Comparison of a New Multi Laterolog Tool and a Formation Resistivity Imager in the Phiops Field of Egypt

Abstract

The Multi Laterolog is a newly developed array laterolog logging device based on the Dual Laterolog principle, consisting of four independent focused measurements of differing depths of investigation with high vertical resolution. A model-based adaptive borehole correction (ABC) technique corrects the Multi Laterolog measurements for borehole effect in very conductive muds and large boreholes by solving for tool position as an unknown. This approach guarantees that in non-invaded intervals, all four laterolog curves are properly "stacked", even in large washouts, while invaded intervals show a consistent resistivity profile. The correction algorithm is very fast and is applied in real time during data acquisition. It also provides an estimate of true formation resistivity (R t ) that can be significantly higher than the deepest laterolog measurement. This results in a more accurate estimation of hydrocarbon saturation. With the addition of a micro-resistivity device, it is also possible to estimate the length of mud filtrate invasion (L xo ). Advantages of the new Multi Laterolog logging tool and advanced processing principles in combination with other wireline logging tools like the Formation Resistivity Imager are illustrated by an example from the Phiops field in Egypt.