Porosity Type Determination Using the Velocity Deviation Technique for The Sheikh Allas Formation in The Kirkuk Oil Field, Northeastern Iraq

Abstract

AbstractThe current study aimed to show the utility of the velocity deviation technique in determining the porosity types of Sheikh Allas Formation in the Kirkuk oil field. Log data collected from two selected wells in the study area were analyzed. 46 thin section slides at certain depths were used to identify porosity types. The sonic log was utilized to estimate the true velocity, while neutron and density logs were employed to estimate porosity. Velocity deviation was calculated by subtracting the porosity log velocity from the sonic log velocity. The results revealed that there is a significant agreement in the directions of increase and decrease between the secondary porosity produced by the dolimitization and the velocity deviation. The dolomitization increased significantly in well k-218, while it has a little effect in well k-246 . By observing the velocity deviation curves, it was found that there is a clear difference between the two wells in the types and depths of the porosities. The secondary porosity in well k-246 does not exceed 5%, while it reaches 15% in well k-218. It is the most obvious difference between the two wells, resulting from the increase in the percentage of dolomite in well k-218. Furthermore, the abnormally high primary porosity that appears at various depths in well k-218 is a feature of this well. A high consistency between the thin section information and the velocity deviation technique in terms of porosity types and their locations was observed.