Application Of Water Flooding Mechanism And Digital Core Analysis Method In Low Permeability Reservoirs

The low permeability sandstone reservoirs in the western South China Sea has the following characteristics:the heterogeneity of the reservoir pores,the complex distribution of the pores and throat,the connectivity between the pores and the throat is difficult to portray and it is difficult to accurately analyze the remaining oil.Therefore,it is of great significance to study the pore structure,microscopic seepage mechanics and the distribution of remaining oil of low-permeability reservoir rocks.Finally,on the basic of these researches,giving some suggestions for improving the development effect of the water flooding has a great significance.In this paper,the low-permeability sandstone in the target block is the research object.The study of the pore structure of the core is based on the micro-X-CT scanning technology and nuclear magnetic resonance technology.By some experiments,including micro-scale X-CT scanning water flooding experiment,water flooding experiment of long core,water flooding experiment of the two-dimensional plate and digital core image analysis,it carried out the multi-scale water flooding mechanism of low-permeability sandstone reservoir and the research on the application of digital core.Some understanding were gotten as follows:(1)Experimental study on the pore structure characteristics of the target low-permeability reservoir core by X-CT scanning technique and nuclear magnetic resonance technique shows that the pore structure of the rock sample is mainly small pores,it has less macrovoid.The pore connectivity of the rock sample is poor,the radius of the throat is small,and the bound water mainly occupies the smaller pores in the rock sample.The three-dimensional image of the pore structure of the rock sample shows that its characteristics are consistent with the characteristics of low permeability sandstone.(2)X-CT scanning image analysis of rock sample micro-water flooding experimental process shows that with the progress of water flooding process,the injected water mainly drives the oil by the large channel in the pore space.The remaining oil is mainly distributed in small pores in the corners of the cross-sectional view in discrete dots or flakes.As a whole,the water flooding process shows obvious influence on the heterogeneity of microscopic pore distribution.(3)In the long core water flooding experiment,as the flooding multiple increases,the oil saturation in the core decreases continuously and the water saturation increases,and the oil saturation gradually approaches the remaining oil saturation.At the same time,the water saturation at different positions in the core at the same time is not the same everywhere,and the core shows the influence of the heterogeneity of the pore distribution.(4)The digital image of the two-dimensional flat model water flooding experiment shows the change of the leading edge position of the water flooding and the distribution of the remaining oil.The dominant channel between the injection and production wells has the higher displacement efficiency.The remaining oil are enriched in the local area where the injected water can not flow.