Study On Sedimentary Facies Of Guantao Formation In Gaoqing Area,Dongying Depression

The major fault in Gaoqing area is a basement fault,which developed successively and it's difficult to restore its structural evolution process.The fluvial facies is characterized by multiple longitudinal periods,rapid lateral changes and difficult to determine sedimentary types.Due to the lack of sequence stratigraphic framework,there are great differences in previous analysis and cognition.Based on the former research results,by use of the related theories and methods of sedimentology,petroleum geology and sequence stratigraphy,using the information of well logging and seismic,we have determined the detailed stratigraphic division and correlation of the the strata of Guantao Formation in Gaoqing area,and the identification of the type of sedimentary facies,integrated analysis of sedimentary facies and sand body distribution rule,finally predicted the location of beneficial zones.By analyzing logging curves of all wells,we totally find eight index horizons.Under the constraints of these index horizons,according to the multicycle feature,with the principle of gradual subdivision,comparison of equal height section and comparison of overlaying channel sand,we divided the Guantao Formation into 4 medium-term cycles and 11 short-term cycles.The mudstone in layers has the most widely distribution featuring classic muddy sand,meanwhile the sandstone concentrated in Ng4 with the content of it decreased gradually from the bottom up.In the observation of core,it is found that Guantao Formation mainly developes medium-coarse sandstone,siltstone,argillaceous siltstone,silty mudstone,mudstone in the study area,and sedimentary structure mainly has horizontal bedding,cross bedding,graded bedding,graded bedding and channel scouring surfaces,which have low compositional and textural maturity.The sand in this area presents a banded and platy distribution on plane,overlapped vertically,and its trend is north-south.The depositional system of Guantao Formation is meandering stream deposit in the upper member and braided stream deposit in the lower member,and the lower has a higer percentage.Through facies analysis,there are seven types of micro-facies,channel,channel detention,marginal bar,mid-channel bar and flood plain,natural levee and crevasse splay.The major sediments originated from the southern Luxi uplift and the western.These sedimentary microfacies controls the distribution of sand body,and is an important factors of influencing reservoir parameters of property.We divided the reservoirs into three types: Class ? reservoirs are developed in mid-channel bar microfacies,Class ? reservoirs are developed in channel microfacies,while Class ? reservoirs are developed in flood plain microfacies.