Mathematical derivation of density log from total gamma ray and neutron logs in clastic rocks, a case study, Egypt

An empirical equation was adequately prepared to calculate the density log values without running the density tool from total gamma ray and neutron log values, on clastic reservoir rocks. This equation was applied to calculate the density log values in three important regions in Egypt (Gulf of Suez, Nile Delta and Western Desert) for hydrocarbon exploration. The derived density log was calculated depending on the neutron and total gamma ray logs, which were used to calculate porosity and volume of shale percentages, and finally sand percentage. Applying the derived equation to calculate the density log values from total gamma ray and neutron logs, and comparing the results with the really measured log in the three wells, located with three different regions; the calculated values were mostly comparable with the measured log values. The computed correlation coefficients of the three linear regression equations attained 0.92, 0.96 and 0.97 for the Gulf of Suez, Westem Desert and Nile Delta regions, Egypt, respectively. In spite of the fact that, the three empirical regression equations revealed different slopes and various intercept values, yet these equations were found to be nearly identical, when applied to the same values and compared to each other. The differences between the slopes and intercepts in the three equations refer to the various depositional environments in the three studied regions as well as their different depths and consequently their diverse pressures.