ABSTRACT

The interpretation of electrical well logs in the brackish water Frio trend of the Texas Gulf Coast is further complicated by thin sands containing numerous shale and dense streaks. Such stratigraphic conditions require measurements of flushed zone resistivity and true formation resistivity over very short vertical intervals. These stratigraphic conditions coupled with the higher resistivity formation water offer the ideal application of the FoRxo-Guard log combination in that fluid content can be resolved in sand stringers as thin as 1 1/2 feet. The combination of logs makes it possible to determine reliably and rapidly formation fluid, percent saturation, and porosity.

The Guard log correlates well with conventional electric logs. It shows more detail and character than the latter, so that correlations between Guard logs are more accurate and permit recognition of less conspicuous stratigraphic changes.