3D Geological Modeling of Complex Lithology of Heterogeneous Reservoirs With Few Wells Offshore—A Case Study of the Thick Sand Reservoir of Huagang Formation of Gas Field A in East Sea

Low-permeability reservoirs of Huagang Formation in the central anticline zone of Xihu Sag in East China Sea Basin belongs to the strong heterogeneity. It mainly develops eight kinds of lithology, such as medium sandstone and coarse sandstone with medium porosity, medium and low permeability, and fine sandstone and siltstone with low porosity and low permeability, and their superimposed combination corresponds to four sedimentary microfacies in diara dam of braided river delta front, main channel, secondary channel, and underwater distributary bay. The well area is characterized by few drilling wells, large well spacing and strong multi-solution of seismic inversion data. It is difficult to characterize the heterogeneity of the reservoir actually revealed by the well point using conventional modeling methods. In order to accurately describe the spatial distribution characteristics of heterogeneous reservoirs in plane and longitudinal direction, the complex lithology was identified by analyzing and testing data of drilled wells and multi-component logging identification methods, and the sedimentary microfacies were divided into four types by vertical combination sequence, and the facies boundary was determined by seismic multi-attribute and stratigraphic section study. The lithologic model under fine phase control is established by the combination of deterministic method and stochastic simulation, and the porosity-permeability relationship based on lithology refinement is used to constrain the establishment of the reservoir attribute model. The results show that the model established by this method has high reliability and is more consistent with the geological understanding, which provides a fine framework for the simulation of reservoirs in the later period and guides the optimization of the overall development plan.