GEOPHYSICS LETTERS

32 Petrophysical studies for recognizing reefhydrocarbon saturation, and mineral volume fractions. It is based onthe minimization of th:~differences of the actual and reconstructed logreadings for the mineral/fluid model chosen. The linear and non-lineartool response equations for the various tools are building into theevaluation package. Hydrocarbon corrections to the density andneutron tools are carried automatically.The outputs from Elan to Nullipore section in wells-7, 20, and 24 asexamples is represented on figs (15), (16), and (17). Those include themineral volume fractions, which represent that the lithology ofNullipore section is limy-dolomite with some anhydritic contents insome intervals. Also the Elan outputs include the volumetric fractionsof the fluids content (hydrocarbon and water). This represents that theNullipore section is a potential reservoir, with hydrocarbon bearing.inmany wells.SUMMARY AND CONCLUSIONSThe Middle Miocene Nullipore rocks of Belayim Formation in RasGharib, and Shoab Gharib oil fields are taken as example in thepresent study. The aim of the study is to illustrate how Wtf canrecognize and interpret the section as carbonate build-up (reefs) bypetrophysical study.The neutron logs (on the available wells) read higher porosities thanthe porosities calculated from density logs, the response of the neutronand density logs indicate positive separation, which is more or lessconstant, but the absolute values may change with porosity or changein anhydrite content. These characters indicate that the lithology ismainly dolomite (carbonate).The neutron-density cross plots and the M-N plots to the HammamFaraun section of the available wells reflect a dolomite log response(limy dolomite).Gamma ray logs, to the Hammam Faraun section, record highreadings in all the available wells. Where the section is interpreted aspure carbonate, then this radioactivity can be interpreted as due to the