properties is better in sandbody of micro channel.4. By analyzing the sedimentation, diagenesis of the sequence stratigraphic framework, it is divided into five kinds of diagenetic phases, which play important implications in porosity development. From the many impact factors of reservoir properties, sedimentation is the basis of reservoir development, which control the macro distribution of reservoir; The diagenesis is the key to reservoir development, which determines the quality of reservoir properties. And the structure is an important condition for the formation of natural gas and the high yield of reservoir.