| The tight reservoirs feature a multisacle pore structure and the water flooding process is complicated.Capillary force often overlooked under medium and high permeability,while nanopores have largest imbibition efficiency in tight reservoirs due to the larger caillary force.Spontaneous imbibition has become an effective oil recovery method with regards to tight reservoirs for the enhanced oil production.Researching the spontaneous imbibition law of tight cores,which has certain guiding significance for the development of tight reservoirs.Based on the basic seepage flow laws,this paper derives a two dimension,two phases imbibition model,and receives a certain understanding of the seepage model.The radial core model is established by using the reservoir numerical simulation software Eclipse,and the model is verified by physical experiments.Theoretical analysis was given,we studied in depth for influencing factors of tight core imbibition.According to the real reservoir imbibition process,there are different boundary conditions.Core models with different boundary conditions are constructed to investigate the heterogeneity,gravity,and interference of end faces and sides.The main research results show that:(1)The main driving force for the imbibition process of tight cores is capillary pressure,and the imbibition recovery rate is mainly concentrated in the early stage.Imbibition rate gradually decreases with the progress of the imbibition process.(2)Spontaneous imbibition in cores is affected by many factors.The imbibition recovery increases with decreasing viscosity and increases with increasing matrix permeability.At the same time,the saturated tight reservoir should be kept under saturation pressure as much as possible.According to increasing the density of cracks,choosing the appropriate interfacial tension,prolonging the time of infiltration,we can give full play to the effectiveness of imbibition.(3)The core imbibition characteristics are different under different boundary conditions.Due to the more open the boundary and the larger the specific area in contact with the water surface,there is the faster the imbibition speed and the higher the imbibition recovery.(4)The superposition of imbibition at the end face and the side shows a suppression effect.The values of the imbibition recovery are smaller than the separate imbibition states.(5)Due to the influence of gravity,the opening direction of the end face is different,and the imbibition recovery factor will be affected.The lower interfacial tension,the more obvious effect.The OEO imbibition curve is opposite to the OEC.(6)The imbibition process is affected by the permeability anisotropy,and the sensitivity is determined by the main interface of percolation. |
