关键词: channel sand body, thin interlayer, inefficient circulation, logging identification, remaining oil potential tapping

Abstract: Inefficient or invalid circulation of the injected water occur in partial high-permeable zones within channel sand bodies after long-term waterflood development in reservoirs, and remaining oil accumulates near interlayers. It is still difficult to identify thin interlayer in channel sand bodies, which goes against the remaining oil potential tapping. Taking the western area of District Beier of Daqing placanticline oilfield as an example and using the data obtained from sealed coring wells with small well spacings, the paper carries out fine description of thin interlayer within channel sand bodies, classifies and evaluates the logging response characteristics of the interlayer and determines its controls on residual oil distribution. The study results show that the interlayers in the study area can be divided into lithological interlayer and physical-property interlayer, both of which are dominated by mudstone and siltstone, mainly distributed at the top of the sedimentary cycle vertically and mainly located in the sedimentary facies transformation zones in the plane. The remaining oil concentrates in the vicinity of the interlayers. Based on the identification results of the thin interlayers and according to the characteristics of the residual oil distributed in different channel sand bodies, different methods are adopted to realize the adjustment of potential tapping in thick sand layers, and the effects of increasing oil production and decreasing water production are significant, which can be the references for the secondary development in similar blocks.

Key words: channel sand body, thin interlayer, inefficient circulation, logging identification, remaining oil potential tapping