Trend judgment of abandoned channels and fine architecture characterization in meandering river reservoirs: A case study of Neogene Minhuazhen Formation NmIII2 layer in Shijiutuo bulge, Chengning uplift, Bohai Bay Basin, East China

Abstract

Based on well logging responses, sedimentary patterns and sandstone thickness, the distribution characteristics of meandering river sedimentary sand body of Neogene Minghuazhen Formation NmIII2 layer in the west of Shijiutuo Bulge, Chengning Uplift, Bohai Bay Basin were investigated. A new approach to calculate the occurrence of the sand-mudstone interfaces using resistivity log of horizontal well was advanced to solve the multiple solution problem of abandoned channel's orientation. This method uses the trigonometric function relationship between radius, dip and length of the resistivity log to calculate the occurrence qualitatively – quantitatively to help determine the true direction of the abandoned channels. This method can supplement and improve the architecture dissection technique for meandering river sandbodies. This method was used to study the dip angle and scale of the lateral accretion layers in point bar quantitatively to help determine the spatial distribution of lateral accretion layers. The fine architecture model of underground meandering river reservoir in the study area has been established. Different from traditional grids, different grid densities for lateral accretion layers and bodies were used in this model by non-uniform upscaling to establish the inner architecture model of point-bars and realize industrial numerical simulation of the whole study area. The research results can help us predict the distribution of remaining oil, tap remaining oil, and optimize the waterflooding in oilfields. Key words: Bohai Bay Basin, meandering river, horizontal well resistivity curve, lateral accretion layers, lateral accretion bodies, architecture modeling, remaining oil distribution