Microfacies subdivision method for three types of oil reservoirs in Lamadian Oilfield

With the transition of first and second type oil reservoirs to polymer flooding development, third type oil reservoirs will gradually become the main targets of water flooding exploitation. In order to meet the precise adjustment requirements of water flooding and prepare for the development of tertiary oil recovery in three types of oil reservoirs, research on the subdivision microfacies of three types of oil reservoirs has been carried out. The three types of oil reservoirs belong to delta sedimentation, which were initially subdivided into six microfacies: underwater distributary channels, underwater sand bars, river controlled sheet sand, lake controlled sheet sand, surface sand, and interbedded mud. The classification has genetic characteristics, but it is still not sufficient to express its planar heterogeneity. To this end, based on core and logging data, starting from the characteristics of rock type, mudstone color, grain size, and sedimentary structure, the subdivided microfacies genesis types were determined, and a logging identification chart was developed. Based on modern sedimentary patterns, microfacies identification and mapping work were carried out. Using the South Middle East as the research area, two sedimentary subfacies were identified: the inner front and outer front of the delta, including 12 sedimentary microfacies such as underwater distributary channels and a type of river controlled sheet sand; A sedimentary model of the delta front has been established, and its sedimentary evolution characteristics have been studied, providing geological basis for tapping the remaining oil potential of three types of reservoirs.