The Study On The Sequence、the Sedimentary Facies And The Distribution Law Of Reservoir Of Feixianguan Formation In The Northeast Of The Sichuan Basin

Based on previous studies on the tectonics and stratigraphic characteristic, the sedimentary pattern and evolution characteristics, using the principle and methods of sequence stratigraphy, by the analysis of the outcrops, drill profiles and logs characteristic, Feixianguan formation in the Northeast of the Sichuan Basin is divided into two third-order sequences, called SQ1and SQ2from from bottom to top, including LST, TST, and HST,among which the LST only exist on the shelf. According to the cyclicity characteristics of rock types and logs cyclicity features, Feixianguan formation in the Northeast of the Sichuan Basin is divided into sleven or sixteen fourth-order sequences, twenty or thirty one fifth-order sequences, and furthermore, framework of third-order sequence and high frequency sequence are established.According to petrological characteristics, tectonics and well-logging etc, we classify carbonate sedimentary facies of Feixianguan formation in the Northeast of the Sichuan Basin, including.carbonate platform, slope, shelf, basin etc,and dfferent regions have different sedimentary facies and vertical sedimentary facies evolution. By the study on distribution characteristics of sedimentary facies and shoals in sequence stratigraphic framework and sequence units,the development of shoals is controlled by sequence and sedimentary facies obviously, and various local areas differ. Particle limestone shoals in Yuanba area mainly develop in the middle and upper part of the HST of SQ1(platform margin) and the TST and the lower part of HST of SQ2(open platform), with the characteristic of progradation to the shelf obviously. Particle dolomite shoals with large thickness in Puguang area mainly develop in the HST of SQ1(platform margin), secondarily in the TST and the middle and lower part of HST of SQ2,with the characteristic of aggradation upwards.mainly and retrogradation to platform interior in the middle and upper part of the HST of SQ1.Particle limestone shoals in Heba area develop wholely in the lower part of HST of SQ2(open platform),with good lateral comparison.After a detailed observation of cores and thin sections, as well as reservoir anatomy of the well profile, three types of reservoirs are mainly developed in Feixianguan formation in the Northeast of the Sichuan Basin,including shoal-facies particles limestone reservoir, shoal-facies particles dolomite reservoir and tidal-flat-facies grain dolomite reservoir,among which shoal-facies reservoir account for the vast majority and tidal-flat-facies reservoir account for a small amount. Through statistical analysis of the reservoir and sequence,sedimentary facies,and the study on distribution characteristics of reservoirs in sequence stratigraphic framework and sequence units, shoal-facies reservoir is strictly developed by shoal facies,and the vertical and lateral distribution and evolution characteristics of reservoirs is In line with the shoal.In platform,most of reservoirs develop in the HST of SQl,and in slope and shelf, reservoirs develop mainly in the lower of the HST of SQ2. Reservoirs develop both in the upper, middle and lower part of the high-frequency sequence with the overall trend of development upwards. The distribution characteristics of reservoirs differ on both sides of the shelf:the reservoir of west side is thin and wide, progradating to the shelf obviously,and the reservoir of east side is thick and small-scale with the characteristic of aggradation upwards. Reservoirs develop in various parts of the shoal and distribution characteristics are unobvious.On the basis of recognization that distribution and evolution of sedimentary facies and shoals have the main control to reservoirs spread, combined with reservoir anatomy of the well profile and outcrop reservoir, regional evaluation of Feixianguan Formation reservoirs in the Northeast of the Sichuan Basin is made in the units of third-order sequences.And four zones for the development of reservoirs are divided into,which have certain guiding significance for further exploration of Feixianguan formation in the Northeast of the Sichuan Basin.