Digital Core And Microscopic Simulation Of Fluid Seepage In Tight Sandstone

At present,tight oil has become a key area for oil and gas exploration and development at home and abroad.With the further exploration and development of low permeability reservoirs,more and more attention has been paid to the study of oil displacement efficiency.Fluid flow in tight reservoirs is different from that in conventional reservoirs.It is quite difficult to displace oil efficiently under physical experiment.This is because of not only high pump pressure requirements,but also low efficiency experiment as well as long timetable.As a result,the existence of the above problems will lead to large errors,which will also make the results lack guiding significance.With the rapid development of the computer industry,the computing speed is greatly improved,and the advanced large computer cluster rental service is convenient,which makes numerical simulation like the most effective way to replace physical experiments.Common numerical models include capillary models,seepage models,ball-and-stick model,etc,which are all built after simplifying the real pore space.There is a certain deviation between the simulation results and the actual core data.In this paper,the micron CT scan of gaotaizi reservoir samples in longhubao area is carried out,and then the image processing technology and advanced visualization software were used to complete the filtering processing,binarization processing and characterization unit analysis of the gray image of core sample.Finally,the fine microscopic 3d digital core model is constructed and its pore throat parameters are quantitatively characterized.In addition,the microscopic oil displacement process of water,carbon dioxide and water-carbon dioxide under constant pressure and speed was simulated by lattice boltzmann method(LBM),and the corresponding oil exchange rate and displacement efficiency were calculated.In summary,a set of techniques for microflow simulation of tight sandstone based on three-dimensional digital core and lattice boltzmann method is established.The study achieved the following main results and understanding:(1)this study perfects the CT image processing ways of core samples as well as determines the characterization unit size of the 3D digital core of the Gaotaizi reservoir core samples in the Longhupao area.Then,the equivalent ball model of the 3D digital core pore space is established,based on the maximum sphere algorithm.(2)The number,volume,radius distribution,pore-throat ratio,tortuosity,connectivity and other parameters of core pores and throat are quantitatively characterized to achieve qualitative and quantitative description of the core micro-topology.(3)The problems of overburden recovery and inaccurate division of pore and mineral in digital core by X-ray CT scanning are explored and the corresponding solutions are given.(4)This research regard the three-dimensional digital core as a platform to simulate three microscopic displacements,including water flooding,carbon dioxide flooding,and water-carbon dioxide alternate flooding,under the Lattice Boltzmann Method.In the case of LBM scale and the same injection volume,the displacement efficiency relationship among three displacement modes is: carbon dioxide flooding > watercarbon dioxide alternate flooding > water flooding.