Research on sand body differences before and after river pattern conversion from braided river to meandering river:a case study of Dong 2 Member of Dongxin area,Dongying Depression
There are great differences in the shape characteristics and distribution laws of sand bodies in different fluvial facies,and the conversion of river pattern controls the plane distribution characteristics,geometric parameters and vertical overlapping relationships of sand bodies in different periods,and thus determines the oil and gas exploration and development strategies of different fluvial facies reservoirs.Based on the core,logging curve and three-dimentional seismic data of Dong 2 Member of Dongxin area in Dongying Depression,and with the help of quantitative core sedimentary structure and seismic geomorphology,it is clarified that:(1)The braided river deposits are developed in sand groups 4,3,and 2 of Dong 2 Member,and meandering river deposits are mainly developed in sand group 1.(2)The average channel depth of braided river in the sand groups 4,3,and 2 of Dong 2 Member is about 17-52 m,20-59 m,and 19-52 m respectively,and the average channel width is about 1589-1 1 602 m,2 154-14 597 m,and 1 862-11 923 m respectively.The quantitative seismic geomorphology indicates channel width of 1 000-7 000 m.The average channel depth of meandering river in the first sand group is 11-30 m,and the average channel width(Wc)is 665-4 221 m,and the width of channel zone is 700-3 000 m as indicated by quantitative seismic geomorphology.(3)The braided river sand body of sand groups 4,3,and 2 in Dong 2 Member is dominated by contact superposition and bottom cut superposition vertically,and is dominated by independent contact laterally,side cut contact and butt contact.The sand bodies in sand group 1 is dominated by divided superposition vertically,and is mainly independent contact laterally.The geometric shape of sand bodies and their time-space cutting and overlapping modes are clarified,which provides practical support for the exploration and development of fluvial facies sandstone reservoirs in Dong 2 Member of Dongxin area.
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