Abstract

Given the knowledge of the rock type, porosity, Archie’s parameters and water saturation can be determined by using different logging devices. For example, if a density logging tool is to be used, the rock matrix density must be known in order to determine the porosity. Likewise, using sonic log for porosity determination, the known parameter must be the matrix travel time and for neutron log, the parameter that must correspond to the rock type is the matrix setting for the neutron logging tool. Many equations have been developed over the years based on known physical principles or on empirically derived relationships, which are used to calculate porosity, resistivity, water saturation, and estimate the lithology. NS oilfield is one of giant oilfields in the Middle East, and the formation under study is the Yammama carbonate formation which is one of the deepest hydrocarbons bearing zone in NS oilfield. Neurology software (V 5, 2008) was used to digitize the scanned copies of the available logs. Environmental corrections had been made as per SLB charts 2005. Results show that the Yammama formation consists mainly of limestone, some dolomite as well as the average formation water resistivity (Rw= 0.0179), average mud filtrate resistivity (Rmf= 0.091), and Archie's parameters (m=1.94, n= 2, and a=0.7). While the porosity, true resistivity, and water saturation values with depth of formation were calculated. This study provides the cross-plots, which can be used to determined lithology of this reservoir and investigated petrophysical properties that should use to estimate original oil in place and detected the perforation zones.

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