| At present,the development of most oilfields in my country has entered the stage of high water cut,but there is still a large amount of remaining oil in the reservoir,and the efficient exploitation of the remaining oil in the reservoir has become the focus of oilfield work.Therefore,it is of great significance to study the microscopic pore structure of the reservoir and the occurrence state,spatial distribution law and formation mechanism of the microscopic remaining oil for the oil field to evaluate the remaining oil in the reservoir and formulate development measures.In this thesis,taking the Gaotaizi oil layer in Labei West 2nd District as an example,core samples with different pore structures were selected for the study area,through CT scanning technology and displacement experiment research,using high-performance GPU parallel computing clusters,and applying numerical simulation theory to develop digital core samples.The seepage simulation clarifies the occurrence characteristics and enrichment law of the microscopic residue in the study area.In this thesis,the core samples with different pore structures in the study area were first finely characterized using CT scanning technology,and a high-precision microscopic 3D digital core model was established.Then micro-displacement experiments,digital core reconstruction and fluid identification were carried out on samples with different pore structures.The oil-water occurrence state of the samples was visualized and quantitatively characterized.The core model was processed to clarify the occurrence state and characteristics of remaining oil.Then this thesis established a digital core oil-water two-phase flow model based on the Lattice Boltzmann Method(LBM)model,and carried out oil-water two-phase flow simulation and relative permeability simulation under different wettability.Influenced by the degree of recovery,weak water wetness > intermediate water wetness >weak oil wetness > strong water wetness > intermediate oil wetness;under steady state conditions,the permeability of the oil phase gradually increases as the wettability changes from oil-wet to water-wet High,the oil-water two-phase permeability decreases with the increase of capillary force.Using the above research results to study the occurrence state of microscopic remaining oil,the results show that the remaining oil in the pores in the early stage of displacement is mainly in a large-scale connected shape,which gradually changes into a network and porous shape as the degree of water washing increases.In general,the poorer the physical properties of the core,the more complex the distribution of remaining oil tends to be.The simulation results under weak oil-wet conditions are basically consistent with the actual displacement experimental results,showing that the remaining oil distribution trends in the same pore structure are basically the same;after water flooding,the microscopic remaining oil spatial distribution is basically the same,showing a highly dispersed overall and relatively local Enriched features.To sum up,this thesis establishes a set of microscopic residual oil research methods suitable for sandstone oil reservoirs combining laboratory experiments and numerical simulations,which provides new research ideas for the efficient recovery of residual oil. |
