Study of the Porosity of Carbonate Rocks (Lidam Formation) Using Well Logs, Al-Hamid Field, Sirte Sedimentary Basin, Libya.

Abstract

The aim of the research is to identify and calculate the different types of porosity by the indirect method (well logs) for the formation of Lidam, and the relationship of porosity to other petrophysical properties such as mineral composition, clay content, oil saturation, modulatory processes as well as the relationship of total porosity to effective porosity and compare it with direct methods, which were calculated in the laboratory by endodontic samples. Two methods for determining and calculating porosity were used in this study, which is the graphic method and the method of analysis by mathematical equations. Through the results, it was possible to divide the Lidam formation in this well into five bands from bottom to top according to the rocky characteristics of the size of dolomite and anhydrite as well as calcite. The results of the study also indicated that the porosity was affected by the petrophysical properties, so the effective porosity values ​​correspond to the values ​​of the total porosity in the zones that contain high percentages of dolomite, and this indicates the occurrence of the dolomite process and thus indicates the secondary porosity, while these values ​​vary at the zones containing clay and anhydrite. As for oil saturation, it occupies most of the effective porosity. Whereas, the high percentage of shale in the Lidam formation in the upper range led to a decrease in the effective porosity ratio, which affected the presence of oil.