Study on Fine Reservoir Description and Connectivity of Chemical Flooding in Class-III Reservoir of Daqing Oilfield

Daqing Oilfield has abundant reserves in Class-III reservoir, which has become the main potential layers for stable production. However, the Class-III reservoir is characterized by numerous thin layers and poor properties. The vertical stacking of sand bodies with different origins and the planar facies changes between injection - production wells lead to unsatisfactory macroscopic sweep volume coefficients, which directly affect the development effectiveness of chemical flooding. In this paper, the Class-III reservoir in Gaotaizi oil layer of the Sa Zhong development zone are taken as an example for the study. Reconstruct a fine logging interpretation model for porosity and permeability with one logging sampling interval of 0.125 m, and do secondary interpretation on chemical reservoir parameter logging in the experimental area. Establish classification standards for the connectivity types of sand bodies between injection - production wells and clarify the development characteristics of the sand bodies in the well groups. The results show that the channel of Gaotaizi oil layer in the central and western part of the Sa Zhong development zone in the Daqing Oilfield development is narrow and small in scale, with vertically stacked channels of different origins in contact or isolated from each other, and the front sheet-like sands are distributed in patches, with the channels embedded within them. By drawing the sand bodies connectivity diagram in the direction perpendicular to the provenance, 10 types of sand bodies contact relationships and 4 types of connectivity quality are obtained. Based on the thickness, effective thickness, sedimentary microfacies type, and reservoir permeability of the target layer sandstone encountered when drilling in the well group, the well group is divided into four categories: a, b, c, and d. The research results are of great significance for the design of chemical flooding reservoir engineering schemes, process tracking and adjustment, and post-evaluation of scheme implementation effects in Class-III reservoir.