A Study Of Invasion Diameter Available to Purchase

This paper presents empirical correlations for the diameter of filtrate invasion, "DI", and for the true formation resistivity, RT, as a function of mud properties, exposure times, and formation properties. To obtain the correlations, "DI" and RT values were calculated using Dual Induction Laterolog-8 logs through 676 zones from 26 wells. These wells were from Oklahoma, Texas, Arkansas, Kansas, and New Mexico. These "DI" and RT values were independently correlated with drilling and logging parameters which will normally be available to the log analyst. Most of the parameters are usually available on the logs or log headings, while a few require access to the drillers logs. Correlations were made both with and without the driller's log parameters with very little difference in accuracy. Equations were obtained which predicted "DI" with an average absolute deviation of 41.8 percent which in turn yielded an average absolute deviation of 13.1 percent for RT when good values are available for RXO and RILD, the deep induction log readings. Though these results are not as accurate as hoped for, they are significantly better than those obtained using our data in the equations of earlier investigators. The correlations are not oriented for hand calculations, but are readily adapted to a computer logging program