Using Geophysical Well Logs in Studying Reservoir Properties of Zubair Formation in Luhais Oil Field, Southern Iraq

Abstract

The characterizations of reservoir require reliable knowledge of certain fundamental reservoir properties. Log measurements can define or at least infer these properties: resistivity, porosity, shale volume, lithology, and water, oil, or gas saturation and permeability. The current study represents evaluation of petrophysical properties in well LU-12 for Zubair Formation in Luhais Oil Field, southern Iraq. The petrophysical evaluation was based on geophysical well logs data to delineate the reservoir characteristics of Zubair Formation. The available geophysical well logs such as (sonic, density, neutron, gamma ray, SP, and resistivity logs) are digitized using the Didger software. The environmental corrections and petrophysical parameters such as porosity, water saturation, hydrocarbon saturation, bulk water volume, etc. were computed and interpreted using Interactive Petrophysics program. Lithological, mineralogical and matrix identification studies were estimated using porosity combination cross plots. Petrophysical properties were determined and plotted as computer processing interpretation (CPI) using Interactive Petrophysics program. Zubair Formation in Luhais oil field is divided into three units according to petrophysical properties: Upper Zubair, Middle Zubair, and Lower Zubair. Middle Zubair is characterized by good porosity but high water saturation. Interpretation of well logs of Zubair Formation founds that Zubair Formation production in well LU-12 is noncommercial but present weak oil shows in some ranges of the formation especially in upper and lower Zubair units but middle Zubair is characterized by free oil shows .Lithological study of Zubair Formation appears that it consists mainly of interbedded sandstone, shale, and shale sandstone whereas mineralogy of Zubair Formation consists mainly of quartz sandstone and Some calcite.