Simulation Study On The Water Flooding Stimulation Measures And The Distribution Law Of Remaining Oil In X Sandstone Reservoir During The Ultra-high Water Cut Period

During the development stage of extra-high water cut stage,due to the high water injection rate and high water cut,the distribution of residual oil is increasing complex,dispersed and concealed.This leads to the residual oil difficult to be produced effectively.The X reservoir is located in Fuyu reservoir formation in the northern transition zone of Sabei Development Zone,Daqing Oil filed.The lithology of the reservoir is mainly fine sandstone with strong heterogeneities.And it has entered the development stage of extra-high water cut stage at present.The comprehensive water cut is 95.29%,and the overall recovery degree of the block is 36.68%.Based on the analysis of its geological characteristics and development characteristics,this thesis puts forward and designs the simulation of water flooding in the field by using laboratory large physical simulation methods,to study the effect of increasing production and the distribution rules of remaining oil in extra-high water cut stage under the measures of increasing injection speed,changing well patterns and cyclic water flooding etc.Based on the similarity theory,the similarity criterion of water flooding is deduced under the hypothetical conditions,and the similarity criterion is determined.The conversion between the model parameters and the actual reservoir parameters is realized,and combined with the strong heterogeneity of the X reservoir,the heterogeneity of the reservoir is well developed.Three kinds of three-dimensional physical models,namely plane homogeneous model,plane heterogeneous model and intra-layer heterogeneous model,are designed and made to carry out the physical experiments of water flooding,including three groups of plane homogeneous model experiments.Two groups of plane heterogeneity model experiment and one group of intra-layer heterogeneity model experiment.A total of 2686 sets of experimental data of all models were analyzed in the whole physical simulation experiment process.The effects of the measures to increase the yield of each model in the ultra-high water cut stage on its harvest degree were analyzed,and 40 sets of key process data of the experiment were analyzed by programming with MATLAB software.The resistivity data are converted into remaining oil saturation data by Archie formula,and the saturation field is used to study the distribution of remaining oil in ultra-high water cut period.At the same time,the numerical simulation and reproduction of all experimental processes are conducted using the commercial simulator CMG,to analysis the increasing trend and verify the experimental results.In this paper,the research shows that:(1)The measure to increase water injection speed is effective to increase well production in the extra-high water cut stage,and it is the main contribution to the increase of recovery degree after the composite water cut reaches 95%.In the later stage of production,the effect to reduce water cut rate by speed increase measure becomes very low due to the existence of the dominant water channel.At this moment using cyclic water injection and well pattern changing can continue to effectively increase production.(2)As for the plane homogenization model,the water cut can be reduced by changing the well patterns.The remaining oil saturation distribution map shows that the sweep efficiency of water drive in homogeneous model is well-distributed,and the phenomenon of "conical propulsion" along the mainstream line is obvious,and the high permeability model has faster growth of sweep efficiency and wider sweep area than the low permeability model.The remaining oil is mainly concentrated in the corners of the two wings of the mainstream line and the diagonal position of the non-main line.(3)As for the plane heterogeneous model,the low permeability area has more potential to increase recovery efficiency than the high permeability area.The remaining oil distribution map shows a large amount of water in the early stage mainly flow along the high,middle permeability area,and the remaining oil scattered in the corner area after plugging the high permeability well in the later stage.Remaining oil is mainly enriched on both sides of the low permeability well location.(4)As for the intra-layer heterogeneity model,the remaining oil saturation distribution map reflects that the sweep area in high permeability layer is wider than other layers in the early stage,the dominant channels are obvious.And the remaining oil is scattered on the two wings of the mainstream line of the high permeability layer.In addition to the two wings of the mainstream line in the middle seepage layer,the connecting parts of the side wells are also enriched with more residual oil.The remaining oil in the low permeability layer is more abundant in the two wings and along the side wells at both ends of the mainstream line.(5)The results of numerical simulation are approximately the same as the results of experimental simulation.Therefore,the validity of the stimulation measures and the reliability of the remaining oil distribution rules were verified.In this paper,the productivity enhancement measures of water flooding and the regular distribution patterns of remaining oil in the extra-high water cut stage of X reservoir are analyzed and summarized in detail,and the verification of physical simulation and numerical simulation is provided,which is expected to improve the recognition degree of the distribution laws of residual oil in X reservoir,to provide guidelines on recovery enhancement in field study.