Method optimization of determining the lower limit of physical properties by mathematical statistics
Some problems of determining the lower limit of physical properties by mathematical statistics are analyzed.Under the condition that the number of valid samples and non-valid samples is roughly equal,the natural distribution percentage method,block number conversion percentage method and forward and inverse accumulation method are used to determine the lower limit of physical properties according to the analysis data of different oil-bearing core properties,their results were roughly consistent,but the accuracy is not high due to the influence of physical properties classification interval.Considering the influence of large differences in sample data bodies,the conversion coefficient of valid samples or the percentage forward and inverse accumulation method of sample normalization is introduced to overcome the problem of low lower limit of statistics due to the absolute advantage of valid samples in natural distribution statistics,but it is still affected by the physical property classification interval,and the accuracy is not high enough.In order to suppress the large difference of statistical data between valid and invalid samples and improve the accuracy,a point-by-point plot is proposed by using the percentage forward and inverse cumulative scatter graph method.By comparing and analyzing the core analysis data in target layer of A oilfield,the lower limit of porosity is determined to be 7.4％by using the percentage forward and inverse cumulative scatter graph method,which is consistent with the measured minimum porosity value of 7.4％.By comparing and analyzing the core analysis data in target layer of B oilfield,the lower limit of permeability determined by the percentage forward and inverse cumulative scatter graph method is 400 mD,which is roughly consistent with the measured minimum permeability value of 410 mD.Both examples show that the method of percentage forward and inverse cumulative scatter graph method is more reliable,the lower limit of physical properties is more accurate.
mathematical statistics methodpercentage forward and inverse accumulation scatter plot methodlower limit of physical property
万方数据
维普
