Sedimentary characteristics and sedimentary microfacies research of Denglouku formation in Changling gas field

Changling gas field of Southern area in Songliao basin is still at the early development stage and the understanding of reservoir sedimentary microfacies and sand body distribution rule is not clear.In order to make guidance for subsequent development,in combination with core observation,thin section identification and logging data,the research on the sedimentary characteristics and sedimentary microfacies has been carried out,and the sedimentary microfacies types,spatial distribution and evolution regularities have been determined.The results show that Denglouku formation in lower cretaceous belong to braided river sedimentary reservoirs and can be subdivided into four kinds of microfacies,namely braided channel,diara,crevasse splay and flood plain.Sedimentary microfacies are of inheritance characteristic;generally presenting SE to NW,with braided channel and beach deposition as the main sedimentary bodies,limited crevasse-splays distribution and symbiosis with flood plain.Among them,the channel belt in depositional stage of d4-2→d3-2 is is not stable,with horizontal swing and local frequent adjustment.In depositional stage of d3-1,the fluvial is weak,with developed flood plain and wholly migrated channels to southwest.In depositional stage of d2-3→d1-1,the channels are stable,with small horizontal oscillation amplitude.Braided river channel and heart beach are good for oil and gas enrichment,93.4% gas layers belong to river channel and diara sand bodies.These research results has deepened the reservoir understandings and provided practical significance for follow-up development and optimal areas chosen.