Comparison Analysis Of Measured And Gassman Calculated P-Velocity Of Saturated Carbonate And Sandstone Using Matlab

Abstract

In reservoir studies, the physical properties of rocks are important to be reviewed. One of the methods that can be used to assess the physical properties of rocks in a reservoir is the seismic method. This method produces the velocity values of P wave and S wave. The velocity of the P wave and S wave is strongly influenced by the fluid content. The relationship between seismic properties and fluid content can be analyzed using log data and the Gassman equation. This equation is used to evaluate the Vp and Vs values in the case of fluid substitution. In this study, secondary data of physical properties of carbonate and sandstone rocks were used. Comparison between the measured Vp value and the Gassman calculated Vp value was carried out to find out how the Vp value from the Gassman calculation and also the regression between the porosity and the measured Vp value and the Vp value of Gassman's calculation was carried out to analyze the relationship related to rock types. Data plotting and regression were done using Matlab. The results obtained in the form of Gassman's calculations yield a prediction of the P wave velocity that is lower than the measured P wave. In the regression results between the porosity value and the measured Vp value, there is a negative relationship, where high Vp values indicate low porosity values. In the sandstone sample, the Vp saturation value is low, both at the measured Vp and the Gassman calculation Vp because of the same porosity value. Whereas for carbonate rocks, the results from the measured Vp graph show a lower saturation Vp value than the Vp graph calculated by Gassman.