Experimental Study On Water Flooding Using Largescale Model For RQ Buried Hill Carbonate Oil Reservoir

RQ buried hill carbonate reservoir is a typical dual medium reservoir which main type is frcactured-porous and fracture is the primary seepage channel,the oil recovery by now is about 30%,water content is very high,the remaining oil is a lot,to further enhance oil recovery,the mechanism of development has become a key issue.Unable to get the real representative core with micro cracks,this paper based on the background of RQ buried hill carbonate reservoir to create artificial core with micro cracks,meet the formation properties.By using the method of physical simulation,using the new three-dimensional physical model of high temperature and high pressure resistance,2 different large crack combinations of water flooding physical model experiments were carried out,characteristics and flow rules of water flooding were correctly understood and evaluated.The research in this paper was supported by the "remaining oil distribution and development mechanism study of RQ carbonate reservoir" program of CNPC,which is of great significance to the development of the reservoir.The main research results are as follows:(1)On the basis of similarity theory,through the sensitivity analysis,it is found that the reservoir permeability and fluid saturation play an important role in the physical simulation experiment.By using numerical simulation model,the mesh size(2.5cm,5cm,10cm)of five point pattern and nine point pattern were studied.The mesh size was found to have almost no effect on oil recovery and remaining oil distribution.On this basis,the array of monitoring data points was determined to be 10cm.(2)Starting pressure gradient experiment,stress sensitive experiment were carried out on three different artificial fracture cores,oil-water permeability experiments were carried out on fracture cores and matrix cores.The analysis on seepage characteristics made of different permeabilities provided the basic understanding of the experimental results for the model.(3)On the basis of the fact that it is unable to obtain the real core,combined with the physical properties of the RQ buried hill reservoir,Through a lot of experiments,finally through the comparative analysis,the core model of micro cracks was made with a mass ratio of cement:sand stone of 1:2:4 and 1%of the total volume of oil Finding out the method of making micro cracks creatively,provided the basis for the model experiment.(4)Using a new type of large scale model which can obtain resistivity and pressure distribution,this paper designed water flooding experiments of 2 different combinations of large cracks in the model(high angle fracture and high angle double cracks).The large model of single crack water flooding oil recovery is 42.88%,double cracks recovery is 52.68%,with the small reservoir core flow experiment,the result of water flooding of the large model was analysed.